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



Joined: Mar 20, 2012
Posts: 2008
Location: Chicago
Audio files: 16

PostPosted: Mon Oct 30, 2017 6:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

Apollo View wrote:
elmegil wrote:
Playing around with a more complex sequence coming out of the Arduino, I found that it sounded interesting if I jumped the input level of the bass drum alternately to over drive it...

Might be an artifact of the battery based 4 input mixer too, but I like it.


I have a working perfboard version of the kick.

I would love to be able to get the overdriven sound you have. Could you please explain how you achieved it?


That was 5 years ago.... Very Happy


I figure either 1) I was using 15V and cranking the accent all the way up or 2) the battery powered mixer. If I'm recalling correctly it was some cheap thing, not much different from this:

https://www.zzounds.com/item--BEHMX400?siid=38044&-zJ8qAljHjJZX1E4X97wMUA9u3l-VlsWuHKKe7WM3ByjsaAitxEALw_wcB=

Though mine was not a Behringer.
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Apollo View



Joined: Sep 24, 2017
Posts: 19
Location: London

PostPosted: Mon Oct 30, 2017 6:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

Wow, 5 years. I'm a little late to the party.

I've got accent tied to +15V.

So i'm guessing the little mixer box can add some serious drive/saturation...

I might have to invest.

Thanks
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elmegil



Joined: Mar 20, 2012
Posts: 2008
Location: Chicago
Audio files: 16

PostPosted: Mon Oct 30, 2017 8:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

I should point out that I actually implemented the *original* accent method, not the workaround that so many have done of tying the accent to a fixed V+.


This is something I've been on about for all of those 5 years Smile

Attached is a more recent schematic that I've been using for some Euro based PCBs.

It differs from what I would have been using all those ages ago in that it actually converts the incoming trigger into a 1ms pulse, its output "cmnTrig" is tied to the "accent" input so-called of the voice and the usual "trigger" input is actually a voice enable gate, so I have tied it to +5V (which again is what it would have been in the original).

When I was triggering from an Arduino, I didn't need to convert anything to a 1ms pulse because I had complete control over that from the Arduino, and I did go ahead and raise and lower the enable gate instead of leaving it tied to +5 all the time.


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Apollo View



Joined: Sep 24, 2017
Posts: 19
Location: London

PostPosted: Sat Nov 04, 2017 6:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

Nice one thanks for the heads up. I might need something like that when I have a few more modules and a more sophisticated way of triggering than just pushing a button.

Did using this circuit affect the timbre? I'm guessing the higher 'Accent' the greater the gain and the more distortion.

I have my kick accent tied to +15 but don't get the same overdrive as you had achieved.

So could lowering the value of the resistors between +15 increase the gain and get more drive? Something like a 1M pot at R10?


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Apollo View



Joined: Sep 24, 2017
Posts: 19
Location: London

PostPosted: Fri Jan 05, 2018 9:44 am    Post subject: Cowbell Reply with quote  Mark this post and the followings unread

Hi all.

I have 'successfully' made the voice board, cymbal, hi-hats and cowbell.

Minus if you are out there still. Do you have the schematic for the cowbell?

I have some strange behaviour. I can get a cowbell sound but not be triggering from the correct node.

It sounds great actually, I have used the specified 1.85ms and 1.25ms tuning and it sounds almost exactly like an original 808.

I was using a 5v connection and momentary push switch, but have now switched to 9V battery for testing.


Essentially what I have. It won't sound from triggering at R15 or T3. However will sound from R4, R8, R13 or T4. In fact, I have now removed T3 completely from the circuit and I still get it to trigger from the wrong above-mentioned points. However, there is a very low-level signal leakage somewhere. I can just about hear the cowbell sound continuously. This was the case even before removing T3

So I'm curious comparing to the original schematic, the triggering circuit, T3 & T4 doesn't seem correct. Why is the T4 emitter and R12 on the same rail as R2, R6 & R7 and all heading off to the level pot? Shouldn't T4 emitter and R12 just be grounded?


