Beyer / info needed : Revox A77 pro model. Using Xformers for other projects?

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doubleroger

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Aug 24, 2008
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paris, france
I have a Revox A77 PRO version, wich is the model with in and out balanced, XLRs. It's been taking space for years on my bench, doesn't work, and now I'd like to use some of its parts.

It has got 2 Beyer inputs transformers (TR/BV35817, can't find anything, even on kubarth site, and I don't know how to read beyer names), and a pair of line driver cards, with output transformers.

It seems there are schematics for all the versions but this one on the internet

Does anyone here have have a shematic for these output cards? Or maybe someone has used those in some other project already?
It would be so cool to use them "as is" for some DIY.
thanks.
 
Bumping this old thread.
I'm still on the lookout about those transformers, also about the ouput cards.

I've seen Danmarks Radio-versions of the A77, mounted with Beyer transformers on the inputs and Neutrik transformers on the outputs. Sounding very, very good indeed.

I have schematics for the A77, but not for the transformer balancing (which should probably not be too difficult)

Jakob E.

I'd like to use those one of these days...

Any info would be great. :)
 
pretty easy to figure out your options,

these Beyer's tend to be simple Pri -  Sec affairs, so just measure the DCR.

if the transformer is really small, you will have to limit the input to mic level,

and it must have more ohms on one side than the other, so it will step up the mic signal,

if the xfmr has the same ohms on both sides and is small, you will have a hard time finding an application.

if the ohms are the same and it is medium size, you could use it as a 600:600 bridging xfmr

if the xfmr is medium size and has more ohms on on side, you can use it as a line input.

i do not think you will want to use it as an innerstage or output, so mic pre, or eq input, maybe 1176

 
Yay! thanks for your answer CJ  ;D

I don't have it just there (stoopid christmas with its mandatory fois gras) but I'll measure DCR as soon as I get back. They are indeed very small in size. I find it odd that the numbers don't seem to relate to the Beyer catalog from kubi's site. All I have is a date code (11-72).

I'll also post some pics of it and of the Studer cards as soon as I finish eating all this stuff (about five days).

 
they probably do a ton of OEM work, which means private labels,

we had to buy a label machine and computer at work because everybody wants their name on our crap,

if they only knew.  :D
 
Hey, those small Beyer are the same size as their mic-input var @16mm.
But they are intended for line-input.
I measured mine of around 5kohm on both prim end sec.
I guess they can handle about the same levels as their mic var.
If you put some +18 dB on the prim. It will be hot.
Cheers Bo
 
bovox said:
Hey, those small Beyer are the same size as their mic-input var @16mm.
But they are intended for line-input.
I measured mine of around 5kohm on both prim end sec.
I guess they can handle about the same levels as their mic var.
If you put some +18 dB on the prim. It will be hot.
Cheers Bo
Yes they are 16mm diameter transformers.

I've measured DCR, and I get 5.65k : 8k .

Should I consider it has a 1 : 1.4 ratio, I seem to remember it is a little bit more complex to get the ratio of an unknown transformer.
I'm thinking of trying those as mic output in a tube Royer mod'd MXL 603. Any idea if that'd fly? (it's originally supposed to be a JT-MDB transformer as 1:2).

Thanks for the answers so far. Pics are coming whenever the girl comes back with the camera...
 
Here we go, girlfriend or not, there's always Photobooth!
revoxlinein.jpg

revoxlinedriver.jpg


I've read somewhere (here) that the output transformer would be a neutrick OEM. Transistors say "BSX45-16"- "BC161-16" (those two are driving the transformer) ,  and the third isolated one is a bsx45-16 too. The Studer epoxied 9 pins thingie (were there opamps around 1972-73?) is called "M240 Y A 101". This one doesn't seem so complicated. I should probably try just to hook it up to something unbalanced, right? (provided it has a low output impedance like an opamp).

 

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