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 Forum index » DIY Hardware and Software
Quad Adjustable Tom
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rpocc



Joined: Jan 23, 2010
Posts: 15
Location: Russia
Audio files: 1

PostPosted: 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.


adjustable_tom_schematics_v3.png
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adjustable_tom_test1.mp3
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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: 187
Location: Rosmalen, Netherlands

PostPosted: Thu Oct 24, 2013 4:26 am    Post subject: Reply with quote  Mark this post and the followings unread

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: 15
Location: Russia
Audio files: 1

PostPosted: Thu Oct 24, 2013 4:49 am    Post subject: Reply with quote  Mark this post and the followings unread

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:
Posted Image, might have been reduced in size. Click Image to view fullscreen.

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.

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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: 187
Location: Rosmalen, Netherlands

PostPosted: Fri Oct 25, 2013 12:46 am    Post subject: Reply with quote  Mark this post and the followings unread

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: 51
Location: uk

PostPosted: Sat Oct 26, 2013 10:43 am    Post subject: Reply with quote  Mark this post and the followings unread

this is good Smile 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: 51
Location: uk

PostPosted: Tue Oct 29, 2013 4:46 am    Post subject: Reply with quote  Mark this post and the followings unread

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: 15
Location: Russia
Audio files: 1

PostPosted: Tue Oct 29, 2013 6:36 am    Post subject: Reply with quote  Mark this post and the followings unread

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.

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donpachi



Joined: Jul 16, 2009
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PostPosted: Tue Oct 29, 2013 12:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

Awesome, just what I need! I guess this will work on dual 15 V power too? Thank you for this project Cool
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feggster



Joined: Sep 12, 2011
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PostPosted: Wed Oct 30, 2013 3:55 am    Post subject: Reply with quote  Mark this post and the followings unread

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
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PostPosted: Wed Oct 30, 2013 6:30 am    Post subject: Reply with quote  Mark this post and the followings unread

donpachi wrote:
Awesome, just what I need! I guess this will work on dual 15 V power too? Thank you for this project Cool


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.

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donpachi



Joined: Jul 16, 2009
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PostPosted: Wed Oct 30, 2013 2:02 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks a bunch rpocc Very Happy
I will give it a try very soon and report back here.
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flab



Joined: Feb 13, 2012
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PostPosted: Wed Oct 30, 2013 4:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

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
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PostPosted: Wed Oct 30, 2013 11:34 pm    Post subject: Reply with quote  Mark this post and the followings unread

donpachi wrote:
Thanks a bunch rpocc Very Happy
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.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

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roglok



Joined: Aug 28, 2010
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PostPosted: Thu Oct 31, 2013 7:37 am    Post subject: Reply with quote  Mark this post and the followings unread

thanks for posting this. will definitely try it out.
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rpocc



Joined: Jan 23, 2010
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PostPosted: Fri Dec 13, 2013 1:06 am    Post subject: Errata Reply with quote  Mark this post and the followings unread

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.
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donpachi



Joined: Jul 16, 2009
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PostPosted: Sun Jan 05, 2014 2:46 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thank you again! My build uses a 4 TE panel, the sound is very nice Cool Please don´t mind the bad quality of the picture.
The circuit is running off a +/-15 V supply and can be triggered by 5 V gates, I made no component substitutions. One of the four toms is not always working, but that will be conquered, too Very Happy
Highly recommended, four great drums made in a single afternoon!


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duff



Joined: Jun 02, 2013
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PostPosted: Sat Mar 22, 2014 3:35 am    Post subject: Reply with quote  Mark this post and the followings unread

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



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PostPosted: Sat Mar 22, 2014 5:55 am    Post subject: Reply with quote  Mark this post and the followings unread

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
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PostPosted: Sat Mar 22, 2014 7:41 am    Post subject: Reply with quote  Mark this post and the followings unread

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



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PostPosted: Sat Mar 22, 2014 8:36 am    Post subject: Reply with quote  Mark this post and the followings unread

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
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PostPosted: Sat Mar 22, 2014 10:00 am    Post subject: Reply with quote  Mark this post and the followings unread

I'm using 3.5mm jacks to test and only did not have them grounded, but I just added some grounds and this appeared not to make any difference.

I am currently using a pulse from an OSC to fire it as the wall wart for my bench supply is also the one that powers my more suitable modules, so it is an either or. Is the 'gate' this produces just too strong?

This mess is the back Rolling Eyes. I have obviously made a few alterations here and there to get to this point, but I have done some continuity checks and all appeared fine on that front.


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donpachi



Joined: Jul 16, 2009
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PostPosted: Sat Mar 22, 2014 2:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

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
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PostPosted: Sun Mar 23, 2014 4:31 am    Post subject: Reply with quote  Mark this post and the followings unread

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 doh

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



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PostPosted: Sun Mar 23, 2014 4:47 am    Post subject:   Reply with quote  Mark this post and the followings unread

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 Cool
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amdagan



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PostPosted: Tue Jun 17, 2014 1:39 am    Post subject: Reply with quote  Mark this post and the followings unread

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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