Electar Tube 10 mods

Since many of you have been asking me for details on what and why my Electar Tube 10 mods accomplish, I thought I would add a section describing the changes from the original design.  Refer to my schematics for part reference designators.

 If you have been to my site before you might have noticed I removed the original mod and the P1-Xtreme mod.  I settled in on the Rev D mod as the best overall, not too difficult for the novice to tackle, improvements to the amp without going overboard trying to completely change the amp.  This set of mods can easily be done in a few hours with little challenge.  The results will be a more tonally-balanced, slightly louder amp with good tube overdrive capability.  BEWARE OF HIGH VOLTAGES!

 Let’s get started and work from the input to the output. 

1st Pre-amp stage - Change R3 from 3.3K to 1.5K.  Change C1 to 10uF.  This is pretty much the standard Fender front-end.  Enough gain and bass response but not too much.

Change coupling cap C2 from 0.47uF to 0.022uF.  The 0.47uF passes way too much low frequency for a small-speaker guitar amp.  Make sure you use a good quality hi-voltage type cap here.  Eliminate R5, it just attenuates the signal between stages and reduces gain.  Experiment with R6, you can just leave the original 120K alone or increase it for less overdrive.  I chose 220K as a good compromise value.  Place a 100pF Silver Mica Hi-voltage cap from the wiper of the GAIN pot to where C2 and R6 connect together.  This will brighten things up a bit.  Again, try different values up to 470pF.

2nd Pre-amp stage - Change R7 from 1K to 1.5K.  Change C4 to 10uF.  Again, pretty much the standard Fender front-end.  Enough gain and bass response but not too much.

The Clean/Dirty switch and R14 don’t really have that much effect and suggest leaving them out, especially since you have to mount a switch somewhere.  Ironically, when you look under the hood, there is an extra cutout in the control panel chassis for a standard toggle switch but is covered by the control panel itself.  This is easy to drill through.  I may put some sort of clipping circuit here (stay tuned for Rev E!).  C5 is redundant, either leave it alone or put a shorting wire in its place.

Tone Stack - I left the tone stack alone as this is the basic Marshall Tone stack and is a good fit for this amp.  If you are looking for more of a Fender Tone stack, you can play with the R and C values, but you will have trouble changing the potentiometer values since they are soldered directly to the Printed Circuit Board (PCB).

Power stage - Pretty much left alone.  I increased C10 from 22uf to 100uF. 

Negative Feedback - Ditch R14 unless you like less gain and more clean. 

Speaker - The first thing you must do is replace the stock speaker.  I replaced mine with a Weber C8SS and it made a big improvement. 

That’s it for now.  There are more extensive mods you can make like adding gain stages, but try this for now if you just want a basic tube amp that doesn’t blow the walls down!

Here is the Rev D Schematic