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PostPosted: 07 Oct 2008, 03:34 
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Location: Philippines
I just built a 6s4a parafeed driven by 6n1p SRPP.

The schematic is based on this: http://www.the-planet.org/6S4.html
Attachment:
6S4_final.jpg
Attachment:
6S4_ps.jpg

But instead of an OPT, I used a 30H plate choke and a Talema Toroidal mains transformer for OPT.

Though low powered, it is one of the best sounding amp that I ever heard or built!

Schema and pictures to follow (though it will look same as my EF86-El84 parafeed am, I used the same chassis and the same OPT and the same power transformer, I literally just replaced the driver and power tubes and the circuit!)


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PostPosted: 07 Oct 2008, 07:44 
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Hi Alex,

I'm not sure I understand how you implemented the output. Looking forward to the pictures and schematics.

Cheers

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PostPosted: 07 Oct 2008, 18:56 
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gmilitano wrote:
I'm not sure I understand how you implemented the output. Looking forward to the pictures and schematics.

Hi Gio, my description is sort of vague.

It is a parafeed output, the plate choke is the load and the Talema toroidal mains transformer is the OPT. I find parafeed circuits to be excellent, there is something magical, for me, about the sound of this topology. The bass seems to be tighter and vocals and highs are more dynamic.

So far I have built a 12at7 driven 6080 parafeed, an EF86 driven EL84 parafeed and this latest, a 6n1p SRPP driven 6s4a parafeed.

The next project will be a 2c51 SRPP driven 2a3 parafeed amp.


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PostPosted: 08 Oct 2008, 01:38 
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Here is the schema:

Image

Talema mains toroidal is 230V primary, 9V secondary, if used with an 8 ohm speaker will have a primary Z of 5.224K.

Pix to follow.


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PostPosted: 10 Oct 2008, 18:28 
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Location: Chillicothe, Ohio
Hey Alex!

I find the idea of building this amp very intriguing. I'm attracted to things a bit out of the norm, so to speak. I've read elsewhere people singing the praises of using toroidal power transformers as OPTs. Think I'll try it.

What model Talema did you use?


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PostPosted: 10 Oct 2008, 20:35 
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Bluesman wrote:
I find the idea of building this amp very intriguing. I'm attracted to things a bit out of the norm, so to speak. I've read elsewhere people singing the praises of using toroidal power transformers as OPTs. Think I'll try it.

What model Talema did you use?

Any of the Talema models, 30VA, 230V primary and 9V secondary. I used their potted toroidal.

At diyaudio.com, shoog has been working on mains toroidal transformer as OPT. I got most of the ideas how to size toroidals as OPT from his work.

I am in the middle of tweaking a PP EL34/KT88 using 120VA talema mains transformer as OPT. It is already sounding great, but I feel it can be better, so I am tweaking the circuit. Driver is paralleled 6n1p and using an autoformer as phase splitter, the whole amp is built "out of norm."


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PostPosted: 11 Oct 2008, 04:22 
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Alex,
Thanks for the reply! This project you are currently tweaking sounds interesting, as well. Hopefully you'll be posting results here.

Thanks for the Talema info.

Cheers, Bluesman


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PostPosted: 20 Apr 2010, 20:38 
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OK, that is the strangest yet most creative idea yet. Could any toroid transformer with the same ratings be used or is it specific to the Talema transformers?

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PostPosted: 21 Apr 2010, 16:20 
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alexg wrote:
At diyaudio.com, shoog has been working on mains toroidal transformer as OPT. I got most of the ideas how to size toroidals as OPT from his work.


I've used them for guitar, but never found them suitable for HiFi.

Cheers!

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PostPosted: 22 Apr 2010, 02:18 
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Btw, shouldn't the OP tranny be "bigger" - 8 or 10K for 6S4??

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