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Dynacomp chip alternatives?

Started by Al Heeley, May 24, 2009, 03:28:32 PM

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Al Heeley

May 24, 2009, 03:28:32 PM
The Dynacomp PCB layout calls for a CA3080E IC as the op amp. I'm having trouble getting one, can it be replaced with a standard LM741 type or is there a better replacement, maybe easier to get hold of, I should be looking out for?
cheers.

mdh

#1
May 24, 2009, 04:38:14 PM
No, it's completely different beast than a regular op-amp (read about operational transconductance amplifiers, if you're interested).  The Ibanez Cp9 compressor (see Tonepad) is supposed to be similar, but uses an OTA that is in current production.  Otherwise, you can get a 3080 from Small Bear.

Al Heeley

#2
May 24, 2009, 05:03:43 PM
Thx Mdh - I'm looking for a UK-based supplier of 3080 chips.

frequencycentral

#3
May 24, 2009, 05:16:11 PM
Plenty on Ebay!
http://www.frequencycentral.co.uk/

Questo è il fiore del partigiano morto per la libertà!

Mark Hammer

#4
May 24, 2009, 05:29:41 PM
Doesn't have to be CA type.  LM work just as well.  There are other OTAs you can use too, but if the goal is to use an existing layout, then its CA or LM.

Al Heeley

#5
May 25, 2009, 03:11:56 AM
thanks Mark, now there's 2 conflicting posts, one says no you can't the other says yes it's fine. Who is correct?

Mike Burgundy

#6
May 25, 2009, 03:30:15 AM Last Edit: May 25, 2009, 03:34:01 AM by Mike Burgundy
Both.
CA3080=LM3080, some others may work although I don't have any numbers on tap. They're not as interchangeable as dual opamps though, plus *opamps* are totally different from OTA's (Operational Transconductance Amplifier). I seem to remember some info on those (what they are, etc) on GEO, but I'm not certain. This board should yield some search results as well.
Smallbear was also mentioned, and rightly so (http://www.smallbearelec.com/Categories.bok?category=ICs+-+Op-Amps+and+Linear&searchpath=41&start=1&total=69). Steve is a great resource for all of us and ships internationally - chips don't weigh much so shipping costs are low.

Al Heeley

#7
May 25, 2009, 04:20:09 AM
Aah - thanks for clarifying, LM 3080 = CA 3080 but a LM741 will be no good, right? I have a spare 741 but I'll save that for another project and see if my UK source has any LM3080's.
Cheers.

Toney

#11
May 25, 2009, 07:16:18 AM Last Edit: May 25, 2009, 07:19:41 AM by Toney

aziltz

#12
May 25, 2009, 08:33:50 AM
Quote from: Al Heeley on May 25, 2009, 04:20:09 AM
Aah - thanks for clarifying, LM 3080 = CA 3080 but a LM741 will be no good, right? I have a spare 741 but I'll save that for another project and see if my UK source has any LM3080's.
Cheers.
Quote from: mdh on May 24, 2009, 04:38:14 PM
No, it's completely different beast than a regular op-amp (read about operational transconductance amplifiers, if you're interested).  The Ibanez Cp9 compressor (see Tonepad) is supposed to be similar, but uses an OTA that is in current production.  Otherwise, you can get a 3080 from Small Bear.

741 is a single opamp.

this 3080 beast serves a different purpose all together.  the LM/CA is just a brand thing.

col

#13
May 25, 2009, 09:35:09 AM
Do a search in your local yellow pages or yell.com under electronic suppliers or similar, but don't try Maplins, they definately don't have them. I got the last ones from Manchester Semiconductors a couple of years ago and they didn't chrge me too much for them. Unfortunately I've used them all up now. There will probably be lots left in drawers or cupboards somewhere.
You can also try www.dalbani.co.uk, they usually have difficult to obtain components including Ge transistors. I think they had the LM type last time I looked. There are schematics for compressors using the dual Tranconductance chip, LM13700 but the two I tried had too much hiss. You'd have to work out which pin corresponded to the earlier chips if you wanted to use one side of an LM13700, I don't even know if that would work, they have come down in price over the last year though. try Rapid or RSH,

Col
Col

ayayay!

#14
May 25, 2009, 08:23:18 PM
Excellent thread here that explains OTAs in layman's terms.  Every time I start to wonder about them I dig up this old thread.

http://www.diystompboxes.com/smfforum/index.php?topic=62487.0
The people who work for a living are now outnumbered by those who vote for a living.

Papa_lazerous

#15
May 26, 2009, 09:24:54 PM
Do yourself a favour and get one from Steve at Smallbear you wont regret it.  If you do the dumb thing and buy one on ebay, dont get a very cheap one from Hongkong the amount of inferior parts coming out of there labelled to be something they are not is crazy right now

Al Heeley

#16
May 28, 2009, 12:00:03 PM
Thx guys, got a reasonable price CA3080E on ebay today. On with the build!
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