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 Forum index » DIY Hardware and Software » Jürgen Haible designs
20 Stage/Tau questions and comments
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defex



Joined: Jun 27, 2008
Posts: 33
Location: Toronto, canada

PostPosted: Tue Sep 20, 2011 7:14 pm    Post subject: 20 Stage/Tau questions and comments Reply with quote  Mark this post and the followings unread

a nice pair:) the transistors are ebay CA3046 from the US "blue dot", supposedly tested somewhere, they seem to work anyways. capacitors in the stages are 5%, vishay BFC237042153 from digikey, and they accidentally sent me 100 extra, hmm what to do with them?

Just bench tested my first one. the only difference from stock, is a slightly slower capacitor for the LFO, and replace the 1u electrolytics in the signal driver with 1u film caps (because i had them, not because of any hi fi freakery)

temporary pots just for testing.

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

It sounds great! and thats just with a function generator.

I am building both of them behind a 2u MOTM synth modular panel, and what i want to do is use an extra pot to feed the output of one side in to the other. my guess is that i can just use another resistor at the junction of r2 and r4 and connect it the same way as the input or feedback pots. does that seem correct?

also, here is how i made a MOTM connector for it, in case anyone is interested.

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

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



Joined: Dec 22, 2005
Posts: 223
Location: Cologne, Germany

PostPosted: Wed Sep 21, 2011 12:11 pm    Post subject: Re: 20 Stage/Tau questions and comments Reply with quote  Mark this post and the followings unread

Nice idea with the MOTM connector. I think I'll copy that although I already soldered the resistors in.

Which capacitor did you choose for the LFO?
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defex



Joined: Jun 27, 2008
Posts: 33
Location: Toronto, canada

PostPosted: Wed Sep 21, 2011 12:38 pm    Post subject: Reply with quote  Mark this post and the followings unread

It is a 0.68u with 500k pot, i might try something even larger, or even 2 with a switch

I just tested the second one and it has a strange problem. even though the resistance from power to ground on the non working and working boards are very close, on the second one, the 10 ohm resistor on the positive side gets very hot and i do not get any output.

never mind, it is fixed. stupid error!

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



Joined: Jun 27, 2008
Posts: 33
Location: Toronto, canada

PostPosted: Mon Sep 26, 2011 10:40 am    Post subject: Reply with quote  Mark this post and the followings unread

They are both working perfectly now, and panelized, just waiting for some supplies to do the graphics.

i really like this module, thanks for the great design!
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mig27



Joined: Mar 09, 2011
Posts: 21
Location: Berlin

PostPosted: Sun Feb 26, 2012 1:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

defex wrote:


I just tested the second one and it has a strange problem. even though the resistance from power to ground on the non working and working boards are very close, on the second one, the 10 ohm resistor on the positive side gets very hot and i do not get any output.

never mind, it is fixed. stupid error!


Funnily I have the same problem.
One of the 10 ohm resisistors gets really hot.
As a matter of fact, I got magic smoke, so I didn't even test my board any further.

Would you like to share what "stupid error" you debugged?
Probably the same here..

Thanks a ton!


Michael
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defex



Joined: Jun 27, 2008
Posts: 33
Location: Toronto, canada

PostPosted: Sun Feb 26, 2012 1:30 pm    Post subject: Reply with quote  Mark this post and the followings unread

I had put an IC in backwards!
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mig27



Joined: Mar 09, 2011
Posts: 21
Location: Berlin

PostPosted: Mon Feb 27, 2012 9:17 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for your quick reply!

Unfortunately, my ICs are not the culprit - all properly mounted.

But it indeed seems that there's an issue with my power rails.
Now I'm wondering if JH's +/-15V implementation is all that good.

I followed the instructions mentioned on his site:

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

However I have the impression most folks did it à la Bill & Will:

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

Any thoughts?
Thanks!

Michael
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defex



Joined: Jun 27, 2008
Posts: 33
Location: Toronto, canada

PostPosted: Mon Feb 27, 2012 9:34 am    Post subject: Reply with quote  Mark this post and the followings unread

you can see in my pic, that i didn't do the power the recommended way at all, but the result should be the same, as long as you have +15v and -15v (i measured on the legs of the 10 ohm resistors) i doubt that is the problem.

if the resistors get hot then something is shorting in the part of the circuit that is powered after them.

if you used sockets, try taking the ICs out and checking to see if the resistors still overheat. then put them back in one by one, and see which one is related to the problem.

it doesnt meant that IC is bad though, it could be something around it.

if it still overheats after you remove the ICs, maybe there is a short somewhere, possibly the SMD capacitors? check the resistance to ground from the positive and negative supplies (after the 10 ohm resistors)
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mig27



Joined: Mar 09, 2011
Posts: 21
Location: Berlin

PostPosted: Mon Feb 27, 2012 9:42 am    Post subject: Reply with quote  Mark this post and the followings unread

Yup I've seen that.
Will probably try out this alternative +/-15V wiring.

A used some older surplus lytics near my burned 10 ohm resistor.
The 22uF ones seen here:

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

Maybe I should replace these too.

Well, at least I saw the two LEDs flashing during the 3 seconds I had my tau board fired up (pun intended) - so a little something working already Smile

Will keep you guys posted.
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marvkaye



Joined: Mar 14, 2011
Posts: 225
Location: Fla

PostPosted: Wed May 02, 2012 8:43 pm    Post subject: Reply with quote  Mark this post and the followings unread

I've been agonizing over which method to use to power my Tau Pipe, chose the Bill & Will method. I stuck with the 10u tants and added 47u electrolytics instead of the 22's, only because I had 47's that fit and my 22's didn't. I also stood the tants up on a couple 3mm glass beads... they act as little heat sinks during soldering and stabilize them after. Of course after I'd done all that and decided to post a message about it I saw the cool application of the MOTM connector, kind of wish I'd seen that earlier, but too late now. Used my label maker to make a legend for the power header so now all that's left is to clean and start testing. Long time coming....


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