Cathode follower

[jeff]

 In a typical Masrhall style preamp gain, gain, gain, cathode follower, tone, If I were to eliminate the tone stack should/could I also eliminate the cathode follower stage?

Is the only point of using the cathode follower to minimize the loss of gain from the tone stack?

[plexi50]

No you cant remove the cathode follower

You can take the Mid pot and lift the grounded end,run a wire from the terminal of the Mid pot end that was grounded
to another 250K pot and lift the tonestack out at variable degree's

The 250K pot becomes the ground reference. By lifting the ground you are lifting the tonestack out of the circuit

Lots of blossoming headroom

[jeff]

 Thanks .The raw looks to me to be a bigger value mid. Seems like switching the mid pot to a 250K pot would be a good test before drilling another hole. Come to think of it, on a Champ I built I accedentally used a 100K in stead of a 10K mid and it was kinda cool but it was linear, audio probally would have had a smoother more gradual effect.

No you cant remove the cathode follower

Could you explain further? You can't just have gain, gain, gain, power tube(SE)

What is the purpose of the CF?

[plexi50]

The cathodes of your preamp tubes set the bias for each preamp tube. They also dictate the gain of each tube according to the resistor value used. I think you may be asking me a different question but for now i will leave it to the pros to better explain as my BRAIN is taxed for the day*

[PRR]

> could I also eliminate the cathode follower stage?

Yes.

WHY?

[38Super]

In a typical Masrhall style preamp gain, gain, gain, cathode follower, tone, If I were to eliminate the tone stack should/could I also eliminate the cathode follower stage?

Is the only point of using the cathode follower to minimize the loss of gain from the tone stack?

The primary reason for using a cathode follower in this application is to drive a load.  You can drive a tonestack with a common cathode gan stage, but the t/s provides a relatively low impedance, loading the common cathode stage down.  The result is significantly lower gain from a c/c gain stage driving a tonestack.

Another factor is the tonal qualities of a cathode follower driving a t/s is different than a c/c stage driving the same tonestack.  It's more than just a lower voltage gain factor.  I have read that the cathode follower driving a t/s gives you more 3rd harmonic distortion (crunchy) than a c/c driving the tonestack, but couldn't tell you for sure.


cheers,

rob

[tubeswell]

Thanks .The raw looks to me to be a bigger value mid.

The raw just puts so much resistance between the tone stack and the ground that the tone stack stops working anything 250k or more will work fine

What is the purpose of the CF?

mainly low-impedance TS driver.  But also when it is in a DC coupled-pair, it imparts harmonic distortion through the way in which the CF steals current from the prior inverting stage