manual and assembly guide

Lola
manual and assembly guide
Hairball Audio, LLC
V1.2
Saftey Precausions
Read and understand all of the instructions before assembling this DIY project.
Improper assembly could result in damage to your property or serious injuries. Hairball Audio, LLC is not
liable for any damage or injury resulting from the assembly or use of this DIY project.
Use caution when assembling and testing. Make sure you are using the appropriate tools and following the
manufatures safey instructions.
Disclaimer of Liability and Warranties
The assembly manual for this DIY project is complete and accurate to the best of Hairball Audio, LLC’s
knowledge and is provided free of charge. Hairball Audio, LLC disclaims any and all liability for injuries
or damage resulting from the assembly or use of this DIY project, including any consequential damages.
Anyone assembling or using this DIY project does so at their own risk.
Hairball Audio, LLC makes no warranty of any kind with respect to the assembly or use of this DIY
project and explicitly disclaims any Implied Warranty of Merchantability. Hairball Audio, LLC warrantee
coverage insures that parts arrive in working order. Assembly support is not offered or included with this
DIY project.
By downloading and/or following these plans, the user acknowledges that he or she has read and followed
the Assembly Instructions and Safety Precautions.
© 2012 Hairball Audio, LLC
HAIRBALL AUDIO, LLC | iii
Contents
1
Welcome1
User Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Gain. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Output. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Pushbutton Controls. . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
DI. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
LED Meter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Assembly Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Patience . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Tools. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Soldering Guide. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Component Sorting. . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2
Populating the PCBs
5
The Printed Circuit Boards. . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Populating The Main PCB . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Op-Amp Sockets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Gain Resistors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Main PCB Resistors . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Semi Conductors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Pushbutton Switches . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Grayhill Gain Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Output Attenuator. . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
DI Jack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Gain Capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Input Transformer. . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
iv | Table of Contents
Output Transformer. . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Testing The Main Board . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Populating The Meter PCB. . . . . . . . . . . . . . . . . . . . . . . . . . 19
Semi Conductors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Resistors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Toggle Switch and Connectors . . . . . . . . . . . . . . . . . . . . . . . 21
Populating The LED PCB. . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3
Assembly24
Putting It All Together. . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Mounting The LED PCB. . . . . . . . . . . . . . . . . . . . . . . . . . 24
Inserting The LED Light Pipes. . . . . . . . . . . . . . . . . . . . . . . 25
Mounting the PCB to the Bracket. . . . . . . . . . . . . . . . . . . . . 25
The Ribbon Connector. . . . . . . . . . . . . . . . . . . . . . . . . . 26
Mounting The Faceplate. . . . . . . . . . . . . . . . . . . . . . . . . 26
Mounting the Knobs . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Final Testing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
4
Appendix29
5 Band Resistor Color Code Guide. . . . . . . . . . . . . . . . . . . . . . . . A
Gain Resistors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B
Main PCB Resistors (10Ω - 33KΩ). . . . . . . . . . . . . . . . . . . . . . . . C
Main PCB Resistors (100KΩ - Inductors) . . . . . . . . . . . . . . . . . . . . . D
Main PCB Semi Conductors. . . . . . . . . . . . . . . . . . . . . . . . . . . E
Main PCB Capacitors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . F
Meter PCB Resistors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G
Meter PCB Semi Conductors. . . . . . . . . . . . . . . . . . . . . . . . . . H
Meter PCB Capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I
Gain Resistor Detail. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . J
Meter Resistor Detail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . K
1
HAIRBALL AUDIO, LLC |
Welcome
User Guide
The Lola mic pre is a fully differential circuit featuring the EA-10468 input transformer, EA-1166
output transformer, and optional John Hardy 990C
op-amps.
The Lola maintains a completely differential signal
path from input to output. The benefit to this topology is lower noise and a high CMRR. It also takes
advantage of the excellent balance of the EA-10468
input transformer. In addition, because there are
two op-amps in parallel, available output drive
current is increased. This lowers output impedance;
improving output transformer performance and
increasing the maximum undistorted gain. In this
regard it’s similar to running a single op-amp design
on 24V rails.
Gain
The gain stage provides 65dB of clean gain in 4.5dB
steps utilizing a Grayhill rotary switch. With 48dB
of adjustable gain, there is no need for an input pad.
Output
The 600Ω Bourns t-pad attenuator sits on the secondary of the output transformer and attenuatates
the output level while maintaining a nominal 600Ω
load. This allows the user to fine tune the output
once the preferred gain setting is selected. It also
allows the user to “push” the gain while maintaining
an appropriate output level to add analog distortion
to the source material.
Pushbutton Controls
There are three illuminated pushbutton switches to
select phantom power, phase, and line mode.
The phantom power control (+48) provides
+48VDC to pin 2 and 3 of the input XLR through
two 0.1% tolerance 6.8KΩ resistors. Phantom
power is activated when the control is illuminated.
The phase control (ø) flips the phase of the source
material by 180 degrees. The differential signal is
phase flipped at the primary of the output transformer. This control uses a DPDT relay.
The line (LINE) control flips the primary and
secondary of the input transformer making it a
step down input and reducing the overall gain by
approximately 14dB. This allows the user to use the
Lola on line level material. The line control uses
two DPDT relays.
DI
The DI jack accepts a ¼” unbalanced cable. Inserting a cable triggers the DI relay to switch the input
from the XLR input to the DI jack. The DI passes
through 2 FET buffers creating a differential signal
to feed the EA-10468 primary.
1
2
| Lola Assembly Guide
LED Meter
The Lola features a 10 segment integrated circuit
controlled LED meter. Located below the meter
is a toggle switch to select VU (low position) and
Peak Programme Metering (high position). Though
the VU mode is actually average metering (90%
of RMS), it’s calibrated to VU metering with little
effect on PPM mode. 0dB on the meter scale is
equal to +4 dBu (1.23V) in VU mode. Peak mode
displays the peak value of the waveform in the same
scale.
Assembly Overview
Choosing to build your own piece of gear is a
rewarding and great learning experience. If it’s your
first time, this guide will walk you through all of the
steps to complete your build. If you’re a grizzly old
pro, you’re probably not even reading this!
Patience
Want to have a failed build and a huge headache?
Rush through the build paying little attention to
the instructions and be as sloppy as you can with
your soldering and assembly. As much as you want
that cool new piece of gear up and running NOW,
take your time and take brakes. It’s the best way to
ensure success with your build.
Tools
You’ll need a few basic tools to complete this build.
Though this list may not be complete, it’ll give you
an idea of what you should have on hand.
Soldering Iron
It goes without saying that you need a soldering
iron. Get a decent one. At the very least you should
have 25 watt pencil style soldering iron. Weller
sells the WP-25 for about $40 USD and it’s a solid
entry level soldering iron. Radio Shack sells a 40
watt model for about $10 USD. I’ve not used that
model, but I bet it’s better than a lighter.
If you’re going to build a few units and do some
repairs, consider getting an adjustable temperature
solder station. The Hakko 936 is a tried and tested
unit that sells for about $70 USD. It’s a fabulous
tool.
