Cathode Capacitor tweak...

[Oddvar]

Hi.  Would it be a possibility to change the CC in a Hoffman 18w Marshall Stout to raise the bass level, and if, does it have to be electrolytic?

https://www.ampbooks.com/mobile/amplifier-calculators/cathode-capacitor/calculator/

[Ed_Chambley]

Yea yow can raise the cap. I would change the cathode resistor too.
No you can use any cap type

[Ed_Chambley]

If you have it like the original it is 22uf with a 2.2k resistor. It is already passing a lot of bass.  If the amp is too bright reduce the Cathode resistor to 1.5k ohm.


This will not change a lot unless the bypass cap is already smaller.


You can change v1b resistor lowering it from 2.2 to 1.5.


Next you can replace temporarily the 100k slope resistor with a pot and reduce the value to what sounds best and measure the pot and install that size resistor.


The .0047 cap is shaving the most bass. Enlarging this one will change a lot. Try a .01 here if you have one handy.
You might even do this first.

[jjasilli]

You can't get more bass vs. Highs by changing the bypass cap.   This ap starts boosting all frequencies at and above a certain specific frequency.   Hence you can only boost hi's in relation to lo's.


A  alternative is to cut highs elsewhere.

[Oddvar]

Ok, thanks, I'll have a try...

[PRR]

22uFd in a small-tube cathode is already "full bass" (to below 20Hz!).

If you want "more bass", what you probably need to do is "less treble", so the bass comes over better.

[Ed_Chambley]

You could try installing a cut control.  Look at the Vox ac 15. Pot and a couple of resistors. I like cut control on all El84 amps as they all seem bright and this tames the highs.

[Colas LeGrippa]

or use a bass guitar