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rpocc
Joined: Jan 23, 2010 Posts: 17 Location: Russia
Audio files: 1
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Posted: Thu Oct 24, 2013 2:29 am Post subject:
Quad Adjustable Tom Subject description: Easy to build compact percussion module |
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Hi there!
I want to share with you one of my very first projects: Quad Adjustable Tom.
The Quad Adjustable Tom is minimalistic percussion module that consists of 4 identical analog electronic toms. The main feature of this module is that it is very compact unit built around one Quad Opamp. It is supposed that pitch adjustment is rare operation which may be done with on-board trimmer potentiometers while the front panel has only gate inputs and audio outputs which consume only 4hp of space. Such modules can be joined to kind of compact percussion cluster. The sound of this module is similar to analogue Boss rhythm-boxes. Of course, the trimmers can be replaced with full-size front-panel potentiometers.
Detailed information including schematics, stripboard layout, BOM and SPICE netlist can be found on the project page on my website. I'm not so good in English, but information on that page is enough to understand how module works and how to build it. Enjoy.
The module can be powered from any bipolar supply, but designed for +/-12v. The power consumpion and other specifitations is missing at this moment.
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_________________ Modularsynth.ru — BLog
SSSR Labs — Eurorack Modules
Quorum — My first band
Eternal Wanderers — my second band Last edited by rpocc on Fri Dec 13, 2013 1:04 am; edited 2 times in total |
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LFLab
Joined: Dec 17, 2009 Posts: 497 Location: Rosmalen, Netherlands
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Posted: Thu Oct 24, 2013 4:26 am Post subject:
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Pretty cool! Did you build it already?
Thinking of making a PCB, but it's so simple, perf/stripboard is quicker probably. |
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rpocc
Joined: Jan 23, 2010 Posts: 17 Location: Russia
Audio files: 1
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Posted: Thu Oct 24, 2013 4:49 am Post subject:
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LFLab wrote: | Pretty cool! Did you build it already?
Thinking of making a PCB, but it's so simple, perf/stripboard is quicker probably. |
A have it built (otherwise, how did I record that sample?), but didn't drilled a panel yet. Right now it looks like this:
The schematics looks pretty simple but by design there are 4 of these and AFAIR i spent much enough time to solder it because of lots of jumper wires and components used.
If you will decide to build it on a stripboard, don't forget to take a look at my layout. It is optimized to fit into minimum space, but can be optimized further to fit all of the sockets ondoard if you have stripboard with 40+ holes stripe length available. _________________ Modularsynth.ru — BLog
SSSR Labs — Eurorack Modules
Quorum — My first band
Eternal Wanderers — my second band Last edited by rpocc on Tue Oct 29, 2013 8:51 pm; edited 1 time in total |
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LFLab
Joined: Dec 17, 2009 Posts: 497 Location: Rosmalen, Netherlands
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Posted: Fri Oct 25, 2013 12:46 am Post subject:
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Ah yes, overlooked that sound sample (I was/am at work).
Does indeed look like a pretty intense stripboard layout, maybe I'll try a dual first. |
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feggster
Joined: Sep 12, 2011 Posts: 52 Location: uk
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Posted: Sat Oct 26, 2013 10:43 am Post subject:
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this is good thanks for sharing
I will attempt to build a dual tom...i have spare tl072 at the moment. |
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feggster
Joined: Sep 12, 2011 Posts: 52 Location: uk
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Posted: Tue Oct 29, 2013 4:46 am Post subject:
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I am trying to build a single tom on breadboard and have not been successful yet!
what is needed to trigger this circuit? |
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rpocc
Joined: Jan 23, 2010 Posts: 17 Location: Russia
Audio files: 1
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Posted: Tue Oct 29, 2013 6:36 am Post subject:
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feggster wrote: | I am trying to build a single tom on breadboard and have not been successful yet!
what is needed to trigger this circuit? |
Normally you need just gate signal with high level about 5v.
How did you powered the IC and a transistor? It is not drawn clear on schematics, but you need to feed +/-12v to OpAmp and +12v to transistor's Collector. Also check your transistor. _________________ Modularsynth.ru — BLog
SSSR Labs — Eurorack Modules
Quorum — My first band
Eternal Wanderers — my second band |
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donpachi
Joined: Jul 16, 2009 Posts: 81 Location: Marburg
Audio files: 2
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Posted: Tue Oct 29, 2013 12:00 pm Post subject:
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Awesome, just what I need! I guess this will work on dual 15 V power too? Thank you for this project |
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feggster
Joined: Sep 12, 2011 Posts: 52 Location: uk
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Posted: Wed Oct 30, 2013 3:55 am Post subject:
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rpocc wrote: | feggster wrote: | I am trying to build a single tom on breadboard and have not been successful yet!
what is needed to trigger this circuit? |
Normally you need just gate signal with high level about 5v.