Soldering Tip
Most decent irons will allow you to insert different
tip styles. For most PCB work, including this build,
you’ll want a small chisel tip. I use the Hakko 936
iron with a D18-D16 tip. This is a 1.6mm radius
chisel tip.
Solder
Solder is kind of like guitar strings in that you really need to feel which one is right for you. I went
through a few types before I found one I liked.
There are a few different considerations such as
lead or lead free, no clean type, and diameter. I use
Kester #245 no clean solder. It is a 0.031” diameter
63/37 alloy. It needs no flux cleaning and is available at many local and online retailers (Part #246337-8800).
Digital Multi-Meter (DMM)
A good DDM is as important as a soldering iron.
An auto-ranging DDM will make sorting resistors a breeze and help avoid time consuming errors.
Testing and troubleshooting will make having a
good DDM a must. An inexpensive model is better
than nothing, but a good model will be a trusted
tool on your bench and in your studio for years. It’s
important to note that cheap meters generally do
not measure AC (audio) level accurately above a
few hundred Hertz at best. In audio we like to deal
with 1KHz test signals so get a nice meter.
Fluke is the standard for DMMs. A Fluke 177 is
another tried and tested workhorse. It’s not cheap,
but it’s not that expensive for something you will
use and depend on every day.
Panavise
Do you need a Panavise? No. Will it make your
PCB stuffing much easier? Yes. These are not that
expensive. Consider getting one.
Pliers, Cutters, and Strippers
A pair of fine needle nose pliers will come in handy
for some of the final assembly work. I bet you
already have a pair of these!
Small diagonal cutters are a must. You’ll need these
for trimming the component leads.
Having a decent pair or wire strippers in the 16-26
AWG range is something you should have.
1/16” Hex Key
Also known as a Hex Wrench, Allen Wrench, and
Allen Key. Whatever you call it, you need one to
install the knobs. Consider getting a set with a nice
storage case.
HAIRBALL AUDIO, LLC |
Nut Drivers
These are not as fun as they sound. You need four:
1/4”, 5/16”, 7/16”, and 1/2”. These are used to
tighten various nuts in assembly, including the face
plate components. Due to the length the Grayhill
and t-pad shafts, you’ll need a nut driver with a
fairly deep channel. I used to use pliers to tighten
these. I’d mare the nuts, scratch the panel and drop
a few F-bombs. Do yourself a favor and get a Nut
Driver set. I picked up a 7 piece set at a hardware
mega-store for about $15.
Soldering Guide
Soldering WELL is one of those things that seems
easy until you try it. Once you try, it starts to seem
kind of difficult. Then finally you figure it out and it
seems easy again.
Rather than trying to explain it to you, I went
online trying to find the best video tutorial I could.
I settled on Dave Jones’ tutorial on the EEVBlog.
Dave’s a wacky a cat, but so are most guys who
inhale lead all day. The tutorial is presented in three
parts: tools, soldering through hole components,
and soldering surface mount components. For our
purposes, I recommend you watch part 1 and 2. The
videos are lengthy at about 25 minutes each, but
they are well worth watching. Even I learned a few
things.
The videos can be seen by visiting:
hairballaudio.com/solder
Component Sorting
The appendices of this manual contains printable
sheets for sorting the components located in the
various bags. DOUBLE CHECK all resistors with
a DDM before soldering them into place. Appendix A is a 5 band resistor color code chart.
3
4
| Lola Assembly Guide
HAIRBALL AUDIO, LLC |
2
Populating the PCBs
The Printed Circuit Boards
Populating The Main PCB
Your Lola mic pre is comprised of three printed
circuit boards (PCBs):
Op-Amp Sockets
Let’s get started! Personally, I like to begin by
inserting the op-amp sockets (Fig. 2).
Fig. 1
1. Main PCB. Contains the mic pre circuit.
2. Meter PCB. Contains the LED meter circuit.
3. LED PCB. Contains the LEDs and current
limiting resistors.
There may be some visual and numerical value
differences between your PCBs and the PCBs used
in this manual. The PCBs used in this manual are
prototype versions.
The PCBs are located in the bags containing the
components for each PCB. Start by locating the
main PCB bag and removing the main PCB.
Fig. 2
You should have 12 op-amp sockets in bag F, 6 for
each op-amp. The sockets must be inserted from
the top side (silkscreen side) of the PCB. This will
ensure there is enough space between the op-amp
and PCB suface for the feedback network that
mounts under the op-amp.
Fig. 3
5
6
| Lola Assembly Guide
There are a few different ways to solder the op-amp
sockets. You can solder from the top, bottom, or
both. The most important part is that you get good
solder flow around the entire socket and PCB pad
connection. I like to tilt my PanaVise so it’s parallel
to my table surface with the silkscreen side up (Fig
3). Place the sockets in the socket pads. The hollow
end should be facing up, this hollow shaft accepts
the op-amp pins. Working from the topside, place
you solder tip so it makes contact with the socket
and pad, just like you would with any other component. Be sure not to apply too much pressure to the
socket or it may lift slighty causing it to sit slanted
on the board. The socket is a large part that will
need about 5 sec of heating time to get good flow.
Applying a touch of solder to the solder tip, PCB,
and socket connection point should allow for good
heat transfer (see 20:00 of solder video 2). When
you start to see that solder flow, apply some solder
to the opposite side of the pad while keeping your
iron tip in the original location. This should give
you a good flow around the pad. Remember less is
more when it comes to solder. If you’ve acheived a
good connection on the topside there is no need to
solder the bottom side. Once you have all the sockets soldered, you can wiggle them to confirm you
have a good electrical and mechanical connection.
It can be a little tricky to identify the resistor placement, so use detailed view in appendix J to confirm
you have the resitors in the right location. Start by
using your finger to bend one of the resistors legs
180 degrees back towards the resistor (Fig 4).
Fig. 4
The virtical reistor symbol has a circle around one
pad and a line the points to a pad without a circle.
The resisor body sits on the pad with the circle surrounding it (Fig 5). The circle represents the resistor
Gain Resistors
Next let’s stuff those gain resistors! These are the 12
resistors that set the gain of the Lola mic pre. They
are located near the Grayhill switch and are labeled
R1-R12. Because of the tight spacing in this region
of the PCB, these resistors are mounted vertically.
Start by removing the 12 resistors from bag D and
check them with your DMM. Appendix B at the
end of the manual is a resistor sorting sheet you
can print and use to simplify this process. You can
insert them in any order you like, but doing them in
order R1-R12 might help you avoid mistakes.
Fig. 5
body and the line points to the pad where you will
insert the other lead.
These parts are not polarized, they can be inserted in
either direction. Following the silkscreen footprint
simply helps avoid exposed legs from touching and
creating a short. Once the componet is soldered
to the PCB you can trim off any remaining leads.
HAIRBALL AUDIO, LLC |
Fig. 8
Fig. 6
When you’re done you’ll have something that looks
like Fig 6.
Main PCB Resistors
Now let’s go ahead and stuff the rest of the horizontal resistors located in bag D. Appendix C and
D are main PCB resistor sorting sheets. Note that
the last spot on appendix D is for the two 4.7 uH
inductors. They may be brown like in Fig. 7 or green
Fig. 7
like in Fig. 8. These are not resistors and cannot be
tested using the resistance tester on your DMM.
