Removing tone stack from RRobs RR763

[jukelemon]

Hi all.


Looking for suggestions/guidance on how to remove the tone stack from the RR763 thus leaving one volume control only.


Would removing everything minus the .1 coupling cap do the job or do you think I would need additional changes?  I am thinking Champish volume circuit here. 


Essentially, the end goal of a tube power amp with Volume control.


RR763 schem attached.


Thank you!

[shooter]

should do it

[jukelemon]

Cool and that is what I was thinking as well.


Thanks Shooter!

[kagliostro]

Which is your purpose on doing that ?


Do you have faceplate space problem to resolve ?


Franco

[shooter]

V1a provides enough gain to drive the TS which sucks out gain, since there is no longer a gain sucker, pretty sure V1b will get over-driven beyond musical

[kagliostro]

You can install a raw control or sub the TS with a James or simply a tilt control


K

[jukelemon]

You can install a raw control or sub the TS with a James or simply a tilt control


K

Hey there.

I am building/tweaking an amp for my Leslie 900 conversion.  Right now it sits at the Proluxe design stage and I have the tone dimed because the EQ comes from the organ.

I am about to install a RR763 circuit in the Proluxe's place and I don't need a tone stack.

[jukelemon]

V1a provides enough gain to drive the TS which sucks out gain, since there is no longer a gain sucker, pretty sure V1b will get over-driven beyond musical

Meaning... removing the tone stack is not going to work here?


I could always use a 12ay or even set the bias points for a 12AU and like the original Leslie 122/147 amps?

[sluckey]

Or you could just turn the volume control down.

[shooter]

removing the tone stack is not going to work here

define "work"


i've typically found the 1st triode gives a good bump to S/N and signal amplitude, the TS typically erases the amplitude, which is made-up + sum in the 2nd triode


an AU would be my goto, it's all about what does this circuit need to produce to make the next circuit n user happy?
i've found though, what makes the engineer happy seldom makes the artist happy 

[jukelemon]

Or you could just turn the volume control down.

Exactly

[jukelemon]

removing the tone stack is not going to work here

define "work"


i've typically found the 1st triode gives a good bump to S/N and signal amplitude, the TS typically erases the amplitude, which is made-up + sum in the 2nd triode


an AU would be my goto, it's all about what does this circuit need to produce to make the next circuit n user happy?
i've found though, what makes the engineer happy seldom makes the artist happy 

Work = having a reasonable sweep on the Volume so that the amp doesn't go from clean to Metallica in 3 clicks lol.

I will try the circuit as is and just use an 12AY at first.

The amp is going to be driving a 75w, 15" WGS alnico and a 60w Jensen V21. 

[mountainhick]

If you want the amp to behave pretty much like it is with the tone stack, or if you find that iot has too much gain with stack removed, you can replace the stack with a coupling cap then a voltage divider.

Important: It is essential to place a coupling cap after the triode to keep high DC voltage off the volume pot.

[RoadShow]

Why not just add a switch to the front or back to select between either the TS or cap?
Just for the flexibility...

[sluckey]

Essentially, the end goal of a tube power amp with Volume control.

If this is truly your end goal, then you should completely eliminate the entire preamp section (V1A and V1B). Connect an input jack to a 250K volume pot and connect the pot wiper to the .001µF PI input cap. Like this...

[jukelemon]

Essentially, the end goal of a tube power amp with Volume control.

If this is truly your end goal, then you should completely eliminate the entire preamp section (V1A and V1B). Connect an input jack to a 250K volume pot and connect the pot wiper to the .001µF PI input cap. Like this...

Nice!!


That looks very much like a 122/147 power amp.  Thank you Sluckey!!