The Sound Lab Mini-Synth
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We will post information here when they are back in stock.
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MFOS Sound Lab Mini-Synth Components Kits
Are Here! Sound Lab mini-Synth kits are here.
You will save significantly by sourcing and buying the parts yourself.
However, if you can afford the instant gratification route and just want a box with all of the parts ready to go, now you can get it.
We've done all the sourcing and shopping for you, saving you a significant amount of time and effort.
Please remember even with the kit this a very challenging project and you will need a lot of project experience and electronics savvy to successfully build it. |
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What is in the kit?
A Sound Lab Mini-Synth PC Board and the parts listed in this Word document: (Sound Lab Kit Parts List.doc)Sound Lab Kit Parts List Document (MS Word Format) |
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What is NOT in the kit
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Introduction
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This project is fun for someone with intermediate to advanced
electronics skills who wants to make cool sounds.
It makes a great first synth project but is interesting enough for
the seasoned synth person too. The board includes 1V/oct scale adjustment
trimmers for the oscillators You will get a couple (maybe three)
octaves of in tune scale. The Sound Lab Mini-Synth is a LOT of
fun to play with and makes some very
cool sounds.
If you like electronic music you will definitely have fun with this. If you have a sampler you
can use this unit as an analog synth sound source to make excellent
samples with. The circuit will run a long time on two 9 volt
batteries. The whole thing draws well under 10 mA. Some of the
wiring is done on the chassis but the drawing I have included will
make it very easy for you to do a neat job while you build it. I
hope you enjoy the project and once built I hope you add some of
your own modifications. If you come up with a cool mod and you would
like to share it with the synth building world send me an email specifically stating that you want it
published along with the details and I'll post it on the
modifications page with appropriate credit to you.
Please browse the whole page and click anything that looks clickable so you don't miss some important information if you decide to build the Sound Lab.
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Click the image to see an excellent block diagram of the Sound Lab Mini-Synth created by Tom Fenn of Birmingham, UK. It will help you imagine the sounds you can make. |
Buy Sound Lab Mini-Synth PC Boards
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Tired of etchant eating your hands and the tedious work of drilling hundreds of
tiny holes. Then buy a ready-to-go, super high quality PC Board!
Purchase Printed Circuit Boards online! Click the Add To Cart button to make a purchase or go to PayPal to sign up for a PayPal account. You can also set the number of boards you would like to buy on the PayPal shopping cart page. Please note that you are buying an un-populated PC board only. The glass epoxy, double sided, plated through-hole PC board is professionally manufactured, pre-drilled and silk-screened with a parts layout legend. You must purchase all of the parts for the project and build it yourself. But since that is the whole idea behind DIY (Do It Yourself) that's a good thing. |
| Sound Lab Mini-Synth PC Board (6.6" x 3.7") | |
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Buy Sound Lab Mini-Synth PC Boards via PayPal |
| (1) Sound Lab Mini-Synth PC Board $35.00 | |
How much will the Sound Lab Mini Synth parts cost?Back to TopWell that depends on where you buy your parts. If you look for deals on pots and switches (which will most likely be the most expensive items) you may be able to find them for as little as 50 cents a piece. Try All Electronics for surplus pots and switches. Jameco sells brand new pots for about 90 cents when you buy ten pieces of the same value. Also keep in mind that a DPDT (Double Pole Double Throw) switch may be on sale when you need a SPST (Single Pole Single Throw) switch. Well a DPDT switch can be used in place of an SPST or an SPDT (Single Pole Double Throw) switch. So don't pay more for an SPST or a SPDT if you find cheap DPDTs. Another example is dual pots. If you find cheap dual pots in the value you want they will work fine as single pots. A dual pot is a pot with two resistive elements, two wipers connected to the same shaft and two sets of terminals (they are typically used as stereo controls). You just use one set of the terminals as if it was a single pot. Resistors and capacitors are relatively cheap but they are only pennies a piece if you buy in bulk (100 or 200 at a time). Values like 100K, 1M, 10K, .1uF, .001uF, 100pF always come in handy as do 1N914 diodes, 2N3904 NPN transistors and 2N3906 PNP transistors so having a few extra around for future projects and experiments is good and you will pay a lot less per part. If you belong to an electronics club or have some electronics buddies that live near you go for bulk buys and split the cost. OK, all that having been said I think that the price for parts will range from about $70.00 (you stock parts that you buy in bulk) to $100.00 (you buy just what you need for a particular project). Here are some good places to order parts from (most have on-line ordering). I hope this is helpful. |
The Clear and Unambiguous PC Board Return PolicyBack to Top
If within 30 days of the original purchase you are unsatisfied you can return the clean, un-marred, un-soldered board and I will refund the price of the board ($30.00) via PayPal. You must include the original email you received from PayPal regarding the transaction and pay for the cost of shipping it back to me. Please remember that the only stipulation to this offer is that the board must be in the same condition as it was when I sent it to you (clean, un-marred, and un-soldered). You can return it to me in the same envelope you received it in if you don't open it or if you open it carefully and tape it back together securely. There will, of course, be no refund if I receive a damaged board or an empty envelope. Paste my address on the outside and when I receive it I will issue a PayPal payment to you of $30.00 US per returned PCB. If the original transaction involved a volume discount then the refunded amount will be price-for-boards/number-of-boards per returned PCB. |
The Clear and Unambiguous Kit Return PolicyBack to Top
If within 30 days of the original purchase you are unsatisfied you can return the clean, un-marred, un-soldered kit and I will refund the price of the kit ($160.00) via PayPal. You must include the original email you received from PayPal regarding the transaction and pay for the cost of shipping it back to me. Please remember that the only stipulation to this offer is that the kit must be in the same condition as it was when I sent it to you (clean, un-marred, and un-soldered). You can return it to me in the same box you received it in if you tape it back together securely. There will, of course, be no refund if I receive an empty box or a damaged or incomplete kit. Paste my address on the outside and when I receive it I will issue a PayPal payment to you of $160.00 US per returned kit. |
Modifying Your Sound Lab Mini-Synth
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Sound Lab Guitar Trigger
Turn your Sound Lab into a guitar effects box.