Since there are only two and they are of identical
value there is no need to test them. Simply install
them as you would a resistor. Placed in parellel
with 39Ω resistors, these create an output isolator
between your op-amp out and output transformer.
Use extreme care when testing and sorting your
resistors! Check every resistor twice. It may take
you an extra couple of minutes now, but it can
save you days of troubleshooting to find where you
mistakingly swapped a 10KΩ for a 10Ω. Take your
time and get it right the first time.
The pad spacing for the horizontal resistors, diodes,
and inductors is identical to the body length with
one exception being the green inductors. This allows us to avoid any specialized bending jigs. Just
use your fingers to apply bending force to the leads
while holding the body.
Carefully work your way through the circuit. Again
double, or even triple, check all of your resistor
values and numerical designations.
Note that R29, R30, R34 and R35 are 2.2KΩ op-amp
resistors with 0.1% tolerence. R16 and R17 6.8KΩ
phantom power resistors with 0.1% tolerence.
The 3.4KΩ R40 and R41 resistors have been hand
matched to 0.1%. These tight tolerences are
required for low noise, make sure you identify them
and solder them in the correct loaction.
Semi Conductors
Let’s talk semi conductors. These are located in bag
B and can be sorted using appendix E. There are
6 protection diodes on the main PCB. They make
sure current is flowing the right way in your Lola.
There is one across the power terminals of each
relay and one on each of the 16V power rails. They
are installed just like a resistor with one MAJOR
difference, they are polarized. Meaning the must
be installed in the proper direction. Luckily this is
pretty simple. All you need to to is line up the grey
stripe on the diode with the stripe on the diode
7
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| Lola Assembly Guide
Fig. 9
symbol of your silkscreen (Fig 9).
The remaining TO-92 pacakge semi conductors get
installed by following the silkscreen footprint on
the PCB. These include the LM317 constant current source for the LED pushbutton switches, the
2N3906 relay trigger, and two J201 DI FET butters.
Relays
K1 and K2 work in tandem. They are triggered by
the “Line” pushbutton switch and their job is to flip
your input transformer from a mic in (step up) to a
line in (step down). I told you they do crazy things!
K3 is the phase reverse and is located between the
op-amp outputs and output transformer primary.
It. of course. is controled by the “Phase” pushbutton
switch. K4 is the switches the Lola input from the
XLR in to the 1/4” DI jack. This one is different in
two ways. First, it’s not switched by a pushbutton
switch. It’s triggered when you insert an unbalanced
cable into the 1/4” DI jack. Second, it’s normally
“on”, meaning current is flowing through the relay
and breaking the ground connection with the DI
jack turns it “off ”. That part really isn’t important,
but you may hear it “click” on when you power up
your Lola.
Enough of this crazy circuit talk, let’s stuff that
PCB! When inserting the relays orientation matters. Like the diodes, make sure you align the white
line of the relay with the line on the silkscreen layer
(Fig 11).
Fig. 11
Once you’ve installed the semi conductors we can
move on to the relays in bag C. These are the
electromechanical switches that do all kinds of crazy
things inside the Lola circuit (Fig 10).
Fig. 10
Once you have them slipped into place, flip your
PCB and bend back a couple leads to hold them in
place while you solder (Fig 12).
The leads are small enough that they don’t need to
be clipped.
HAIRBALL AUDIO, LLC |
some tiny reading. The two 100pF feedback caps
will have the value 101J printed on them. The zobel
cap will have the value 681J printed on it. Once
you have identified them, you can insert and solder
them. They are non-polarized capacitors so the
orientation in not important.
Now move on to the two grey film capacitors. These
are two 0.1uF capacitors (C10 and C11) used to
Fig. 14
Fig. 12
Capacitors
There are a handful of capacitors in the Lola,
certainly a lot less than many circuits you may have
encountered. This is a real advantage since it is
generally precived that the less capacitors you have
in your audio path, the better. The capacitors are located in bag A and can be sorted useing appendix F.
There are two op-amp feedback capacitors and one
input zobel network capacitor. These capacitors are
the small blue multilayer ceramic capacitors (Fig
13).
Fig. 13
To Identify which two are the 100pF feeback capacitors (C7 and C9) and which is the 680pF input
transformer zobel capacitor (C2) we’ll have to do
block DC from the DI buffer circuit. They have the
value 104 printed on them (Fig 14).
These are also non-polarized and can be installed in
any direction.
Since we have op-amps we should probably add
some bypass capacitors. This is usally done with a
0.1uF and a 47uF on each op-amp power supply
pin to ground. The JH-990 has the 0.1uF bypass
capacitors inside the op-amp (awesome), so all we
need to do is add some polarized 47uF electrolitic
capacitors to each op-amp power supply pin. These
are the 47uF/25V polarized electrolic capacitors
(C3, C4, C5, and C6) in your kit (Fig 15).
Use extreme care when inserting these capacitors.
They are polarized and must be inserted with the
proper polarity. Failing to do so will result in a
small match like fire and a stink you won’t be able
to get rid of for days.
9
10 | Lola Assembly Guide
Fig. 15
Along one side of the capacitor there is a gray stripe
containing several “-” or negative symbols. That
stripe lines up with the negative termainal. On your
PCB, one of the pads will have a “+” or poitive symbol beside it. This is the pad which will recieve the
positive lead. Another indicator is that the square
pad is for the positive lead and the round pad is for
the negative lead.
Next up is the 47uF/50V capacitor for the phantom
power circuit (C1). It looks simular to the previous
capacitors except it is slightly larger and rated for
the 48V phantom power supply (Fig 15). It is also
polarized so be sure to insert it correctly before you
solder.
You still have a giant 1000uF (C8) polarized capacitor in your kit but let’s set that one aside for now. It
can interfere with your PanaVise so we’ll install it
towards the end.
Ribbon Header
Now is a good time to insert the header for the
ribbon cable that connects your main PCB to your
Meter PCB (Fig 16). It’s located in the large Meter
package in bag D. There are two but you just need
one for now.
Fig. 16
Inserting this connector should be fairly straightforward. Obviously you do not solder the plastic
locating pegs. When soldering the 6 connector pins
try to work fairly quickly to limit the heat applied to
the header material.
If you have not done so already, TAKE A BREAK.
You’ve reached a pretty big milestone!
Most of what’s left are the larger parts. You’ll need
to take your time to get through these so try to
avoid rushing at this point.
You may have noticed that there is a capacitor
labeled “OPT-C” and a resistor labeled “OPT-R” that
you’ve not populated on your PCB. This is the optional output zobel network needed for some non
Hardy op-amps. If you are using the JH-990 leave
these empty.
HAIRBALL AUDIO, LLC | 11
Pushbutton Switches
Fig. 18
Let’s mount the switches. The three illuminate
pushbutton switches (SW1, SW2, and SW3) are
polarized. However, they can only be inserted in
one direction. The most important thing to ensure
when mounting these switches is that they are sitting completely flush with the PCB surface (Fig 17).
