Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: harryk on July 20, 2010, 10:41:55 am

Title: A big choke or not to a Fender Pro 5E5-A clone ?
Post by: harryk on July 20, 2010, 10:41:55 am

 :rolleyes: I made one of those amps according original schem and with a big choke filtering also B+ current, but now when I am starting another similar project, I am considering to do filtering a`la BF amps and use a smaller choke in filtering chain with maybe bigger caps. What I am now asking, if there is a big difference in sound and overall feel if I change filtering as I planned. I know that in past days capacitors were expensive and that was the main reason to use a bigger choke. I would like to have more life and dynamics to forecoming 5E5-A sound and less hifi ??? Any ideas how does it change this amp character? Harry

Title: Re: A big choke or not to a Fender Pro 5E5-A clone ?
Post by: tommytornado on July 20, 2010, 11:25:32 am

I've done two 5E7's with the big choke before the plates and two with the smaller choke between the plates and the screens.  I can't tell any difference..   

Title: Re: A big choke or not to a Fender Pro 5E5-A clone ?
Post by: jjasilli on July 20, 2010, 11:38:14 am

There are formulas to compute the effects on frequency fitering (120Hz ripple).  But to complicate matters, the power supply is the return path to ground for signal, through the AC load of the plate resisitor on the small bottle tubes.  Therefore the value of components in the B+ rail has an effect on signal.  Everything is so interactive that it would probably take a supercomputer to sort it all out.  But to what end?  How does a set of numbers on a computer screen relate to your ear?

Weber makes an inductor substituon box.  Or, why not rig-up an array of 2 or more switchable chokes, and see how you like the results?

The input choke (instead of cap input) makes a stiffer power supply -- i.e., more voltage regulation = les sag = more "hi=-fi".  

All that being said: Tweed, BF and SF Fender amps, whether they have chokes or not, are not known to sound hi-fi-ish.

Title: Re: A big choke or not to a Fender Pro 5E5-A clone ?
Post by: FYL on July 20, 2010, 12:33:28 pm

A larger cap at C1 (plates), say 47µ, a 4H choke and another larger cap for C2 (screens) gives excellent results in tweedy Pro/Super/Bandmaster/... amps.

 

Title: Re: A big choke or not to a Fender Pro 5E5-A clone ?
Post by: harryk on July 20, 2010, 12:37:44 pm

Thanks! I think that I first try lighter choke. If it does not sound right, I can easily change filtering to original schem.