Sound Lab Drum Trigger
Turn your Sound Lab into an excellent electronic drum.
Add More CV Inputs For The Oscillators
Need more CV inputs not a problem. Here's how.
Single Chip Simple Sample & Hold
Build this on a small Radio Shack breadboard and add it to your Sound Lab. Its a great little source of variety.
Use Rotary Switches To Change Timing Capacitors
Carlos Adriano B. Blanco of Brazil shares this mod:
I also want to share 3 simple “mods” I made on my own using single pole 10 position non shorting rotatory switches as follow:As a result I’ve achieved different and cool sounds (may I say almost limitless). I’d be glad if you could publish the modifications in order to share with the electronic music enthusiasts, synth building world and DIY’ers community like me and all over the place as you said. Carlos has given permission to contact him if you have questions concerning the mod. email Carlos
- For C8 and C9 (I kept the original 0.001 uF and then I
added 0.0022, 0.0033, 0.0047 .. and so on)- For C3 (I did the same but the first position is a 0.5
uF then 1.0 uF, 2.2 uF …..47 uF)- For C14 also (I kept the original cap then added different
caps for each position)
How do I patch out the Sound Lab instead of building it with switches?
The Sound lab is normallized with switches to set the connections between modules but you can use banana plugs and jacks and connect whatever you want to connect to get the most out of the modules.
How do I modulate oscillator 1 with oscillator 2's output?
Make some cool modulation effects: birds, bells, etc. by modulating Oscillator 1 with oscillator 2's output.
How do I add fine tuners to the oscillators?
Fine tuners make it WAY easier to tune the oscillators to set intervals. The coarse adjustment provided by the original pots works but if you want to use the unit for music you will want to add the fine tuners.
How do I scale the Sound Lab for a 1V/Octave keyboard?
The Sound lab can be used as is (with no additional mods). If you connect an external synth keyboard that puts out 1V/Octave or a MIDI to CV converter that puts out 1V/Octave the unit will respond appropriately (the pitch will increase as higher notes are pressed). However, the pitch will not go up in exactly 1/2 steps and the octaves may be stretched or compressed unless you add the 1V/Octave scaling modification. The modification permits the oscillators to be trimmed to track at 1V/Octave so that they more accurately produce 1/2 steps and octaves are true doublings of frequency.
How do I protect the external CV inputs from voltage higher than 9V?
Zener diode protection scheme.
| When printing these pages You need to set your page orientation to landscape and set the margins as low as they will go. If necessary use cut and paste to put the larger images into your word processor or image editor and then print them from there. I have not been able to figure out why Internet Explorer adds several blank pages (does Bill have stock in some paper companies?). |
Static Electricity and ICs
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| Be aware of static electricity when handling the ICs and transistors for the project. Just walking across a carpeted floor on a dry day can charge you up with tens of thousands of volts of static electricty. If this energy jumps from your hand to your active component (IC or transistor) you may damage it so badly that it doesn't work anymore. To avoid this, discharge yourself before handling ICs or transistors. You can buy grounding straps that you wear on your wrist which are connected to earth ground VIA A 10 MEG RESISTOR. NEVER STRAP YOURSELF DIRECTLY TO EARTH GROUND!!! You can also buy discharge pads in computer stores. You touch the discharge pad when you arrive at your work station and thereafter touch it again from time to time to stay discharged. |
Sound Lab Sound Samples (MP3)
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I resisted the urge to add any effects to these
so all of them are dry. Of course you can add whatever effects you
like and then layer sounds with Cakewalk or whatever you use to record
on your computer.