Notice how the four feet of the pushbutton switch
are pressed flush to the PCB surface. Since the
switches are designed to snap into place, they should
naturally sit flush. Just make sure not to push them
out when you solder the pins on the reverse side.
These need to be flush to match the pushbutton
holes on the L-bracket and faceplate.
Fig. 17
Grayhill Gain Switch
Let’s talk about the gain switch. It’s a single deck
12 position shorting Grayhill rotary switch. This
switch sits between your op-amp feedback networks
and allows you to select a gain range from 16.5dB 65 dB in 4.5 dB steps. There are three parts in the
Grayhill assembley (Fig 18).
1. The Grayhill Switch w/ Nut and Washer
2. The Stop Pin
3. The Retaining Sticker
Remove the nut and washer and set them aside
in a safe place. Your kit may have included 2 stop
pins. You only need one, but keep the other handy.
If you drop one you’ll never find it. Before it get’s
lost, lets insert that stop pin. Without the stop pin
the switch will just endlessly turn. When you get
to the maximum gain setting it will allow you to
turn through to the lowest setting. Maybe you want
that? Then don’t insert the pin. However most
people would probably find this annoying so let’s get
it in there. It needs to be placed in a specific hole
that will tell it which position is the end position.
Hold the switch so that the PCB mounting pins are
facing down and place the stop pin in the 12 o’clock
position (Fig 19). Needle nose pliers work well for
this step.
Fig. 19
12 | Lola Assembly Guide
Push the stop pin into the hole until it sits flush
with the switch surface. Next peel the retaining
sticker from its backing and place it over the shaft
and on to the switch surface (Fig 20).
Fig. 20
Output Attenuator
Between the output transformer secondary and
the output XLR you’ll find a Bourns 600Ω t-pad
attenuator. The default position should be the fully
clockwise position. The attenuator accomplishes
three things.
1. Allows you to fine tune your gain setting within
the 4.5dB Grayhill switch steps.
2. Allows you to lower the output signal when
pushing the input gain so the Lola distorts
(good) while protecting your A/D converters
from distortion (bad).
Remove the plastic PCB pin protective covering
and insert the Grayhill into the PCB. Like the
pushbutton switches, they Grayhill switch must sit
flush to the PCB. Try to keep it as upright as possible so that the shaft is parallel to the PCB surface.
There will be a little room for fine tuning once the
component is soldered in place. For now, make sure
it is pressed flush to the PCB (Fig 21).
3. Maintains a nominal 600Ω impedance on the
output transformer secondary. This will keep
Lola happy.
Now what exactly does this magical component
look like? If you purchased a kit before mid-June
2016 it’s the blue t-pad shown in fig.22.
Fig. 22
If it looks something like Fig 21, then well done!
Fig. 21
If you purchased a kit after mid-June 2016, it’s
the grey t-pad with a 1/8” shaft shown in the grey
t-pad install section on the following pages. If
you have the grey t-pad it will come with a PCB
spacer for setting it at the correct height off the
PCB. The grey t-pad also has an anti-rotation tab
on the front that you should clip off with your
lead cutters. It will keep you from being able to
mount the faceplate later in the guide.
HAIRBALL AUDIO, LLC | 13
Fig. 24
Fig. 23
Note the t-pad attenuator and DI jack do not sit
flush on the board. To ensure that these parts align
with the L-bracket and faceplate holes please follow these steps carefully.
Here’s the thing. You probably want your gain
switch, t-pad and DI jack to line up on your faceplate. I wanted the same thing, that’s why it is so on
the Lola. Let’s go through the steps to make this
happen. Don’t skip any, it’s just not worth it.
(Fig 26). At this point there is no need to use the
locking washer or over tighten. Just tighten the
screw and nut enough to set the final mounting
position. Now slip the Lola faceplate into place and
hand tighten the Grayhill nut and attenuator nut
(Fig 27). Again you don’t need to use the locking
washers for this step. There is a little room to move
the t-pad around in the hole. Position it so it’s as
centered as possble with the scale before you tigten
Fig. 25
Blue T-Pad Install (Pre Mid-June 2016)
For both the attenuator mounting and DI jack
mounting, you are going to need your L-bracket,
faceplate, Grayhill nut and washer, (4) #4 nuts, (4)
4-40 1/2” flat screws, and (4) 1/4” standoffs. Mount
the 1/2” machine screws and standoffs onto the Lbracket as shown in Fig 23.
Do not tighten the standoffs so they are flush to the
bracket. They need to be loose because we’ll need a
little wiggle room shortly.
Next insert the attenuator into the PCB. It’s not
going to be easy, you have 9 PCB pins and 4 bracket
pins that all need to line up properly. Take your
time and use pliers to line up each pin. After a minute or two and 3-4 F-bombs you should have it in.
Leave it floating off the PCB unsoldered (Fig 24).
Now take the PCB and insert it at an angle into
the L-bracket (Fig 25). Now place a #4 nut on
each screw to set the PCB in place on the bracket
Fig. 26
14 | Lola Assembly Guide
the nut. Your t-pad should now be at the right
height for final soldering. With the face place still
attached, solder the three accessible t-pad rail pins
from the top side. These are marked with red circles
in Fig 28.
Fig. 27
Grey T-Pad Install (Post Mid-June 20016)
You do not need to assemble the bracket to mount
the grey t-pad, it comes with a PCB spacer. You
will still need to follow the bracket assembly in the
blue t-pad install to install the DI jack in the next
section.
Fig. G1
With these three pins soldered, your t-pad will be
locked into place for final soldering. Remove the
faceplate and L-bracket. You can now solder the
t-pad PCB pins and remaining unsoldered bracket
pin from the bottom of the PCB (Fig 29). Be sure,
as always, to trim and excess leads after soldering.
Slide the PCB spacer onto the pins of the t-pad. It’s
made to slide on in any direction (Fig G1). Now
sandwich the spacer between the t-pad and PCB
and solder the 9 t-pad pins on the bottom side.
Make sure it’s all snug against the PCB. Easy!
Fig. 28
Fig. 30
Fig. 29
DI Jack
The next component to mount is the Neutrik 1/4” stereo PCB mount jack. Although this is a stereo jack, it’s
meant to only receive an unbalanced cable. The extra
contact is need as part of the relay trigger circuit.
HAIRBALL AUDIO, LLC | 15
Fig. 31
The safest place is probably on the component
shafts!
Your DI jack will not be fully stable. Because only
The Neutrik DI jack has three parts.
1. The DI Jack
2. The Silver Nut
3. The Black Washer
Fig. 32
Fig. 33
one side it soldered it’ll move a little on the unsoldered side. We want to solder all the pins in place
but also ensure it stays perfectly parallel to the PCB.
If you have a little spacer to use between the jack
and the PCB, use it! If not here’s how I do it.
Load a little solder on your iron tip. You know, exactly like they tell you NOT to do. Hold the PCB
in one hand and use a finger on that same hand to
hold the jack parallel to the PCB (Fig 33).
This part also needs to be mounted off the PCB.
