Phase Linear 3000 Series Two - Technical Questions

[jeffsplat88]

Hello AK
I have a PLS2 3000 pre-amp. I like the looks and the sound. Good phono section.
I have noticed that when I power it off, the LED's stay lit dimly, and you can still hear the relays click when you switch inputs and such. When I look at the schematic, I see a 3.3K ohm resistor across the power switch. So there is still volts being applied to the whole system even when it's "Off". Anyone know the reason why? Could I remove that resistor? I'm concerned that the 24/7 heating of the relays will eventually kill them - many already have discolored casings from heat.

Also, the pre-amp is using some TL-074 quad op-amps. Good op-amps but the ones in there are some weird brand and they are kinda noisy. Has anyone have recommendations for a drop-in replacement that would lower the noise floor? Even just switching brands of TL-074?

Thanks!

 

[llwhtt]

Certain SAE preamps use a resistor across the power switch to keep about half voltage in the unit to supposedly to cut down on the turn-on thump. I don't know what PL's reason is but you should no problems removing the resistor. What are the voltages in and out of the regulators when the unit is off?

Craig

 

[jeffsplat88]

Hi Craig,
Thanks for your response. I'll need to check on those voltages. Funny thing is that the PL3000S2 has an output relay that in theory should be blocking the thumps? Or maybe it's only there for the HP disconnect. I'll have to look into that.

 

[llwhtt]

Paragraph 3-2 in the Service Manual explains why there is a "standby" voltage when off.

 

[jeffsplat88]

Thank you so much. I hate to say that I never read through the service manual. It does clearly say that the resistor is there to keep the CMOS circuits active but the relays should prevent transients. However, is there a reason to keep the CMOS circuits active? I can still hear the relays clicking when I push inputs when the unit is off.