Ever try this?

[Andy Le Blanc]

I was looking at some Garnet schematics and I found this.

I thought it would be neat to try as a stage, always digging for ideas.

A lot of feedback with both stages sharing a bias resistor, can anybody model
the circuit for a gain figure?

[Jana]

Because of the 25uf bypass cap on the shared cathode resistor I would break it into two sections. Really, it is just two cascaded gain stages. To figure the cathode voltage, hence the bias voltage, double the 1.5k and pretend that each stage has a 3K cathode.

[Andy Le Blanc]

So ...I scabbed it up on an octal socket in my noodling chassis....

Would have gotten to it sooner but the premeir needed a ride home, chores.

I had another reissue fender with bad resistors to get past the bench too.
Amazing they don't pony up and have a recall, way to many people paid way
to much money, to have back line screw the pooch on a gig.
Fender is starting to give it self a bad name......

Anyway.... with around 210 supply voltage I got 88v on the plate and 3.7v
at the cathodes, static.

with 1k 1v signal at the input it made 16v signal at the grid of the second stage
and 74v output...... woof.. can't wait to see it's harmonic spectrum.

[Andy Le Blanc]

The Rightmark program gave some interesting results...

even order harmonic products predominate over the fundamental....

might be worth a try in a wreck...... Trans-Canadian Express......

Gar was ahead of his time.

[John C]

Do you have any THD images saved of some some other type stages that you care to share? Any kind of stage would be great - a typical stage (Ra=100k, Rk=1k5), an atypical stage, anything...

Thanks for sharing the cool images on the Garnet stage!

[John C]

Do you have any THD images saved of some some other type stages that you care to share? Any kind of stage would be great - a typical stage (Ra=100k, Rk=1k5), an atypical stage, anything...

Thanks for sharing the cool images on the Garnet stage!

[Andy Le Blanc]

the rightmark software is free.... I would love to do just that... but I have to
invest time to build..... it's great to use real circuits to run the test program with
its a different approach to a CAD, all the variables are real world.
but it does take time..... how busy is your bench, you can do the same.

[dave g]

As Jana said, there is no feedback happening. I think the distortion spectrum you see is simply the result of the 2nd stage clipping. Give each stage its own 3k cathode resistor bypassed with a 25uF cap and I bet you'll see the same thing.

[Rich M]

What amp is this from?

[Andy Le Blanc]

Its the circuit above, using a 6sn7, I'd love to post the whole right mark report
but its not a allowed file type. >.001% distortion. I had thought the same but
I got consistent results for several tubes.

It came out a Garnet schematic, he used it in a couple model's. The point is
to run tests on a real circuit, as they are. Jana is right but that would modify
the circuit under test.

Some times the harmonic distortion is the point, I'd love to see it repeated.
being wrong is for whatever reason is good too, that why I posted it.

[FYL]

Gar was ahead of his time.

He was one of the true great amp designers, but isn't very well known South of Ontario. Or even West.