Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: dwinstonwood on April 13, 2025, 05:42:07 am
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Searching back through the various guitar amp forums it's obvious that lots of people have experimented with Octal tubes over the years: there's nothing new in what I'm doing. It's a hobby and it's all for fun.
But, I've gotten to like these tubes because they are easier for me to wire up and they're affordable (compared to NOS 12AX7's and 6L6GC's, etc.). I also think they look cool, especially the metal ones.
At any rate, I've always wanted a 6G* harmonic tremolo amp. So, here's my first rendition of a "fictional" Fender 6G4 Super Octal. :icon_biggrin:
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You going to use metal 6L6 tubes?
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Should work great. I love those octal preamp tubes. Room to solder and only two heaters to hook up. :icon_biggrin: The older I get the more important that gets. My only suggestion would be that I have been happier with a somewhat lower B+. Not to save the tubes but I think they just sound better.
Interesting to note that as the voltages went up for the Brownface amps, they marked the filter caps as 600p. I think the P stands for peak voltage rating? Not sure, but curious to know.
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You going to use metal 6L6 tubes?
danhei, I'm considering that! But, plate dissipation is rated at 19w with 360v max for plates and 270v max on the screens. The problem is finding a PT with B+ voltages this low while still providing enough current. It's actually easier (and less costly) to go with a proper 6L6GC PT with higher voltages, or just use 6V6's with a lower voltage PT that won't be over-stressed.
...I have been happier with a somewhat lower B+. Not to save the tubes but I think they just sound better.
I'm in the same camp bmccowan. My last amp build runs its metal 6V6 at about 324 plate volts and I love the way it sounds. And, using the Star B+ filtering method I can easily keep preamp voltages as high (or low) as I want.
Thanks,
David
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I have done several all octal tube amps, I love Octals...
I often find the 6SL7 has too much gain and drop to the 6SN7
I prefer the heater light look through glass
have also found for some reason metal is more microphonic than glass
here's one using 6SN7 for pre and PI with 6BL7 Push Pull
https://stillampd.com/weekender
this one uses 6SC7s for Pre and PI; 6V6 Push Pull
https://stillampd.com/black-and-blues-05
This has two stage 6SL7 pre with 6SN7 PI 6BL7 Push Pull
https://stillampd.com/westy-02
The 6BX7 is interchangeable with 6BL7 but the BX is to hot for my taste.
I am also a big fan of point to point wiring as well.
Gives me an opportunity to be a little "artistic" with the layout.
Although more difficult to make changes