Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: morton on August 29, 2015, 07:39:22 pm
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Hi all, ran across this layout on a previous thread. Looked like a easy way to add a MV on a 5E3 which I plan as my next build. Just looking for opinions on if it looks feasible or if there are better alternatives?
Thanks,
Gary
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With respect, of course it's feasible. Doug Hoffman wouldn't publish it if it weren't.
(If someone modifies a Hoffman drawing, it would be nice if they indicated that it was NOT his work on the drawing.)
Are there other ways to add a master volume to this circuit? Of course. Just do a search here and with Google. However, this has the virtue of simplicity plus reducing the possibility of concertina phase inverter distortion (typically ugly - search for nipple distortion) as you turn the MV down. The MV pot simply replaces the grid return (or leak) resistor for the PI triode.
See schematic: http://el34world.com/charts/Schematics/files/fender/Fender_DELUXE_5E3.pdf (http://el34world.com/charts/Schematics/files/fender/Fender_DELUXE_5E3.pdf)
Chip
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With respect, of course it's feasible. Doug Hoffman wouldn't publish it if it weren't.
Not sure who's mod that is
Someone on the forum here editing one of my drawings
You would have to ask that person about that mod
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Kagliostro did that drawing.
http://el34world.com/Forum/index.php?topic=18647.msg190784#msg190784 (http://el34world.com/Forum/index.php?topic=18647.msg190784#msg190784)
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Gary,
Your question was answered in the thread Sluckey linked to where you found the layout:
Kagliostro and anyone else who may be interested,
I did this mod last night and have been playing with this master volume and it works! It's pretty cool. It allows you to turn down and still get good tone and does seem to modify the heavy distortion profile as described above to some extent when running the normal volume way up and just turning the master down slightly. It's also true that the amp seems pretty much back to stock with the master volume all the way up. I prefer the mods that let you get back to the stock sound at the flip of a switch or turn of a dial.
I used a 1 Meg audio taper pot and still the range of usable master is pretty small. It's works nicely with the feedback switch mod I did previously, though the feedback doesn't have as much effect at lower master volumes (as you might expect).
The 5E3 is such a good sounding base for all of these modifications and options that it makes me want to try a few more. Rather than build a 5E5 Pro or A, I think it might be nice to just build a more powerful 5E3 with as little other changes as possible. I understand that just putting 6L6 tubes in won't do much, but larger transformers, 6L6's and a different rectifier would? How close could one build a more powerful version while staying as close to the Hoffman 5E3 as possible.
Paul Robinette advocates the same mod, but adds a treble bleed cap and a grid stopper.
(https://robrobinette.com/images/Guitar/5E3P_Build/5e3_Pre_PI_Master_Volume_Mod.png)
Discussion: https://robrobinette.com/5e3_Modifications.htm#Add_Master_Volume
Cheers,
Chip
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Thanks, I found the drawing back on a thread from April. Just added it to a new one because the thread was so old. I plan to build it stock, it just looked like a simple reversible mod that you could try after the build was tested. Was just looking for some more recent feedback. Didn't mean to create any confusion.
Thanks,
Gary
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Paul Robinette advocates the same mod, but adds a treble bleed cap and a grid stopper.
I really dislike Robinette's positioning of the master volume; the wiring to the added master volume cross wiring for control running to earlier points in the preamp, which could invite oscillation.
I prefer the arrangement in the original post for that reason.