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Matched transistors for Moog Rogue filter ladder/SSM2020

Matched transistors for Moog Rogue filter ladder/SSM2020

2012-05-17 by Mark Wallis

Hi folks, could anyone recommend a UK source of precision-matched 2N3904s for this Rogue that I'm working on? It's been fiddled with before and the filter sounds absolutely foul..
The signals are nice and clean at the foot of the ladder and everything else seems to be ok.

I'm also looking for an SSM2020 VCA to finish off a Crumar Trilogy that's been sitting on the bench for far too long... and a few keys for the same, ideally.

Best Whooshes,

Mark Wallis
Birmingham


Re: [vintagesynthrepair] Matched transistors for Moog Rogue filter ladder/SSM2020

2012-05-17 by Paulo Palmieri

Dear Mark,
I suppose that Ebay is the best source for SSMs and not always they are available...
Good luck,
Paulo Palmieri
Show quoted textHide quoted text
----- Original Message -----
Sent: Thursday, May 17, 2012 8:11 AM
Subject: [vintagesynthrepair] Matched transistors for Moog Rogue filter ladder/SSM2020

Hi folks, could anyone recommend a UK source of precision-matched 2N3904s for this Rogue that I'm working on? It's been fiddled with before and the filter sounds absolutely foul..
The signals are nice and clean at the foot of the ladder and everything else seems to be ok.

I'm also looking for an SSM2020 VCA to finish off a Crumar Trilogy that's been sitting on the bench for far too long... and a few keys for the same, ideally.

Best Whooshes,

Mark Wallis
Birmingham


Re: [vintagesynthrepair] Matched transistors for Moog Rogue filter ladder/SSM2020

2012-05-17 by Alan Probandt

2N3904 is a very common and cheap transistor. Instead of buying matched sets, consider buying 50 or so and matching them by hand. It takes a few resistors and a fair-to-good digital voltmeter, but it wouldn't be hard to find several that are similar. With transistor sets it matters that the transistors in the set have the same operating characteristics. It is not so important what those characteristics are.
Or consider buying an integrated circuit that has four to six matched simple NPN 3904-class transistors on it.
SSM chips can be expensive and hard to find. But their characteristics and functions can be duplicated with inexpensive microcontrollers coupled with inexpensive opamps and digital-to-analog convertors. So an old SSM VCA chip that might cost $30 might be functionally replaced by an AVR Tiny24 microcontroller (that has a 10-bit analog-to-digital convertor internally, and that costs $1.50 USD) coupled with a 10-bit digital potentiometer for a few dollars more. The programming of the Tiny24 microcontroller would make the digital pot act like the old voltage-controlled-amplifer chip in the Crumar Trilogy.

Show quoted textHide quoted text
From: Paulo Palmieri
To: vintagesynthrepair@yahoogroups.com
Sent: Thursday, May 17, 2012 6:13 AM
Subject: Re: [vintagesynthrepair] Matched transistors for Moog Rogue filter ladder/SSM2020



Dear Mark,
I suppose that Ebay is the best source for SSMs and not always they are available...
Good luck,
Paulo Palmieri
----- Original Message -----
Sent: Thursday, May 17, 2012 8:11 AM
Subject: [vintagesynthrepair] Matched transistors for Moog Rogue filter ladder/SSM2020

Hi folks, could anyone recommend a UK source of precision-matched 2N3904s for this Rogue that I'm working on? It's been fiddled with before and the filter sounds absolutely foul..
The signals are nice and clean at the foot of the ladder and everything else seems to be ok.

I'm also looking for an SSM2020 VCA to finish off a Crumar Trilogy that's been sitting on the bench for far too long... and a few keys for the same, ideally.

Best Whooshes,

Mark Wallis
Birmingham






RE: [vintagesynthrepair] Matched transistors for Moog Rogue filter ladder/SSM2020

2012-05-17 by Mark Wallis

Thanks for the suggestions. The reason I asked was because I would prefer to just buy in if possible rather than sit there for a few hours with a handful of Maplin's finest as I have a lot of other work on. My customer doesn't mind paying the price of an SSM2020 if one shows up and I'd rather replace like-for-like. So any source would help, wherever in the world.

Thanks again folks!

Yours,

Mark.



To: vintagesynthrepair@yahoogroups.com
Show quoted textHide quoted text
From: alan_probandt@yahoo.com
Date: Thu, 17 May 2012 09:00:05 -0700
Subject: Re: [vintagesynthrepair] Matched transistors for Moog Rogue filter ladder/SSM2020


2N3904 is a very common and cheap transistor. Instead of buying matched sets, consider buying 50 or so and matching them by hand. It takes a few resistors and a fair-to-good digital voltmeter, but it wouldn't be hard to find several that are similar. With transistor sets it matters that the transistors in the set have the same operating characteristics. It is not so important what those characteristics are.
Or consider buying an integrated circuit that has four to six matched simple NPN 3904-class transistors on it.
SSM chips can be expensive and hard to find. But their characteristics and functions can be duplicated with inexpensive microcontrollers coupled with inexpensive opamps and digital-to-analog convertors. So an old SSM VCA chip that might cost $30 might be functionally replaced by an AVR Tiny24 microcontroller (that has a 10-bit analog-to-digital convertor internally, and that costs $1.50 USD) coupled with a 10-bit digital potentiometer for a few dollars more. The programming of the Tiny24 microcontroller would make the digital pot act like the old voltage-controlled-amplifer chip in the Crumar Trilogy.

From: Paulo Palmieri <paulopalmieri@...>
To: vintagesynthrepair@yahoogroups.com
Sent: Thursday, May 17, 2012 6:13 AM
Subject: Re: [vintagesynthrepair] Matched transistors for Moog Rogue filter ladder/SSM2020



Dear Mark,
I suppose that Ebay is the best source for SSMs and not always they are available...
Good luck,
Paulo Palmieri
----- Original Message -----
Sent: Thursday, May 17, 2012 8:11 AM
Subject: [vintagesynthrepair] Matched transistors for Moog Rogue filter ladder/SSM2020

Hi folks, could anyone recommend a UK source of precision-matched 2N3904s for this Rogue that I'm working on? It's been fiddled with before and the filter sounds absolutely foul..
The signals are nice and clean at the foot of the ladder and everything else seems to be ok.

I'm also looking for an SSM2020 VCA to finish off a Crumar Trilogy that's been sitting on the bench for far too long... and a few keys for the same, ideally.

Best Whooshes,

Mark Wallis
Birmingham







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