Point me to the discussion

[gingertube]

The Robben Ford #102 schematic

I'm scratching my head over the feedback on the post volume control triode.
40M + 0.05uF feedback with 220K parallel 500pF Input.

I'm sure this must have been discussed - can anyone point me to where.
A quick search did'nt help, probably cause I had wrong search terms.

Off for a few days will check back in start of next week.

Thanks,
Ian

[gingertube]

Still would like to find the discussion but took the time to fire up B2Spice to see what it would tell me.

Gain drops from 58 to 46 when you add the feedback BUT the most noticable effect (at least according to the simulator) is the total elimination of a 2dB dip in the frequncy response above 1kHz extending out to the high frequency limit which is up around 1MHz for the circuit with and without feedback. It flattens the frequency resonse.
That would boost the harmonics by that same 2dB but not affect the fundamental note from the strings.
Feedback also drops lower frequency roll off (-3dB) from 25Hz to 14Hz but I don't think that is significant.

Cjheerrs,
Ian

[Smitty]

Try searching these terms:

nfb
v1B

https://tubeamparchive.com/viewtopic.ph ... hlight=v1b

https://tubeamparchive.com/viewtopic.ph ... hlight=v1b

https://tubeamparchive.com/viewtopic.ph ... hlight=v1b

https://tubeamparchive.com/viewtopic.ph ... hlight=v1b

[Teleguy61]

It is also referred to as LNFB, Local Negative Feed Back.

[gingertube]

Thank You,
The links above tell the story.
Cheers,
Ian