What I've Seen in the Vintage Amp Repair Business

[JackD201]

I think Win was referring to a guitar tube amp manufacturer micro.

 

[DonH50]

LOL, Don! Good one!

<elided>

I have been asked a number of times if I would consider designing my own line of guitar amps. I have some ideas for a new concept, based on a powerful, clean output stage and doing all the tone shaping on the low level stages. My intent is to design circuits with ample 2nd harmonic output. Just how to maximize that without introducing 3rd, 5th etc is where the engineering comes in.

Thanks!

I once built a distortion box using a frequency doubler circuit to allow the player to add a desired amount of 2HD. Don't recall the circuit off-hand but I think it was out of the old National op-amp app books, or maybe one of Garcia's notes...

 

[DonH50]

I could add 2H level equal to or greater than the fundamental.

As to the sound, that was up to the player, and I have heard (and played with) some real winners, and losers...

Changing strings and picks would also impact the sound quite a bit.

 

[microstrip]

What parameters do you measure for your "match"?

Plate current at a fixed grid voltage and transconductance. Both measured at the operating point of the particular amplifier.
I also check for noise and microphonic tubes.

 

[Mosin]

I think Win was referring to a guitar tube amp manufacturer micro.

Unfortunately, no.

 

[Mark (Basspig) Weiss]

I test all of my tubes on a Tektronix 576 curve tracer. It is simply impossible to get a perfect match by testing tubes at one voltage and current level, due to non linearity in the curves. When you achieve a perfect match on a curve tracer, the tubes are matched. The biggest problem is that they will quickly go out of match due to the nature of wear and tear on the tubes.