How did you powered the IC and a transistor? It is not drawn clear on schematics, but you need to feed +/-12v to OpAmp and +12v to transistor's Collector. Also check your transistor. |
I did power the transistor and op amp correctly, I will have to check it again today, I have noticed parts of the breadboard seem to be dead! |
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rpocc
Joined: Jan 23, 2010 Posts: 17 Location: Russia
Audio files: 1
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Posted: Wed Oct 30, 2013 6:30 am Post subject:
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donpachi wrote: | Awesome, just what I need! I guess this will work on dual 15 V power too? Thank you for this project |
The pitch may be lower on 15v rails and trigger curcuit may be less sensitive. If I remember the Ohm's law right, you can try following values for components to correct it:
C2: 180n
C3, C4: 8.2n
R8: 820R
But this to be confirmed by somebody. Right now I have no time at all for breadboarding or experimenting. _________________ Modularsynth.ru — BLog
SSSR Labs — Eurorack Modules
Quorum — My first band
Eternal Wanderers — my second band |
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donpachi
Joined: Jul 16, 2009 Posts: 81 Location: Marburg
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Posted: Wed Oct 30, 2013 2:02 pm Post subject:
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Thanks a bunch rpocc
I will give it a try very soon and report back here. |
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flab
Joined: Feb 13, 2012 Posts: 65 Location: Glasgow
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Posted: Wed Oct 30, 2013 4:57 pm Post subject:
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i build a dual version of that two days ago -tryed manydifferent values for C3 and C4- do you think that it needa amplification at the output ? a buffer maybe |
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rpocc
Joined: Jan 23, 2010 Posts: 17 Location: Russia
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Posted: Wed Oct 30, 2013 11:34 pm Post subject:
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donpachi wrote: | Thanks a bunch rpocc
I will give it a try very soon and report back here. |
By the way, I taking back my words about values.
It is not necessary to tweak values for components of the bridged t-network filter, you may only try to tweak values for R2/C2
flab wrote: | i build a dual version of that two days ago -tryed manydifferent values for C3 and C4- do you think that it needa amplification at the output ? a buffer maybe |
You can always try. I didn't find a use for it.
Keep in mind that values for R6—R8 and C3—C4 is calculated to achieve reasonable frequency range with maximum available Q value. They are all depend on each other.
_________________ Modularsynth.ru — BLog
SSSR Labs — Eurorack Modules
Quorum — My first band
Eternal Wanderers — my second band |
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roglok
Joined: Aug 28, 2010 Posts: 202 Location: uptown
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Posted: Thu Oct 31, 2013 7:37 am Post subject:
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thanks for posting this. will definitely try it out. |
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rpocc
Joined: Jan 23, 2010 Posts: 17 Location: Russia
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Posted: Fri Dec 13, 2013 1:06 am Post subject:
Errata |
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Sorry guys, I don't know how it happened, but value of R6 on the Schematic and BOM was incorrect. Right value should be 10M instead of 1M! Files are updated. _________________ Modularsynth.ru — BLog
SSSR Labs — Eurorack Modules
Quorum — My first band
Eternal Wanderers — my second band |
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donpachi
Joined: Jul 16, 2009 Posts: 81 Location: Marburg
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duff
Joined: Jun 02, 2013 Posts: 11 Location: UK
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Posted: Sat Mar 22, 2014 3:35 am Post subject:
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I have just built up one of these and it appears to work, but I find I get a lot of gate sound through the outputs. And not just the output that the gate relates to. I.e. a gate in to input 1 and I can hear it on all outs (and in fact the other inputs ). Is this expected? |
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donpachi
Joined: Jul 16, 2009 Posts: 81 Location: Marburg
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Posted: Sat Mar 22, 2014 5:55 am Post subject:
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duff wrote: | I have just built up one of these and it appears to work, but I find I get a lot of gate sound through the outputs. And not just the output that the gate relates to. I.e. a gate in to input 1 and I can hear it on all outs (and in fact the other inputs ). Is this expected? |
Do you mean a DC plop kind of sound? It does not happen with my build, all four toms are independent and do not transmit any DC as far as I can tell.
