Improving a FirstWatt-built F4

[jeffreybehr]

I understand I'm treading on shaky ground, but here goes.

Would there be any degradation in SQ if I replace the 47.5K input-load resistors with 100K or 150K resistors? I ask because each preamp channel will be driving two F4 channels plus a 67K-input channel of a subwoofer amp for a net of 17K-odd Ohms. That moves the filterpoint of the preamp's output-coupling cap to about 4.5Hz, about an octave higher than I'd like, and I prefer not to have to buy and install more expensive Teflon-film caps.

Thx in advance.

 

[Nelson Pass]

No degradation. Pick any value that amuses you. Probably 1Meg is OK.

 

[jeffreybehr]

No degradation. Pick any value that amuses you. Probably 1Meg is OK.

TYVM.

 

[jeffreybehr]

No degradation. Pick any value that amuses you. Probably 1Meg is OK.

TYVM. 220Ks get me to 1.9Hz.

 

[jeffreybehr]

Improving a FirstWatt-built F4--question #2

Probably I'll change them all to 100uF/50/std. pol. BlackGates bypassed with 1uF SoniCap Platinum (Teflon-film) caps.

But first, I'll listen (before improving parts) for as long as this compulsive tweakist can stand before turning on the soldering iron.

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From an e-mail exchange:

Sure. If you like. They can be smaller, no problem.

np

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From: Jeffrey Behr
Sent: Friday, February 10, 2012 5:06 PM
To: 'Nelson Pass'
Subject: FirstWatt F4--capacitors 1 and 2

I know you're a busy man, but perhaps you didn't see this, and I'd really appreciate your help:
1. Would it make sense to replace Cs 1 and 2 (in new-to-me, FW-manufactured-last-fall amps) with something like BlackGates?
2. Could they be any smaller…say 100uF or 150uF…and still work correctly? I have plenty of 100uF BGs so I could make them all (8 caps in 2 amps) 200uF caps.

TYMV.


Jeffrey Behr, Phoenix, AZ USA

 

[jeffreybehr]

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[didik wiryawan]

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Nice picture, Jeff !

 

[flg]

I understand I'm treading on shaky ground, but here goes...

Wowwa, cool, go for it dude!!!
But?
That's all???
Hey, I don't suppose I'm hi-jacking if:
I propose 1A minimum/Comp. FET Pair???
How about if we dump the Fairchild/IRF devices and go to 2SK1530/2SJ201???
Along with that, we should just put those Rs in the right area with .2-.22??? .1-.15 if you have balls(eggs-huevos, or matched FETs etc.)???
I suppose we need to work on that TL thingy for proper bias???
So do you want classA?// We'll Lower the 24V rails to 19-21V rails??? (a 15-0-15 0r 16-0-16 xfmr)...
I just thought those would be improvements???

 

[Gyuri]

Hm, I think I would leave it alone, as is.
Rather, I would build another one.
But I only say this.

 

[Zen Mod]

possible improvement is to make it dual mono ( another toroid + another rectifier+filter block) ;

puttin' laterals instead of IRFP's will not gain much ( if anything) ;

I made somewhere schm of biasing for lat's for someone

I'll try to find it in my PC Arc

edit - found it