Why two GZ34 in this schematic?

mfaughn · 20th June 2011, 06:48 PM

Hi,

Here is a schematic from an amplifier that I own. It is a Knight KA95 integrated EL34 PP. I am trying to educate myself about power supplies. Why were two rectifier tubes used like this? Correct me if I'm wrong (which is entirely possible) -- the diodes from each tube are simply paralleled and it is a conventional full wave rectifier, right? It appears that other EL34 based PP amps usually get away with a single tube for a full wave. Did the added load of the preamp circuitry necessitate this arrangement?

Thanks,
Michael

PS -- the PS is in part 2 of the schematic.

kevinkr · 20th June 2011, 06:56 PM

Probably down to the amplifier power output rating and the additional circuitry. Stereo amps like the ST-70 just squeaked by with a single 5AR4. Pairs were sometimes used in higher power amplifiers where more than 250mA was needed, and relatively low forward drop (for a tube) along with reasonably good regulation was also wanted.

mfaughn · 20th June 2011, 07:13 PM

Thanks for the help. Kinda what I figured but its good to hear it from somebody who knows.

CharleyW · 20th June 2011, 09:27 PM

The GZ34 was designed to drive one pair of EL34 - not two.

20th June 2011, 06:56 PM	#2
kevinkr diyAudio Moderator Join Date: Sep 2004 Location: Boston, Massachusetts Blog Entries: 6	Probably down to the amplifier power output rating and the additional circuitry. Stereo amps like the ST-70 just squeaked by with a single 5AR4. Pairs were sometimes used in higher power amplifiers where more than 250mA was needed, and relatively low forward drop (for a tube) along with reasonably good regulation was also wanted. __________________ www.kta-hifi.net

20th June 2011, 09:27 PM	#4
CharleyW diyAudio Member Join Date: Aug 2002 Location: Arlington, TX	The GZ34 was designed to drive one pair of EL34 - not two. __________________ Hey is for horses.

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20th June 2011, 07:13 PM	#3
mfaughn diyAudio Member Join Date: Nov 2009 Location: Sylva, NC	Thanks for the help. Kinda what I figured but its good to hear it from somebody who knows.

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