tremolo connection to 5879 cathode?

[firemedic]

Would a 5E9A-type tremolo circuit, connected to a 5879 cathode, work? I can't see why not but maybe some values need to be changed. The cathode nominal voltage on the 5E9 driver is 2.4v, & on the 5879 (56T circuit) it looks like @ 0.87v.

[firemedic]

Bueller?

[PRR]

I think you are a pioneer.

What's the cathode resistor values? You may need to scale the trem feed to that. I think experimentation will be needed.

[firemedic]

There are plenty of pioneers here, I'm definitely not one of them. I just try to copy their work.
The 5879 input stage (ala HoSo56, 56T) cathode resistor is 470R. The 5E9a driver has a 1.5k resistor.

I'm trying to design an effects box with tremolo & overdrive. The hand-drawn Matchless Hotbox schem looks good for this purpose but I'm substituting the stages, V1a will be a 5879, V1b will be a parallel triode tube, V2a, parallel triodes, and I plan on trying a parallel cathode follower for V2b. I'll adjust the plate resistors, and separate the cathodes to keep the gain under control and get the max tonal benefit from the parallel triodes. I've got plenty of room, sockets, & current available for this. And I'm curious.

But the only tube common to both the clean & overdrive channels, is the 1st stage, 5879. Thus the dilemma.

I'll probably be using headphones (Z= 16 ohms) with this thing half the time so I think the lower impedance of a parallel cathode follower would be a step in that direction. I can switch the 2nd cathode in & out of the circuit, maybe, if I have to. I can't find an all-tube preamp-to-headphones schematic anywhere. The power-amp-to headphones schems I have found don't really apply to a preamp, which is really what this is. But I'm getting off subject. First, the tremolo problem.

 

[topbrent]

Why not use the VibroChamp style trem?  

To me, this type of trem offers the easiest way to wiggle the ground connection of your cathode.  

Also, the VibroChamp trem is not dependent on the bias of the power section in any way.  Nice self contained wiggler.

Insert directly at the cathode, before the 5879 cathode resistor and wiggle away.
-  (note: ignore the NFB resistor and other stuff on the VibroChamp schematic.  Just remember the trem inserts at the cathode, and in your case, the 5879 cathode resistor comes after that.)

 http://www.el34world.com/charts/Schematics/files/fender/VIBRO_CHAMP_AA764.pdf

[firemedic]

That looks a little closer than the 5E9, thx topbrent. It will take a little time to get all the parts but I'll let you know when it's up & running.

[HotBluePlates]

I think you are a pioneer.

If someone copied a vintage Gibson amp, they'd be a true pioneer. Maybe because Gibson made some many dang models, and so many wildly different variations with the same names.

But for an example of tremolo injected at a 5879 cathode, look at the Epiphone EA-25, and Gibson GA-20T (another drawing of the GA-20T).

You see the trem oscillator tube is a 6SQ7. Visualize this tube as 1 section of a 12AX7. The 6SQ7 is a single triode (with a mu of 100) and 2 small-signal diodes in an octal package.

This should get you started; the 5879 and oscillator triode use a shared cathode resistor, which is how the trem is injected into the signal path.

[firemedic]

Thanks HTB, it's nice to know that this has been done. The Vibrochamp cathode resistor & voltage are closer to the 5879 stage I'm using, & I've already started building that version with parts I have laying around. It's also sort of like a shared cathode so my fingers are crossed.
Plus topbrent said "wiggle away". Heh heh.