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| These samples do have a bit of reverb and I am controlling my Sound Lab Mini-Synth with my sequencer and my sample & hold to give you more of an idea of the kinds of sounds you will get out of the unit. These are longer samples and subsequently larger files. |
My Sound Lab Mini-Synth Front Panel
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 Click image for a larger view |
I took a cue from Jörgen Bergfors and made my front panel by laminating a piece of paper onto a 1/16 inch thick aluminum panel. I wrote a program to let me easily lay out front panels and then I laser printed the design onto some bright green paper. The adhesive I use to apply the paper onto the aluminum is acrylic polymer (you buy it in art stores). I coat the aluminum and the back of the paper and then while both are still wet I apply the paper to the aluminum. I then brush polymer onto the front of the paper so that the panel is dirt and water proof. The result is very useful and much nicer looking than my previous efforts to scribble with a Sharpee pen. |
Suggested Front Panel Layouts for Sound Lab Mini-Synth
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 Click image for a larger view |
When I print from my panel design program I
don't get the jaggies you see here. I included a function to output a
BMP to the clipboard so I can post drawings on the web. This template
is actual size and will work even if it is a bit jaggie. I have
provided a X2 version that you may be able to use to get a less jaggie
reduction. X1 Scale X2 Scale Front Panel PDF |
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Front Panels contributed by other buildersPlease bear in mind that if you use another front panel design that the panel wiring diagrams I provide will not apply. You will be on your own with the panel wiring. I suggest that you make your own panel wiring drawing and carefully transpose the connection information. Good wiring. |
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Sound Lab Mini-Synth Panel Wiring [Click for PDF]
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| I found a 1/16 inch thick aluminum plate big enough for the front panel. I drilled it, cleaned it and then labeled it (as described above). After this I installed the pots and switches. Use this drawing to wire the front panel. Use a flexible stranded wire for best results. There is no rhyme to the color scheme but I think I did stay with red as +9V, black as -9V, and green as ground throughout. It should go without mentioning but who knows you may be very new to the synth scene. You need to strip the ends of the wire and solder them to the termination points (the places where wires touch pots, switches and other components). |
View Rev 000 Version (here for reference only)
Sound Lab Mini-Synth AR (Attack - Release) Envelope Generator
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| With S2 is in the off state and S3 set to "Trig'd"
the circuit functions as follows. When S1 is momentarily pressed it
discharges C2 (to about 1.6 volts) through R2 which causes pin 2 of
IC1-A to go high. This pushes a positive pulse through C1 and D1 which
sets the flip flop made up of IC1-E and IC1-F. IC1-F pin 12 goes high
and C3 begins to charge at the rate set by the Attack pot R10 from -8
volts to about 6.5 volts (this voltage is buffered by IC2-B voltage
follower) at which point IC1-B's output goes low and IC1-C's output
goes high and the IC1-E/IC1-F flip flop is reset by the high logic
level presented to pin 13 via D5. This causes IC1-F pin 12 to go low
and discharge C3 at a rate determined by R11.
When the Repeat switch is on and the voltage at IC2-B is lower than -6 volts then IC1-D pin 8 goes high and sets the IC1-E/IC1-F flip flop again thus causing the cycle to begin again and subsequently repeat. Notice that I am allowing negative voltages to reach the inputs of the schmidt triggers but that they are protected from drawing high current through their internal protection diodes during that time by the high value resistors in series with their inputs. When S3 is in the "Gated" position the repeat function is disabled. In this configuration a high level is presented to the "Attack" diode/pot combo as long as S1 is held pressed (because the output of IC1-A is high when S1 is held pressed). Gate mode allows C3 to charge from -8 volts to about +8 volts maximum. When S1 is released a low level is presented to the "Release" diode/pot combo (because the output of IC1-A is low when S1 is not pressed). The output of IC2-B is fed to R15, the AR Envelope output level adjustment pot. The circuit point "AR" is the wiper of R15, which is fed to the AR-Gen switches of the modules. While contemplating this circuit remember that the inverters are schmidt triggers and that their inputs must go lower than 1/3 of the supply voltage before their output goes high and then the input must go to greater than 2/3 of the supply voltage before the output goes low. This characteristic is know as hysteresis. The zener on the external gate is meant to protect against gate signals greater than 9 volts. When the gate is high transistor Q8 will discharge C2 the same way switch S1 does. NOTE: If you don't plan to use the external gate capability of the device you can eliminate the following components: D7, R199, R1, D8, Q8 NOTE: C2 has been changed from .01uF to .001uF to allow the AR generator to be triggered faster from external sources. |
Schematic PDF
Sound Lab Mini-Synth LFO (Low Frequency Oscillator),
Noise Source, and +/- 9 Volt Battery Power Supply
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| Two 2N3904s walk into a bar. One makes a lot of noise and
gets thrown out, the other one sits and quietly drinks his stout. The
punchline... some transistors are noisier than others. So how do we
get noise out of ANY 2N3904? With this circuit. Notice that we do the
usual... reverse bias a low V(ebo) emitter base junction, listen to
the junction through C10 and a gain of about 1000. If this transistor
is whispering it is still whispering into a lot of gain. This circuit
does not care if this transistor is in a confessional you are going to
get at least 100 mV of noise from the first stage. We take whatever we
are getting from the first LF444 and feed both inputs of a second
LF444 through two 1M resistors. We hang a capacitor off of the
inverting input and voila the inverting input always lags the
non-inverting one. As the noise voltage is taking its time trying to
go up and down (due to the cap) on the inverting input it is racing up
and down on the non-inverting input. This results in the voltage on
the non-inverting input randomly being higher or lower than the
voltage on the inverting input as the noise voltage randomly changes.
Since the op-amp is wired as a full blast comparator its output is
swinging up and down between the voltage limits of the LF444 in time
to the noise fluctuations. Varying the cap and varying which input you
hang the cap on will change the characteristics of the noise at the
output of the second stage.
The LFO is the same as the Super Simple Ramp and Sawtooth LFO. Notice that the switch is changed to be center off so the circuit produces a triangular wave too. This was suggested synth-DIYer Harry Bissell (I remembered the little email logo H^) that came with the suggestion.) thanks. Additionally, you can change the range of oscillation for the LFO with the range switch. In low range a 2uF cap (C13) is placed in parallel with the integrator capacitor (C14) to reduce the range of frequency provided by the Frequency pot R90. Two 9 volt batteries power the circuit and the two by-pass caps absorb the larger current spikes. I am planning on re-evaluating all of my circuits with the LF444 (low power op amp). These things are great. You get decent slew rates and much lower current consumption than with TL084s and TL082s. All of the circuits in the Sound Lab together draws less than 6mA. Hooking up two batteries for + and - 9 volts |
Schematic PDF
Sound Lab Mini-Synth VCA (Voltage Controlled Amplifier) and
VCF (Voltage Controlled Filter)
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| These two circuits are practically straight out of the
National Operational Amplifiers Databook data sheet for the LM13700.
