Tube mixer VU mod

[Quayhog]

A general question here.  I have several ancient tube mixers, 4 or 6 inputs to 1 output.  Grommes G5M, Berlant MCM-2 and Altec  1567a. I have two VU800 analog 8 channel 1U meter system by SM Pro Audio.  I'm wondering if it would be ok to tap the mixer circuit at each volume control between the wiper and the channel separation mix resistor and feed that signal to the meter circuit? How would I adjust the impedance for each tap?

With the exception of the Berlants these mixers have a single VU meter that sums all channels at the output.  My plan, if it makes sense, is to use the Altecs to sum the outputs of my Four Grommes mixers before I send it to my tape recorder.  Without a meter for each channel it's awkward to set and verify levels.

The Four Grommes mixers have all been electrically restored as well as the Altec's.  They all sound wonderful. I'd just like to increase their usability.

 

[Pip]

http://jlmaudio.com/shop/vu-buffer-peak-led-kit.html

 

[Quayhog]

I've looked at this kit.  The kit does what is already inside the VU800 assembly.
It doesn't answer the basic question of where to tap the signal off of the mixer.

 

[ruffrecords]

I think that you are not going to be able to do this on the Grommes. I have looked at the schematic and it looks like the channel faders are 500K pots. This means and VU meter, even a buffered one, would seriously load the pot and the stage driving it.

Cheers

Ian

 

[Quayhog]

Thank you Ian for looking.  I think you're probably correct.  I don't have a schematic of the VU800 meter panel.  It's a shame if I can't find a work around because the panel Assembly looks nice and sure would solve my major issue.

I'm thinking of making a small box with a few 12AX7 and send the tapped signal to the meter bank.

I use these mixers to record my bluegrass band practices, it's awkward to set levels and I was hoping to make it easier.  These Grommes mixers are sure nice, I've rebuilt them so they'll last through my son's life and maybe even his kids.

Too many projects to do, so little time.

 

[ruffrecords]

I don't know how much of a mod you are prepared to do but one option would be to buffer the pot outputs with a FET op amp and feed its output to your VUs. The FET op amp would need to be physically close to each pot to avoid HF losses dues to cable capacitance.

Cheers

Ian