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[BUILD] Manhattan Analog Discrete Transistor Amplifier (DTA)
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author [BUILD] Manhattan Analog Discrete Transistor Amplifier (DTA)
It's been brought to my attention recently that I've neglected to post build notes for this one... my bad! Let's fix that.


[2] 8.2R
[1] 62R
[2] 100R
[3] 120R
[1] 150R
[2] 330R
[1] 470R
[1] 510R
[3] 680R
[1] 820R
[2] 1k
[1] 3.3k
[1] 6.8k
[1] 33k
[1] 47k
[1] 150k
[1] 270k

[2] 100nF Ceramic (C3/4, decoupling)
[2] 10uF Electrolytic (decoupling)
[1] 10uF Electrolytic (audio path)
[1] 4.7uF Electrolytic
[2] 220uF Electrolytic
[1] 1uF Film - silkscreen on v1.0 PCBs is incorrect.

[2] Ferrite Bead (you can sub a ~10R resistor or wire link)
[2] 1N4001
[2] PTC Resettable Fuse (Mouser #652-MF-R005-0)
[2] 2N458/1N914/1N4148/etc
[1] LM78L05
[3] 2N3906 or similar
[6] 2N3904 or similar

[1] 20R Trimpot (Bourns 3362 or similar)
[1] 100R Trimpot (same)
[1] A50k (Alpha 9mm or similar)
[2] B50k (same)


1) The CV and VOL jacks need to have a 5V signal applied to the N/C connection. That's what the +5V output pad is for. I simply run a resistor clipping between the two jacks' normal lugs and then connect that to the PCB.

2) Calibration - the two trimpots are for minimizing CV bleedthrough, one for each stage. (CV and VOL.) To calibrate, monitor the audio from the output. First run a 10VPP audio signal into the CV jack and adjust the 20R* trimmer for minimum amplitude. Then repeat with the VOL jack and 100R* trimmer.

* = I may have these reversed. I'm building a handful of these as we speak, when I calibrate them I'll fix this description. [/list]
Seaweed Sound
What is the output level like on this?

With all three controls at max and a 10Vpp sinewave going into the input, the output yields:

1000 Hz sine ==> 2.1Vpp
150 Hz sine ==> 360mVpp

All controls and CV inputs seem to operate correctly but the output is fairly quiet and seems to decrease as input frequency decreases (bass rolloff) making it unusable for basslines.

+/-12V rails measure okay and the +V pad is at 4.95V. I believe it's calibrated correctly and have checked component orientation and for bad solder joints. Any ideas?
I'm building 2, finding something does not match
so bom says 1x 680R; 1x6.8K; 47K* (...)
but on pcb I find 2x680r; 68k; 47K
cad you clear it please?
and what about ptc ad ferrite, what you imegined in designing?
(thanks for you modules cool )
Seaweed Sound
Yes use the resistor values as listed on the PCB (2x 680 ohm and 68k).

Also my bass rolloff issue above was due to an incorrect capacitor value: the 1nF film cap is mislabeled and should be a 1̶0̶0̶n̶F̶ 1uF cap. I'm sure there'll be an official update from MA but heads up in the meantime.
Thanks for the tip off. My pcb and panel set should arrive next week
Every MA thing I've built has stayed in my rack long after most of my earlier stuff. I expect this one will be no different!
Yep, as Seaweed Sound says, the 1nF film cap is a typo on the PCB. It should be a 1uF cap. (I know he said 100nF, but I mis-typed my explanation to him in the email so that is also my fault.)

Eventually I'll sort out where and how many zeroes this all needs. Dead Banana

That aside, though, everything else seems proper and correct with the silkscreen. thumbs up

(I also added the Mouser # for the PTC fuses to the BOM. Corrected the number of 680R resistors. Clarified the beads.)
All done!! Paired with the Haible Living VCO and SVVCF hyper

One idea for normalisation, rather than normalising 5V to both jacks, you can normalise 5V to Vol, and then normalise the output of Vol to CV.

Plugging a cable into VOL, it becomes normalised to both and you can set both pots to create a variable snappier response. Plugging into just CV, youve got VOL still connected to 5V so its normal operation.
Can someone be so kind as to spell out for me exactly how to wire the jacks. Or just upload a close up picture. The only pic I can find of the wiring is below from Schneiders and it isn't entirely revealing as to exactly what to do. It appears the unlabeled pad to the left of the +V pad is also used - what is happening with that? Also, jimi23, your way of wiring the jacks sounds interesting but my ignorance of circuitry keeps me from knowing exactly what you mean. I can assemble, I can't improvise.

