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Input transformer [message #11290]

Wed, 22 February 2006 19:23

colinhester
Messages: 1349
Registered: May 2009
Location: NE Arkansas

Illuminati (3rd Degree)

I ran across a schematic (Practical Amplifier Diagrams, pg. 2, Audio Amateur Press) of a tube rectified SE 6V6 producing 5W that looks intersting. The amp uses 4 caps, three are in the power stage, and one resistor. The input is taken into the tube by an unspecified input transformer. My question: what am I looking for in sourcing an input transformer that would perform well in this circuit? I would like to post the schematic, but I think copyright laws would soon haunt me......Colin

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Re: Input transformer [message #11291 is a reply to message #11290]

Thu, 23 February 2006 06:01

Damir
Messages: 1005
Registered: May 2009

Illuminati (2nd Degree)

It`s probably a step-up input transformer, maybe 1:5 (or so) turns/voltage ratio. "Lundahl" is a specialist in those and similar types of audio transformers.
What`s a connection of output tube, pentode/triode/UL? Don`t need to post the schematic, just describe it...

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Re: Input transformer [message #11295 is a reply to message #11290]

Wed, 01 March 2006 14:40

PakProtector
Messages: 935
Registered: May 2009

Illuminati (2nd Degree)

Hey-Hey!!!,
One little TX I have had good results from is the UTC A-18. 15k:80k with dual split windings. They do well SE:SE or SE:PP when I have done some experimenting.

Either way, they can be semi-expensive. I saw a pair go for $150 and that was enough for me to list a few after that.

If you want to try a pair, I think it could be aranged. Call me.
cheers,
Douglas

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Re: Input transformer [message #11296 is a reply to message #11295]

Wed, 01 March 2006 20:19

colinhester
Messages: 1349
Registered: May 2009
Location: NE Arkansas

Illuminati (3rd Degree)

I'm still in the "head scratching" phase of the schematic. In your opinion, are there any sonic benefits of using an input transformer over a driver tube?

Would this be an item that Heyboer(sp?) would have the ability to wind at a reasonable cost? Also, related to the question I posed to you on the GB forum, does Heyboer have a good off-the-shelf SE OPTx?.....Colin

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Re: Input transformer [message #11297 is a reply to message #11291]

Wed, 01 March 2006 20:21

colinhester
Messages: 1349
Registered: May 2009
Location: NE Arkansas

Illuminati (3rd Degree)

Damir, Thanks for the reply. I'm sorry it's taken me this long to get back. I'll try to post a verbal description this weekend.

Why did you suggest a 1:5 turn ratio?.....Thanks, Colin

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Re: Input transformer [message #11301 is a reply to message #11297]

Thu, 02 March 2006 06:30

Damir
Messages: 1005
Registered: May 2009

Illuminati (2nd Degree)

No problem :-), about turns ratio - I guessed, `cos your SE 6V6 is probably "biased" somewhere around -15V, and then "needs" 15Vp=10,6Vrms for full output, and 1:5 input transformer "enables" this with 2Vrms input. Full desription would help, though.

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