Stumped on a 5e3 proluxe

[newguitarsmell]

Hi Guys
I'm building basically a 5e3 with bias control. .. David Allen suggested I use his PT TP40D which is 320v-0-320v @ 180 ma
My filter caps are 47uf - 30uf- 30uf with a 50uf bias cap.

The thing sounds like crap...completely distorted no matter what.
6L6 tubes sound just as overdriven as 6v6 tubes. Rectifier is 5au4 or a Weber Cooper cap wz34...

Weber suggested three 40uf filter caps, but the Boothill guy sent me something a lot less. I am thinking of removing the bias pot.
Thoughts?

[newguitarsmell]

Schematic. Different PT which is 540v-680v@150ma -- Weber W025130..
Here it says three 40s..

[Pietro]

Hi,

The filtercaps won,t matter that much. 50-16-16 or 50 - 40 - 40 wil be fine. Triple 50's would be overkill.
The normal bias resistor would be 250 ohms.

On output tubes, measure the cathode --> ground, and cathode --> grid voltage. Then report back. Cathode --> grid should be around -18volts i believe.
Also check for DC on the grids of the 6v6's.

See what you find and report back. 

grtz...

[DummyLoad]

>My filter caps are 47uf - 30uf- 30uf with a 50uf bias cap.
allen 180mA 640VCT transformer with TW WZ34 SS with 47uF for first filter cap is fine. 47uF first filter will probably arc with GZ34, 5U4GB will probably work.

> The thing sounds like crap...completely distorted no matter what.
you have a wiring error. find it and that amp will have clean headroom. cathodyne PI is easy to mis-wire.

post voltage chart of all plates and cathodes. some high res photos would help (dropbox.com or photobucket.com link?).

with 350ish volts to screens of 6L6GC bias V target would be around -32V to -34V, however, start with about -40V and work down to get idle plate dissipation where you think it sounds best.
bias supply better suited for 6L6GC - may be a bit too cold for 6V6 - 50uF filter for bias supply is fine. range should about -22V to -60V.   
 
--pete 

[ac427v]

You may have several things going on. Probably none related to filter cap size.
My reference says that a 5au4 rectifier needs a 3.75 amp filament supply. Your power transformer is rated for 3 amps maximum. I don't know any commonly available guitar amp transformers that would be happy with that rectifier. The copper cap should work fine with that transformer although it will produce fairly high voltage on the tube plates which can give a hard edge to the sound.
The Proluxe is very different from a 5E3 in that it uses adjustable fixed bias of the power tubes and calls for a 12AX7 preamp input tube. So its gonna distort. The 12AY7 in the original 5E3 has less than half the gain and will stay clean at lower volumes than a 12AX7. I prefer the sound of a 12AY7 in that circuit.
To make the power amp work properly, you must adjust their bias to the correct range. Most builders add 1 ohm bias measuring resistors to the cathodes of the power tubes to make biasing easier to do safely.
These thoughts assume that every component and every wire is correct. If you still have ugly distortion then more systematic troubleshooting is needed.

[DummyLoad]

5u4g - 5u4gb are rated at 5V/3A.


--pete

[SILVERGUN]

> The thing sounds like crap...completely distorted no matter what.
you have a wiring error. find it and that amp will have clean headroom. cathodyne PI is easy to mis-wire.

The troubleshooting method of using a highlighter against a schematic works 100% of the time for me.
Not only do I trace the circuit, but I double-check the value of every resistor and cap along the way.
I've built close to 30 amps now and there is still a chance that I'll slip in a 1K where I should have a 1M or vice versa.

[PRR]

Agree.

1) Hi-lighter

2) Volt-meter

These two tools will lead to the majority of build errors.

Main cap sizes is a fine trim, not a "sounds like crap" issue.