Place the jack on the PCB and repeat the temporary
assembly steps in the attenuator section. Mount the
L-bracket, faceplate, and attach the Grayhill and
attenuator nuts. Add the DI jack nut and washer as
illustrated in Fig 31.
Now that the DI jack is locked into place you can
solder the exposed pins on from the top side of the
PCB. In this case the only accessible pins are the
three on the PCB edge circled in Red in Fig 32.
You can now remove the faceplate and L-bracket
and set them aside. We won’t need them for a
while. Be sure to place you Grayhill switch, attenuator, and DI jack nuts and washers in a safe place.
While holding it in place turn the PCB over and
place your solder blobbed tip to one of the unsoldered leads. Yes, that right, make a cold solder joint.
Don’t worry, we’re going to fix this. This is just temporary.. Before properly soldering the remaining
2 pins on the unsoldered side, confirm your jack is
parallel to the PCB. If it’s off, fix it now while you
only have one pin tacked in place. Once all the pins
are soldered, it’ll be a pain to fix. If it looks good,
go ahead and solder the 2 remaining pins properly.
Once they are done go back and reheat and solder
the tacked joint. You should also solder the three
top soldered pins on the outer edge from the bottom at this point.
Looks good? Congratulations! Mounting the at
tenuator and DI jack is probably the most technical
part of the build.
16 | Lola Assembly Guide
Gain Capacitor
This is that large polarized 1000uF/50V electrolytic
capacitor we set aside earlier (Fig 35). It’s an insurance policy to eliminate any DC that finds its way
into the feedback/gain network. Be sure to mount
the capacitor flush to the board and straight to avoid
interference with other components.
Fig. 36
Starting at the board edge and moving towards the
center these are:
Fig. 35
Input Transformer
The Lola uses an EA-10468 (Fig 36) input transformer. The EA-10468 is a talented transformer,
designer Ed Anderson’s take on the classic Marinair
10468. The 10468 is most known for being the mic
in transformer for the classic Neve 1073 channel
strips.
♦♦
BLK=Black
♦♦
BRN=Brown
♦♦
GRY=Grey
♦♦
YLW=Yellow
♦♦
RED=Red (Wow!)
♦♦
WHT=White
♦♦
VLT=Violet
♦♦
ORG=Orange
♦♦
GND=Green
Mount transformer using the supplied (2) 1/2” 4-40
panhead screws from the bottom of the PCB into
the threaded holes on the bottom of the transformer. Trim the leads to prepare for soldering. Be very
careful not to over trim.
The leads are not hair, they won’t grow back. You
can always trim each lead to the perfect length as
you solder them into place. The leads have corresponding pads labeled by lead color.
Fig. 37
HAIRBALL AUDIO, LLC | 17
The GND label is for the two pads that are overlapping. These are for the 2 green leads. There are two
separate transformer grounds that we are connecting to the ground at this point. It does not matter
which green lead goes to which GND pad.
to avoid any shorts. If you take your time you can
probably even make it a little cleaner than I have
(Fig 40).
Strip about 1/4” of shielding off the first lead, in this
case black, tin the lead, and insert it into the pad
with the BLK label (Fig 38).
Fig. 40
Fig. 38
On the bottom side of the PCB. pull the lead
through so the cut edge of the wire insulation
sit flush with the top side of the PCB. Bend the
exposed wire like you would a component lead (Fig
39).
Output Transformer
The output transformer used in the Lola is Ed Anderson’s version of the classic LO-1166 line output
transformer (Fig 41). It is used in many designs,
most notably the Neve 1073 channel strip.
Fig. 39
Fig. 41
Solder the lead and trim the excess. Now start
moving across the board stripping and soldering
each lead into place. Make sure you do not leave
any exposed wire on the top side of the PCB pads
and keep your leads trimmed on the reverse side
Let’s start by laying out the hardware we’ll need to
mount the transformer to the PCB (Fig 42).
You’ll need (2) 4-40 7/8” pan screws, (2) flat #4
washers, (2) #4 lock washers, and (2) #4 nuts. These
are located in hardware bag A. Start by sliding the
flat washer onto the screw (Fig 43).
18 | Lola Assembly Guide
Fig. 45
Fig. 42
too short. Those solder pads on the edge are further
out than you think (Fig 46).
Fig. 46
Fig. 43
Now do this with the other flat washer and screw
and drop them into the transformer holes from the
side with the leads on the top side (Fig 44).
Fig. 44
Now drop the transformer onto the PCB with the
lead out facing towards the board edge and the
transformer solder pads. Flip the PCB over and
place a locking washer and nut on each screw to
secure the transformer in place (Fig 45).Now trim
your leads. Be careful, it’s very easy to trim these
Solder them in to place using the input transformer
method.
♦♦
BLU=Blue
♦♦
PLR=Purple
♦♦
GRN=Green
♦♦
GRY=Grey
♦♦
BRN=Brown
♦♦
RED=Red
Grab your JH-990 or op-amp of choice and seat
them into the op-amp sockets (Fig 47). Congratulations! You now have a working Lola!
HAIRBALL AUDIO, LLC | 19
The mic pre circuit is now fully functional. It’s not
a bad idea at this point to test your build. Confirming the main board works correctly can help with
troubleshooting should you run into issues when
adding the meter daughter board. If you want to
test your main board, go ahead and remount the
bracket and faceplate and skip to page 26 if you
need help mounting the knobs and shaft adaptor.
Now insert a 1/4” unbalanced instrument cable into
the DI jack. A relay will “click” but you may not be
able to hear it over the sound of the cable insertion.
If the instrument you play through the Lola DI jack
is amplified you’ll know the relay is flipped. You’ll
also know that your Lola passes basic functionality
tests!
Populating The Meter PCB
You know what’s awesome? Audio level meters.
Let’s give your Lola an awesome LED audio level
meter. Start by locating the red “Meter PCB” bag
and pull out the contents. Inside you should find
five smaller bags. Four are labeled A, B, C, and D
and the fifth contains the meter PCB.
Fig. 47
Testing The Main Board
Let’s get testing! After mounting your Lola in a
500 series rack, power up the rack. Hopefully you
won’t see any smoke. Check the 3 pushbutton
LEDs and confirm the light to a nice soft blue. You
should hear a relay internally “click” when turning
on the PHASE (ø) and LINE push buttons. The
PHANTOM (+48) button is not connected to a
relay so it won’t have a “click” other than the latching of the pushbutton.
You can use a condenser microphone (not your
U47) to test the phantom power and confirm your
Lola is passing signal. With the OUTPUT knob
fully clockwise, start with the GAIN knob at its
lowest setting and confirm your signal increases
as you tun it clockwise. Now turn the OUTPUT
counterclockwise to confirm the signal decreases to
zero.
Semi Conductors
Open meter bag B, sort using appendix H and
locate the four 1N914 diodes (Fig 48).
Fig. 48
These diodes are of course polarized and must be
inserted in the correct orientation. The line that
indicates the cathode on the meter board screen is
a bit hidden. Another indicator is the square pad
solder pad. The cathode (side with the line) should
be soldered to the square solder pad (Fig 49).
Once you’ve installed all four diodes, install the
three integrated circuits (Fig 50).
