question about Derek Trucks' amp????

[rockeye]

I was browsing the net and came upon a post by Lord Valve who works on Derek Trucks' amps. Besides the fact that he leaves V1 empty and has the tremolo circuit lifted, he also has "The 5AR4 rectifier feeds a 50uF input capacitor, rather than the stock 35uF value." --Lord Valve.

What does having a different capacitor with the rectifier do?
Is this a normal mod for Super Reverbs?

The link to the post is here http://newsgroups.derkeiler.com/Arch.../msg02893.html

[Blue Strat]

It tightens the low end and makes the amp run a bit cleaner.

Normal mod? "Normal" is a quantitative, not qualitative, term meaning "more than average". From that perspective, it's not normal but it's technically "OK".

[rockeye]

Cool thanks. Thats not for me then.

[Blue Strat]

Originally Posted by rockeye

Cool thanks. Thats not for me then.

At the big stage volumes he's playing at, and with the preamp mods that have been done, he needs the extra tightness in order for the tone not to turn into mush.

It's all about how loud you're playing. Seeking the rig of guys who play large stages, when you play in clubs, is a very bad idea.

[Nolatone Ampworks]

Originally Posted by rockeye

I was browsing the net and came upon a post by Lord Valve who works on Derek Trucks' amps. Besides the fact that he leaves V1 empty and has the tremolo circuit lifted, he also has "The 5AR4 rectifier feeds a 50uF input capacitor, rather than the stock 35uF value." --Lord Valve.

What does having a different capacitor with the rectifier do?
Is this a normal mod for Super Reverbs?

The link to the post is here http://newsgroups.derkeiler.com/Arch.../msg02893.html

Are we talking about the first filter cap after the choke? I thought the stock value for that was 20uf.

[GearHeadFred]

Originally Posted by nolatone

Are we talking about the first filter cap after the choke? I thought the stock value for that was 20uf.

You are correct!

http://schematicheaven.com/fenderamp...b763_schem.pdf

This would add "stiffness" to the power supply, yielding slightly less sag.. Mike is correct in that the only time you would ever have a chance of noticing this would be at or near full volume.

[tlpruitt]

Originally Posted by nolatone

Are we talking about the first filter cap after the choke? I thought the stock value for that was 20uf.

No. I believe he is referring to the two 70uf filter caps connected in series that are between the GZ34 rectifier and the choke (TR2 in the schem). Two 70uf caps in series give you 35uf. It is not uncommon to replace those two 70uf caps with two 100uf caps in series which would give you 50uf.

-Tim