I'm not starting this thread because I'm an expert. Actually, I'm a bit tech challenged. This concept may seem a little obscure to some of you, but it's pretty basic stuff - as far as the actual swapping of op-amps. But there's more behind it, which is what I want to learn about.

I started last year collecting op-amps and swapping them in an API 3124. The op-amps are those little square snap-on modules just behind the front plate. Changing the op-amps can change the sound and performance [ for better or worse ] of the mic preamp.

I've had long conversations - many of them dizzying – with some of the top designers about this, John Hardy, Vince Poulos, Fred Forssell – also Avedis at Brent Averill and Peter Cornell from 1176neve.tripod.com - a great DIY website, BTW.

Anyway, I've started down a long road and will post more as this is also research for an article.

Collecting these types of op-amps and finding out more about them is one of my recent obsessions.


API 3124 Mic pre with various op-amps. Ch #1 - Vintage 2520. Ch #2 - Vintage 2520. Ch #3 - Stock 2520 from 1999. Ch #4 - Millennia MM-99

Dan Richards
The Listening Sessions
Pro Audio Consulting & Equipment Sales
Direct Toll-Free (866) 409-3686

Article: Op-amps are More Fun Than Tubes by Junji Kimura

API 2520 op-amp data. [ Datatronix version ]

Dan Richards
The Listening Sessions
Pro Audio Consulting & Equipment Sales
Direct Toll-Free (866) 409-3686

Great stuff!

I'm going to be taking an op-amp course next term for my electronics degree so this should be great for getting ahead of the game.

-tkr

______________________________
'Cause I don't wanna read the book, I'll watch the movie.

Tekker, you are a sandbagger! You can't be an electronics student and be in the 101 Forum. Sorry.

Dan, I thought that opamps were much smaller. The ones in my console (TL0.. something or other)are. I've heard anywhere from workable to bad about my opamps so maybe size matters

Jason A.

Hi all

Thanks to Dan for the mention. I am from the hobbiest "I've got a soldering iron & I'm gonna use it" school of malpractise, & am not an EE. So dont ask difficult questions please

My website is basicaly a reflection of what I have attempted to fill my spare time with, and being a bit of a headroom fanatic, the discrete opamp e.g. API 2520 shown above & Jensen 990 ideas are quite interesting for me. So I have built a couple but I am yet to use them in me day job.

I am still to find a good schematic for the API 2520, anyone got one?

Regards
Peter

quote:

---

Originally posted by Jason A.:
Tekker, you are a sandbagger! You can't be an electronics student and be in the 101 Forum. Sorry.

---

Hey man, I'm just here to learn like everyone else! lol

-tkr

______________________________
'Cause I don't wanna read the book, I'll watch the movie.

Cool thread, DOT.

Sheesh! And I thought I was going to get to bed early tonight!

I'm not sure what you would do to a 3124 that could make it sound better. I just did a VO session tonight where the engineer used a TLM103->API 3124 and it sounded great. It's actually the first time I've liked the 103.

I know changing socketed opamps is easy to do but I'm not sure I'd have the guts to mess with a good thing.

Jason A.

quote:

Originally posted by Jason A.:
I'm not sure what you would do to a 3124 that could make it sound better.

Have you ever tried one of the older hand-made 2520's made in Huntington, NY?

I think a lot of this is not about an absolute "better", but a "better" for a given application. In the same way that API pres are great but not the best for all applications.

The 2520 went through something like five different incarnations and designs, so even though they share the same model name - there are differences.

Dan Richards
The Listening Sessions
Pro Audio Consulting & Equipment Sales
Direct Toll-Free (866) 409-3686

hey that's my 3124! i use a 103 often and the older api op amps make the 103 sound a bit bigger and a tad bit less bright maybe than the 1999 op amps. this is also the case with almost any mic i plug into the sucka. i love the older amps..as well as the millennia op amp! don't be afraid to change them out it's too easy and you just might leave them in for good like i have for now. thanks goes to dan!

b!

somethingaboutvampiresandsluts.com

quote:

---

Originally posted by Jason A.:
I'm not sure what you would do to a 3124 that could make it sound better. I just did a VO session tonight where the engineer used a TLM103->API 3124 and it sounded great. It's actually the first time I've liked the 103.

I know changing socketed opamps is easy to do but I'm not sure I'd have the guts to mess with a good thing.

Jason A.

