B251 meter calibration and input sensitivity

[MilanMilosevic]

Hello Revox friends,

I have two questions about B251 settings and I am kindly asking for your opinions. In my understanding, B251 was built with the higher standard signal level, which is 0dB=1V (B7xx series are on old standard 0dB=0,775V). You can read that on the program meter glass which says 0dB=1V. The new standard was introduced to accommodate the new digital sources which are louder, such as CD which has max. output of 2V (sources from B7xx series have 1,55V max. output). Now, here are the questions:

SETTING THE SENSITIVITY OF INPUTS
The user manual says that the sensitivity of inputs should be set in such a way that the "loudest passages" (I understand this as peaks) should not exceed 0dB on input level meter. Now, this instruction is obviously attenuating down the input signal by 6dB. For example, if I play the test CD with max level signal (0dB digital for 2V at the CD output) should I set the input sensitivity on B251 to 0dB as the manual says or higher, to +6dB?
Another question is about setting the input sensitivity for tuner. My B261 has cal tone which is approximately 0,8V or -2dB with reference to 0dB=1V. Which input level on amplifier should I set with cal tone?
I am just curious to determine the correct input settings for optimal performance as I would like to avoid oversaturating inputs.

CALIBRATING THE PROGRAM METER
The service manual explains how to calibrate the program meter: to switch to POWER, feed approximately 500mV sinus tone to the input, adjust and measure 28V at speaker outputs and calibrate to 100W with the trimpot on uP board. This is clear. But I found that more precise calibration can be achieved by setting the meter to recording level and feeding exact 1V signal to the input and adjusting the meter to 0dB with trimpot. Can you please confirm this is valid procedure?

Thank you in advance for advice.

[Wolfgang/Wien]

AW: B251 meter calibration and input sensitivity

I would like to avoid oversaturating inputs.

Hello!

The high-level inputs are able to work with a maximum level of 6V.

There is no danger to "oversaturate" the inputcircuits.

regards from vienna

[MilanMilosevic]

Re: B251 meter calibration and input sensitivity

Many thanks for your response. It is good to know that the input amplifier allows that much headroom. But again, how do you set the sensitivity in cases described in my first post and what do you do with B261 cal tone at the amplifier input?

[Wolfgang/Wien]

AW: B251 meter calibration and input sensitivity

if I play the test CD with max level signal (0dB digital for 2V at the CD output) should I set the input sensitivity on B251 to 0dB as the manual says or higher, to +6dB?

Hello!

The mainreason for the setting is to give you for all inputs the same speaker level, so you dont have to adjust when you change the inputs.
It´s a matter of your like.
I think 0db is correct.

Program meter:
The service manual explains how to calibrate the program meter: to switch to POWER, feed approximately 500mV sinus tone to the input, adjust and measure 28V at speaker outputs and calibrate to 100W with the trimpot on uP board.

The meter-display gives you a very simple information "how much the amp has to work".
It makes no difference how "exact the calibration is", it is a SIMPLE INFORMATION.
I think the service manual is the right information.

Regards from vienna