They have linear voltage control but for a sound box they're fine. The
transconductance characteristic of these Op Amps makes them perfect
for VCAs and VCFs.
In the VCA the control voltage controls the current flow through the amp and subsequent level of the signal at the output. S4 switches the AR Gen control voltage on or off. When on, the level of the AR Generator output pot determines how much the AR Generator controls the signal amplitude at the output of the VCA. S5 switches the LFO control voltage on or off. When on, the level of the LFO output pot determines how much the LFO controls the signal amplitude at the output of the VCA. R19 controls the initial amplitude at the output of the VCA. When S4 or S5 is on it is best to turn R19 off or nearly off. In the VCF the OTAs act as voltage controlled resistors which change the pass-band (in band pass mode) and cut-off frequency (in low pass mode) from low (for low control voltage) to high (for high control voltage). The resonance control adjusts the feedback around the circuit and thus the gain at the cut-off frequency. At high resonance settings the filter rings adding harmonics to the filtered signal which give the classic synthesizer wahhhhh sound when the cut-off frequency is swept from low to high. The filter also acts as the mixer as all of the signal sources are presented to its input via attenuation pots (R29, R38, and R44). The input to the VCA is either the low pass output or the band pass output determined by the setting of switch S6. S7 switches the AR Gen control voltage on or off. When on, the level of the AR Generator output pot determines how much the AR Generator controls the cut-off frequency of the VCF. S8 switches the LFO control voltage on or off. When on, the level of the LFO output pot determines how much the LFO controls the cut-off frequency of the VCF. R37 controls the initial cut-off frequency of the VCF. When S7 or S8 is on it is best to turn R37 off or nearly off. |
Schematic PDF
Sound Lab Mini-Synth VCOs (Voltage Controlled Oscillators) Rev 001
Back to Top| The sound lab uses two voltage controlled ramp oscillators.
IC5-B and IC5-A and associated transistors and components comprise a
linear voltage to logarithmic current convertor. The control voltages
which are summed by IC5-B range from -8 to 8 volts. The corresponding
current ranges from around 1uA to 1mA and since the oscillators go up
approximately 1 octave every time the current doubles this gives the
oscillator a nice range from a sub-audible 0.6 Hz to beyond human
hearing (This is since changing the values of C8 and C9 to
.001uF from .02uF)
The explanation of the operation of oscillator 1 follows (oscillator 2 works the same way using its associated components). Oscillation occurs because as the current is sucked out of the input of integrator IC5-D its output goes high until IC5-C (comparator with hysteresis) pin 8 goes high and turns on the N-Channel FET (Q5) which shorts the integrating capacitor (C8) which causes the cycle to begin anew and subsequently repeat. IC6 is used in a similar configuration. The output of IC6-D (point ZZ) is fed into comparator IC2-A in order to provide a square/pulse wave shaper for Oscillator 2. The control voltage fed into IC2-A pin 2 via resistors R86 and R87 determine the comparator threshold and thus the point at which the output (pin 1) goes high and low. Varying R85 will change the pulse width which will vary the timbre of Oscillator 2 when Rect Wave is selected. S15 permits the LFO output voltage to modulate the pulse width which can cause the output of Oscillator 2 to sound like 2 oscillators tuned very close together (when approximately 1HZ LFO frequency is used). S11, S13, S12, and S14 are used to feed the AR Generator and LFO outputs to the CV inputs of the VCOs. When on, you will hear the obvious effect as you advance the LFO and/or AR Gen output adjustments. S9 causes Oscillator 2 to sync to the frequency of Oscillator 1. This provides some very cool timbres which you will hear if you turn on Sync and then tune Oscillator 1 lower than Oscillator 2 and sweep Oscillator 1 upward in frequency. NOTES: If you don't plan to use the external CV (Control Voltage) capability of the device you can eliminate the following components: R62 and R63. To obtain the most accuracy of scaling of the oscillators for
control via Ext CV1 and Ext CV2 do as many of the following mods as
possible:
Reduced the value of the integrator cap for the VCOs from .02uF to .001uF. This changes the range of the oscillator so that it attains a higher top frequency and allows the integrator cap to discharge 20 times faster. Since the oscillator is inherently higher in pitch the wiring of the "Frequency" pots was changed so that the voltage at the wipers of R55 and R58 is able to go lower when turned all the way down and not as high when turned completely up. The oscillators will still go sub-audio (a few hertz) to beyond hearing (18 to 20 KHz). Additionally the sync works better since the integrator can be reset with a shorter pulse than before. The panel wiring diagrams have been updated to reflect the change. Replace C8 and C9 with .001 uF caps (temperature stable type) and rewire pots R55 and R58 on the front panel. Remember that R50 and R52 are not only moved as shown in the panel wiring diagram but that their values change to 39K.
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Schematic PDF
Sound Lab Mini-Synth PCB Shown Parts (Top) Side Up Back to Top
Previous Board Revisions and Strip Board Layout
Sound Lab Bottom Copper
Sound Lab Top Copper
Sound Lab Silk Screen
| In order to use this artwork you need to print it so that the DIP IC pad holes are exactly 1/10 inch apart and 3/10 inch across. I put a lot of extra holes for any modifications you might want to make. Inspect your board to make sure none of the lands or pads are shorted. Make sure none of the lands are open. Scrape away any shorts with a Xacto knife and solder some small copper wire between any opens. |
Important Information Pertaining to the 1V/Octave modification.
