UREI op amp

[hitchhiker]

Nice to see you working on this one!

Since I made the low-fi dig I have pulled one input transformer and tried it elsewhere, I was not too impressed.  I put it back in the channel for now. I also tried better output transformers on the Mod1 out cards (which also use this opamp) and got a big improvement.
  If I had money for this kind of experimenting I would put decent iron on the in and out , probably Jensen, just to hear what the opamp does with an even playing field.  I would choose line step down inputs because opamp pres are not my go to faves on most sources. That would delete the input pad scheme.

 

[michal_k]

am I the only one who doesn't see any pictures?  :-[

 

[iomegaman]

Here's some pics...first one is the headphone amp card...


misc cards..



Front of the unit



Front without channel strips



This is the back of the amp card...all the slot tabs are gold...



this is the front of the amp card...with the DoA

 

[iomegaman]

Some more



As you can see this is where the channels slip in...


I took out the cassette and cart channels...


This is where the "amp" modules pop in, there are 5 slots for the cards in the previous pics...


I'm gonna do some test and see where the slot provides power, these cards don't look that hard to make, so I was thinking a neve module or api...which they are kinda like already...

 

[hitchhiker]

more or less the same console I have. Just wondering why you call yours MOH 110 ?

Upgrade the iron and I think this may be a funky sleeper with much more to offer!

 

[iomegaman]

more or less the same console I have. Just wondering why you call yours MOH 110 ?

Upgrade the iron and I think this may be a funky sleeper with much more to offer!

Little tag on the back "MOH 110"

 

[hitchhiker]

Ah!  I'm thinking the M is for mono?

 

[iomegaman]

That was my guess as well.

One thing I really dig is the channel strip switch changing color by position (the light on the tip of the selector switch) way cool but then again it is eye candy.

Did a little reading the manual, from my best estimate the input tranx's are all cinemags, and the outputs look to be UTC's...could be reading the manual wrong though...

(I dug up the part number on the input tranx and checked it online thats how I think its cinemag)

Jensens might clean it up a bit though...from what I've read the inputs are the same ones used in the La4a

By the way it looks to be no big deal to make a mono version stereo, even the cards are ready for that.

Is your's a stereo?

 

[hitchhiker]

Yup, mine is stereo.  I know these inputs are on other Urei  stuff,  like 1109 or somthing ..  still they sound like shit compared to the good iron, no highs or lows to me. big fat iron up size on the output would be the first step then some nice 2:1 input.
  I wiish there was an easy upgrade to the the opamp but I'm not betting on it.  I have an old Sphere broadcast board with SPA62 amps, it has one more transistor and I thought maybe?  But they are a long way off a 990 or a Quad8 AM10 or many of the amps forum members have shared here.

 

[iomegaman]

Ok I tried some different mics/went thru all the channels and while not exactly "low-fi" I see what you mean about no highs or lows, it has a nice character/color to it but not much definition...BUT...

After exploring the motherboard I have come to the decision that with 5 available slots and a 24+- rail it would be very easy and quite cool to drop in some other modules, such as a Neve, an API, or another D-OA, I just need to figure out how to change the input circuit on the slider channels and perhaps see if your idea of changing out the input tranx can be done as easy as it looks to be done...

The dicey issue becomes using a Neve module and tacking the input thru the slider channel, OR finding a way to bypass that strip...

This WILL become a very cool desk/baby 500 stylee module container...

 

[hitchhiker]

I had to use my MOD1 in my home studio for a few months. I had sold my CAD and was waiting for my MCI 416b to arrive.

I modded about 5 of the channels to have a reverb send. Used one of those spare bus traces on the mother board.

Between my old console and the MCI this board has to be labeled lo-fi IIHO.

I tried better output transformers from Quad8 CA127 on the MOD1 line amps and the jump was considerable. They were too big to fit the boards. It would be nice to find high quality iron that could mount on the amp cards. Then maybe mod the inputs to unbal line input and then hear what we have.

But no, thare would have to be input transformers because these boards want telescopic ground, they won't tolerate amp ground connection. (mics OK though)

 

[thermionic]

Hi,

Can anyone see the original schem in Peter's post? Has anyone got it to post?

Many thanks in advance,

Justin

 

[pyjaman]

hi,

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...

I verified. Page 61, exactly!
Laurent.

 

[gar381]

http://www.groupdiy.com/index.php?topic=30816.msg373803#msg373803

http://www.groupdiy.com/index.php?topic=22699.msg280210#msg280210

http://www.avensonaudio.com/tech/Quadeight/mm100schematicsm1.jpg

Different varations

GARY