my first amp: the PSU

jerome · 4th October 2002, 01:52 PM

hi,

as part of building my first valve amp, I am trying to understand
how tube work and how PSU and amplifier are designed.

Regarding the PSU. If one hasn't got a tranny with a center tap,
is it possible to use a 'bridge' made of four rectifier tubes to obtain the fullwave rectification? From what I understand so far about tube it should be possible but I just haven't seen it anywhere.
If I use such a design, is their any drawback?

thanks

Jerome

Tom Bavis · 5th October 2002, 02:29 AM

Drawback? The number of tubes, the extra voltage drop, extra filament windings... you could do it with two 6BY5s (two isolated diodes in each) or a 5U4 and two 6AU4s, or four 6AU4s. Watch out for filament cathode voltage ratings, or use separate windings for tubes on opposite sides of the bridge. You could also mix a tube rectifier with two solid-state ones and retain the slow warmup.

Colt45 · 5th October 2002, 04:07 AM

biggest drawback IMO is the fact that youre burning off half of the filament winding on the rectifier stage.

but, 2 6AL5's would make for a nice little FWB, maybe for bias or something. i dont know.

45drive45 · 5th October 2002, 04:17 AM

well instead of using 4 tubes, why not just build a hybrid with 2 SS diodes and one tube rectifier for example GZ34 etc.

Much simpler!

For details see:

http://www.audiodesignguide.com/

I have used this and its great!

Brett · 5th October 2002, 08:14 AM

<b>You could also mix a tube rectifier with two solid-state ones and retain the slow warmup.</b>

The drawback with this arrangement is you still get the switching spikes from the SS diodes, which are not eliminated by either the filter capacitors or chokes. IIRC Lynn Olson and Matt Kamna did some research into this and measured the results as well as listened.

Full tube bridge, hybrid or SS all have their advantages and drawbacks. If it was me, I'd get a little filament trans for the rectifiers or a power trans with the correct secondaries and a centre tap, and use a pair of good damper/booster diodes like the 6D22S.

4th October 2002, 01:52 PM	#1
jerome diyAudio Member Join Date: Sep 2002 Location: cardiff, uk	my first amp: the PSU hi, as part of building my first valve amp, I am trying to understand how tube work and how PSU and amplifier are designed. Regarding the PSU. If one hasn't got a tranny with a center tap, is it possible to use a 'bridge' made of four rectifier tubes to obtain the fullwave rectification? From what I understand so far about tube it should be possible but I just haven't seen it anywhere. If I use such a design, is their any drawback? thanks Jerome

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

5th October 2002, 02:29 AM	#2
Tom Bavis diyAudio Member Join Date: Jun 2002 Location: Macedon NY	Drawback? The number of tubes, the extra voltage drop, extra filament windings... you could do it with two 6BY5s (two isolated diodes in each) or a 5U4 and two 6AU4s, or four 6AU4s. Watch out for filament cathode voltage ratings, or use separate windings for tubes on opposite sides of the bridge. You could also mix a tube rectifier with two solid-state ones and retain the slow warmup.

5th October 2002, 04:07 AM	#3
Colt45 diyAudio Member Join Date: Feb 2002 Location: Canada	biggest drawback IMO is the fact that youre burning off half of the filament winding on the rectifier stage. but, 2 6AL5's would make for a nice little FWB, maybe for bias or something. i dont know.

5th October 2002, 04:17 AM	#4
45drive45 diyAudio Member Join Date: Dec 2001	well instead of using 4 tubes, why not just build a hybrid with 2 SS diodes and one tube rectifier for example GZ34 etc. Much simpler! For details see: http://www.audiodesignguide.com/ I have used this and its great!

5th October 2002, 08:14 AM	#5
Brett diyAudio Member Join Date: Jan 2002	<b>You could also mix a tube rectifier with two solid-state ones and retain the slow warmup.</b> The drawback with this arrangement is you still get the switching spikes from the SS diodes, which are not eliminated by either the filter capacitors or chokes. IIRC Lynn Olson and Matt Kamna did some research into this and measured the results as well as listened. Full tube bridge, hybrid or SS all have their advantages and drawbacks. If it was me, I'd get a little filament trans for the rectifiers or a power trans with the correct secondaries and a centre tap, and use a pair of good damper/booster diodes like the 6D22S.