Using the 1V/Oct mod (Parts Side View)
| To implement the 1V/Octave modification insert (2) 100 ohm trimmers and (2) 475 ohm resistors in the areas indicated by the silk screened parts legend. |
NOT Using 1V/Oct mod (Parts Side View)
| To NOT implement the 1V/Octave modification just insert (2)
wire jumpers in the indicated areas. Do not install the 100 ohm trimmers or the 475 ohm resistors. |
Sound Lab Mini-Synth Parts Layout
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| I like to start with the IC sockets, then the jumpers, then the resistors, and finally caps. Essentially working from low parts to high parts will make the whole job easier. Put in about ten components at a time bending the leads to hold them in place. Now, trim the leads and solder in place, keep going until you are done. Radio shack sells a very nice "Nippy Cutter" which is excellent for trimming component leads. Remember to leave enough lead to solder to (about an 1/8 inch) and be sure that adjacent leads aren't shorted. Parts Legend PDF |
Pots: R44, R38, R29, R85, R58, R55, R48, R37, R27, R15,
R11, R10, R92, R90, R19 PLEASE NOTE Q7 is mounted
on the board but as the schematic shows it only needs two holes because
you cut the collector off.
LIST OF PARTS MOUNTED ON THE FRONT PANEL AND NOT THE PC BOARD
These parts are not mounted on the PC board they are mounted on
either the control panel or the input/output panel.
Switches: S6, S8, S7, S15, S14, S12, S9, S10, S13, S11, S19, S5,
S4,S 2, S3, S1, S18, S16, S17
Resistors: R104, R84, R52, R50, R32, R41, R94, R6, R88, R23
Diodes: D4, D3, D9, D10
Caps: C13, C22
Jacks: Gate In, Osc-2 CV, Osc-1 CV, Output
February 2008 Parts Layout
A slight change to the layout has been made. The change allows SSM2210 matched pair transistor packages to be used for Q1/Q3 and Q2/Q4.
To do this with prior boards see recommendation below. This layout began shipping in late March 2008.
SSM2210 Data Sheet
May 2007 Parts Layout
To accomodate SSM2210s with May 2007 layout boards I recommend that you solder some clipped resistor leads to an 8 pin DIP socket (only 6 of the leads, pins 1,2,3 and 8,7,6) and then insert the leads into the boards and solder them. Then insert the SSM2210s into the sockets. SSM2210 Data Sheet
Fabian Meier's Excellent Part Value Layout
Fabian Meier of Switzerland was kind enought to share this great part value drawing for the Sound Lab. This view helps when you're stuffing the board. Instead of going back and forth between the schematic and the parts layout you can just go from here and stuff away. Click here for a PDF version. Thanks Fabian!
Sound Lab Mini-Synth Panel Wiring Diagram With Wiring Labels [Click for PDF]
View Rev 000 Version (here for reference only)
Sound Lab Mini-Synth Parts Layout With Wiring Labels
EXCEPT FOR X1, X2, and X3 shown below which are related to both
the circular schematic references AND the PCB connection points
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Sound Lab Mini-Synth Output and Input Connections [Click for PDF]
EXCEPT FOR X1, X2, and X3 shown below which are related to both
the circular schematic references AND the PCB connection points
| The sound lab can be controlled by external equipment (keyboards, sequencers, etc). I recommend that you don't apply voltage greater than 9 volts to the inputs or you may damage the components. I used 1/4" jacks for all in/out connections but you can use smaller ones if you want. If you can't find a 1uF non-polarized cap then just use two 2uF electrolytic caps connected back-to-back (i.e. connect the negative terminals of the two together and use the positive terminals as the cap leads). |
| The sound lab is powered by 2 nine volt batteries connected
as +/-9V as shown here. Radio Shack sells 9V battery clips (Radio Shack #s 270-325 or 270-324) |
Sound Lab Mini-Synth Project Parts List
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Parts Lists Submitted By Users
LIST OF PARTS MOUNTED ON THE FRONT PANEL AND NOT THE PC BOARD
These parts are not mounted on the PC board they are mounted on either the control panel or the input/output panel.Pots: R44, R38, R29, R85, R58, R55, R48, R37, R27, R15,
R11, R10, R92, R90, R19
Switches: S6, S8, S7, S15, S14, S12, S9, S10, S13, S11, S19, S5,
S4,S 2, S3, S1, S18, S16, S17
Resistors: R104, R84, R52, R50, R32, R41, R94, R6, R88, R23
Diodes: D4, D3, D9, D10
Caps: C13, C22
Jacks: Gate In, Osc-2 CV, Osc-1 CV, Output
PLEASE NOTE
Q7 is mounted on the board but as the schematic shows it only needs two holes because you cut the collector off.
