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



Joined: Jan 14, 2016
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PostPosted: Wed Apr 12, 2017 3:20 am    Post subject: Reply with quote  Mark this post and the followings unread

Yes Sir your are right ! Rectified.
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elmegil



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PostPosted: Wed Apr 12, 2017 5:28 am    Post subject: Reply with quote  Mark this post and the followings unread

Don't ask why I'm going over it in such detail Wink
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dcjim



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PostPosted: Wed Apr 26, 2017 1:38 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi

If I replace the 2M pots for hi-hat and cymbal decay with 1M pots, will this shorten the maximum decay time or lengthen the minimum decay time?

Thanks
Jim
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elmegil



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PostPosted: Thu Apr 27, 2017 3:59 pm    Post subject: Reply with quote  Mark this post and the followings unread

The way I read it, it would reduce your total decay.

2M pots other than huge sizes are hard to come by though. You could conceivably increase the series resistor some to compensate, but you don't want to cut off too much of the other end.....
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Sebo



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PostPosted: Thu Apr 27, 2017 4:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

What I do in my clone is using a stereo 1M pot, and put the "sides" in series, so it actually go from 0 ohms to 2M. Only works when the pot is in variable resistor configuration (not in divider configuration).
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lysergist



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PostPosted: Thu May 18, 2017 4:41 am    Post subject: Reply with quote  Mark this post and the followings unread

I have updated my post above. The clap works perfectly well !
But i still have a little issue with the maracas, the noise is constantly leaking through the vca and can be heard even if the clap is selected. I had to cut the right jumper coming from the noise to the maracas to avoid this constant leaking that spreads troughout the module. I have checked the maracas vca section but looks ok.
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LektroiD



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PostPosted: Wed Jun 28, 2017 2:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

The track cuts don't match the topside (to the left of R334 and next to D65), I don't know if there's any more yet, I've not studied it closely enough

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

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LektroiD



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PostPosted: Wed Jun 28, 2017 6:32 pm    Post subject: Reply with quote  Mark this post and the followings unread

Not Alphas, but 2M linear pots... HERE!
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lysergist



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PostPosted: Thu Jul 06, 2017 12:07 pm    Post subject: Reply with quote  Mark this post and the followings unread

LektroiD wrote:
The track cuts don't match the topside (to the left of R334 and next to D65), I don't know if there's any more yet, I've not studied it closely enough


yes you're right, edited. The clap sounds awesome, but still trying to solve this noise bleed issue in the maracas mod, the vca part has been verified 10 times.
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lysergist



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PostPosted: Sun Jul 09, 2017 12:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

Just spotted a little mistake in -minus- cymbal layout, R38 should be 4.7k instead of 47k
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-minus-



Joined: Oct 26, 2008
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PostPosted: Thu Jul 27, 2017 9:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

lysergist wrote:
Just spotted a little mistake in -minus- cymbal layout, R38 should be 4.7k instead of 47k


Thanks for the correction. I have changed the component list on page 1. Embarassed
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j202



Joined: Aug 13, 2017
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PostPosted: Sun Aug 13, 2017 8:12 am    Post subject: Reply with quote  Mark this post and the followings unread

elmegil wrote:
Some more goodies from the Service Manual...

TRIGGER PULSE

"Common Trig with pulse width longer or shorter than 1ms will be a cause of deteriorative voices."

I was talking about how the trigger from the CPU into the common trigger circuit was likely to be 5V, but that's not the case. It's 5V out from the CPU, but then it goes through a transistor inverter and a monostable multivibrator, the purpose of which is to level shift to 15V and widen the pulse from 10us to 1ms. It is a negative going pulse because it's inverted.

(I am still pretty sure that the "gate" inputs to each voice are supposed to be 5V positive pulses)

So the input to Q31 - Q34 which combines the trigger with the accent level is 15V. And again, we have the "1ms" requirement mentioned.

It's interesting that you had to decrease the two Cowbell oscillator resistors; the original units had 390K and 330K respectively instead of 150K and 100K. I'm guessing that differences between the original 4584 hex inverter and the 40106 may have something to do with it, but....

I'm going to try and take this from a different angle. I'm going to set up my arduino to generate the timing pulse and two instrument gates--one for the voice I will test and one for accent. Once I can do that under pot control, I'll add in the accent circuit to generate a common trigger, and then see how those behave with the voices as I build them. This will let me filter out any complications due to using a cheapo sequencer (in my case a 555 timer, in minus' a baby8) and make sure I have the supposedly optimal trigger conditions.

Of course, I'm supposed to get a module from someone to repair here in the next couple of days, so that will likely take my attention away from this for a bit too....


Hi, I have been following this and the other thread for the 808 Bass drum.
What was the final or definitive way to trigger the Bass Drum circuit from Eric Archer? Is it just the addition of the trigger enhancement like this Posted Image, might have been reduced in size. Click Image to view fullscreen.

