UA776 replacement?? For the Papareil Polivoks

numbernone · Joined: Aug 16, 2006 Posts: 477 Location: new york city

Anyone have a possible replacement or near equivilant for the UA776. Have this Polivox board itching to go...

Thanks

fonik · Posted: Sat Oct 27, 2007 11:10 am Post subject:

i built it using the LM4250. some say it sounds different (don't know), but different is not be better or bad, it's a question of what you like...

Funky40 · Posted: Sat Oct 27, 2007 2:36 pm Post subject:

they are also as LS776 available.

there must be a replacment chip from DDR ,
but i don't know the Name.

goldenechos · Posted: Sat Oct 27, 2007 3:58 pm Post subject:

That 4250 is much easier to come by afaik...

If you are concerned about the difference in sound, use a socket and swap a UA776 in for the 4250 when you can get your hands on one.

For now, get the 4250 and start enjoying the filter.

Tony

Serenadi · Joined: Jul 03, 2007 Posts: 89 Location: Germany

Its not only to change the progr. OpAmp, you have also to change two resistors (R10, R11 in Marcs schematic, afair).

The sound of the UA776 is slightly more balanced.
We discussed this in the german forum, someone called it "frequency holes" in the lower cutoff range, especially with higher resonance.

I tried all the chips, the UA776, LM776, LM4250 and the GDR production of the russian original, called B176.

At least I ended up leaving the UA776 and the B176 in the sockets.

franck · Joined: Oct 01, 2009 Posts: 13 Location: Italy

Hi.
I have a small stock of UA776 (metal case) and UA776 (plastic case, DIP).
contact me.
Regards

elettromusic · Joined: May 12, 2006 Posts: 14 Location: italy

All.
For AY-1-1313, please, visit:

http://www.vintagechip.altervista.org

Regards

radek tymecki · Joined: Mar 22, 2009 Posts: 85 Location: PL

http://www.tme.eu/en/katalog/?search=ua776&page=1,20#search%3Dua776

Boerge · Joined: Sep 02, 2009 Posts: 82 Location: Germany

sneakthief · Joined: Jul 24, 2006 Posts: 569 Location: Berlin

I finally got my M. Bareille Polivoks board working after ...5 years Razz

The damn thing was taunting me in my rack, especially seeing as I never had any problems building 40 other modules.

I used DDR B176D's.

The problem was two-fold:

1. Futurlec sent me 3k resistors that were actually 30k! Lesson learned: Always check resistor values with a multimeter.

2. M. Bareille has Q1 (2N3904) upside-down on his PCB component layout - THIS IS INCORRECT FOR 99% of 2N3904's:

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.

Lesson learned: It always makes sense to also double-check the transistor orientation with an hFE meter, even when you don't think it's going to be a problem.

I have an extra two functional B176D's if anybody wants to buy them from me for 7 euro plus letter-mail shipping from Berlin.

Hit me up at michel AT sneak-thief DOT com.

fluxmonkey · Joined: Jun 24, 2005 Posts: 708 Location: cleve

sneakthief · Joined: Jul 24, 2006 Posts: 569 Location: Berlin

Symptoms or reversed 2N3904? It doesn't filter at all!

As for the range, try increasing the value of R8 and attaching the CCW of the cutoff pot to -15v instead of ground.

Marc says: