That "ahaaaaa" moment....

[arjepsen]

I've been messing around with my version of the Soho. The circuit is pretty close to the original, except for the OT and PT which in my case is a regular 18watt OT, plus a 290-0-290 pt I had lying around.
Anyways, I've had a bit of a "meh" experience of the amp, not quite getting the tones I heard from youtube clips etc. (way too bassy, not really chimey, not enough gain)
I was reading up on cathode followers in Merlins books, and decided to try a large grid stopper, and started soldering... then I couldn't quite make the cathode pins match with the schematic.
hmmm... Oh.... AAAAAH..... DOH!
I'd managed to switch components on the cathode pins of the tube, putting 180k on the cathode of the gain stage before the cathode follower, and the 33k/10K on the cathode follower....ooops.
Switched around, and it's really starting to sing

[frankdrebin]

Original Soho had a 100k on the gain stage and 180k on cathode follower, 470k /22n to the blackface tonestack.

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[arjepsen]

Original Soho had a 100k on the gain stage and 180k on cathode follower, 470k /22n to the blackface tonestack.

Exactly, although from photos I've been given, I believe they now use 68k/22n to the tonestack.
(my fault was putting the right components on the wrong triode cathode.
To my ears the differnce between 68k and 470k is quite subtle - the 68k might be slightly brighter/clearer.
I'm also experimenting with a grid stopper in the hundred k's on the cathode follower.
That 180k on the cathode follower's cathode is puzzling me though - I haven't seen such large value in that spot before.

[frankdrebin]

Original Soho had a 100k on the gain stage and 180k on cathode follower, 470k /22n to the blackface tonestack.

Exactly, although from photos I've been given, I believe they now use 68k/22n to the tonestack.
(my fault was putting the right components on the wrong triode cathode.
To my ears the differnce between 68k and 470k is quite subtle - the 68k might be slightly brighter/clearer.
I'm also experimenting with a grid stopper in the hundred k's on the cathode follower.
That 180k on the cathode follower's cathode is puzzling me though - I haven't seen such large value in that spot before.

I followed all the videos on 65 yt channel and more, believe me, there is not much logic in there...

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