These can be a bit tricky to install as your board
20 | Lola Assembly Guide
Fig. 51
Fig. 49
becomes populated so lets get them in there now.
The two smaller ICs are labeled TL071CP and
TL072CP. Make sure you place these in the correct
footprint. They are NOT interchangeable. You’ll
notice the larger IC (meter controller) has a notch
at one end and the two smaller ICs have a dot at
Fig. 50
These 11 pad holes must be kept free of solder until
the right angle connector is installed. When soldering the LM3916 make sure you don’t use too much
solder or it may flow into these holes. If you’re not
confident in your soldering skills, leave this side
unsoldered and solder it after the connector is
inserted.
Lastly, install the LM317 voltage regulator paying
close attention to the silk-screen orientation shape.
one end. You’ll also notice that the PCB footprints have little notches out of one end. You must
align these notch or dots for the IC to be properly
installed.
You’ll have to pinch the IC legs in a little to get it
to fit into the footprint. You’ll be a pro once you’ve
installed about 200 of these.
You’ll notice that one side of the LM3916 pads are
joined or bridged to other pads (Fig 51). These 11
pads are for the right angle connector that will attach the LED PCB to the meter PCB.
Resistors
Next grab meter bag C. It contains all of the
resistor required for the meter PCB. Just like the
gain resistors, they will be inserted vertically. Use
appendix G to carefully sort your resistors for this
Fig. 52
HAIRBALL AUDIO, LLC | 21
next step. Appendix K is a detailed view to help you
confirm reisitor placment.
Capacitors
Next install the contents on meter bag A and sort
them using appendix I. These are the various capacitors needed for the meter circuit. You have three
polarized electrolytic capacitors. Two are labeled
47uF and one is labeled 2.2uF. or 3.3uF These must
be oriented correctly. Again, the negative lead is
labeled by a stripe containing a negative or - Symbol
on the side. Insert the positive lead with the + symbol on the PCB. The + lead is also the square pad
which is opposite to the diode where the cathode or
negative is a square pad (don’t ask).
You also have three non-polarized capacitors. These
can be inserted in either orientation. You have two
0.22uF (labeled XXXX) capacitors and one 0.47uF
(labeled XXXX) capacitor. Insert these into their
proper footprints.
Toggle Switch and Connectors
Finally you’ll be left with meter bag D. Remove the
toggle switch and one of the two small PCB mount
ribbon connector headers. Set the rest of the bag
aside for now.
Inserting the toggle switch and header are fairly
straight forward. They footprint will help you with
orientation. All you need to do is make sure they
are solder flush to the PCB. It’s best to start by
soldering one pin and confirming the part is flush to
the PCB before moving on. When you’re done. you
should have something that looks like Fig 53.
Remember, your PCB is a newer production version
that may look slightly different. For example, the
right side of your meter PCB will look slightly different than the one pictured in this manual.
Fig. 53
Populating The LED PCB
Congrats, you only have one PCB left to populate
and it’s the smallest. Don’t be fooled however, take
your time with this one to ensure the LEDs will
align properly with the light pips. Without further
adieu, let’s populate the LED PCB!
There are two versions of the LED PCB. If you
have the current blue faceplate your LED PCB will
be marked “Rev B” and have 6 small horizontally
mounted resistors (Fig 54). If you have an older
kit with a green hammered faceplate, your LED
PCB will be marked “Rev A” and have 10 vertically
mounted resistors (Fig 55).
The LED PCB allows us to mount the LEDs flush
to the PCB eliminating the need for any trickery or
LED lead bending. It also allows us to have current
limiting resistors for LEDs as needed which creates
a lot of flexibility for different LEDs and different
LED color combinations.
Start by mounting the current limiting resistors.
For the current rev B PCBs horizontally mount the
6 47K resistors into DR1-DR6. If you have an older
rev A PCB, the 6 white LEDs each get a 10K resistor, the 3 orange LEDs get 8.2K resistors, and the
violet LED gets a 3.4K resistor.
22 | Lola Assembly Guide
Fig. 54
Fig. 56
Fig. 55
Next we’ll mount the LEDs. Try not to mix them
up! You want these to sit as flush and as straight to
the PCB as you can get them. It’s not 100% critical
that they are perfect, just take your time and get
them close.
The longer lead is the anode (positive) and should
be inserted into the sqaure pad...which is opposite
to the diodes...again, don’t ask.
I like to hold the PCB with one hand and insert
the LED with the other. Press the LED close to
the board with you index finger and use your thumb
to spread the leads apart bending them against the
PCB (Fig 56).
You have a fleshy chunk of skin hanging off your
cuticle (Fig 56 circled in red), now would be the
time to trim that off with nail clippers or your wire
cutters.
Note that the LEDs footprints on the current rev B
PCBs are labeled W for white, Y for yellow, and R
for red. Older Rev A PCBs are labled W for white,
O for orange, and V for violet.
Fig. 57
When you flip the board you should see something
like Fig 57. Solder the LED into place and clip the
leads.
Continue along down the line. Note that the top
red/violet LED solder pads will back up close to
the Meter board 0.22uF caps once it’s installed. To
keep things tidy don’t put a big glob of solder here
(or anywhere) and clip the leads very short after
soldering.
Next let’s mount that right angle connector (Fig
58). It mounts to the opposite side of the PCB than
the LEDs and resistors. This is yet another component that must be mounted flush and straight. It’s
not difficult at all, just take your time and solder one
or two pads then double check that they are still
flush to the PCB. I find that if you orient the part
HAIRBALL AUDIO, LLC | 23
like in Fig 54/55 and solder it in place using some
downward force with the iron you can get it just
right.
Note the smaller leads on the right angle connector
are soldered to the LED PCB and the longer leads
will be soldered to the meter PCB.
Now let’s take a moment to survey our work.
Congratulations! All of the electronics work is
done! All that’s left is final assembly.
Let’s finish this off ! Grab the meter PCB and
insert the LED PCB so the LED face the same
side as the toggle switch. As you may have guessed,
it’s important the LED PCB sit flush and at a 90
degree angle to the meter PCB (Fig 59).
Fig. 60
Stuffed PCB’s ready for final assembly!
Fig. 59
Flip the board and solder the right angle connector
into place. Again, confirm the LED PCB is flush
and straight after the first few pads are soldered.
Flip the PCB and trim the long leads of the connector. When you trim these leads place your hand
over them as a shield or hold them as they are
clipped. These leads fly far and fast when the are
cut.
24 | Lola Assembly Guide
3
Assembly
Putting It All Together
We’ve reached the point where we finally get to
put it all together. Most of this is fairly straight
forward, as always take your time. Rushing through
this is a great way to strip a screw or add a hideous
scratch to your build.
Now place the meter PCB over the standoffs and
use the two remaining screws to screw it into place.
(Fig 63)
Fig. 62
Mounting The LED PCB
Grab the hardware bag and locate bag A. Carefully
empty the contents on to your work bench (aka
dining room table) and Grab four 5/16” 4-40 pan
screws and two 5/8” #4 standoffs (Fig 61).
Do not tighten these top screws until you have the
bracket and faceplate in place.
