Cathode follower to drive D*mble tone stack?

[Darkbluemurder]

Has anybody tried this? The background to my question: in both of my modded Fenders I run a parallel triode as first stage which I could convert to a single stage with a cathode follower. I am thinking about whether the low impedance of a CF would be beneficial for the tone stacks.

Any input is most welcome.
Thanks and best regards,
Stephan

[Smitty]

The blond bassmans had buffered tone stacks on the bass channel. That's the only production amp I am aware of that runs a buffered tone stack in this configuration: input voltage gain stage direct coupled into a cathode follower driving the tone stack.

Dave Funk started modding Super Reverb Vibrato channels to this configuration and then telling folks how great it sounded. I liked it and started doing it to Supers.

My Bluetron Blueverb amps have this arrangement with a simplified D-style tone stack. The customer response has been very positive.

I think there may be an article in Tonequest on the Blueverb next month.

[Darkbluemurder]

Cool, I am a subscriber to TQR and I am looking forward to the report. Thanks for your input.

[dogears]

Sounds like reinventing the wheel to me.....

[Smitty]

Scott,

I don't understand your comment. Would you care to elaborate?

Smitty

[dogears]

The tonestack is a load on V1a. If going for the "tone", I would want the loading to be as accurate as possible. Maybe the CF tonestack is a great sound, but is it "the sound"....

Scott,

I don't understand your comment. Would you care to elaborate?

Smitty

[jaysg]

I found that each technique resulted in a unique overall tonality for the amp. I ended up sharing the grid on two independent triode sections. Please ignore the values on this schematic. It's WIP.

hmm...can't post a bitmap...this may take some time.

[Smitty]

OK. If you're talking about the 5F6A/Plexi preamp, then yes. I understand.

Input ==> gain stage ==> gain stage direct coupled to a cathode follower ==> 5F6A tone stack ==> PI...

Blueverb is a Super Reverb derivative with a buffered D-style tone stack.

Input ==> gain stage direct coupled to a cathode follower ==> D-style tone stack ==> gain stage ==> gain control ==> gain stage ==> gain control ==> PI ==> gain control ==> output

Reverb sends after the third gain stage instead of the second and has an independant twin triode return circuit so you mix wet and dry at the PI. Vibrato on dry signal only. No Vibrato on the Reverb signal (cooler).

I like the tone stack up front because that allows the player to set the tone for the next two gain stages. With the deep switch you can dump off some low bass for better overdrive.

Reinventing the Super Reverb!

[Darkbluemurder]

I found that each technique resulted in a unique overall tonality for the amp.

Jay,

I thought I had read a comment (probably on Ampage) that you tried this. Can you please describe this in a bit more detail?

Thanks
Stephan

[jaysg]

Over a succession of mods, I tried all three approaches with the Concert. I tried the Cathode follower to drive the KOC standard London Power preamp. I can't recall much, except that the clean was not properly Fendery and the distortion channel wasn't right either. The explanation is that the tonestack Z reacts a lot with whatever is driving it, to affect high end response.

I tried the parallel triode with the ODS circuit and the result was a significant thickening of the tone. For example, I had to run with the bright switch on and no plate to cathode caps in OD1 & OD2. It made for a very Robben Ford kind of thing with a strat.

[groovtubin]

Has anybody tried this? The background to my question: in both of my modded Fenders I run a parallel triode as first stage which I could convert to a single stage with a cathode follower. I am thinking about whether the low impedance of a CF would be beneficial for the tone stacks.

Any input is most welcome.
Thanks and best regards,
Stephan

E-mail me @ this if you`d like, Omegaamps@wilkes.net

[Darkbluemurder]

I tried the parallel triode with the ODS circuit and the result was a significant thickening of the tone.

I recently experimented by changing the parallel triode to single triode in the Deluxe Reverb II. I agree to your conclusion - the single triode is less midrangey and seems to fit the *umble circuit better. I will try the same arrangement with the Concert and hopefully the result is repeatable.

I tried the cathode follower in a different amp (comparison single triode before tone stack to single triode plus cathode follower before tone stack) and found that the cathode follower made the amp louder and a little more biting.

[mlp-mx6]

I have a "triple-drive" style amp where the first stage feeds 2 tone stacks. I made this first stage a common-cathode followed by a cathode-follower (like the 5F6-A Bassman or Marshall circuits). Worked great in this application.

[Darkbluemurder]

So maybe I should check this out. Haven't noticed any disadvantage by using a single triode to drive 2 tone stacks though.

[drz400]

Has anybody tried this? The background to my question: in both of my modded Fenders I run a parallel triode as first stage which I could convert to a single stage with a cathode follower. I am thinking about whether the low impedance of a CF would be beneficial for the tone stacks.

Any input is most welcome.
Thanks and best regards,
Stephan

Cathode follower tone stacks are harder sounding and low impedance, you should scale you components