UREI 1008 Mic Preamp Schematic

[edanderson]

thanks for the additional info.  i think i remember seeing that info before, but always good to get it out there.

i put in an email to magnequest to see if they know anything about the peerless part mentioned.

while we're talking about the 1108/1008, does anyone have docs for the 508 passive eq module that worked with them?  i haven't seen that schematic floating around anywhere.

ed

 

[Lukpio]

Well...

http://amtecaudio.com/UA508A.jpg
http://amtecaudio.com/UA508B.jpg

 

[edanderson]

thanks Lukasz!  is there a page on your site that lists all the schems you've posted?  dig your EQs by the way...

ed

 

[Lukpio]

Thanks Ed!
There are just a few schematics on my website. I post them only when someone asks and I have it...

Out of curiosity... Does anyone know what kind of core does the 5946 output transformer use? Is it EI steel core?

 

[opacheco]

i put in an email to magnequest to see if they know anything about the peerless part mentioned.
ed

Ey edanderson let us the comments from the magnequest!!!!...

opacheco.

 

[opacheco]

Now that's the kind of info I like to see around here.  Curious what your experience is that leads you to this info? 

Hi,
A good buddy gave me scans of some of his docs as a backup and also for a few projects in the works.
I'll leave it up to him to decide if he wants to post any more info himself or if I can.  I don't have everything myself but I know he has the full winding info
for some of this stuff.


J.L.

Aardman, What did you buddy about this issue???

I will be pending
Opacheco.

 

[opacheco]

OK, here's "some" info regarding the input transformer for the 1108, 1008 and 1016.  Enough to get you close anyway.

Spec calls for:

Primary Z of 600, 150 and 37.5 ohms.
Primary being Bifilar wound.
Secondary Z of 65K +/- 2K although the Peerless version measured 70K - shock!!!!
Core may be EI-375 HYMU .014  3/8" stk or equiv.

Various manufacturers used and the internal part numbers:

Microtran: Micro W5127
Also Microtran M1-A
Peerless: 4786
UTC: 6448
EE (Electro Engineering Works): EE4786-E14650

I have windings DCR of the UTC, the Peerless and the EE but not the Microtrans..............A UTC 0-1 was also considered and tested but not used........I do have the full info for the 1008, 175 output (the 5946).....

Winston O'Boogie that is great info!!!!.......but could you post the full DCR information and the 1008 and 175 output 5946 full information please???

Thanks a lot,
Opacheco.

 

[Winston OBoogie]

Winston O'Boogie that is great info!!!!.......but could you post the full DCR information and the 1008 and 175 output 5946 full information please???

Thanks a lot,
Opacheco.

Maybe at another time.  As I said:

Part of my wishing to keep a lot of this stuff to myself "for now" is that there is a Universal Audio tube desk that has been restored and the owner wants to expand it.  He will be having the 1008 outputs and inputs made as part of that process and I may get to earn some money from this old paperwork for a change!  Some of this stuff has cost me dearly over the years, either in cash or in sweat and tears chasing it down. 
Not trying to be a hoarder or a jerk. I'm sure you understand.

 

[opacheco]

Maybe at another time.  As I said:

Part of my wishing to keep a lot of this stuff to myself "for now" is that there is a Universal Audio tube desk that has been restored and the owner wants to expand it.  He will be having the 1008 outputs and inputs made as part of that process and I may get to earn some money from this old paperwork for a change!  Some of this stuff has cost me dearly over the years, either in cash or in sweat and tears chasing it down. 
Not trying to be a hoarder or a jerk. I'm sure you understand.

Ok Thanks a lot!!....
Opacheco.

 

[Ian]

Hey Mr. O'Boogie, would you be willing to share these docs at this point? I think a lot of people are looking for info on this thing (myself definitely included)! If not, it's totally cool. But worth a shot.

 

[opacheco]

Hey Mr. O'Boogie, would you be willing to share these docs at this point? I think a lot of people are looking for info on this thing (myself definitely included)! If not, it's totally cool. But worth a shot.

Mr. O'Boogie, That's will be great!!!.......Give us this info please!!.....jejejejejeje

Opacheco.

 

[peters]

I built the Drip 175B using the specified Sowter 8650 transformer, which is 9CT:1 but it seems to be the limiting factor in the frequency response of the unit (have already changed out the input trans).

http://www.sowter.co.uk/specs/8650.htm

In this application it is -2.5db at 40Hz; I was hoping for better low end...

Sowter also offers a 7.3CT:1 transformer intended for the Sta-Level output, their 9185. There does not seem to be a spec sheet but its rated for 8kCT/150 +40 dBu DCR 40 ref secondaries on their vintage page:

http://www.sowter.co.uk/vintage-audio-transformers.php

The Sta Level has a similar output stage as the 175 but I am guessing that the 6V6 tubes put out a bit more than the 12BH7 so it might be a bit over rated.

Would the Sowter 9185 make a noticeable improvement over the 8650 for the 175B?
I would expect that the lower ratio would mean higher bandwidth. It also seems to be closer to the original design (7CT:1).

thanks,
--Peter

 

[Bill Wilson]

For the input transformer a UTC A-10 would do very nicely. It has a winding ratio of 1 to 10 & has the necessary taps on the primary. The secondary impedance is 50k ohms & will take +15dbm before the core saturates. The freq response is down only 1 db @ 30cps & .5db @ 20kcps,
(oop's hertz), forgive me but I cut my teeth on tubes back in 52.

The A-10 will work for the 1008 & 1108 as they are to single grid & single FET; it will not work for 1016 as it is a balanced circuit configuration & requires a split primary. A UTC HA-114 will work well as the output xfmr. for the 1016, it is 30k ohms split primary w multiple secondaries covering all the pro output impedances & will handle +23dbm. It is perfect for a 12AY7/6072 in push pull. Freq. response -1db 30hz to 40khz. Input trafo. for 1016 would be a UTC A-12, it has split windings on the secondary for push pull.
Have not take the time to look @ 1108 in detail so cannot give you anything but a guess on the output trafo's impedance but could be around 600 ohms.

I can guarantee the frequency response of the A-10 as I used them in a 6 input 3 channel mike muxer in 64; when I was doing on location mastering for a couple of small rcord co's.

Hope this helps.
Bill W.

P.S.: the dbm figures on the transformers are for the 600 ohm impedance.

 

[Piscolabis]

Hi to all,

Anybody knows the values of the 508 eq Inductors?
Maybe the Carnhill VTB9050 will match?
Some interesting post to diy indcutors?
To much questions  ;D?
Thanks a lot

Nacho