Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Garrett335 on June 25, 2018, 01:25:47 pm

Title: Post phase inverter master volume, and Tremolo circuit issues
Post by: Garrett335 on June 25, 2018, 01:25:47 pm
Hey guys!
Having a little bit of trouble with a new build, I am modding the Marshall 2022 schem, I have built this circuit with the tremolo and it worked wonderful.
I then decided I wanted to add a PPI master volume. Now that I've added this the tremolo is very weak in intensity, and very fast hardly working at all.
My question as the Trem is manipulating the output and the Master Vol is also manipulating the output, or signal to the Out tubes, are they interfering with each other?
I've attached the original schem, and my updated schem with the trem and MV.
Thank you for any input.
Title: Re: Post phase inverter master volume, and Tremolo circuit issues
Post by: sluckey on June 25, 2018, 02:50:49 pm
Yes, they are interfering with each other. Maybe if you wire your intensity pot and MV pots in a more standard way, they wont affect each other so much. The .1µF should connect to the top of the INT pot and the wiper should connect to the junction (ground side) of the dual MV pots. And the .022µF caps should connect to the tops of the MV pots and the 2.7K resistors should connect to the wipers. IOW, swap all wipers and hot ends of the three pots. See if that helps.
Title: Re: Post phase inverter master volume, and Tremolo circuit issues
Post by: Garrett335 on June 26, 2018, 12:54:17 am
Quote from: sluckey on June 25, 2018, 02:50:49 pm
Yes, they are interfering with each other. Maybe if you wire your intensity pot and MV pots in a more standard way, they wont affect each other so much. The .1µF should connect to the top of the INT pot and the wiper should connect to the junction (ground side) of the dual MV pots. And the .022µF caps should connect to the tops of the MV pots and the 2.7K resistors should connect to the wipers. IOW, swap all wipers and hot ends of the three pots. See if that helps.

Thank you so much! That worked and it sounds great!
I'm having one other issue though... The Trem only comes on when the intensity pot is maxed out, if I back off from say 10 to 9 it cuts out completely.... Any ideas on this? And I did what you said with switching the wiring of the .1 to the top and the wiper to the junction.

Thanks again as always :D
Title: Re: Post phase inverter master volume, and Tremolo circuit issues
Post by: sluckey on June 26, 2018, 01:28:30 am
Change the 100K plate resistor to 470K. Any better?
Title: Re: Post phase inverter master volume, and Tremolo circuit issues
Post by: Garrett335 on June 26, 2018, 09:07:35 am
Quote from: sluckey on June 26, 2018, 01:28:30 am
Change the 100K plate resistor to 470K. Any better?

I changed it to the 470k and now I can only hear the trem as the amp warms up, and the effect fades when amp is completely on.
I just switched it to a 68k to see if that helped, and figured out that when I move the input coax wire around the effect will feed back and also stay on for the full intensity sweep as long as I keep the input to the grid in the right place.
I used coax and grounded the shielded wire, I wonder why this is affecting it?
I'm not using shielded wire on any of the pots, maybe that would help?

(Update after reading other posts)
I'm going to try and use a regular wire from the input to V1G and see what that does, have to wait until this evening when I get home from work : /
Title: Re: Post phase inverter master volume, and Tremolo circuit issues
Post by: Garrett335 on June 26, 2018, 05:45:59 pm
Okay I think I fixed the issue.
I was using one of those grounding washers for the cliff jacks, and had a separate ground for the turret board.
I grounded the input and the board to the same location (still using the shielded cable on input to grid v1) and the hum is gone, and the trem is fully functional now.
Thank you for your help Sluckey!!!!