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 Forum index » DIY Hardware and Software » Thomas Henry designs
My twin SN-Voice
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Adam-V



Joined: Jan 29, 2007
Posts: 300
Location: Australia
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PostPosted: Mon Jul 23, 2007 4:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi Bambam,

It would appear from the link in your post that you're looking at my front panel design which does contain some enhancements and changes in terminology to those listed on the circuit.

The attached document outlines my front panel designations and their equivalent circuit designations. (EDIT: This attachment is now living with my original layout post further up the thread.)

The mix jacks and switches are an enhancement to allow me to use gates to select pulse, noise or a mix of both. In my opinion, it is not really worth using the other mix options of the chip.

I went with two switches on the PWM selection simply because the rotary switches I needed were more expensive and I'm building 6 of these beasties so I wanted to save some money.

Hope this helps to reduce your confusion.

Cheers,
Adam-V

Last edited by Adam-V on Tue Aug 21, 2007 2:47 am; edited 2 times in total
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bambam



Joined: Feb 20, 2007
Posts: 60
Location: australia

PostPosted: Mon Jul 23, 2007 9:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks Adam Wink

Just what i was after!

Brett
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State Machine
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PostPosted: Tue Jul 24, 2007 9:59 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
bbob - re. bcd's: uhh, take a peek at page 1 of this thread


Ahh yes, cool way to control those mixer inputs Very Happy I forgot about that .....

Bill
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State Machine
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PostPosted: Tue Jul 24, 2007 10:01 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
The attached document outlines my front panel designations and their equivalent circuit designations.



Very useful Adam ... good work !

In light of all of this, it really does pay to study, in detail, both the schematic diagrams provided in the documentation and the interconnect wiring from the board to the front panel. These documents together will answer many a question. Very Happy

Bill
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bambam



Joined: Feb 20, 2007
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PostPosted: Tue Jul 24, 2007 4:51 pm    Post subject: Reply with quote  Mark this post and the followings unread

Good point Bill, once i used the schematics and the info Adam gave me it all came together.....i feel a tad stoopid now!

Thanks adam and bill for the help Wink
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State Machine
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PostPosted: Tue Jul 24, 2007 5:08 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Good point Bill, once i used the schematics and the info Adam gave me it all came together.....i feel a tad stoopid now!


Not at all, this is the place to ask questions and we all pull together to help out. Very Happy

Bill
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Dan Lavin



Joined: Nov 09, 2006
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PostPosted: Sun Jul 29, 2007 6:06 am    Post subject: Reply with quote  Mark this post and the followings unread

Here's a photo of MY twins! Thomas H may recognize the rack design. It has served me faithfully since he first published that article in the early days of Electronic Musician magazine.


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State Machine
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PostPosted: Sun Jul 29, 2007 7:41 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Here's a photo of MY twins! Thomas H may recognize the rack design. It has served me faithfully since he first published that article in the early days of Electronic Musician magazine.


Dan "Antman",

Those panels look great! I love using 19" rack panels myself! Those were the days when EM actually had electronic circuits to build Very Happy

Nice work ......... The SN Voice still goes strong and I have a list of 20 folks in a "request list" for more of these great little synthesizer boards!

Bill
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bambam



Joined: Feb 20, 2007
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Location: australia

PostPosted: Mon Aug 20, 2007 3:46 pm    Post subject: Reply with quote  Mark this post and the followings unread

Has anyone else bought the on-on-on switches from hongkongsuperseller on ebay? i did and got them but did notice the pin outs are kind of reversed, not a problem but figured its worth mentioning
Last edited by bambam on Wed Aug 29, 2007 4:40 pm; edited 1 time in total
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Dan Lavin



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PostPosted: Tue Aug 28, 2007 6:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

Well I learned something new today. I finished my second SN Voice today and was having a devil of a time getting the last bit of trouble shooting done. Everything on the SN Voice was working as expected except the Pulse Wave output was nearly non-existent. The only way I could get it to work was to kick start it by taking the frequency up into dog whistle range and backing it down into normal audio. It would only work with the square wave output. The 30% pulse and lfo and ar options wouldn't work. As soon as I flipped the pwm switch, the output would die and I'd have to kick start again. Worse, the triangle wave was strong as always, so the problem had to be in the pwm circuit.

My first rule of troubleshooting is that it is almost never a bad IC: it is almost always a bad connection, solder bridge, etc. I spent 2 evenings checking over everything a million times. Finally, tonight I convinced myself to swap the SN76477 chip and guess what? Yup, everything works. Now before you say it was probably poorly seated and putting the new part in was essentually re-seating it: no, I re-seated it several times before replacing. Now to be fair to the SN76477 chip, it does have a 1978 date code on it!

Now, normally I would toss a bad chip, but even with the flaky internal pwm circuit, it should work fine as a Super Controler since that circuit doesn't use that portion of the chip. Well....at least until something else crashes and burns inside the little dickens!
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Dan Lavin



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PostPosted: Tue Aug 28, 2007 6:50 pm    Post subject: Reply with quote  Mark this post and the followings unread

One other thing I would like to say about the SN76477 chip, there is a phenomenon in its output that I call, for lack of a better term, aftertaste.

All 3 chips I have here exhibit the same thing: a backwards "J" output signal. I'll play anything on the main output of the SN Voice and after about 5 seconds of silence, I'll hear a steady output of low level VCO, even on the noise out setting. There maybe even some noise in there, I just really notice the VCO. The only circuit I've built with the SN76477 I haven't noticed this on is Thomas Henry's Snare+ Voice, but that had a CA3080-based VCA following the SN acting as a noise gate for that residual noise. (By the way, I loved my Snare+! It gave its life for an SN Voice).