---

Hey, Dan.
Where you been findin' 2520's and 2510's? BTW, how does the millennia compare to the APIs?

Hey b! Good to see you here.

Peter, could you give us a little info behind the Melcor opamps stuff you've been doing and your take on the world of op-amps in general?

Dan Richards
Digital Pro Sound
The Listening Sessions

quote:

Where you been findin' 2520's and 2510's? BTW, how does the millennia compare to the APIs?

flat, the older 2520's have come out of an old API console that someone in town here has been chopping up. I think b! has 2-4 of them. The Millennia MM-99 was sent to me by John La Grou at Millennia. b! should make some comments on the MM-99, too. I think it gives a cleaner sound with a rounder low-end. We also have a 2520-type op-amp made by Avedis at Brent Averill - we need to take some time and listen more to that one. We have more op-amps on the way from Fred Forssell, JLM Audio and Peter Cornell.

Dan Richards
The Listening Sessions
Pro Audio Consulting & Equipment Sales
Direct Toll-Free (866) 409-3686

Here's a schematic of a JLM Audio JLM990 opamp with a modification to run it in API.



Comments by Joe from JLM:

I have attached
a circuit for the API312 with the extra cap needed to drop a JLM990 in
to it. This is due to the +1vdc on the output because the JLM990 is more
of a Vintage Neve module on Steroids then a normal modern opamp type
design like all the other 990's. A dc trim pot circuit or DC servo can
be added to remove this offset if needed. Also the JLM990 works best on
+/-34vdc regulated rails. I can send you a JLM990 when you are ready to
do your review.

Dan Richards
The Listening Sessions
Pro Audio Consulting & Equipment Sales
Direct Toll-Free (866) 409-3686

quote:

---

Originally posted by Dot:
...We have more op-amps on the way from Fred Forssell, JLM Audio and Peter Cornell.

---

You know, I completely forgot about the JLM990, and didn't even know about Peter Cornell. Do you have any info on Peter's 990 such as a web site, etc...?

Hi Flatpicker

My site is 1176neve.tripod.com Please be aware that I did not get my version of the 990 to operate stably. If you want o try this project,please read the notes....

The Melcor 1731 discrete opamp was the predecessor to the 2520. According to an interview that I read with Paul Wolff a group of engineers came to API & brought the design with them.

Regards
Peter

quote:

---

Originally posted by Peter Cornell:
Hi Flatpicker

My site is 1176neve.tripod.com Please be aware that I did not get my version of the 990 to operate stably. If you want o try this project,please read the notes....

The Melcor 1731 discrete opamp was the predecessor to the 2520. According to an interview that I read with Paul Wolff a group of engineers came to API & brought the design with them.

Regards
Peter

---

Hey Peter. I was wrong - I have been to your site and remember reading about that project. High gain amps like that are hard to get working consistantly. That's why I'm just going to buy some one elses and plug it in.

Maybe at a later time I'll tackle my own opamp design, but for now I gotta get moving on my first pre.
Thanks.

yeah dan's right on about the millennia op amp ..........this guy sound great on bass and floor tom. tight low end and clear top with a bit of the api color is what i get outa the millennia.
like it!!!!!!!!!

b!

quote:

---

Originally posted by Dot:

quote:

---

Where you been findin' 2520's and 2510's? BTW, how does the millennia compare to the APIs?

---

flat, the older 2520's have come out of an old API console that someone in town here has been chopping up. I think b! has 2-4 of them. The Millennia MM-99 was sent to me by John La Grou at Millennia. b! should make some comments on the MM-99, too. I think it gives a cleaner sound with a rounder low-end. We also have a 2520-type op-amp made by Avedis at Brent Averill - we need to take some time and listen more to that one. We have more op-amps on the way from Fred Forssell, JLM Audio and Peter Cornell.

Dan Richards
http://www.digitalprosound.com
http://www.thelisteningsessions.com<font color=white>

[This message was edited by Dot on 09-06-03 at 08:07 AM.]

---

FYI, folks – b! is Brian McKenzie, who's played on a lot of the sessions for The Listening Sessions.

We also have a John Hardy M-1 here and we're going to try some op-amps in that. I'll try and get John in here – because I want to make sure I don't blow up his pre or something.

I'll see if I can get Avedis from Brent Averill to pop in here, too.

Dan Richards
The Listening Sessions
Pro Audio Consulting & Equipment Sales
Direct Toll-Free (866) 409-3686