My guess is that some filtering caps could have a wrong value (e.g. C2, 220 nF?), but I am far from being a circuit pro. If the problem transfers to all four toms, the gate somehow affects the power rails, I think. |
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duff
Joined: Jun 02, 2013 Posts: 11 Location: UK
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Posted: Sat Mar 22, 2014 7:41 am Post subject:
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donpachi wrote: |
Do you mean a DC plop kind of sound? It does not happen with my build, all four toms are independent and do not transmit any DC as far as I can tell.
My guess is that some filtering caps could have a wrong value (e.g. C2, 220 nF?), but I am far from being a circuit pro. If the problem transfers to all four toms, the gate somehow affects the power rails, I think. |
Thanks for the reply, and yes, that is exactly the sound.
I am pretty sure I have the right values of caps in the right places but it is the same on all 4 inputs so I probably have done something wrong thinking it is right, hence can't see the error. I'm still learning component markings, let alone electronics, but C2 should have all come from a bag labelled 220n and are marked .22 on the package (which I assume to be .22uf and hence 220n) . See below (note everything is 1 column left of the schematic as my power connector is 1 row - although the plastic covers the links on the second row)
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donpachi
Joined: Jul 16, 2009 Posts: 81 Location: Marburg
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Posted: Sat Mar 22, 2014 8:36 am Post subject:
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duff wrote: | donpachi wrote: |
Do you mean a DC plop kind of sound? It does not happen with my build, all four toms are independent and do not transmit any DC as far as I can tell.
My guess is that some filtering caps could have a wrong value (e.g. C2, 220 nF?), but I am far from being a circuit pro. If the problem transfers to all four toms, the gate somehow affects the power rails, I think. |
Thanks for the reply, and yes, that is exactly the sound. |
Thank you for the picture, those cap values are correct. Could you post a picture of the bottom of the board? Maybe someone or even myself can spot something. Also, are your I/O jacks grounded on the sleeve (assuming that you are not using bananas)? |
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duff
Joined: Jun 02, 2013 Posts: 11 Location: UK
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donpachi
Joined: Jul 16, 2009 Posts: 81 Location: Marburg
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Posted: Sat Mar 22, 2014 2:19 pm Post subject:
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Hmm, there is no error that is obvious to me. Your continuity checks say that the traces were cut where they should be cut. Assuming that you used 2N3904 transistors as suggested, their orientation is correct. Did you measure whether the TL074 is getting the correct voltages at its power pins? +12 or +15 V at pin 4, -12 or -15 V at pin 11. You could swap that opamp for another one just to rule out that part as the culprit.
No more ideas from me today, I will check one tom section in detail tomorrow.
Gate signals are usually between +5 and +10 V, so your oscillator should be OK. I used a square wave LFO which cycles between -5 and +5 V to trigger the toms. |
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duff
Joined: Jun 02, 2013 Posts: 11 Location: UK
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Posted: Sun Mar 23, 2014 4:31 am Post subject:
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Thanks for your ideas. The transistors are all 3904s and the TL074 is getting +/- 12 at the correct pins and I have swapped it out for another with no change.
However as I typed that I noticed one significant difference between my build and the schematic - R5 is 100R not 100K as I have used
I'm guessing (possibly wild) that this means the transistor isn't switching and I am getting the gate through the divider.
Whilst double checking that I also notice the BOM states R8 as 680K, but I have gone with 680R as per the schematic. |
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donpachi
Joined: Jul 16, 2009 Posts: 81 Location: Marburg
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Posted: Sun Mar 23, 2014 4:47 am Post subject:
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The 100R problem sounds like the solution. I was just about to check the resistor color codes, but will postpone, probably you solved it yourself.
I used 680R for R8, and I guess that is the correct value |
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amdagan
Joined: Jun 21, 2013 Posts: 9 Location: Iron mountain
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Posted: Tue Jun 17, 2014 1:39 am Post subject:
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rpocc, thanks for posting this!
I'm wondering what C1 does, and why it is so big (470nF)?
100k and 470nF gives a tau of 47ms, seems like this would introduce a delay in triggering the tom. Not sure if it would be long enough to be noticeable but I'm thinking perhaps I'll reduce C1 to maybe 47nF or so, in order to be sure that the delay won't be noticeable.
What does C1 do, anyway? My best guess is, it filters out short spikes at the input that might cause false triggers, or multiple triggers if the trigger waveform is not a nice clean pulse. Am I barking up the wrong tree?
Yeah I know, I should just try it and report back, unfortunately my time at the workbench is very limited at the moment. |
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