Ruby zener mod (for 18W etc.) on a... paraphase?

[EFK]

Thread title says it. A lot of the 6973 Supro amps have the same fizzy/buzzy problem as the Marshall 18W amps, but w/ a paraphase inverter I can't see how to implement the Ruby mod. It could be done to one power tube grid leak (the non inverted one), but the first stage (the inverted one) feeds the grid of the second half of the paraphase so I don't see how it could be implemented.

Any problems or benefits to using it on the second grid leak only? Maybe get rid of 'some' buzz? Or maybe create problems?

Any other ideas for the paraphase amps? Already have tried the big 1000uf cathode cap....

[Chuck H]

Any problems or benefits to using it on the second grid leak only? Maybe get rid of 'some' buzz?

It should. I've seen amps that were imbalanced enough on the PI drive to cause a crossover notch on only one side if the final clipped wave form. They didn't have the bwizz problem. So eliminating one side of the crossover distortion may work.

Or maybe create problems?

Shouldn't hurt anything.

Any other ideas for the paraphase amps?

Change it to a long tailed pair?

[EFK]

Thanks for the thoughts Chuck. I just remembered an old post in which I was asking about converting a paraphase to fixed bias, and Steve Connor came up with a cool little trick which only required an extra cap and grid leak/bias resistor. I can leave the cap off the first stage feeding the divider for the second half of the paraphase, but also run *another* cap off that first stage plate, add a new 470K resistor to match the other one and feed the first power tube from that. Then, in this situation I can simply leave it set up in cathode bias and try implementing the zener approach. Will give that a try.

[EFK]

For anyone interested, the Ruby mod can indeed be implemented on a paraphase either on one side only or (as described above) w/ an extra cap and grid leak resistor off the first stage of the PI. In the end though, while it does help a bit, I think I just don't like the el84/6973 sound. I keep trying to like amps with these tubes but *never* have found one to my liking. I think the OD characteristics just aren't for me, because other people hear them and love them. Oh well.

[Chuck H]

If you do Voxy semi distorted jangle or balls out OD el84's are great. If you want tighter OD like el34's or bell tone cleans like 6l6's they really fall short.