Resistor Question

[lpd]

How integral are the carbon comp 100K 3W resistors to the power supply circuit? I used metal film but am now wondering if carbon comps would have a different impact on overall tone.

[Mark]

No difference what so ever. The resistor bleeds off DC when you turn the amp off.

[lpd]

No difference what so ever. The resistor bleeds off DC when you turn the amp off.

Ok that makes sense. What exactly "browns" out an amp? I'm running 40 volts low across the required voltages and am going to swap another transformer in to bring closer to spec but the amp has a colder sterile feeling to it.

[Mark]

I'm not sure I understand what you mean by browning out, my metal image of browning out is substantial power supply sag.

An Express or Liverpool isn't about power sag, my experiences lead me to believe the relativity stiff power supply ensures consist tone when the amp is turned up.

There are probably other opinions out there, though I did build a prototype in 2004 and I observed the tone radically changing as the rail voltage radically changed.

[lpd]

I'm not sure I understand what you mean by browning out, my metal image of browning out is substantial power supply sag.

An Express or Liverpool isn't about power sag, my experiences lead me to believe the relativity stiff power supply ensures consist tone when the amp is turned up.

There are probably other opinions out there, though I did build a prototype in 2004 and I observed the tone radically changing as the rail voltage radically changed.

Seems to me my amp should be warmer than it is. I'm going to try playing with voltages and see what happens.

[Mark]

Have look at some of the Blue Guitar circuits in the bowels of this forum. People were putting caps across the plate resistor of the second stage to ditch top end response.

https://tubeamparchive.com/files/wreckxpr.pdf

You can also try doubling the 0.002uF coupling cap.

[Zippy]

No difference what so ever. The resistor bleeds off DC when you turn the amp off.

Ok that makes sense. What exactly "browns" out an amp? I'm running 40 volts low across the required voltages and am going to swap another transformer in to bring closer to spec but the amp has a colder sterile feeling to it.

What are your actual voltages?

"Cold, sterile" usually indicates improper bias. Have you checked that?

Depending on the amp, running low voltage overall is not so terrible if you compensate the dropping string to get the preamp and PI voltages in spec and leave the output tubes running a lil' low (making sure that the bias is correct). I'd try that before swapping out the PT.