| Qty. | Description | Value | Designators |
|---|---|---|---|
| 1 | LF442 or TL072 Dual Op Amp | LF442 | IC2 |
| 3 | LF444 or TLO74 Quad Op Amp(s) | LF444 | IC5, IC6, IC7 |
| 2 | LM13700 or Mouser# 513-NJM#13700D Dual Transconductance Op-Amp | LM13700 | IC3, IC4 |
| 2 | MPF102 (or 2N5457) N JFET(s) | MPF102 | Q6, Q5 |
| 1 | CD40106 (74C14) Hex Inverter | CD40106 | IC1 |
| 8 | Silicon Switching Diode(s) | 1N914 or 1N4148 | D7, D1, D2, D3, D4, D5, D9, D10 |
| 1 | Silicon Zener Diode | 9.1Volt Zener | D8 |
| 6 | Transistor NPN(s) | 2N3904 | Q8, Q3, Q1, Q4, Q2, Q7 |
| 4 | Ceramic Capacitor(s) | .001uF | C2, C1, C8, C9 |
| 1 | Ceramic Capacitor | .0047uF | C14 |
| 1 | Ceramic Capacitor | .01uF | C12 |
| 5 | Ceramic Capacitor(s) | .1uF | C10, C11, C19, C20, C15 |
| 2 | Ceramic Capacitor(s) | 100pF | C7, C6 |
| 1 | Ceramic Capacitor (or non-polarized aluminum) | 1uF | C22 |
| 1 | Ceramic Capacitor (or non-polarized aluminum) | 2uF or 2.2uF | C13 |
| 2 | Ceramic Capacitor(s) | 330pF | C21, C17 |
| 2 | Ceramic Capacitor(s) | 560pF | C5, C4 |
| 2 | Electrolytic Capacitor(s) | 100uF | C16, C18 |
| 1 | Tantalum or Aluminum Electrolytic Capacitor | 2uF or 2.2uF | C3 |
| 4 | Audio Taper Potentiometer(s) | 100K | R27, R29, R38, R44 |
| 2 | Audio Taper Potentiometer(s) | 1M | R10, R11 |
| 9 | Linear Taper Potentiometer(s) | 100K | R15, R19, R48, R37, R58, R55, R85, R90, R92 |
| 2 | Multi Turn Trim Pots(s) | 100 ohm | Parts for 1V/Oct Mod |
|
Use metal film 1/4 watt 1% resistors where specified for the least amount of frequency drift.
You may use 1/4 watt 5% resistors in place of 1/4 watt 1% but the oscillators will drift more. | |||
| 8 | Resistor 1/4 Watt 1%(s) | 100K | R68, R69, R74, R54, R57, R63, R62, R73 |
| 2 | Resistor 1/4 Watt 1%(s) | 10K | R64, R65 |
| 4 | Resistor 1/4 Watt 1%(s) | 1M | R67, R66, R59, R56 |
| 2 | Resistor 1/4 Watt 1%(s) | 2K | R60, R61 |
| 2 | Resistor 1/4 Watt 1%(s) | 39K | R50, R52 |
| 2 | Resistor 1/4 Watt 1%(s) | 47K | R76, R75 |
| 2 | Resistor 1/4 Watt 1%(s) | 475 ohms | Parts for 1V/Octave Mod |
| 9 | Resistor 1/4 Watt 5%(s) | 100K | R4, R14, R1, R12, R36, R24, R86, R79, R93 |
| 5 | Resistor 1/4 Watt 5%(s) | 10K | R199, R26, R32, R103, R102 |
| 4 | Resistor 1/4 Watt 5%(s) | 150K | R17, R30, R33, R39 |
| 7 | Resistor 1/4 Watt 5%(s) | 1K | R22, R23, R45, R34, R35, R88, R98 |
| 9 | Resistor 1/4 Watt 5%(s) | 1M | R8, R9, R2, R87, R96, R97, R95, R99, R91 |
| 4 | Resistor 1/4 Watt 5%(s) | 200K | R28, R31, R84, R89 |
| 8 | Resistor 1/4 Watt 5%(s) | 20K | R42, R40, R47, R43, R46, R80, R70, R72 |
| 4 | Resistor 1/4 Watt 5%(s) | 220K | R77, R82, R78, R83 |
| 2 | Resistor 1/4 Watt 5%(s) | 2M | R5, R13 |
| 1 | Resistor 1/4 Watt 5% | 33K | R21 |
| 1 | Resistor 1/4 Watt 5% | 3M | R7 |
| 2 | Resistor 1/4 Watt 5%(s) | 4.7K | R41, R81 |
| 2 | Resistor 1/4 Watt 5%(s) | 4.7M | R3, R100 |
| 4 | Resistor 1/4 Watt 5%(s) | 470K | R18, R16, R20, R71 |
| 3 | Resistor 1/4 Watt 5%(s) | 47K | R49, R104, R101 |
| 2 | Resistor 1/4 Watt 5%(s) | 510 ohms | R6, R94 |
| 1 | Resistor 1/4 Watt 5% | 620K | R25 |
| 1 | DPST Toggle Switch | DPST | S19 |
| 1 | SPDT Toggle Switch (center off) | SPDT | S16 |
| 4 | SPDT Toggle Switch(s) | SPDT | S3, S6, S10, S18 |
| 12 | SPST Toggle Switch(s) | SPST | S2, S4, S5, S7, S8, S14, S12, S11, S9, S15, S13, S17 |
| 1 | SPST Mom. Push Button | SPST | S1 |
| 1 (4 if using optional ext CV ins and Gate) | Phone Jack(s) | 1/4" Jack | J1 (optional: Osc-1 CV, Osc-2 CV, Gate In) |
| 2 | Battery(s) | 9V | B2, B1 |
| 2 | 9V Battery Connectors | 270-325 or 270-324 | Radio Shack Part# 270-325 or 270-324 |
Miscellaneous
| Capacitor Substitution You should know that where ceramic capacitors are specified below you could substitute: Mylar, Polyester, Polystyrene, Polypropylene, or Mica. The value should be within 10% of what is specified below. In other words you can substitute a .022uF for a .02uF or a 2.2uF for a 2.0 uF. The circuit is forgiving enough to handle that variation with no problem. Do not substitute electrolytic caps with non-electrolytic caps. And don't forget that you can put caps in parallel or series to get a capacitance value you don't have on hand.
