discrete opamps. melcor 1731 build Qs

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neilwight

Well-known member
Joined
Apr 13, 2005
Messages
49
looking into building a simple discrete opamp to go into my EQ project.

im leaning towards a melcor 1731 type. anyone got any experiences of how these sound/work in operation especially with regards noise and headroom.

am i right in thinking this should be a pretty straightforward build, certainly as far as opamps go. it seems just some simple transistors, diodes and resistors. is there way more to it than that. i know more complex ones require very strict matching of components to get them to operate.

im fitting into a 2520 footprint so if anyone has any other suggestions im all ears.
 
Yes, they are pretty simple and straight forward to build, check the black market, someone did make PCBs for it, and I think they are still around but not sure, if not someone probably has some they can sell you, they are even 2520 footprint I think.

No idea on the noise and headroom, low enough for most needs and high enough for most as well. Never measured, but I have had no problems with noise or headroom. As for sound, most people agree they are colored, thats as far as I will go with that other then to say I like the sound.

adam
 
Neil, are you based in the UK?

I have some PCBs you could have depending on how many you need....

Read this and this - it should answer all of your questions and then some but you'll have to trawl through it.

-Tom
 
thanks for the replies guys.

its to go into a sontec EQ im building, discretes will sound better than ICs but its what discrete op amp to go for thats got me puzzled.

george massenberg was on saying that the 990 is too slow and the api 2520 while fast enough really lacks headroom and is noisy.
doesnt really leave much else that i can think off to put in going a DIY route.

is the melcor older than the api 2520? and will it therefor be technically "worse" than the 2520? what about a quad8 AM10?

i like the musicality of discrete opamp circuits but dont want to compromise on noise in the signal.

anyone got any ideas?
 
[quote author="neilwight"]its to go into a sontec EQ im building, discretes will sound better than ICs[/quote]
Are you sure about that? The Melcor is a forerunner to the 2520 and not renowned for super performance - its a distortion amp really, in terms of modern day measurements and probably anything GML uses. George has also mentioned that the Sontec is designed for a FET input opamp...the only person who has tried Melcors in the Sontec is Flo (infernal death) and he had major issues. All working clones use FET input amps I believe.....Jaakko's Forssell version or Flo's OPA604....

Is the melcor older than the api 2520? and will it therefor be technically "worse" than the 2520? what about a quad8 AM10?
The Melcor is older and I believe it performs worse than the 2520. I don't think the AM10 is in the correct footprint so you'll have to do a new PCB layout for that....

I like the musicality of discrete opamp circuits but dont want to compromise on noise in the signal.

anyone got any ideas?

I am planning to build this EQ but further down the line, and I think I'm going to go for ICs in the filters (OPA604s) and discretes as the main I/O. Forssells or maybe the new Purple Audio amps. I think FET input is less important on the I/O amps. Whatever you do you'll need 14 amps IIRC, so its not cheap if you want great performance.

HTH Tom
 
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