Fig. 61
Locate the two large holes near the pushbutton switches and feed two of the pan head screws
through the bottom of the PCB. Now take the
standoffs and thread them over the screw shafts and
tighten them (Fig 62).
Fig. 63
HAIRBALL AUDIO, LLC | 25
the edge to push it toward the back of the faceplate
(Fig 66).
Inserting The LED Light Pipes
Get out that sexy faceplate!
Fig. 64
Fig. 66
Grab bag B and VERY carefully remove the contents. The light pipes are not easy to find if dropped
on the floor. so be careful. You should find 10 clear
light pipes and 10 black rubber retainers (Fig 65).
Mounting the PCB to the Bracket
By now you’ve done this a few times. The only difference is that this time use a #4 lock washer located
in bag A on each of the mounting screws before
tightening the #4 nut (Fig 67).
Fig. 65
Insert the shaft of the light pipe through the front
on the faceplate. Pressing your index finger against
the top of the light pipe, slip the retaining ring over
the light pipe shaft. Once you have all of the light
pipes and retainers installed, tighten the fit on each
retainer by holding the light pipe tight with your
index finger and sliding the retainer down tight
with the edge of a pair of needle nose pliers. Don’t
squeeze the retainer or pipe with the pliers. Just use
Fig. 67
26 | Lola Assembly Guide
The Ribbon Connector
In the meter bag D you have a ribbon connector.
The ribbon connector is polarized in that one side
of the PCB header has a thin vertical tab, and the
other has a thick vertical tab. If you look at the side
of the connector you’ll see a thin slot and a thick
slot. Line up the tabs and press the cable into place
at the meter and at the main PCB between the
transformers (Fig 68).
Now tighten all three nuts with a nut driver or tool
of choice (Fig 70). The required nut drivers are:
♦♦
DI Jack - 7/16”
♦♦
Output T-Pad - 1/2”
♦♦
Gain Grayhill Switch 5/16”
Fig. 70
Fig. 68
Mounting the Knobs
Mounting The Faceplate
Dig out the DI nut and washer as well as the nut
and lock washer for the t-pad and Grayhill switch.
Mount the face plate and loosely screw the nuts and
washers into place. Align the face plate by running
your finger along the edge on the faceplate and rear
of the L-bracket (Fig 69).
Fig. 69
This is it, the last step. Let’s wipe the tears from
our eyes and get this done. Open up hardware bag
C and grab the two knobs with 1/8” and 1/4” shaft
holes. Older kits will have two 1/4” shaft knobs and
a shaft adaptor (Fig 71).
Fig. 71
HAIRBALL AUDIO, LLC | 27
The 1/16” hex wrench is not included but you’ll
need one for this step.
Mounting the output knob is straight forward.
Rotate the output knob fully clock wise. Each knob
has two set screws. Loosen both with your hex
wrench so the knob will filly slide over the output
Fig. 74
Start by rotating the Grayhill switch to the fully
clockwise position. You may need to do his with a
pair of needle nose pliers to get the necessary torque
and grip. Your Grayhill shaft should resemble Fig
73.
Fig. 72
Fig. 75
t-pad shaft. Align the white line with the last large
dot in the fully clock wide position and tighten both
set screws (Fig 72).
The gain knob is a little trickier if you have an older
kit because of the adaptor and the Grayhill D shaft.
Place the knob on your bench with the white line
where it would be in the fully clockwise position.
There is a set screw in the 8 o’clock position, loosen
this set screw (Fig 74).
Fig. 73
If you have a current kit with a 1/8” shaft knob,
mounting is staright forward and you can skip the
next part.
The set screw in Fig 75 is going to mount against
the solid side of the adaptor. The second set screw
is going to pass through the slot in the set screw
and mount against the rounded side of the Grayhill
shaft. Having the flat side of the Grayhill D shaft
behind the solid side of the adaptor will allow the
knob to mount evenly.
28 | Lola Assembly Guide
Flip the knob over. Both set screws are loosened
but the one we loosened in Fig 74 is in the 4 o’clock
position. This is the screw that will mount against
the solid edge. The other set screw is in the 11
o’clock position and will pass through the slot.
Final Testing
Depending on your level of expertise and available
equipment, there is a wide variety of test you can
run. I’ll guide you through a few basic test points.
Run the tests from the Testing The Main PCB section (page 19).
Fig. 76
Place the adaptor in the shaft with the thicker end
facing up. Make sure the adaptor is aligned so that
the 4 o’clock screw will hit the solid adaptor edge
and the 11 o’clock screw will pass through the slot.
Tighten the 11 o’clock screw so it passes through
the slot. Now tighten the 4 o’clock screw to set the
adaptor in place. You’ll wand to place your finger on
top of the shaft to keep it level. Because the thicker
end was inserted facing up, the adaptor will stick
out from the mounting hole. We want this, it will
help the knob float off the faceplate a little and level
it with the output knob.
With the adaptor securely in place, mounting the
knob is fairly straight forward. Loosen the set screw
that is trough the slot and place the knob over the
shaft and align the white line with the 65 dB setting
(Fig 76). Now you’ll only need to re-tighten the
set screw that passes through the adaptor slot and
secures the knob to the Grayhill shaft. It should
now be located in the 1 o’clock position..
Lastly, step back and admire your work. You’re
done!
Feed a signal through Lola and adjust the input
and output so you are getting +4dBu (1.25V) at
output. You’ll need to figure out the best way to
do this based on your available equipment. With a
+4dBu output, your LED meter should light to the
first orange LED in VU mode. Switch output to
+1dBu (0.869V) output and the meter should light
to fith LED in VU mode. With the same output
level switch to PPM mode (0.869V = 1.25V Peak)
and the meter should light to the first orange light
(0dB).
