GU-32/GI-30 tube PP amp

DragosB · 16th October 2008, 02:21 PM

I want to start buiding a PP amp using one of those tubes. I already have two OTP having 2300 turns in primary (plate-to-plate, center taped) and 90+45+45 turns in secondary.

Using the 90 turns secondary with 8ohm speaker, I will have around 5200 ohm plate-to-plate load. Looking to all schematics found for those tubes, that load seems too low. is it possible to use that OTP, and what would be disadvantages of using it?

p.s. power transformer has 300V in secondary.

Thank you

Dragos

azazello · 16th October 2008, 04:45 PM

How square surface is the Your transformers ? This is begin to calculate Your Transformer! If You want 10-20 wats per channel, Your
transformer must be equivalent to 100-200 W AC power! Or 12-15-18
sq. sm of coil!

Wavebourn · 16th October 2008, 05:32 PM

For Gu29 and GI30 you may use a transformer designed for 829, but GU32 is a different beast if I remember right.
Also, there is a "civilian" version of GU-29 called 6R3S-1 that is horrible, though more expensive.

kuroguy · 16th October 2008, 11:37 PM

I'm sure someone will correct me if I'm wrong. I believe GU-32 is equal to 832. The 832 PP amp likes about 8.5K transformers.

DragosB · 17th October 2008, 07:00 AM

Quote:

Originally posted by azazello
How square surface is the Your transformers ? This is begin to calculate Your Transformer! If You want 10-20 wats per channel, Your
transformer must be equivalent to 100-200 W AC power! Or 12-15-18
sq. sm of coil!

The transformer has around 8 square cm in section.

Quote:

Originally posted by kuroguy
I'm sure someone will correct me if I'm wrong. I believe GU-32 is equal to 832. The 832 PP amp likes about 8.5K transformers.

I know tha 832 PP amp likes 8.5k transformers. My question was: what are the effects of using my 5.2 k transformers with 832 tube
? Would be that transformer more suitable for 829 PP amplifier?

Colt45 · 17th October 2008, 08:08 AM

Yes it's equivalent to a 832.

GI-30 is odd though, intended for HF pulse stuff.. low dissipation iirc.

Quote:

I know tha 832 PP amp likes 8.5k transformers. My question was: what are the effects of using my 5.2 k transformers with 832 tube ? Would be that transformer more suitable for 829 PP amplifier?

If you don't change the operating point, and just the iron to a lower load, generally, power is up, distortion is up.

5k sounds about right for GU-29, as it's basically a pair of 6L6's, and that's near what they like...

vladn · 18th October 2008, 06:55 AM

You may want to check this thread - I've run some numbers for 829B PP AB1 at various plate voltages:

budget xformer for 829B pentode mode PP (class AB) ?

I couldn't resist grabbing a pair of RCA 829B from ebay for the looks alone

so this is my current project.

16th October 2008, 02:21 PM	#1
DragosB diyAudio Member Join Date: Jun 2006	GU-32/GI-30 tube PP amp I want to start buiding a PP amp using one of those tubes. I already have two OTP having 2300 turns in primary (plate-to-plate, center taped) and 90+45+45 turns in secondary. Using the 90 turns secondary with 8ohm speaker, I will have around 5200 ohm plate-to-plate load. Looking to all schematics found for those tubes, that load seems too low. is it possible to use that OTP, and what would be disadvantages of using it? p.s. power transformer has 300V in secondary. Thank you Dragos

16th October 2008, 05:32 PM	#3
Wavebourn diyAudio Member Join Date: Sep 2006 Location: Pleasant Hill, CA	For Gu29 and GI30 you may use a transformer designed for 829, but GU32 is a different beast if I remember right. Also, there is a "civilian" version of GU-29 called 6R3S-1 that is horrible, though more expensive. __________________ The devil is not so terrible as his mathematical model! Wavebourn: We Create Creativity!

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16th October 2008, 04:45 PM	#2
azazello diyAudio Member Join Date: Aug 2008 Location: Bulgaria	How square surface is the Your transformers ? This is begin to calculate Your Transformer! If You want 10-20 wats per channel, Your transformer must be equivalent to 100-200 W AC power! Or 12-15-18 sq. sm of coil!

16th October 2008, 11:37 PM	#4
kuroguy diyAudio Member Join Date: Sep 2007	I'm sure someone will correct me if I'm wrong. I believe GU-32 is equal to 832. The 832 PP amp likes about 8.5K transformers.

18th October 2008, 06:55 AM	#7
vladn diyAudio Member Join Date: Feb 2008	You may want to check this thread - I've run some numbers for 829B PP AB1 at various plate voltages: budget xformer for 829B pentode mode PP (class AB) ? I couldn't resist grabbing a pair of RCA 829B from ebay for the looks alone so this is my current project.

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