gz34 question...

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michaeltstocks
Junior tube assistant
Posts: 1
(3/29/04 2:34 pm)
  gz34 question...
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 Folks,

Hi! I have a quick question. It's probably dumb, but here goes. I'm designing power supply for an SE amp and want to use (2) GZ34 rectos each as a single wave unit (plates on each unit tied together). My charts give a voltage drop if 17V per unit at 200ma. I'm shooting for 350V DC out at 220ma, so by my calcs I get:

ACin = (350V + (2)*17)/1.414
ACin=271.5V

My question is: if I'm wiring each of the rectos as half-wave units, do I use double the voltage drop or just the single voltage drop?

Any guidance appreciated!

Thanks!


Mike

 
GroundhogKen
Forum Moderator
Posts: 2335
(3/29/04 2:49 pm)
  Re: gz34 question...
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 Two GZ34s in parallel will give about a 8.5v drop at 225mA.

You will also need 4 amps of 5vac for the GZ34 filaments.

The correct term is FULL wave rectifier--a half wave is just a single diode or 1/2 of one GZ34.

I use 1.3 to convert from AC in to DC out with GZ34s. Your calculation would be ( 350 + ( 17 / 2 ) ) / 1.3 = 276Vrms. A ( 275 - 0 - 275 ) @ 200mADC transformer should suffice as long as it has a 4 amp 5v winding.


What power tubes do you intend to run?

If you want a beefy power supply, why not use a solid state full wave rectifier instead of two hot, expensive space hogging tubes?


Ken
 
michaeltstocks
Junior tube assistant
Posts: 2
(3/29/04 3:01 pm)
  gz34 more
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 Ken,

Thanks, but I think you misunderstood. Each GZ34 has its plates wired together to act as a half wave unit. I'm using two, but they are not in parallel. Each is functioning as a half wave unit at each end of the secondary tap.

Any further suggestions?

Thanks,

Mike

 
GroundhogKen
Forum Moderator
Posts: 2336
(3/29/04 7:40 pm)
  Re: gz34 more
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 OK, so each GZ34 is two parallel diodes ( a diode with double the usual current capacity. )

I don't think you method or my method are different.

You are connecting pins 4 and 6 of one tube to one end of the HV secondary and 4 and 6 of the other GZ34 to the other end of the secondary.

My way has pins 4 and 4 ( other tube ) at one secondary lead and 6 and 6 ( other tube ) at the other secondary lead.

It's the same circuit. Your paralleled diodes share the same glass envelope. My paralleled diodes are in separate glass envelopes.

You way has one tube fully on while the other is fully off. My description has each tube at 50% duty cycle.


Ken

EDIT: Technically speaking, I guess either method is 50% duty cycle.

Edited by: GroundhogKen at: 3/29/04 8:43 pm
 
ganzonimx
Hey get your own solder
Posts: 441
(3/29/04 8:31 pm)
  Re: gz34 more
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 Why do you use a tube rectifier in a SE amp? If you look for sag, the tube rectifier will give you no sag, it make you just spende more money...

Cris
 
michaeltstocks
Posts: 3
(3/30/04 7:51 am)
  Thanks!
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 Ken,

Yep - you are absolutely correct! I went home last night and searched my Radiotron book and both your way and my way are electrically equivalent. Thanks again for the help!

BTW, for those asking, the reason I'm using tube rectos is a personal choice - I like the way they look in the model I've created and the folks that this amp is intended for want tube rectos.

Thanks,

Mike

 
GroundhogKen
Forum Moderator
Posts: 2337
(3/30/04 5:42 pm)
  Re: gz34 more
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 Yes, tube rectifiers do look cool.

Cris is right. A class A amp will have no more sag when it is being pushed than when it is idling.

Even in a Class AB amp, dual GZ34s will have very little sag. They will make a lot of heat and suck a lot of 5v juice though.

Ken
 
Andy Poupart
Senior tube assistant
Posts: 137
(3/31/04 2:11 am)
  Re: gz34 more
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 That's just a waste of one GZ34. I can see using a dual rectifier setup with weaker rectifiers, or tubes that have a lot of sag. Heck, I've built a low power twin faithfully to the two 5U4G configuration. But paralleling two GZ34s? If you're building an amp that requires more current than one GZ34 can provide, it's time to go solid state.
 
 
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