Fig. 77
4
Appendix
APPENDIX | A
5 Band Resistor Color Code Guide
B | APPENDIX
Gain Resistors
Value
Name
QTY
Value
Name
QTY
3.9Ω
R2
1
100Ω
R8
1
Value
Name
QTY
Value
Name
QTY
6.2Ω
R1,R3
2
160Ω
R9
1
Value
Name
QTY
Value
Name
QTY
10Ω
R4
1
300Ω
R10
1
Value
Name
QTY
Value
Name
QTY
16.9Ω
R5
1
620Ω
R11
1
Value
Name
QTY
Value
Name
QTY
27Ω
R6
1
1.2KΩ
R12
1
Value
Name
QTY
51Ω
R7
1
APPENDIX | C
Main PCB Resistors (10Ω - 33KΩ)
Value
Name
QTY
Value
Name
QTY
10Ω
R31,R32,R36,R37
4
2.2KΩ
R29,R30,R34,R35
4
Value
Name
QTY
Value
Name
QTY
22Ω
R22,R25
2
3.4KΩ
R40,R41
2
Value
Name
QTY
Value
Name
QTY
39Ω
R33,R38
2
6.8KΩ
R16,R17
2
Value
Name
QTY
Value
Name
QTY
470Ω
R15,R28
2
18KΩ
R27
1
Value
Name
QTY
Value
Name
QTY
1KΩ
R14,R39
2
33KΩ
R23,R26
2
D | APPENDIX
Main PCB Resistors (100KΩ - Inductors)
Value
Name
QTY
Value
Name
QTY
100KΩ
R18
1
3.3MΩ
R20
1
Value
Name
QTY
Value
Name
QTY
330KΩ
R19
1
4.7uH
L1,L2
2
Value
Name
QTY
1MΩ
R21,R24
2
APPENDIX | E
Main PCB Semi Conductors
Value
Name
QTY
Value
Name
QTY
1N4004
D1-D6
6
2N3906
Q1
1
Value
Name
QTY
Value
Name
QTY
LM317
IC1
1
J201
Q2,Q3
2
F | APPENDIX
Main PCB Capacitors
Value
Name
QTY
Value
Name
QTY
100pF
C7,C9
2
47uF/25V
C3-C6
4
Value
Name
QTY
Value
Name
QTY
680pF
C2
1
47uF/50V
C1
1
Value
Name
QTY
0.1uF
C10,C11
2
APPENDIX | G
Meter PCB Resistors
Value
Name
QTY
Value
Name
QTY
10Ω
R116,R117
2
1.4KΩ
R112
1
Value
Name
QTY
Value
Name
QTY
240Ω
R115
1
10KΩ
R111
1
Value
Name
QTY
Value
Name
QTY
510Ω
R110
1
100KΩ
R101,R103,R104
7
R106-R109
Value
Name
QTY
732Ω
R114
1
Value
Name
QTY
200KΩ
R102,R105,R113
3
H | APPENDIX
Meter PCB Semi Conductors
Value
Name
QTY
Value
Name
QTY
1N914
D101-D104
4
TL072
IC103
1
Value
Name
QTY
Value
Name
QTY
LM3916N
IC101
1
LM317
IC104
1
Value
Name
QTY
TL071P
IC102
1
APPENDIX | I
Meter PCB Capacitors
Value
Name
QTY
Value
Name
QTY
0.22uF
C101,C102
2
3.3uF
C106
1
Value
Name
QTY
Value
Name
QTY
0.47uF
C105
1
47uF/25V
C103,C104
2
J | APPENDIX
Gain Resistor Detail
APPENDIX | K
Meter Resistor Detail
Specifications
Controls and Switches: Mic Gain, Output Level, Phantom Power, Phase, Mic/Line, Di, Average and Peak Metering
Microphone Preamp Gain: 15.5dB to 65 dB (4.5dB stepped with output trim)
Microphone Mode Maximum Input Level: +13 dBu, balanced, < 1% THD
Line Mode Maximum Input Level: +25 dBu, balanced, < 1% THD
DI Input Maximum Input Level: -1 dBu, unbalanced, < 1% THD
THD + Noise : < 0.05% (1 kHz, 50 dB gain, +17 dBu output)
CMRR: > 90 dB (40 dB gain, 20 Hz to 20 kHz)
Maximum Output: +30 dBu balanced, 20-20 kHz, >1.6k ohms, <2% THD
Frequency Response: +/- 0.5dB 20 Hz – 20K Hz (-40dB, 1K input, 0dB output)
Current Draw: 130mA max
Microphone Input Impedance: 1.6K Ω, balanced line-to-line
Line Input Impedance: 10K Ω, balanced line-to-line
DI Input Impedance: 1MΩ, unbalanced line-to-ground
Output Impedance: 200Ω, balanced line-to-line
Metering: 10 Segment LED bar graph
Metering Scale: -20 to +3 VU (0 VU = +4 dBu)
Metering Modes: Average and Peak
+16V
ADJ
1
VO
S
SN
R
RN
T
TN
GND
IN-LO
IN-HI
SW1(+48)
VI
2
1K
R15
470
R16
R19
330K
R14
6.8K
R17
6.8K
3.3M
R20
100K
R18
47uF
8
1
D6
GND
+16V
K2(IN-)
TQ2-24V
-16V 10
8
1
TQ2-24V
-16V 10
D5
Q3
J201
-16V
GND
3
K1(IN+)
3
+16V
Q2
J201
-16V
8
SW3(LINE)
6.2R
Main PCB
Schematic
Q1
2N3906
+16V
GND
C1
C11
IC1
LM317
R21
3
0.1uF
0.1uF
C10
+48V
J1
7
9
7
1M
470R
2
1
Black
White
+16V
-16V
T1
10
P$9
GND
Grey
Violet
Orange
Yellow
GND
-16V
TQ2-24V
K4(DI)
3
P$10
EA-10468
D2
Brown
P$12
Red
P$11
GND
GND
R28
R22
R23
1M
9
R24
R27
P$8
C9
2.2K
R34
100pF
680pF GND
C2
R7
51R
R29
2.2K
C7
P$7
100pF
27R
R6
P$6
R35
R5
R40
4
2
4
22R
33K
S4
7
9
R41
18K
P$P1
3.4K
3.4K
R1
22R
33K
R25
R26
4
2
1000uF
C8
P$5
R8
100R
XLR OUT -
XLR OUT +
P$4
-16V
-16V
JH-990
100K
R107
R109
100K
GND
+16V
2
3
1.2K
R12
R106
-16V
100K
TL071P
5
6
IC102
P$2
R11
620R
JH-990
GND
+16V
P$3
R10
300R
GND
+16V
160R
R9
R37
10R
2.2K
R30
2.2K
R31
10R
R32
10R
R36
10R
C101
C102
C5 47uF
C3 47uF
16.9R
0.22uF
0.22uF
GND
C4
47uF
GND
GND
C6
47uF
GND
100K
10R
R108
R4
7
1
4
8
R3
P$1
GND
39R
R38
L2
4.7uH
39R
R33
L1
4.7uH
R101
TL072P
1
IC103A
R104
100K
3
8
TQ2-24V
K3(Ø)
+16V
200K
R113
47uF
C103
47uF
C104
GND
R105
C105
6
5
GND
200K
0.47uF
TL072P
7
IC103B
510
R110
+16V
Red
IN
1
3
4
2
5
ADJ
GND
R115
GND
10K R111
Grey
Purple
Blue
Green
240R
OUT
6S101
GND
2.2uF
C106
EA-1166-500
T2
IC104
LM317
Brown
GND
Meter Schematic
2
3
100K
R103
200K
R102
-16V
1
D4
10
SW2(Ø)
7
9
4
2
6.2R
100K
R39
10R
1K
10R
R116
R117
R2
R114
R112
3.9R
732R
1.4K
OPT-R
+16V
1
2
3
4
5
6
7
8
9
LM3916N
LED2
LED1
LED3
VLED4
V+
LED5
DIVLO
LED6
SIGIN
LED7
DIVHI
REFOUT LED8
REFADJ LED9
MODE LED10
IC101
OPT-C
1
4 3
7 6
9
18
17
16
15
14
13
12
11
10
8
5
2
3.4K
8.2K
8.2K
8.2K
10K
10K
10K
10K
10K
10K
+7
+6
+5
+4
+3
+1
-1
-3
-8
-16
OUT-HI
OUT-LO
Hairball Audio, LLC • 6523 California Ave SW • PMB 291• Seattle, WA 98136 • www.hairballaudio.com