Revox brings a new B77 Mk III to market!

[dminches]

Victor, what do you mean by “EQ adjustment?” Do you mean the ability to go from NAB to IEC?

 

[Foxbat]

No, I mean tweaking the high frequency playback response. Many machines have it, but B77 doesn't. I believe PR99 has it, but not the lower models.

I discovered that when checking one of my two B77's - I thought a correction was required so I looked for the usual control... and it was not there.

People have been coming up with various solutions, replacing the fixed resistors with trimpots, but it is not a clean solution.

 

[dminches]

Gotcha. I have a PR99 MKII and it does have a high frequency adjustment for calibration.

My PR99 has an NAB reproduce card. I converted it to IEC by changing 6 resistors.

 

[Foxbat]

Yes, EQ conversion is not too hard, but a switch would be "even more better".

Some machines have it, and Chuck Ziska put it into my ancient Crown CX-822... that machine produces an amazing sound.

 

[adrianywu]

You are correct, and they also don't have playback EQ adjustment, which I think is even more important.

Even if you buy some upgrade boards those usually don't have the EQ adjustment.

The native B77 repro boards have pots for EQ adjustments for bass and treble. They are accessible via holes at the bottom of the machine, after removing the case. The Audvance boards (both the recording and the repro) have selectable EQ using jumpers, and a switch can be installed on the machine to do this without removing the case. The EQ pots are located in the same place as the native boards.

 

[Foxbat]

No, Adrian, they only have treble for the record amplifier, nothing on the reproduce ones.

Here is the original B77 board, and there are only two level trimpots.

 

[adrianywu]

No, Adrian, they only have treble for the record amplifier, nothing on the reproduce ones.

Here is the original B77 board, and there are only two level trimpots.

View attachment 138945

Yes, the original board only has one pole. The Audvance board has two, and the new Revox.de board (which I presume is used in the new machines) has four pots per channel.

 

[dminches]

Yes, the original board only has one pole. The Audvance board has two, and the new Revox.de board (which I presume is used in the new machines) has four pots per channel.

I have the Audvance board. The 2 poles are for 400 Hz and 10 kHz.

 

[Foxbat]

For clarity - the original B77, and many upgrades do not have any EQ adjustment in playback circuits. I spoke to several providers of such upgrades. They of course claim it is best that way.