Monkeymatic Tamalpais - build in progress

[matt h]

(deleted)

[xtian]

As I'm relistening to it (through non lappy speaks), I hear what you're talking about--I also remembered the comment about your bass control. you might wanna drop the cathode bypass cap on the first stage to 1uF or less, especially if you're gonna keep throwing buckers at it. Should also give you more room with the bass. Of course, I've never met a fender that sounded anything other than flatulent with the bass above 3, so, eh...

I "fixed" the bass control by replacing the 250K pot with 50K. Much better, at least from a user interface perspective. Tone didn't change, but that's OK. Not concerned with the amount of bass. Sounds good clean, and rolling the Bass off when cranked up works nicely.

I'd also consider some tube rolling in there, if you've got a 5751, for instance, that should make a killer tube choice in this amp.

I'll look. Don't think I have one.

I also can't remember offhand what value coupling cap you've got between the preamp and the input to the PI, but don't be afraid to use something tiny in there.

500p, as spec'd in the 6G6B schematic.

[Structo]

Looks like a cool build.

I noticed on your layout you didn't have a ground on the two 220K grid leak resistors on the power tubes.
You probably did it on your amp.

[xtian]

Looks like a cool build.

I noticed on your layout you didn't have a ground on the two 220K grid leak resistors on the power tubes.
You probably did it on your amp.

True, Tom. I have another layer in my Illustrator drawing for the grounds. Turned off for simplified viewing.

[xtian]

Played this amp in the city plaza last night. Simply awesome. Set at edge of breakup, with a little boost from the Mid lift pot. Closed the set with Godzilla.

Mic. Dropped.

[xtian]

Revisiting this amp. Great tone. Great distortion when it's possible to turn it up.

The Mid lift pot is THE mod--I love what it does, changing from Fender to Marshall.

I had put in a VVR but took it back out--served no good purpose, as distortion not nearly as nice sounding when dialed down.

433v plates, 500R cat resistor, 77mA current puts me right on 100%. Getting max 22 watts output before distortion. Sound about right?

[pdf64]

433v plates, 500R cat resistor, 77mA current puts me right on 100%. Getting max 22 watts output before distortion. Sound about right?

What is the voltage difference between the cathode and HT at the point of clipping?
HT will sag and cathode voltage will squish under the higher current draw, so to assess whether 22 watts is reasonable, need to know how much voltage is available for signal swing across the load.
I think it's probably a reasonable output, as the cathode voltage will likely get up to ~50V and HT fall to ~380V, so a rough and ready 330^2/6000 = ~18 watts.