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Re: master volume on 5e3 homebrew..?

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5/13/2003 5:23 PM

Re: master volume on 5e3 homebrew..?

Adding a master volume pot to the circuit will in most cases alter the tone / gain / frequency response.
If added in front of the PI, it will basically turn the amp into a different animal completely.
You could then alter the circuit to compensate for this & eventually (depending on if you use trial & error or math) come up with an amp that is similar in tone/gain/freqresp to the original.
Using this MV schem with a dual-ganged pot after the PI seems to make a much less significant change in the amp, although you probably will have to play with the value of the caps before & after the MV pot to stay true to the original.
I recently turned my 2xEL84 into a Matchless Spitfire, which uses a single pot connected across the 2 signal wires going to the power tubes:
http://www.schematicheaven.com/
I am going to try it on my 5E3 & compare it to the results of the dual-ganged pot version.
I am really happy with the results of the dual pot in my 5E3, I just want to compare.
-Ed

5/14/2003 12:25 AM
PaulC	That matchless style MV doesn't work very well at all with a cathodyne inverter. The problem is the cathode side is a much lower imp than the plate side. It dumps all the plate signal not letting it phase cancel. this is also why the cut control doesn't work well in these types of designs. Later - PaulC

5/14/2003 1:05 AM
Curly	Paul, glad you said that, 'cause I just don't get the need for a master volume on this amp. Aren't the TWO volumes enough? sorry, guys, this amp is all about TONE

5/14/2003 2:17 AM
Ed	Great tone! But also a little too much volume around the living room sometimes. Thanks to Paul for saving me an experiment doomed to failure. -Ed

5/14/2003 2:18 AM
Ted R.	I agree with Curly. I had a master volume on an earlier hot rod hack job and will be putting one on my son's Crunch Monster that I am currently building for him, but those are not 5E3's. The tone on a 5E3 repro, when you get it right, IMHO, is too good to mess with. Ted

5/14/2003 4:41 AM
Curly	thanks for agreeing... the 5E3 has limitations, but within those limitations, it is also perfect in many ways

5/14/2003 6:38 PM

I spent a lot of time contemplating this before I built this 5E3.
The 1st one I built had no master volume, but instead was equipped with a triode switch.
I tried this approach because I didn't want to mess with the famous 5E3 sound- you could put it in triode mode to get more distortion at low volumes, but in pentode mode, it was stock 5E3.
However, I found that the triode mode was not the classic 5E3 sound & therefore I was not satisfied with that solution for more distortion at easy listening volumes.
So, I did a lot of checking on various ways of implementing a MV without destroying the classic 5E3 sound.
The dual-ganged pot did just that.
It still has that saturated PI distortion- even at low volumes.
Of course, there is no substitute for power tube distortion except to open her up wide & rattle the windows.
And, of course, MV's are not for everyone.
But, if you want to try adding a MV to a 5E3, the daul-ganged pot is the way to go.
-Ed

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