That +v needs to go to CV and VOL jacks SWITCH, the pin that isn't TIP or GROUND. What exactly? It depends on what type of jack you use. This information is in the top post of this thread.
Thanks for your response, JanneI. I'm using these jacks:

Please forgive my ignorance, but I do not know which pin is which on these jacks. Neither a magnifying glass nor a google search have helped me figure it out. I have assembled quite a few modules successfully, but I guess I had more explicit instructions / images to guide me prior to this.

From above:
The CV and VOL jacks need to have a 5V signal applied to the N/C connection. That's what the +5V output pad is for. I simply run a resistor clipping between the two jacks' normal lugs and then connect that to the PCB.

I had seen that prior to posting but I can't decipher it. What is the "N/C connection?" What is / where are the "two jacks' normal lugs?" Is that the lug closest to the front of the jack, which I believe corresponds to the sleeve on a plug?

What is the black wire in the picture I posted going to?

A picture from a better angle would be so helpful.
Don't get me wrong..but.. I strongly advise to google around (normalized mono jacks), this is basic stuff. Finishing modules with step by step build guides is fine, but most of the basic electronic stuff is really, really simple to learn. Like this one you have now.

You have an eurorack patch cable and a multi-meter? If not, buy one! Plug the patch cable in to that jack and with continuity mode figure out which is which. Patch cable tip is signal, sleeve is the ground. The third connector in the jack is the switch (N/C), which is connected to the tip when there's no cable in the jack and when cable is connected this normalization breaks.

Try, fail, try again and learn! Good luck!
Ok. Thanks for responding again, JanneI. I will google some more. Have you built this module? Could you just tell me how to wire the jacks or take a pic of your jack wiring for me? If you haven't built the module and you're just trying to be helpful, thanks. I do appreciate it.

I have a multimeter. I will google what "continuity mode" is. Looking back, I think everything I've built either had a pic of any wiring or they were just pcb mount components. Maybe I'm just more of a visual learner.

I can see how my ignorance of "basic stuff" might seem silly, but frankly I don't really care to know what exactly I'm doing. I just want to finish my current crop of DIY modules. DIY has just been a much cheaper way to try to get the sounds I'm after, but I think I'll be done with DIY after this. It's been more than a year since I built anything and this time it's more tedious than I remember. It's taking too much time that I could be spending making music. I remember now that's why I stopped DIY in the first place.

I still would like a pic or some specific instructions. I don't feel like it's too much to ask for. Perhaps if negativspace sees this. I'm sure a picture of the jack wiring in this thread would be helpful for future builders of this module.

Hope I don't sound like a jerk or anything. I'm just a bit weary and frustrated at the moment I guess.
about wiring,
I connected the pads:
- (minijack ground all together) then to the last point near the power header.
- the one named V+ to normalled pins of CV and VOL as instrucion (it depends on the minijack you use, as said before one is ground, one is tip of patched cable, one is normalling connection, connected when no cable, disconnected when cable inserted)
- OUT, VOL, CV, IN to respective minijack pins.

about behaviour,
I built 2, I have the same behaviour, but I expected somethings to behave differently (all components are in the right place, and I used the 1u film cap)

- no cv cables, signal at input: I have a signal at out only if all the 3 pots are open, if 1, no matter wich, is CCW it closes the signal.
- the 3 pots behave in the same way: drive does not saturate, cv pot acts like vol,

I think it can be logic as it has the 5V as offset, and disconnecting the 5v from cv minijack silences the module...
but I imagine CV pot as attenuator for incoming cv signal, in this case CV doubles the VOL pot/cv acting as offset. as practical exapmple: if I pacth a singal at in, all pots at CW, if i turn CV pot CCW the signal closes

I expected to have 1 offset, so to open the vca, then sum an external cv to desired response, or I simply think about vca and this module is intended differently? (so "volume" make me think to the out overall volume, "drive" to a gain stage and "cv" to an attenuator af an incoming signal)
? hmmm.....
Hello, there's any Stripboard/Veroboard version? Circuit it's very simple and easily Stripboardable.
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