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 Forum index » DIY Hardware and Software
TR-808 Voice STRIP Boards...
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mrand



Joined: Mar 30, 2014
Posts: 27
Location: Ottawa

PostPosted: Thu Jun 19, 2014 4:45 am    Post subject: Reply with quote  Mark this post and the followings unread

Best wishes to you in your difficult times, minus.
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Snaper



Joined: Feb 28, 2014
Posts: 170
Location: Hungary

PostPosted: Thu Jun 19, 2014 4:47 am    Post subject: Reply with quote  Mark this post and the followings unread

Yeah, all the bests!
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Alfredo



Joined: Nov 20, 2008
Posts: 20
Location: Spain

PostPosted: Fri Jun 20, 2014 4:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

Big thanks -minus- and don´t lost dreams man, best wishes, my life is shit but I found some fresh air in the modular hobby so let´s go rim shot master!!
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isak



Joined: Dec 13, 2009
Posts: 812
Location: Israel
Audio files: 18

PostPosted: Sat Jun 21, 2014 4:10 am    Post subject: Reply with quote  Mark this post and the followings unread

dear minus

may there will be light in dark places for you.
i wish you all the best my friend.

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-minus-



Joined: Oct 26, 2008
Posts: 779

Audio files: 13

PostPosted: Sat Jun 21, 2014 9:21 am    Post subject: Reply with quote  Mark this post and the followings unread

Hey, thanks for all the kind messages- it means a lot to me. Life can be shit at times but I'm learning to be more positive (or that's the theory anyway). I can be such a negative depressing person at times. Laughing

The diy synth thing is great therapy. It takes ones mind from the troubles of life. It teaches us patience. Builds confidence. There are some really smart people on this forum. Everything I have learnt in this field has come from this site and I'm grateful of that. I'm a great believer in informal education. You can teach yourself anything if you really want to. It's easy to look at that 2014 build pictures thread and scroll past those photos. But there is a lot of work in each of those builds, and years of knowledge in many. I'm in awe.

I'm looking at all my bagged up boards tonight, which is a good start. I'm going to try get back to this next week. Keep on building everyone! It's a damn good hobby.
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Lysergist



Joined: Jan 14, 2016
Posts: 8
Location: France

PostPosted: Thu Jan 14, 2016 6:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi everyone ! And many thanks to you minus ! You have made my months ! Everything works perfectly and sounds awesome !

I only have a little issue with the snare module, it works great but there's a constant HF, i'm sure the noise leaks, any idea how to fix it ? By changing the noise pot maybe ?

Cheers, and you have my eternal gratitude
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elmegil



Joined: Mar 20, 2012
Posts: 1754
Location: Chicago
Audio files: 15

PostPosted: Thu Jan 14, 2016 10:53 pm    Post subject: Reply with quote  Mark this post and the followings unread

How are things wired up? Maybe you need shielded wire from the output to the jack?
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Lysergist



Joined: Jan 14, 2016
Posts: 8
Location: France

PostPosted: Fri Jan 15, 2016 7:02 am    Post subject: Reply with quote  Mark this post and the followings unread

Mhh it doesn't comes from the jack, other modules are clean with the same jack, it's not a ground loop. What i here is a constant noise coming from the snare. It's weak but enough to disturb me, it's a bit noisy. I think there's something to adjust in the noise part, the pot is ok so maybe some resistors in the noise part circuit.
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elmegil



Joined: Mar 20, 2012
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Location: Chicago
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PostPosted: Fri Jan 15, 2016 7:07 am    Post subject: Reply with quote  Mark this post and the followings unread

I'm talking about the output jack. Perhaps the noise generation is inducing noise on the output wiring that you're picking up as you feed the output signal further downstream.

Obviously it's not "The jack", but the wiring could be -- if you shield the connection you can rule it out.

Also, stripboard uses lots of long parallel runs, you should check where the noise signal runs through the stripboard and what other traces are nearby and could be inductively coupled.

If you're hearing it constantly, even when there are no triggers, it will have to be somewhere after the "vca" section though. That's why I jump to the wiring to the output jack.
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elmegil



Joined: Mar 20, 2012
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Location: Chicago
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PostPosted: Fri Jan 15, 2016 7:59 am    Post subject: Reply with quote  Mark this post and the followings unread

So, here's the schematic for the snare. Obviously the standalone stripboard has its own white noise generation as well, that comes into this circuit in the lower right and into the base of Q48.

If you have the level (VR7) *all the way down* and you're still getting the noise generator's output, then you're likely getting inductive coupling between the trace that goes from the white noise to Q48 and the trace that goes from the op amp tot he 1K resistor and out to the wiring going to the jack.

Question: does the snappy control affect the sound of the bleed in the output? If so, then it's not that initial trace, but some other trace within that "snappy" section in the bottom center.

I don't see the SD stripboard in this thread, so I don't know which one you're working from to speculate further. I've never had a lot of luck finding old stuff on these forums, even when I know it's out there somewhere. My own SD that I mentioned above in this thread was built on protoboard rather than stripboard, straight from the schematic.

As noted, I think your best first option is to get some shielded wire, ground the shield (on one end only) and run that in place of whatever wire you have running from the board to the jack. After that, you need to actually look at how things are routed on the stripboard.


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Lysergist



Joined: Jan 14, 2016
Posts: 8
Location: France

PostPosted: Fri Jan 15, 2016 8:14 am    Post subject: Reply with quote  Mark this post and the followings unread

Wow thank you so much for your implication ! I'll check this !
You can find the stripboard version on this thread :
http://electro-music.com/forum/topic-45134.html
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elmegil



Joined: Mar 20, 2012
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Location: Chicago
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PostPosted: Fri Jan 15, 2016 8:49 am    Post subject: Reply with quote  Mark this post and the followings unread

So the noise path does not appear to run particularly close to the output path, BUT both the output op amp and the noise op amp are on the same chip, IC2, so that could be relevant.

