Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: dude on April 25, 2017, 01:15:54 pm

Title: Tremolo intensity too deep or intense
Post by: dude on April 25, 2017, 01:15:54 pm

The tremolo on the J20 Ampeg modelled after the 6G3, has way too much intensity. I usually have the pot set at 1 just enough to get tremolo.
I looked at the 6G3 pretty much the same as this J20, schematic attached. speed works great, just way too deep.


I searched this topic here and elsewhere but found nothing.


I was thinking if I raised R27, to 470K this might cut some intensity but looks like a voltage divider with the (2) 220K's..?


al 


 

Title: Re: Tremolo intensity too deep or intense
Post by: kagliostro on April 25, 2017, 01:47:17 pm

And leave the 220K adding the 470K resistor between R27 and C20

connecting the other side ot the added 470K resistor to ground ?

This way your oscillator signal will be around 30% lower to the intensity pot

K

Title: Re: Tremolo intensity too deep or intense
Post by: sluckey on April 25, 2017, 01:50:35 pm

You're on the right track but you may have to increase R27 to 1M or even higher. Also put a .1µF cap from the right end of C 20 to ground.

I believe you are the first dude to complain this bias vary trem is too strong.  :icon_biggrin:

Title: Re: Tremolo intensity too deep or intense
Post by: dude on April 25, 2017, 02:15:04 pm

Quote from: sluckey on April 25, 2017, 01:50:35 pm

I believe you are the first dude to complain this bias vary trem is too strong.  :icon_biggrin:

Must be those used old stock tubes I'm using.... but it is very deep... :icon_biggrin:  BTW, your plexi drawing of Mark Huss's is just like the November, I copied. Works great but I lost a leg on the switch, I have to get that iron off sooner, tight spots and poor eye site,  :laugh: 
When I get a new switch, hopefully that pop will be gone.


I'll try the 1meg, then K's suggestion. (that added 1uf  e-cap's a filter..?)


thanks,
a


 

Title: Re: Tremolo intensity too deep or intense
Post by: sluckey on April 25, 2017, 03:02:33 pm

Quote

(that added 1uf  e-cap's a filter..?)

It's not a 1µF. It's .1µF. Maybe even just use a .047µF. You can look at it as a smoothing filter cap or you can look at it as part of a capacitive voltage divider, the other part being the existing .1µF cap. Just another way to knock the tremolo signal down some more. You may not need the bigger resistor and the cap, but a lot of circuits have both.

Title: Re: Tremolo intensity too deep or intense
Post by: kagliostro on April 25, 2017, 03:46:31 pm

Quote

.... you can look at it as part of a capacitive voltage divider .....

I like to think so

Franco