Any help is gratefully received.
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Apollo View



Joined: Sep 24, 2017
Posts: 19
Location: London

PostPosted: Fri Jan 05, 2018 10:20 am    Post subject: Re: Cowbell Reply with quote  Mark this post and the followings unread

Ok, so I have possibly solved this myself, any feedback would really be appreciated.

I the solution hasn't stopped the slight signal leak, however, the output is now much louder, so my input gain to the soundcard is lower so the 'noise' is less noticeable.

I have made two cuts to isolate T3 and R12 from the Level pot path, added jumpers so R2, R6, R7 still go to the level pot. And added a jumper so T3's emitter and R12 now go to ground.

Hope this helps others in future.


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Apollo View



Joined: Sep 24, 2017
Posts: 19
Location: London

PostPosted: Tue Feb 13, 2018 4:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

Help Please...

I'm pulling my hair out and was hoping someone could check my working...

I stupidly didn't just copy lysergist's stripboard layout of the rimshot/clave as I was trying to learn how to use Fritzing, and potentially get a PCB fabricated.

However, as far as I can see my schematic matches the original 808 schematics,
which should mean my layout is fine, but for both sounds, I get metallic 'PINGS' rather than the appropriate Rimshot/clave noises.

I know its a big ask, but any chance someone could have a look at my fritzing file and see where I must have done something wrong?

https://www.dropbox.com/s/fgwoaetpe78z07i/808%20Rim%20Shot%20%3A%20Clave%20TL074%20PCB.fzz?dl=0

Thanks in advance.
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elmegil



Joined: Mar 20, 2012
Posts: 2008
Location: Chicago
Audio files: 16

PostPosted: Tue Feb 13, 2018 5:59 pm    Post subject: Reply with quote  Mark this post and the followings unread

First thing that jumps out at me is that you can't power an op amp off of +5V and -12V.....


edit: but I see that you're calling +12V 5V for some reason so that's just confusing, not wrong Smile
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elmegil



Joined: Mar 20, 2012
Posts: 2008
Location: Chicago
Audio files: 16

PostPosted: Tue Feb 13, 2018 6:39 pm    Post subject: Reply with quote  Mark this post and the followings unread

Why are C9 and C10 increased from 4.7nF to 100nF? I see your notation looks like that's deliberate....

Same with C13 & C14

All your diodes are 1N4001's which is atypical. Normally these would be signal diodes, so 1N914 or 1N4148.

Note that Q1 is a FET, not BJT. I know you've got the transistor noted there, but your symbol is for a BJT....

C6 has the dual notation, but "your" notation is 0pF?? Similarly for C5. Right value in parens, what's the "0pF"?

C3 is marked as .022pF but it should be .0022 just like C1 & C2.

I don't see a resistance value in the original for R324 (your R27), how did you arrive at 220K?



I suspect the most likely problems are the 100nF instead of basically 5nF caps, those will likely move the frequency of those bridged-T networks way down (20x!), and/or C3 having the wrong value.
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Apollo View



Joined: Sep 24, 2017
Posts: 19
Location: London

PostPosted: Wed Feb 14, 2018 3:27 am    Post subject: Reply with quote  Mark this post and the followings unread

Wow, thanks for the speedy reply. Sorry for the confusion, I should have tidied up the labelling and I should have said in my original post some of the teething problems I have run into with Fritzing.

For some reason, it wouldn't allow me to change the values on many of the components, so I used what was available and included the true value with the part number.

You're absolutely right
So yes +5V is +12. The diodes I'm using are 1N914. I couldn't find a JFET symbol.

The 0pF was just to force me to look at the parens.

Good spot I mis-labelled C3, but actually used a 0.0022 in the circuit.


The 100nF caps are all 4700pF as the original.

I think I got the value of R324 from lysergist layout. Would changing this value affect the tuning?

Thanks again for running your keen eye over this and sorry for the confusing labelling, I'm just getting to grips with Fritzing. But all values are as original except the R324 220K guess. So I'm still scratching my head with this!

Hahahah argh
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Apollo View



Joined: Sep 24, 2017
Posts: 19
Location: London

PostPosted: Wed Feb 14, 2018 3:37 am    Post subject: Reply with quote  Mark this post and the followings unread

Things I should also mention.

