Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: J3ona1 on December 22, 2024, 04:07:41 pm

Title: Deep Tremolo wanted on Cathode biased Princeton Reverb
Post by: J3ona1 on December 22, 2024, 04:07:41 pm

Hi Folks!

I have a cathode biased princeton reverb build (one 6v6 has an 814ohm resistor, and the other has an 812 ohm resistor) , and it sounds great but I'd love for the tremolo to be stronger.  The bias for one tube is about 88% and the other tube is at 91% (399V on the plates and about 29V at the cathode. The oscillation triode is biased with a 3.3Kohm resistor and bypassed with a 22uF cap. I've also reduced the resistor coming off the tremolo oscillator plate from 1meg to 330K. I can see the output tubes getting their bias wiggled but I'm a trem lover and would like a lot more depth. Any suggestions?

Title: Re: Deep Tremolo wanted on Cathode biased Princeton Reverb
Post by: SEL49 on December 22, 2024, 04:49:20 pm

Quote from: J3ona1 on December 22, 2024, 04:07:41 pm

The oscillation triode is biased with a 3.3Kohm resistor and bypassed with a 22uF cap.

Replace the 3.3k and 22µF with a 5mm red LED.

Title: Re: Deep Tremolo wanted on Cathode biased Princeton Reverb
Post by: Willabe on December 22, 2024, 05:02:32 pm

Who has Sluckey's tremolo circuit schematic with notes on it for increasing trem strength?

Please post that, thank you. 

Title: Re: Deep Tremolo wanted on Cathode biased Princeton Reverb
Post by: SEL49 on December 22, 2024, 05:07:25 pm

It's buried somewhere in Hoffman's Tube Amp Library.

Title: Re: Deep Tremolo wanted on Cathode biased Princeton Reverb
Post by: J3ona1 on December 22, 2024, 05:08:15 pm

Thank you yall!!!

Title: Re: Deep Tremolo wanted on Cathode biased Princeton Reverb
Post by: tubenit on December 22, 2024, 05:18:14 pm

There lotsa great info in the ARCHIVES under "frequently asked questions"!!  :icon_biggrin:


Trem-o-nator (Sluckey's) (https://el34world.com/Forum/index.php?topic=26328.0)


Hoffman AB763 Tremolo 6L6 mods? (https://el34world.com/Forum/index.php?topic=604.0)

Title: Re: Deep Tremolo wanted on Cathode biased Princeton Reverb
Post by: Willabe on December 22, 2024, 05:34:13 pm

It's in the Hoffman Trem mods, thanks tubenit.  :icon_biggrin:

Title: Re: Deep Tremolo wanted on Cathode biased Princeton Reverb
Post by: SEL49 on December 22, 2024, 06:00:57 pm

easier to see...

(https://el34world.com/Forum/index.php?action=dlattach;topic=604.0;attach=68444;image)

Title: Re: Deep Tremolo wanted on Cathode biased Princeton Reverb
Post by: J3ona1 on January 05, 2025, 05:57:01 pm

Thank you so much for your help folks. Trem sounds beautiful!! In addition to adding the red LED i did the following.

1. jumpered the .02uf cap from the oscillator plate to ground (based on note 3)
2. Changed the trem intensity pot to a 1Meg from a 250k
3. Increased the .1uF cap going from the oscillator plate to the 6v6 grids to .2uF
4. Jumpered the 1Meg resistor that goes from the oscillator to the .1uF (now .2uF cap) based on note 2
5. Thank all yall including sluckey for pointing me ro the Ampeg Jet J12 schematic.