B+4

[Karl]

Hello Ampgarage

I am planning my next build. It is going to be a vibro king clean channel with ODS overdrive section and 3 tube fender reverb.

I don't have my ODS on hand to measure it myself. How many volts is the average B+4 in an ODS??

[JimiB]

Karl,
Which node are you refering to as B4

[Structo]

That would be the OD tube B+.

I don't have a #124 but the general consensus is around 190-200v on the OD tube for smooth overdrive. Lower will be smoother.

I don't know what that translates to the B4 node because it also depends what value plate resistors you use.

#124 used 100K plates and 1K5 cathode resistors.

IF you are not going to build the FET input then use a 150K or so resistor in the power supply at the end of the cap string to ground.

Here is a D'Lite power supply showing the resistor at the end of the supply.

This is for a 325-0-325v PT.

EDIT:
I found my voltage chart and I have 319v on B+4.
But I also have the higher plates at 220K/150K

[massygt6]

In my current HRM version I've got 180v and its buttery smooth, yet articulate and not at all muddy...
On the PI nodes I've got 378V on the left side and 387V on the right side.ù
410V on power tubes, biased at 35mA.
I'm on the low side of the thing, but the amp seems to run fine and smooth, got plenty of volume and bloom.

[Structo]

Are you sure you have 387v on the PI?

I have 295 and 291v.

BTW I have 204 and 205v on V2.

[massygt6]

Are you sure you have 387v on the PI?

I have 295 and 291v.

BTW I have 204 and 205v on V2.

OPS, my fault...
Typed a 3 instead of a 2...
Got 287v and 278v...