If I want to use a 606 gate out from the Tom or a gate out from the tr-09, will that additional circuit above allow me to trigger the circuit?
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elmegil



Joined: Mar 20, 2012
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PostPosted: Sun Aug 13, 2017 11:12 am    Post subject: Reply with quote  Mark this post and the followings unread

I don't know that I'd say anything is "definitive" Smile

I have my way, and everyone else seems happy with Eric's original trigger circuit.
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j202



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PostPosted: Sun Aug 13, 2017 12:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

Reading the prior strip-board thread with Minus, it seems as though triggering using the "trigger glue" as Eric puts it was never fully resolved and that inconsistent results were achieved.
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elmegil



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PostPosted: Sun Aug 13, 2017 2:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

One thing you could do with that circuit is to tie the accent gate to 5V, use the trigger input as a trigger (with Eric Archer's diode/cap gate->trigger conversion in front of it) and when you don't want accent, just turn the accent level all the way down. Gives the same effect as no accent gate.

Pete
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j202



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PostPosted: Sun Aug 13, 2017 2:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

I've seen a lot of posts about tying the accent to the positive 12/15v rail.
I have a split power supply from Adafruit 12V+\- that ill be using for this. Would I use a voltage divider to get +5V to that accent?
Am I correct to say that the minimum it needs is 5V and 15V is the max (accent as in the original 808)?
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elmegil



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PostPosted: Sun Aug 13, 2017 4:24 pm    Post subject: Reply with quote  Mark this post and the followings unread

The posts talking about tying accent to V+ are *not* using the circuit you quoted that's my transcription of how the actual 808 created its timing pulse.

They're just using Eric Archer's project as he wrote it.

Go back a ways in this thread, I wrote a summary or exactly how the 808 actually generates its triggers, and why that isn't at all like anything anyone (that I've seen) is doing with accent/gate/trigger inputs.
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j202



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PostPosted: Sun Aug 13, 2017 6:53 pm    Post subject: Reply with quote  Mark this post and the followings unread

Right, I understood that. I am was referring to the original EA design. That is the design I am going to work from (for triggering using a TR606 etc)

I do have several Arduino UNO boards however, and I would also like to use your additional extensions to the accent and trigger once I complete the first stage (above).
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elmegil



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PostPosted: Sun Aug 13, 2017 9:39 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ok, I don't think I followed that. Smile

So yeah, I've seen two solutions to the Eric Archer piece.

1) tie accent input high when not in use (e.g. switched jack), normally to V+. Use trigger input to trigger the voice.

2) tie accent input to trigger input when not in use. Use trigger input to trigger the voice.

I've done the latter, myself, when not using the original method.
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j202



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PostPosted: Tue Aug 15, 2017 3:00 am    Post subject: Reply with quote  Mark this post and the followings unread

So using option 1 any drum sound should be enough to open up the transistor and let the circuit fire?

I saw a PCB derived from this design by JMej over at muffw triggered by a tr505 it sounds amazing, this is what I want.

https://www.youtube.com/watch?v=-TC2LyNyp6I
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elmegil



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PostPosted: Tue Aug 15, 2017 7:25 am    Post subject: Reply with quote  Mark this post and the followings unread

j202 wrote:
So using option 1 any drum sound should be enough to open up the transistor and let the circuit fire?


Yes indeed.
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lysergist



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PostPosted: Mon Aug 28, 2017 2:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

I have better results omitting that accent circuit, i plug a CV signal directly to the accent of all the voices so i can have a velocity modulation instead of a fixed accent that can only be modulated manually by the potentiometer
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helix_modular



Joined: Aug 31, 2017
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PostPosted: Thu Aug 31, 2017 11:45 am    Post subject: Reply with quote  Mark this post and the followings unread

First post here at em. I am very happy and excited that this particular thread is still alive and thriving.

Ok, now for tech:

lysergist wrote:
I have better results omitting that accent circuit, i plug a CV signal directly to the accent of all the voices so i can have a velocity modulation instead of a fixed accent that can only be modulated manually by the potentiometer


I have settled for similar a setup as well. I'd like to suggest to use switched jacks for inputs though. I have installed a pot that supplies DC voltage as an input for accent. This is wired to the switch of an ACCENT input jack. The output of the jack is connected to the board.
This way I could set a fixed ACCENT with the pot or plug in (ie open the switch) a source of modulation.

The pot is 100kB tied to 15V and ground respectively. As the accepted range for accent is somewhat lower (as stated above, about 4-15V) one could definitely install a smaller value with a resistor to keep it above ground. This should increase resolution, too. Otherwise about a third goes to waste.
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lysergist



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PostPosted: Thu Oct 05, 2017 3:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ok i have fixed my issue on the maracas, just a bad transistor to change. So i can confirm the Clap/Maracas is verified and fully working.
It sounds really nice to me, added a potentiometer for clap noise decay. The stripboard layout is on the previous page ( 8 ).


maraclap.wav
 Description:

Download
 Filename:  maraclap.wav
 Filesize:  5.04 MB
 Downloaded:  200 Time(s)

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Apollo View



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PostPosted: Mon Oct 30, 2017 2:35 pm    Post subject: Reply with quote  Mark this post and the followings unread

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?

Many thanks...
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