UREI op amp

[peter purpose]

Gentlemen,
Here is a nice little discrete op amp from UREI, that is super simple to build and sounds very nice. 990 footprint.

Enjoy.

artwork 1.1" x 1.1"

overlay-ish

 

[NewYorkDave]

The basic textbook op-amp... a fun and useful afternoon project. Thanks for posting.

 

[laitue5]

:thumb:

Thanks

 

[fallout]

Awesome! Thanks Peter! :thumb: :guinness: :guinness:

-Jay

 

[soundguy]

peter-

what generation is that from, any idea what that was used in?

dave

 

[Viitalahde]

Sweet! :thumb:

 

[peter purpose]

You're welcome lads.

Dave... I found it buried in a urei mixer manual that I can no longer find, but seem to think it was 70's era.

peter

 

[hitchhiker]

This DOA is used all through the broadcast mixer UREI MOD 1 ,I have one here. I too saw that schematic and when one came up on Ebay I got it. No other bidders. :grin: The sound is kinda low-fi but still very good. I think likely this opamp has a very slow slew rate. I'm going to try better doa's on the sum and outputs because it may sound better to have the audio going through only one stage of this early doa at input rather than all three stages . The other option would be to slightly mod all the doa's to a little better design. As it is the MOD 1 is very funky but it sure is going to define your sound. I think it would still have huge character with a tad faster DOA. Any suggestions would be welcome.


BTW ...These consoles are specified in the manual to not be ground connected with the audio cables. Some folks call it telescopic ground. Anyway, when used this way the console has no hum issues. Ive read somewhere on the net where a self appointed expert claims these console are a real problem with RFI etc. I doubt it.

cheers,
Lance

 

[peter purpose]

Yep.... Lance is on the money... MOD 1.
Date on the schematic is 20th Jan 73.

Ayethengyaw

 

[mnats]

From the transistor footprints it looks like they might be substitute devices. What components did you use in yours?

 

[peter purpose]

Hi Mako,
I used BC184C for the input pair, BC141-16/BC161-16 for the output pair and a naughty little BC560C between them.

peter

 

[dukasound]

Can this opamp be used in a place of "standard" opamp like 2520, 1731 etc.
What is a overal gain? I check in CM and I saw about 27db.
Am I wrong :?
Duka

 

[peter purpose]

Sounds about right.
Must use an output cap, as there is offset.

 

[dukasound]

[quote author="peter purpose"]Sounds about right.
Must use an output cap, as there is offset.[/quote]
Gain?

 

[peter purpose]

27.634551dB

 

[dukasound]

[quote author="peter purpose"]27.634551dB[/quote]
I find 27,117 :grin:
Thanks Peter

 

[iomegaman]

I got one of these MOH 110's recently and was wondering how/what changes hitchhiker may have made.

From what I can tell, this is a really cool concept where you could possibly plug different modules in (the amp modules give you 5 slots), of course you would have to make your own pcb's but frankly the manual gives about everything you need.

I like the idea of the DOA as the main source, this uses the same input tranx'z as the LA4a...

What changes need to increase the slew rate?

thanks-Io

p.s. the manual can be had http://www.jblproservice.com/pdf/Vintage%20JBL-UREI%20Electronics/UREI-MOD1.pdf


p.s. the DOA is probably page 61 of the manual...

 

[iomegaman]

OK so here's what I'm gonna do with this unit:

Since the main psu provides 24 volt rails I think I'm going to try to modify a Neve stylee pcb to fit into the module stand, an API perhaps, and I am going to mod up the existing DOA .

By using the selection switches I can defer the audio path to whichever module I engage so this desk will become a sorta "500-series" desk.

If I get REALLY heady I might try modding out some of the channel strips to become EQ's.

I have five slots where the modules go, I think with some slight modification I can make this into a plug and play 500 module desk!!!!

Will post pics and beg for help as I go.

 

[gar381]

This looks like peter's 525 input DOA

GARY

 

[iomegaman]

Yes it looks very familiar...wondering what the sonic differences between the transistors might be from the original Urei to Peters, although I see  a different transistor he has used in the past...

Urei uses 2N5210 on input, Peter has suggested BC 184C
Urei uses 2N3053 (2N4037) on output, Pete suggested both BC141-16 and BC560C

Bc560C used in-between...


By the way built a psu (thanks mnats) and fired this thing up. I have no idea why anyone would suggest its got RF issues, I am a freak about the littlest noise and this thing with the lid off is very quiet...


TONS of gain if you go out the Program Amp...and still relatively quiet...

I get no "low-fi" sense out of it either...of course this is preliminary testing just plugging in a SM57...will try a mo-butta mic later tonite...