C21 and C22 are the decoupling caps for that chips power supply, you might want to make sure they've got good solder joints. Measure the power supply pins and see if you are getting any extra noise there, and possibly increase the size of those two?

I'm still going to bet on the shielded wire though Very Happy
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Lysergist



Joined: Jan 14, 2016
Posts: 8
Location: France

PostPosted: Fri Jan 15, 2016 9:25 am    Post subject: Reply with quote  Mark this post and the followings unread

Hahaha ok i've just spotted something. I'm so stupid. The constant noise is normal i think, i worked with the level pot (the volume, not the noise) all the way up. The output volume was low. I did it for compensate the low volume caused by the low trigger. I've a beatstep pro wich triggers almost everything. All the other modules are well triggered. But it seems that in this case the snare needs higher voltage to works correctly. With higher trigger, i've to lower the volume, and the noise problem disapears. So stupid... Sorry haha. In fact there's only one problem, the triggering. So maybe i have to change a resistor in the trigger part.
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elmegil



Joined: Mar 20, 2012
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Location: Chicago
Audio files: 15

PostPosted: Fri Jan 15, 2016 10:28 am    Post subject: Reply with quote  Mark this post and the followings unread

No need to apologize Smile

The original circuit expects a 4V -> 14V level on the accent input.

What are you putting into that? How do you have the trigger and accent hooked up when you're using the BSP?

Edit:

the BSP is supposed to send 10V gates which should be plenty high, but you might check the width of the trigger as well. Original circuit expects 1ms triggers on the accent input and wider than that for the "trigger" input. (Long story, ask if you like Smile )
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Lysergist



Joined: Jan 14, 2016
Posts: 8
Location: France

PostPosted: Fri Jan 15, 2016 11:20 am    Post subject: Reply with quote  Mark this post and the followings unread

Well, after few hours... A 220ohm instead of 10K in the trigger section... LOL.
Everything works fine now.
I've found some differences between the original version and Eric Archer's one, I thought TRIG and ACCENT were inverted.
But in fact that's only the inscription in the original schematic that are inverted.


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elmegil



Joined: Mar 20, 2012
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Location: Chicago
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PostPosted: Fri Jan 15, 2016 3:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

That's an artifact of that long story....

The way the original worked, the sequencer itself was done by a microprocessor.

There was a common trigger bus that went to all voices all the time. This is the "TRIG" input you see in the picture I posted. The trigger was 1) 1ms wide and 2) varying height, depending on the setting of accent for the given clock step. If accent was not active it was 4V or so. If it was active, it would vary from there up to 14V. How much it varied was set by the accent level pot.

So then you ask: why don't all the voices sound every single time?

Because there was a second input that was basically a "gate" for the voice. If you look at that schematic again, if the SD input is 0, then the NPN connected to it is off, and when the trigger comes through, there's no where for the voltage to flow. If it's on, then that transistor conducts, and the trigger comes in and effectively goes through a voltage divider that turns on the PNP transistor and actually injects the trigger into the voice.

So in the normal course of things, if the snare was to fire on "this step", the microprocessor would raise the gate for the snare, then generate the common trigger with it's accent level, then lower the gate.


When Eric Archer adapted the circuits for standalone voices, I think he felt it was more straightforward to make the accent a "level" input to the voice, and use a trigger in place of the gate. And in most cases that works just fine. On my own standalone 808 BD module I have normalled the trigger to the accent, but I could just as well have put it on the wiper of a pot doing voltage division.


I could definitely see how having a 220 in place of that 10K would be a problem Very Happy.
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Lysergist



Joined: Jan 14, 2016
Posts: 8
Location: France

PostPosted: Mon Jan 18, 2016 9:17 am    Post subject: Reply with quote  Mark this post and the followings unread

I admire your knowledge ! Thanks for helping ! Yes i've seen this way to do it.


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elmegil



Joined: Mar 20, 2012
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PostPosted: Mon Jan 18, 2016 9:53 pm    Post subject: Reply with quote  Mark this post and the followings unread

That should work fine.... though you may want to put an additional resistor between the 50K and ground. Back of the envelope suggests about 15K should put the bottom side of the pot at 4V, which was the minimum the original circuit expected to be at the accent point.

Also, I don't think the stripboard layout you're working from has it, but you'll notice that Eric Archer's version also puts a gate -> trigger converter on the front end of the trigger input, to be sure that is just a pulse rather than a possibly extended gate (which won't respond the way you expect). If you're tying accent to a steady voltage, I think that's a good idea to do as well.
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LektroiD



Joined: Aug 23, 2008
Posts: 991
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PostPosted: Tue Feb 02, 2016 4:38 am    Post subject: Reply with quote  Mark this post and the followings unread

Any thoughts on stripboarding the sequencer?

I'm also thinking of consolidating all the individual voice boards to a single large stripboard. Wondering how easy this will be...

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elmegil



Joined: Mar 20, 2012
Posts: 1754
Location: Chicago
Audio files: 15

PostPosted: Tue Feb 02, 2016 6:54 am    Post subject: Reply with quote  Mark this post and the followings unread

I put the four pieces that use the same noise source (cymbals, hats, cowbell) on two 4x5 stripboards.... it was doable, but just barely. I'd expect an 8x4 to be difficult at best without redoing significant bits. I haven't seen much bigger stripboard....
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