6G6 Bassman Output Transformer

[RightLurker]

Sorry to bump this back up to the top, but I thought this might be useful information to some people here. While I've been busy working on my Bassman, I missed the article in the current (April 2010) issue of Vintage Guitar magazine, in which appears an article titled Fender Amps by the Number(s) by Greg Gagliano. From that article I quote:

"Another anomaly in '61 was the 6G6-A Bassman. In the fall of that year, it seems some were fitted with an output transformer from the blond Twin Amp. These examples have the GZ34 rectifier tube (as found in the 6G6), yet the tube charts are 6G6-A. The 6G6-A lost its rectifier tube in favor of solid state rectification, and its 1 x 12 speaker cab with 8-ohm speaker in favor of a 2 x 12 four-ohm cabinet in December '61. However, on the first examples of this amp made in December '61 and the first half of January '62, Fender didn't change one very important item - the output transformer. Rather than waste the 8-ohm output transformers from previous 6G6 production, Fender used them up on the first 6G6-A[s] with four-ohm speaker cabinets. Yes, Fender went with a deliberate mismatch, not unlike the 3 x 10 brown Bandmasters that shipped with 8-ohm output transformers. Very few of these were made, and those who own one of these oddballs can either be happy with the fact that it is a rare amp or be sad that the mismatched impedance means the amp is less efficient. Regardless, it's still a good sounding amp."

Thanks to you folks here - especially Martin Manning - I've got my tube-rectified 6G6 (that's what the label says) with a Twin Amp OT (45548) driving a four-ohm 2 x 12 cabinet sounding as good as it's ever sounded, and that's pretty good. (The presence circuit now works, with the 10K/ 5K-L/1K5 components in place.) Now all I need is a reverb unit, and maybe some tremolo, and a Jazzmaster . . . it never ends. But that's the point, right?

Thanks to all. Hope this information is helpful to someone, someday.

RL

[martin manning]

Glad to hear it has worked out for you, and good work tweaking the presence circuit! It has been interesting.

If you've got a 10K feedback (series) resistor and 1K5 shunt instead of 100K and 4K7 you've increased the feedback voltage almost 3x, and moved the knee of the frequency response up a couple of octaves (as long as the same 0.1 cap is there). Since you now have more feedback to dial out with the presence control, the effect is more pronounced. The fact that it's shifted up to act on higher frequencies may be making it more noticeable too.

Cool stuff on Fender production, I'll have to go find that article, thanks for the pointer.

MPM