Resistor Substitution
Potentiometers Linear or Log Taper? Potentiometer Values? Op Amp Substitution? MPF102 Substitutes |
Getting Everything Working
Back to Top
| Introduction |
|---|
| I will be putting answers to emailed questions and requested help here. I imagine that eventually everything will be covered. The main thing to realize is that when wired according to the documentation I have provided on this site the circuit works perfectly. When you get it put together right and make sure you don't have any bad active components or misconnected or unconnected circuitry it will work. Look here for general trouble shooting information: General Trouble-shooting Info |
| VCF Control Range Change |
| The filter will hit the bottom of its range at various
settings depending on what you are controlling it with. If you find
that it makes the passband too low to pass anything of interest when
you still have several degrees of pot rotation no matter what you have
connected to it then increase the value of R41 (resistor from pin 3 of
the Cut-Off Frequency pot to -9V). That will raise the bottom of the
control range. Try something between 4.7K and 10K to start. It won't
hurt to go higher than that in resistance if you want to try.
Signal bleed-through? A two pole filter will always allow a bit of the original signal to pass through but just a itsy bitsy teeny bit so if you have a lot of bleed-through at the bottom of the range look over all of the components associated with the filter to make sure everything is the correct value and connected properly.
|
| VCA Voltage Controlled Amplifier |
| If the the VCA is acting totally strangely make sure
everything is wired correctly and that you have a good LM13700. Check
the panel wiring to make sure that a ground or power connection hasn't
been missed.
The input to the VCA goes through R21 (33K) and is dropped across R22 (1K resistor to ground). Any patched in signals should go (via 100Ks) to the junction of IC3-B pin 14, R22 pin 2, and R21 pin 1. All this part of the circuit does is feed an attenuated signal to the non-inverting input of the LM13700 (the inverting input is grounded). Now on to the control voltage portion of the VCA. As you can see we are only applying current to pin 16 of IC3-B from the various control voltage inputs and we have biased the input toward the low end by R17, 100K to -9V. The VCA initial gain only applies a voltage of between -9V and +9V to pin 16 of IC3-B (via R18 470K). All of the control voltage inputs to the VCA are adding to or subtracting from the current arriving at pin 16 of IC3-B. So this is one of the simplest modules and it definitely works when everything is connected properly. Another thing to check is the average voltage at the junction of S6 pin 1 and R21 pin 2. This should be near ground and if the VCF has something connected improperly it could be applying a DC offset to this input thus causing the VCA circuit to misbehave so check that. All I can suggest is that you check all of the wiring, soldering and component values (including the components in the filter circuitry). Last but not least try another chip (LM13700) if something is amiss with this circuit module. R26, R42, and R43 must be tied to -9V or the bias of the circuit will be wacky. Also the biasing of the output buffer in the VCA is very critical make sure R24, R25, and R26 are all connected properly.
|
| Pulse Width Modulation Circuit |
| The output of IC6-D needs to be present for the pulse width
modulator (IC2-A) to work. Check pin 14 of IC6. A sawtooth wave should
be present and the frequency should vary when R58 is adjusted. The
same saw tooth signal should be present on pin 1 of R79 (the side not
connected to pin 3 of IC2A). The sawtooth should also be present on
pin 2 of IC2-A (it may look a bit attenuated depending on the
impedance of your scope probe). Make sure S15 is turned off for the
following checks. When you adjust R85 the voltage present at pin 1 of
R86 (the side not connected to pin 2 of IC2-A) should vary in the same
manner as the voltage seen at the wiper of R85. If it does not then
check that the wiper of R85 is connected to the circuit board via a
wire. If the voltage at the wiper of R85 does not vary when it is
adjusted then the resistive element terminals may not properly
connected to both +9V and GND via R84 and R104 respectively. If it is
connected then you may have a bad pot. If the voltage is varying
properly on R85 then check the output of IC2-A (IC2 pin 1). You should
see a pulse wave whose frequency is the same as the sawtooth you saw
on pin 1 of R79 and whose pulse width varies in response to adjusting
R85. If you have checked everything so far and still don't have a
pulse wave on the output of IC2-A you may need to replace IC2. If you
have the pulse wave on pin 1 of IC2 then make sure you have it at pin
3 of S10 (it will be attenuated by a factor of about 5). If you have
it there then make sure that the schematic point O2 is properly
connected to R38. You should see the same attenuated pulse wave on pin
1 of R38. The wiper of R38 should be connected to R33 on the PCB. IF
you have the signal to here you are good to go as far as the Pulse
Width Modulated waveform is concerned.
|
| Attack Release Generator |
| As always, check the associated part values and orientations
to ensure they are correct. Disconnect the external gate if you are
using the external gate feature. With no external gate connected, S3
(AR Mode switch) set to "Gated" and S1 not pushed you should
see +8 to +9 volts (depending on your meter's impedance) between pin 1
of C2 and ground. In this state IC1-A pin 2 should be low. When you
press S1, you see about 1.5 volts between C2 pin 1 and ground and
IC1-A pin 2 should go high and return low when you release S1. You
should see a positive 8V to 9V pulse across R4 whenever you press S1.
