Transfromer value of this 300B circuit

[VR2ZXP]

Hi all, How are you? May I have the value of the interstage and final stage transformers of this circuit which came from SunAudio in Japan?
Please teach, thanks very much!

[Tweeker]

They dont give out the specifications of their propriety transformers. In any case, when selecting an output transformer for SE, its a tradeoff between power output and distortion. Generally a higher impedance output transformer gives less power and less distortion.

The Western Electric Datasheet gives quite a few operating points.

[VR2ZXP]

Hi Tweeker, thanks for gave me the datasheet. I tried to attach the original circuit here but it cannot be displayed. It should a 6SN7 in parallel for the input stage and connecting to a pair of 300B for PP by a interstage transformer.

Circuit :
http://www.diyaudio.com/forums/showt...?postid=539568

[phn]

For 6SN7 in parallel, 10K should do, figuring I'm right about the impedance of the 6SN7. The Tamura B-5001/6001 or B-5006/6006 should work. An input step-up trafo might be in place as well.

[Tweeker]

Ah, I didnt know which Sun Audio you were building, and I assumed it was one of the SE models.

Given the lack of feedback around the 300Bs, and the cancellation of 2nd harmonic in push-pull, Id suggest a relatively high load impedance. 3rd order distortion drops dramatically with higher load and will be the dominant type. See fig 9 in WE datasheet. From what I can tell Tamura only offers 3.5K and 5K PP OPTs off the shelf, so with that vendor Id go 5K. Each tube sees about half this in class A.