Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: pc1093 on May 04, 2021, 11:35:08 pm

Title: power transformers for 6SN7-KT88 PP
Post by: pc1093 on May 04, 2021, 11:35:08 pm

Hi All,
I got a diagram about 6SN7-KT88 PP. I find that 4XKT88 I(f) need 6.4A and 4X6SN7 I(f) need  2.4A.
However, the diagram showing that the transformers got 6.3V @ 5A.
1. Is the transformer only work for one channel?
2. are there any power transformers that support both channels in one?

Title: Re: power transformers for 6SN7-KT88 PP
Post by: Latole on May 05, 2021, 03:30:02 am

This power supply (can only) feed one channel. We see 2 X KT88 and 2 X 6SN7


Hammond transformers don't have one PT to do the job of  two PT you need.
Their bias voltage are too low. You have to tap bias on H.V winding.

https://www.hammfg.com/electronics/transformers/classic/300?referer=787
 

Title: Re: power transformers for 6SN7-KT88 PP
Post by: DummyLoad on May 05, 2021, 02:18:09 pm

for two channels use hammond 379WX will work for 2 channels, however, you will need to change the B+ rectifier to full wave rather than a bridge.


--pete

Title: Re: power transformers for 6SN7-KT88 PP
Post by: pc1093 on May 05, 2021, 10:48:58 pm

if i use one power transformer,such as hammond 379WX, need i change the choke to 10H@1A?

Title: Re: power transformers for 6SN7-KT88 PP
Post by: DummyLoad on May 06, 2021, 03:26:33 am

Quote from: pc1093 on May 05, 2021, 10:48:58 pm

if i use one power transformer,such as hammond 379WX, need i change the choke to 10H@1A?

yes.

--pete