Keeley compressor clone

[puretube]

http://www.nxp.com/acrobat_download/datasheets/BCV61_3.pdf

[R.G.]

Yep, those and the complements will do nicely for the current mirrors. Do they make a monolithic matched diffamp?

[Jay Doyle]

Yep, those and the complements will do nicely for the current mirrors. Do they make a monolithic matched diffamp?

I actually was able to design a pretty good replica of the3080 using a CA3086 chip which has a diffamp and four other matched transistors on the chip.

Unfortunately, it was discontinued along with the rest of the CAxxxx line... 

[analogmike]

>> The 2K trimmer is substantially useless. It can be effectively replaced by two 1K resistors.

Functionally correct, this will always work with any of the CA3080E chips we have used, we have resistor areas on our boards for doing so.

>> This MAY be a clue as to what is wrong.  I've found in MANY (all even?!?!) cases that you can hardly notice a difference to the sound even when adjusting that trim pot quite a bit from one extreme to the other...sure at the very ends, there will be a problem... but in general I think I've noticed much more play "allowed" before 11 oclock and 2 oclock.  So if it only works at the noon position but no where else, this is an indication that something may be wrong. <<

No, this is why we keep the 2K BIAS trim pot in our pedals. Turn up the sustain and the ambient sound will die out at about 1/8 turn of the trimpot either direction away from 12:00. That is how we calibrate them, and this feature is usefulfor debugging sick pedals.

have fun!

[puretube]

Yep, those and the complements will do nicely for the current mirrors. Do they make a monolithic matched diffamp?

dunno `bout "matched",
but various companies make duals (2xNPN; 2xPNP; 1xP/1xN) on a die
in SOT-cases...

[Jay Doyle]

dunno `bout "matched",

I always thought, perhaps incorrectly, that when the transistors were grown on the same die that they were matched by default. I thought this was the purpose of putting them in the same die/package.

[puretube]

they`ll be close - closer than 2 individuals - also: thermally identical -
but: not "trimmed to match" by purpose.

(= close, but no cigar...  )

[StephenGiles]

Oh that life was so simple!

[Jay Doyle]

they`ll be close - closer than 2 individuals - also: thermally identical -
but: not "trimmed to match" by purpose.

(= close, but no cigar...  )

That's it, I was thinking thermally matched. I guess they would be close enough though...

[davph30]

Panasonic list the 2sc3311A as an alternative to 2sc1849 has anyone tried or lookied into it?

[RobertKeeley]

Turn up the sustain and the ambient sound will die out at about 1/8 turn of the trimpot either direction away from 12:00. That is how we calibrate them, and this feature is useful for debugging sick pedals.

have fun!

mmmkay....

[Hiwatt25]

What's that meant to mean Bob?

[Jay Doyle]

What's that meant to mean Bob?

I think it means that he doesn't understand what analogman is saying, or questioning that AM's procedure may not be the best. To me this sounds like a continuation of the bloviating of above.

BUT, AM's procedure makes complete sense to me and follows the same procedure I always recommed for setting the trim: Turn the trim until you hear the MOST noise. At about 1/8th of a turn away from the 'MOST noise' portion of the trim, the + and - inputs become unbalanced and the sound cuts out completely; until you hit it with a signal that brings it back through the balanced portion. And this is why it sounds gated when the trim is not set correctly.

Jay Doyle

[markm]

What's that meant to mean Bob?

I think it means that he doesn't understand what analogman is saying, or questioning that AM's procedure may not be the best. To me this sounds like a continuation of the bloviating of above.

*sigh*
The saga continues.....I'm awaiting for the ring of the bell on monday morning and round 3 to begin....or would that be four? 

[RobertKeeley]

What's that meant to mean Bob?

I think it means that he doesn't understand what analogman is saying, or questioning that AM's procedure may not be the best. To me this sounds like a continuation of the bloviating of above.

BUT, AM's procedure makes complete sense to me and follows the same procedure I always recommed for setting the trim: Turn the trim until you hear the MOST noise. At about 1/8th of a turn away from the 'MOST noise' portion of the trim, the + and - inputs become unbalanced and the sound cuts out completely; until you hit it with a signal that brings it back through the balanced portion. And this is why it sounds gated when the trim is not set correctly.

Jay Doyle

That is a valid method for doing it by ear for sure.  We did something very close to that for years.
Using modern CA3080E devices by Harris and 1% tolerance resistors has made it a worthwhile change to our version of the circuit (leaving out the 2K trimmer).
Now people don't adjust it thinking that it is an attack control!!!  SO, it is a much better feature to NOT have it in terms of customer service and mistakes that people may make by trying to adjust it.  You want to leave out as many trimmers as possible in designs right?!?!?!?  The Bean Counter gets mad when he/she looks at the bottom line (parts and labor to have a trimmer).

Take care folks and have a great weekend,
Robert

[davph30]

Hi guys just to let u know everything is working great now.

I used the tonepad schematic and only changed the transistors to MPSA18's which produced less noise but not that noticabe.

Thanks for all your help

Dave

[Jay Doyle]

That is a valid method for doing it by ear for sure.  We did something very close to that for years.
Using modern CA3080E devices by Harris and 1% tolerance resistors has made it a worthwhile change to our version of the circuit (leaving out the 2K trimmer).
Now people don't adjust it thinking that it is an attack control!!!  SO, it is a much better feature to NOT have it in terms of customer service and mistakes that people may make by trying to adjust it.  You want to leave out as many trimmers as possible in designs right?!?!?!?  The Bean Counter gets mad when he/she looks at the bottom line (parts and labor to have a trimmer).

Take care folks and have a great weekend,
Robert

Great point, I wouldn't have ever thought of it like that, having to design for people who may mess with the trimmers thinking they are something that they are not! Guess that is the difference between building for yourself and building for the masses.

I don't think of it in the commercial/"have to sell it sense"

Jay Doyle

[markm]

I have some of the Harris 3080's and find them all consistant.