Set both Attack and Decay to the fully counter-clock-wise position
(minimum attack and decay times). When you press S1 the voltage
between C3 pin 1 and ground should go to between 8 and 9 volts (IC2-B
pin 7 should also go to 8 to 9 volts). When you release S1 the voltage
between C3 pin 1 and ground should go to 0 volts (IC2-B pin 7 go to
between -8 and -9 volts). You should see the same voltage on pin 1 of
R15 as you see on IC2-B pin 7. When IC2-B pin 7 is greater than about
+6 volts IC1-C pin 6 should be at 9 volts. Set S3 (AR Mode switch) to
Trig'd. Pressing S1 should cause IC1-E pin 10 to go to ground and then
almost immediately return to +9V. Pressing S1 should cause IC1-F pin
12 to go to +9 volts and then almost immediately return to ground.
Turn R10 a bit clockwise. Pressing S1 should cause IC1-E pin 10 to go
to ground and then return to +9V after a delay. Pressing S1 should
cause IC1-F pin 12 to go to +9 volts and then return to ground after a
short delay. The further clockwise you turn R10 the longer the delay
should become. The voltage envelope on IC2-B pin 7 should have an
attack curve and a very very short decay curve. The further clockwise
you turn R10 the longer the attack curve should become. Advancing R11
clockwise should cause the decay curve to lengthen. Return to a very
short attack and decay time setting and set S2 (AR Repeat) to on. You
should see a repeating attack decay envelope at IC2-B pin 7. Changing
R10 or R11 should cause the envelope to change appropriately.
Some causes for problems include:
|
| White Noise Generator |
| As always, check the associated part values and orientations
to ensure they are correct. Once you've done that make sure that you
have the emitter and base of Q7 oriented correctly on the PCB. You
should see a positive voltage at the emitter of Q7 of between 4.5 to 6
volts (depending on the impedance of your meter or scope it could be
lower but it should at least be a couple of volts above ground). Check
the output of IC7-C (pin 8) you should measure a voltage that is near
ground (depending on the leakage of the IC). You should see white
noise at a level of at least 100 mV or more at pin 8 of IC7-C when you
look at it with an oscilloscope. If you do, great, if you don't then
hold one end of a short wire and touch the other end of it to IC7-C
pin 10. The output of IC7-C (pin 8) should oscillate at 60 hertz at or
near the rails (+/-9V). If you don't see this oscillation or IC7-C
(pin 8) is stuck high or low replace IC7 and try again. If you see the
oscillation but you don't see noise you probably have a quiet 2N3904
and you are going to have to dig through your box of general purpose
NPNs and test them until you find a noisy one. YOU DO NOT NEED
TO CUT THE COLLECTORS OFF JUST TO TEST THEM. When you finally find the
noisiest one cut its collector off and use it. The reason you do this
is because the collector acts like an antenna and unless you WANT
radio signals in your white noise you probably want to reduce the size
of this impromptu antenna to the shortest possible length. OK once you
have noise at pin 8 of IC-7 the rest of the circuit should work. You
should see rail-to-rail digital looking noise at the output of IC7-D
(pin 14). If you don't see that then make sure the associated
components (R95, R99 and C17) are soldered to the board and that you
have ground on pin 2 of C17. If you have noise at pin 8 of IC7 and you
don't have noise at pin 14 of IC7 try replacing IC7. The point marked
NS should see 1/6 the level of noise you see at the output of IC7-D.
The most likely cause of no noise is the transistor not being noisy.
|
| Overall Signal Check |
| Here is a way to make your amp into a signal tracer. http://www.musicfromouterspace.com/analogsynth/oddsandends.html#AMPSIGNALTRACER Now... It sounds like you have an incorrect value or resistance somewhere or have missed a critical wire in the panel wiring. 1) Review the panel wiring thoroughly. 2) Follow directions here: http://www.musicfromouterspace.com/analogsynth/troubleshoot.html Once you have verified that both the panel wiring is correct and all component values are correct try observing the following circuit points. A good place to start looking is at the Sound Lab Mini-Synth VCA (Voltage Controlled Amplifier) and VCF (Voltage Controlled Filter) schematic. You will notice several circuit points (circles with letters in them) throughout the page. O1 - Raw Oscillator 1 output. O2 - Raw Oscillator 2 output NS - Raw Noise output. BP - Raw output of bandpass filter. LP - Raw output of lowpass filter. AR - Attenuated output of the Attack Release generator. LFO - Attenuated output of the Low frequency oscillator. Locate these points in your sound lab and listen to them (or observe them with your oscope). You should have a hefty signal at each of these points which is several volts in amplitude. If you don't then trouble shoot any of the circuits that seem too low. As you test O1 sweep the Oscillator 1 frequency knob to insure you are listening to (or observing the right point). Do the same for O2, additionally flick the Ramp/Rect switch up and down a bit to make sure the waveform changes properly between ramp and square. Point NS should be the raw noise output (very noisey). BP is the output of the bandpass filter. Sweep the cutoff frequency as you observe this point. Turn the resonance down all the way. As you advance it the sound should become more resonant (contain more harmonic overtones). LP is the output of the lowpass filter. Sweep the cutoff frequency as you observe this point. Turn the resonance down all the way. As you advance it the sound should become more resonant (contain more harmonic overtones). The filter may oscillate when resonance is all the way up (that's OK). Observe the signal level at pin 9 of IC3. This should be the main output prior to the output pot (which is wired as an adjustable voltage divider). The signal at R27's wiper should go from 0V to the same signal seen at Pin 9 of IC3 as you advance it. LFO and AR should go from 0V to the same levels as observed at LFS (on low frequency oscillator schematic) and pin 7 of IC2 (on Attack Release envelope generator schematic) respectively as you advance their respective controls (R92 and R15).
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