PL 700 II REPLACEMENT MAIN VOLUME POTS

Look how the gain and phase changes on the graph. Going to print these out when I get home and study them. Thank you Joe!
 
Any experimentation with a 10k pot?

That’s what I have for “fine balance” on the phono pre and the stepped attenuator is (essentially) a 10k pot as well.
 
I agree with "pot delete" from the circuit myself... Just curious.
 
The volume pots on my 700B were deactivated for simplicity’s sake. The pots are still there for something to keep the (unused) knobs in place.

But….when preamps have stepped volume controls, being able to attenuate the power amp would be useful.

Circumstances dictate that my listening level is low. It often seems that one “click” up on the pre-amp’s volume control is too loud and the one “click” below is not loud enough.

From time to time, I will substitute a pre-amp with a continuously variable volume control even though I prefer the one with a stepped volume control for various reasons.
 
So Joe what happens if you remove the 220k resistor. That is not used in 400 and I believe is part of the high pass filter4793B15C-185F-423B-9CA2-C07B6D4D0D9E.png
 
No, that shorts any large current induced into the RCA cables...like dragging your feet across 30 feet of carpet, then grab the ol RCA..
 
50% pot setting, 100K pot. Input impedance = 55.54K ohm at 100 Hz or greater, 220K at DC

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Any other variants you want to see Glen?

The 220K is to bleed off any residual charge stored on C2, you can see by the circuit that C2 is shunted by R1 and P1 to bleed off any residual DC component.
 
Gepetto said:
Any other variants you want to see Glen?

The 220K is to bleed off any residual charge stored on C2, you can see by the circuit that C2 is shunted by R1 and P1 to bleed off any residual DC component.
Click to expand...
Thanks Joe. I think I’m done with this exercise. I’ll carry on with bypassed pots and no high pass cap and Resistor.
 
grapplesaw said:
Thanks Joe. I think I’m done with this exercise. I’ll carry on with bypassed pots and no high pass cap and Resistor.
Click to expand...
The PL400 series 1 has the best configuration, no pots and direct wiring to the control board. All that wiring and separate potentiometers are just a noise antenna. Nice eye candy on the front panel but it actually degrades performance

You can see the detrimental effect of that input cap to the low frequency performance at 10Hz
 
grapplesaw said:
So Joe what happens if you remove the 220k resistor. That is not used in 400 and I believe is part of the high pass filterView attachment 72429
Click to expand...
Glenn, they left that switch out on the 700 Pro. The coax runs directly from the RCA jack to the pot, then to the control board. Best I remember, none of that was in the Pro, especially the switch. The 220K may be on the control board.
Thinking about a LED pilot light to fill the pot hole. On the S2, the Cylon meters are powered by 12 VAC via the transformers secondary. Many 12 VAC LED assemblies are available, but what about taking DC off the WOAD Cylon meters Phoenix Connecters? That would be slick and elegant. Maybe another product Joe can offer.
When I get home this weekend I'll print the schematic and see what's available for DC.
Maybe someone has a better idea than a LED pilot light or ?. How about laser pointers :).
 
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