Now, for me, this won't be a problem as I will be processing the SN Voices with a VCF, VCA and a couple of ADSR's and the VCA will, like Thomas's Snare+ VCA, act as a noise gate.

Maybe it's just the date codes of the Sn76477's I have. Or perhaps it only occurs with wide body designs. I don't know but it's really the only thing that bugs me (a little) about the SN Voice.
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sneakthief



Joined: Jul 24, 2006
Posts: 529
Location: Berlin

PostPosted: Wed Aug 29, 2007 6:36 am    Post subject: Reply with quote  Mark this post and the followings unread

i'm using the wide-body and never had this issue.
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bambam



Joined: Feb 20, 2007
Posts: 60
Location: australia

PostPosted: Wed Aug 29, 2007 4:48 pm    Post subject: Reply with quote  Mark this post and the followings unread

woohoo my snvoice lives...well kinda Sad

I am getting no noise output from the snvoice and was wondering if anyone can suggest a few things i can try to see if i've gone wrong somewhere?

I'm assuming because i'm getting the VCO output that the sn76477 is working fine, i've also tried 3 different SN's so dont think thats the issue.

If i use the mix switch to get noise only i can hear pops as i'm running a sequence in so i assume thats just the envelope responding to the gate which i guess is a good thing.

Can anyone suggest maybe some voltages etc to check at various points to try and diagnose the problem?

Thanks in advance

Brett
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Dan Lavin



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PostPosted: Wed Aug 29, 2007 5:38 pm    Post subject: Reply with quote  Mark this post and the followings unread

bambam, congratulations! It's fun isn't it? Even without noise. Anyway, even though it appears the mix switch is working, I would suggest you probe the SN76477 at pin 25 and make sure it goes from 0 in one position and near 5 volts for the other position. Check the connection from S4 (the noise range switch back to pin 21 for continuity and the associated cap selections back to the pcb. Lastly check contin. from R54 Noise filter pot back to pin 5, and R48 Noise Initial Freq back to pin 9 of IC3. I'm sure the problem is in one of those lines.
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Dan Lavin



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PostPosted: Wed Aug 29, 2007 5:44 pm    Post subject: Reply with quote  Mark this post and the followings unread

One thing I failed to mention: you may have the noise tuned below audio range. Make sure the Noise Init pot is set to mid point along with the Noise Filter pot. If it still isn't working, make sure the noise init, voltage gets back to pin 9 of IC3.
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Thomas Henry



Joined: Mar 25, 2007
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PostPosted: Wed Aug 29, 2007 6:33 pm    Post subject: Reply with quote  Mark this post and the followings unread

If it was me, the first thing I'd check is the noise clock. Check the output of the 4046 to make sure it's oscillating. Remember, that's CMOS so take all of the usual precautions.

Thomas Henry
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bambam



Joined: Feb 20, 2007
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PostPosted: Wed Aug 29, 2007 8:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks Guys for the quick suggestions and letting me know what to test. I'll go home tonight and do some probing Wink
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bambam



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PostPosted: Sun Sep 02, 2007 5:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks thomas and antman, turned out just to be the 4046! once i swapped it out i had noise Wink

Wow I'd heard the samples of course but this is even better then i expected!
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Dan Lavin



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PostPosted: Sun Sep 02, 2007 7:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

Once again, Thomas proves to be the master!
Quote:
Thanks thomas and antman, turned out just to be the 4046! once i swapped it out i had noise
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State Machine
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PostPosted: Mon Sep 03, 2007 10:27 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Thanks thomas and antman, turned out just to be the 4046! once i swapped it out i had noise


Just curious, did you purchase the 4046 from me? Just wondering .. Wink

Bill
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bambam



Joined: Feb 20, 2007
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PostPosted: Mon Sep 03, 2007 5:01 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi Bill

No mine came from futurlec.....it would be the first bad part i got from them, allthough there just as much chance that i did something to it as well!

I used another one i got from a local supplier as a replacement and its fine, maybe i should check the rest of the flec ones just in case.

B
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State Machine
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PostPosted: Mon Sep 03, 2007 7:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
maybe i should check the rest of the flec ones just in case.


Yes, especially if they are the same date code as the bad one ... otherwise, it might just be an random pad part Mad

Thanks
Bill
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State Machine
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PostPosted: Mon Sep 03, 2007 7:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

I was thinking a bit on the noise clock problem. If you have no noise output but everything else seems to be OK with your SN Voice and you don't have a spare 4046 hanging around or an oscilloscope, here is a way to see if the noise generator in the sound generator is OK or no clocks are applied to the external clock input. Take a 47K resistor and strap it across pins 2 and 4 of the SN76477 (be careful). This will enable the chips internal noise clock and you should hear noise (make sure you tweak the noise filter setting across it's range). This would prove if the 4046 and associated support components were not working. Very Happy

Bill
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bambam



Joined: Feb 20, 2007
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PostPosted: Sun Sep 09, 2007 8:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

I got my snvoice all paneled up on the weekend Smile 28 panel components in a double dot com fits quite well.
unfortunately i now seem to have a problem where LFO PWM seems to be on all the time.....i cant get a clean output from the VCO Sad I have done the PWM mod where the middle of a switch connects to the pole of another to provide 50\20
It was working before i mounted it all so was wondering if anyone would have any ideas?
I'm going to pull the associated switches off the panel tonight and have a poke around but any suggestions would be great.
I have to say the snvoice is one amazing module!

cheers
Brett
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janvanvolt



Joined: Nov 24, 2005
Posts: 285
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PostPosted: Fri Sep 14, 2007 7:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi all,

i started to re-work on the cabling of the sn-voice frontpanel but i am stuck.
i cannot find my old information about what is what on the J1/J2/j3 jumpers.

anybody able to help me ? please mail me at: jan (at) czmok (dot) de

thanks

jan
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