My new filiment PS for Push Pull GM70

djn · 18th April 2011, 03:22 AM

A friend just gave this to me. 2 channles of 24volt, 6 amp DC power. I think it would be a great filiment PS for a push pull GM70 amp. The GM70 needs 20v, 3a. It weights 38lbs!!! Talk about a boat anchor....and that is just a fraction of the whole amp. I think it will do nicely.

Bandersnatch · 18th April 2011, 10:27 AM

hey-Hey!!!,
For PP Dh amps I have not found DC heating required...at least not with 10V 813's. 5V tubes absolutely not, and 2.5V tubes...not even close.
cheers,
Douglas

djn · 18th April 2011, 11:04 PM

Hey D, sorry we missed you yesterday. I know this might be over kill and I still have three amp projects on the bench, but what the hey! George asked me if I wanted it, so what the heck.

Bandersnatch · 19th April 2011, 11:15 AM

Quote:

Originally Posted by djn

Hey D, sorry we missed you yesterday. I know this might be over kill and I still have three amp projects on the bench, but what the hey! George asked me if I wanted it, so what the heck.

That's mighty strange, I've never known you to go in for 'overkill'...LOL

Douglas

djn · 19th April 2011, 11:52 AM

Bad habits die hard

kevinkr · 19th April 2011, 04:41 PM

Quote:

Originally Posted by Bandersnatch

hey-Hey!!!,
For PP Dh amps I have not found DC heating required...at least not with 10V 813's. 5V tubes absolutely not, and 2.5V tubes...not even close.
cheers,
Douglas

These are 20V tubes and DC is advisable if you need really low hum even in PP. I found with 300B PP amps driving very efficient speakers (>100dB) that DC was also advisable, although not strictly required if you can live with a mVrms or so of hum/buzz on the output..

djn · 19th April 2011, 06:56 PM

I agree Kevin. I generally run compression drivers that are 115db eff. and any hum is audable. Besides that, it is a simple one piece unit that just needs wire hooked up. no muss, no fuss.

radiostar · 19th April 2011, 09:05 PM

Good starting point and good luck with new project djn!!!

GM70 PP would be a beast ...

djn · 19th April 2011, 09:21 PM

Thanks Radio. I have three other amps on the bench but getting ready to move, so I dont think this one will be up and running any time soon, but that only means I have time to collect parts.

Should do well with 800v B+. I don't know how to figure what the WPC will be but I'm sure it will be more than my GM70 SET.

Bandersnatch · 20th April 2011, 11:07 AM

Quote:

Originally Posted by kevinkr

These are 20V tubes and DC is advisable if you need really low hum even in PP. I found with 300B PP amps driving very efficient speakers (>100dB) that DC was also advisable, although not strictly required if you can live with a mVrms or so of hum/buzz on the output..

I have 813's on AC with horn-loaded EV DL10x and don't hear anything unless I stick my shoulders into the horn. I can live with that. Individual coils for each tube and their own hum pot. Variac on the primary to dial in exactly 10V, though it seems to be quite happy with 10.2-10.5V on them.
cheers,
Douglas

18th April 2011, 03:22 AM	#1
djn diyAudio Member Join Date: Oct 2004	My new filiment PS for Push Pull GM70 A friend just gave this to me. 2 channles of 24volt, 6 amp DC power. I think it would be a great filiment PS for a push pull GM70 amp. The GM70 needs 20v, 3a. It weights 38lbs!!! Talk about a boat anchor....and that is just a fraction of the whole amp. I think it will do nicely.

18th April 2011, 10:27 AM	#2
Bandersnatch diyAudio Member Join Date: Jul 2003 Location: Ann Arbor, MI	hey-Hey!!!, For PP Dh amps I have not found DC heating required...at least not with 10V 813's. 5V tubes absolutely not, and 2.5V tubes...not even close. cheers, Douglas __________________ the Tnuctipun will return

19th April 2011, 09:05 PM	#8
radiostar diyAudio Member Join Date: Apr 2009	Good starting point and good luck with new project djn!!! GM70 PP would be a beast ... __________________ tubes.rs facebook.com/tubes.rs

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18th April 2011, 11:04 PM	#3
djn diyAudio Member Join Date: Oct 2004	Hey D, sorry we missed you yesterday. I know this might be over kill and I still have three amp projects on the bench, but what the hey! George asked me if I wanted it, so what the heck.

19th April 2011, 11:52 AM	#5
djn diyAudio Member Join Date: Oct 2004	Bad habits die hard

19th April 2011, 06:56 PM	#7
djn diyAudio Member Join Date: Oct 2004	I agree Kevin. I generally run compression drivers that are 115db eff. and any hum is audable. Besides that, it is a simple one piece unit that just needs wire hooked up. no muss, no fuss.

19th April 2011, 09:21 PM	#9
djn diyAudio Member Join Date: Oct 2004	Thanks Radio. I have three other amps on the bench but getting ready to move, so I dont think this one will be up and running any time soon, but that only means I have time to collect parts. Should do well with 800v B+. I don't know how to figure what the WPC will be but I'm sure it will be more than my GM70 SET.

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