My pot doesn't affect the level at all?

I am powering this from +-15V

and accent is tied to +15 could this be overdriving the circuit too much?
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elmegil



Joined: Mar 20, 2012
Posts: 2008
Location: Chicago
Audio files: 16

PostPosted: Wed Feb 14, 2018 6:44 am    Post subject: Reply with quote  Mark this post and the followings unread

Accent at 15V is maybe a bit high. Spec is 4V to 14V.

But it looks like you have a Euro connector, are you not connecting to +/- 12V?

I suppose as a percentage of Vcc that still puts accent pretty high, you might try putting an additional 1 or 2K between VCC and the junction of R35 and Q5.

I did *not* look over your stripboard, BTW, to ensure it was right. I have found that stripboard work can be a lot more problematic to troubleshoot than other things, so....

Maybe wire a 1M pot in for that R324 thing and if changing the value there changes your circuit's behavior?

Otherwise my main guess is that metallic pings are definitely a sign of too *high* a frequency, so I'd guess there's either a short in one of the bridged T's or else an incorrect resistor value (which in the symmetry of this thing is more likely than an incorrect cap).
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Apollo View



Joined: Sep 24, 2017
Posts: 19
Location: London

PostPosted: Wed Feb 14, 2018 6:50 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks so much.

I know what you mean about Stripboard being problematic to troubleshoot. I've been going over it for the last 2 weeks trying to find the error, and still no luck.

I put a 2.3M resistor before accent top reduce it to 12.5V and it had no effect.

Greta idea about the 1M pot. I'll see what it does.

And I'll check again for shorts, wrong cap/resitors.

Cheers man.

In the meantime I'm just soldering lysergist's layout to compare.

many thanks
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Apollo View



Joined: Sep 24, 2017
Posts: 19
Location: London

PostPosted: Wed Feb 14, 2018 7:13 am    Post subject: Reply with quote  Mark this post and the followings unread

Oh and yes.

I decided to use eurorack connectors, but my power supply is variable 12-15v. FC Routemaster by Rick Holt. so I decided to leave it at 15V as the Original 808n PS.
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Apollo View



Joined: Sep 24, 2017
Posts: 19
Location: London

PostPosted: Wed Feb 21, 2018 4:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

Sooooo I've been bashing my head against the wall and tearing my hair out of the rimshot.

I've checked over everything a million times.

I can't see a single fault. Just as I was about to throw it in the bin.

I noticed it actually makes a rimshot sound when I turn the power supply off.

I don't have the mental skills to analyse this behaviour to diagnose the problem, but I'm sure there's someone out there clever than me who can help...

My thoughts were it could be transistor related.

Does this, power off = make the right noise mean I have one specific Transistor back to front? Are all my resistors back to front?

Had anyone had experience with this before who can shed some light?

Many thanks in advance.
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Apollo View



Joined: Sep 24, 2017
Posts: 19
Location: London

PostPosted: Yesterday, at 10:51 am    Post subject: Reply with quote  Mark this post and the followings unread

Update,

Currently working to get my version of the layout working, as per the link to my Fritzing file.

I can now get to trigger the sounds but from the wrong place.

Applying a voltage to any resistor connected to the base of Q60 will trigger the sounds. They sound authentic but have a large amount of hum/noise with them. The hum is only present when triggering so the muting circuit is working.

I have made a little high pass filter to make it more acceptable but the hum is still present. But I'd much prefer for it to not need the high pass filter, it cuts out important frequencies from the rimshot.

And I can't get my head around why this won't trigger from R297?

Please help.

Last edited by Apollo View on Yesterday, at 11:04 am; edited 1 time in total
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Apollo View



Joined: Sep 24, 2017
Posts: 19
Location: London

PostPosted: Yesterday, at 10:52 am    Post subject: Reply with quote  Mark this post and the followings unread

note:

I have changed all my transistors from BC546/BC556 to BC549/BC559 as i thought the low noise versions might solve the hum but no luck.

And the VR16 100kA still does not affect the level?
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