CF vs CF w/Bootstrapping

[big_teee]

The Valve Wizard
Was wondering what the practical aspect of a regular CF at the top of the Web page, Vs the CF with Bootstrapping at the bottom of the V-Wizard web page?
According to Merling the Bootstrap method is under used.
http://www.valvewizard.co.uk/CathodeFollower5.jpg
Trying to get a little more gain out of the JCM- 2204.
Has anyone tried this?
Looks like all That's required is to replace the 100k Resistor with 2-4.7ks on V2, and run a 47n Cap to the CF Lead on the board.
T

[pdf64]

Yes, I use it, it's a nice simple way of getting another ~6dB out of the stage.
See http://www.webphix.com/schematic%20h...l_50w_2204.pdf just replace R12 with 2 x 56k and connect the node to the cathode follower via a 0.1 or 0.047uF cap.
Can be made switchable!
At high signal levels, the waveform seems to get more asymmetric than normal but it sounds fine, it's not like the bass craps up etc.
My amps are either NMV or PPIMV turned up full; this arrangement helps to even up the overall system gain between (the otherwise same circuit) using, say, EL84 and KT66.
Pete

[uneumann]

Yes, I use it, it's a nice simple way of getting another ~6dB out of the stage.
See http://www.webphix.com/schematic%20h...l_50w_2204.pdf just replace R12 with 2 x 56k and connect the node to the cathode follower via a 0.1 or 0.047uF cap.
Can be made switchable!
At high signal levels, the waveform seems to get more asymmetric than normal but it sounds fine, it's not like the bass craps up etc.
My amps are either NMV or PPIMV turned up full; this arrangement helps to even up the overall system gain between (the otherwise same circuit) using, say, EL84 and KT66.
Pete

Yes, you get gain and/or response shaping from bootstrapping. See this figure for two examples with cascode stages (at the top of the figure). I use these as a second channel in a Deluxe Reverb.

https://sites.google.com/site/string...deluxeplus.png

You can use a CF to bootstrap any prior stage.

[jazbo8]

Since it is a form of FB, it alters the BW, input/output impedance as shown below, only the higher output impedance might be of some concern in certain critical applications, but for guitar amps, there is no reason not to use it all the time.