Suhr SL67 mkII master volume type?

[What?]

I have seen lots of mentions that the Suhr SL67 mkII master volume is very effective down to whisper volumes, eliminating the need for an attenuator. And supposedly it is something different than the Lar/Mar PPIMV on the SL67. Anyone know what type of master volume is being used on the SL67 mkII?

 

[Pete Farrington]

Any decent photos?
Is it supposed to maintain presence control functionality at low master volume settings?

 

[What?]

Any decent photos?
Is it supposed to maintain presence control functionality at low master volume settings?

I'm keeping an eye out for pics. I haven't found any yet.

 

[961le]

 

[What?]

That is the first version. The master volume was changed in the MKII.

 

[dtier]

This has got me thinking of the Rich mod that I had tried years back and liked then. I forgot about it and presently have the Lar-Mar type 2 installed on one head. I'm gonna change it to the Rich mod as I think it may sound better at lower volumes? The rich mod appears to load down the grid leaks and the inverter inversly. It's a weird circuit. Am I seeing this correctly?

 

[dtier]

Actually I see it's the same but they are using the original grid leak as the safety resistor. The values are just different. However, that arrangement may yield an audible difference.


I have heard recently of just shunting the grid leaks with a dual pot, that would be connected as a rheostat.

 

[Emiel]

This has got me thinking of the Rich mod that I had tried years back and liked then. I forgot about it and presently have the Lar-Mar type 2 installed on one head. I'm gonna change it to the Rich mod as I think it may sound better at lower volumes? The rich mod appears to load down the grid leaks and the inverter inversly. It's a weird circuit. Am I seeing this correctly?

I have the Rich Mod II MV in my '68 1987 clone. The amp obviously sounds better with the MV cranked but it works well enough at low volumes. The MKI Suhr looks like to have the Rich Mod, I too wonder what they changed in the MKII. Guess we'll have to wait for inside pictures to show up!!

 

[What?]

I sniffed around and ran into this yesterday, which is obviously what Friedman is using. I think it is likely what Suhr is using too. Go to 49m12s.



Friedman is describing it as just a 250k pot in parallel with the bias splitter resistors to reduce the values of the resistors, with resistor values of 130k but saying that 220k resistors sound the same.

Anyone know where that type of PPIMV originates or what it is called? I think I would like to try it on my Ceriatone Plexi 51 in place of the LarMar PPIMV.

 

[What?]

From the comments of the video below:

How is the MVC wired? Dave claims it's not a regular PPMV. I ran a few tests over here based on his description and
I believe he flipped the connections to pins 2 and 3 on the pots, added an extra pair of coupling caps and used 2.2M
bias/grid resistors in place of the standard 220k. Is my assumption correct?

I can recheck the wiring of the pot in 2 days. Add caps I didn‘t notice. Output side of PI CCs are 100nF if I recall
correctly. No grid Rs yes. Two 2M2 yes ( as in LarMar). Will let you know.

Pot is wired like a variable resistor instead of a divider, which changes mostly the taper.

 

[Emiel]

So the PPIMV is basically a Lar/Mar without grid resistors? Can anyone confirm?

 

[What?]

So the PPIMV is basically a Lar/Mar without grid resistors? Can anyone confirm?

That is what it sounds like is being described in the posted comments in that last video for the Plex.