Api 2520 and MM990 how different do they sound ?

[andre tchmil]

what's the difference between a blue labelled 2520 and a black one ?

 

[jrmintz]

I ask can I use 990 with same circuit

Yes Duka, I've used 990Cs in place of 2520s in API circuits. You shouldn't have a problem.

:thumb:

 

[Flatpicker]

If you want some API color and a little higher noise, use the 1:8 with the 990C. If you want super low noise and perfect, crystal clear, unadulterated audio, use the Jensen 1:2. (I'm sure that's what cj was trying to say. :wink: ) Of course, your output circuit will have something to do with that as well.

 

[dukasound]

Thanks guys :thumb:
Does 990C have higher gain?

 

[jrmintz]

Does 990C have higher gain?

I'm not sure, but I can do a little test later today or tonight when I get a minute and see.

:thumb:

 

[dukasound]

[quote author="jrmintz"]

Does 990C have higher gain?

I'm not sure, but I can do a little test later today or tonight when I get a minute and see.

:thumb:[/quote]
Thanks for reply
I need this information because I will make API circuit with Jensen or Cinemag on input and profile on out. I make pcbs for op amp and need transistore and small parts for it and but probably I will order one JH990 or find some used opamp like it.
Best
Duka

 

[FredForssell]

John Hardy wrote...

Regarding the 990 used by K-Disc, that was made by ME! Back then (early 1980s) I made my 990 op-amps in a clear epoxy package using silicone molds.

That clear epoxy package was some of the best potting work I have ever seen. Great stuff.

 

[CJ]

I saw one at AES.
John said he quit using it because the coeficient of thermal expansion was ripping the diodes apart. It does look pretty cool though. Almost as cool as the VP Transamp.

 

[jrmintz]

Hey Duka,

I tried the 990C in a 312 as well as three different 2520s - two gray and one blue. Gain and THD for all was EXACTLY the same at 1k, 10k, and 100Hz.[/u]

 

[fum]

That's all fine and well(and nice to know by the way) :wink: But have you built a 1731 and tried it too? :grin:

ju

 

[jrmintz]

Hey, I was just thinking - watch out! API has two opamps, John Hardy has a couple of versions of one model, Melcor had one, where do they get these numbers? Does this mean that API went through 2,519 versions before it worked?

:green:

Time to occupy myself productively before I start thinking again.

 

[John Hardy]

The Valley People TransAmp was the inspiration for me to do the clear epoxy version of the 990. The engraving of the dollar bill image on the top of the TransAmp was kinda cool. Thanks, Fred. There was also the fact that the circuit of the 990 was well known thanks to Deane Jensen's paper about it, so there was nothing to hide and something to be gained by showing it off.

In 1981 I had some problems with 1N914B diodes being pulled apart by the expanding epoxy as the clear 990 modules warmed up, so I changed suppliers of the diode (was Fairchild) and changed the curing procedure for the epoxy to use a lower curing temperature for a longer period of time. That seemed to solve the problem. But ultimately I wanted to improve the package, so the aluminum shell with silicone encapsulant was developed around 1989 when the "A" and "C" versions of the 990 were introduced.

The K-Disc 990 modules were the original 990 circuit but using a black potting shell (like the 2520) and black epoxy so that K-Disc could put their own labels on them.

John Hardy
The John Hardy Co.
www.johnhardyco.com