Revox A77 Alignment tape and replay level

D

demto

New member
I have a Revox A77

I want to use Quantegy 456 on the machine. This is a 355 nWb/m [+6dB] tape.

I have a test tape. This is 355 nWb/m [+6dB] tape.

My question is what voltage do I set the replay level to when running the test tape.

I know that the initial setting of replay level will affect the record level and
Vu meter settings if I then carry on and align the machine fully.

The question of setting the replay level correctly is bugging me and I would be very gratefull to anyone out there who can give advice.

Thanks, Demto
 
Believe me, if anyone here knows the answer off the top of their head they will happily answer.

Myself, I am not familiar with your Revox model.

You have the manual but it’s not clear, correct? Does it list input and output levels in dBv anywhere in the specifications? Regardless of the flux level, this value will remain the same.

Regards :)
 
My references give +6db/185 as 370Nw/m^2, not 355, so it may need some clarification.

But,... given that caveat,...

Using a [+6db/185Nw/m^2], (370Nw/m^2) test tape to set the recorder for Quantegy 456, you'd set the "reference playback tone of 1kHz @ 0VU" to "+3db(VU)" on the meters.

This sets "+3db(VU)" on the meters to [+6db/185Nw/m^2], 370Nw/m^2, (456's Maximum Operating Level),...

while keeping "0db(VU)" on the meters at [+3db/185Nw/m^2], 250Nw/m^2, (456's Standard Operating Level).

This provides for optimal recording levels at "0db(VU)" average, while allowing the needles to bounce comfortably to "+3db(VU)" before reaching the MOL, above which distortion will occur.

;)
 
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Beck

Thank you very much for answering

Yes, I have the manual, and yes its not clear.

The Vu meters do not work in playback mode on the A77 [not just mine, on all of them] So you cant just play the tape and set meters to 0vu for a +6dB replay level.

The manual says play the "test tape" and set the replay volts to 2 volts. Problem is
manual doesn't say what the output of the test tape is.

In a later add on to the manual it then says the machine should be set up for 257 nWb/m [ +3dB] and the replay volts should now be reduced to 1.55 volts. The manual
is unclear whether this is using a new test tape or the original, but I think it means the original

From this I am assuming that the replay level using a 355 nWb/m [+6dB] test tape should be lowered by -3dB. This would the go down from 1.55 volts to a new level of 1.1 volts.

I know that the record level would then have to be reset, and Vu meters also altered
to complete the +6db setting. This is not a problem. I can do this. The real problem I
have is setting the initial replay voltage using a +6dB test tape.

Beck, what do you think of my reasoning on the replay level. Do you think I am
somewhere near the mark, or am I way off ?. I would greatly appreciate your view on
this if you can spare the time to reply
 
Davemania

I had just finished replying to Becks info [above] and when I sent it and checked it
was on the board I saw you had also sent me some info. Thankyou.

I,m in the UK and its gone 3 AM here so you must also be up late or I guess you may
live in the USA.

The problem is that I want to do a full alignment on the A77. I dont know what it is
set up for at present. It will mean setting the replay level, the record level, Vu meters,
bias etc. A revox repair man I spoke to a couple of years back explained how to do
this plus I have the manual and necessary equipment. At the time I/we didnt go into detail about which test tape and exact details of which voltage for which test tape. Its too late now as I have mislaid his phone number.

The other problem when setting the replay level is that the Vu meters on Revox A77s
do not work in playback mode. They were all made that way.

I know is that setting the replay level is one of the cornerstones of the alignment, and that once I know this I know how to set up the rest.
The final ins/outs would be as follows.

0 Vu on record Vu meters would be for a +6dB record level
The replay output would be 1.25 volts for 0 dB record level

Its just choosing the right replay voltage thats bugging me. any assistance you can
give would be great.

Demto
 
Beck

Re "does it list input and output levels anywhere" ?.
I forgot to answer this part of your question.

This might be relevant... from the manual

AUX Max input 35 mv
AUX Max output 2.5 V
Max distortion 3%
 
Demto,

I haven't forgotten you today. I have managed to contract the flu (actually for the last several days, but getting worse), and I feel like doggie doo -- dizziness, sinus pressure, Rupert Holmes “Pena Colada Song” stuck in my head (probably from the fever), and a general malaise. I often hear music in my head, but it’s usually my own, or at least some classic rock.

But I’m intrigued by this A77, so I will be back in the discussion just as soon as am past the worst of it (Geez, I hope it’s not the bird flu, or the dreaded Kung Flu).
 
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