Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: SteveZ616 on December 26, 2010, 02:13:43 pm
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First of all - GREAT FORUM! almost going blind trying to read and absorbe all the info at once...wow.
I have decided to finally do a build for myself based off of Mr. Hoffman's stereo power amp project. Will be using his basic configuration to drive one of my 4x12 cabs in stereo mode. Main tone shaping is from Fractal Audio's Axe-FX Ultra. Been using the Ultra exclusively with IEM's and direct sends to FOH. Want the option to drive cab if mood hits me.
My main "change" is that I desire an adjustable bias rather than the cathode bias(reading schem correctly?) per his diagram. Will be using the EL84 pairs per side/channel.
From my knowledge (not "dangerous" but certinaly not all-in-the-know), the EL84 can produce an amazing tone, but is a little more tricky in cathode biased amps - change tubes to change tone. I would rather "adjust" to a given tube set rather than throwing tubes at the beast or modifing components if I'd like tweak for best tones to my ear.
Any tips/tricks/voodo? Power tranny will be twin 200VAC secondary @ .4 amp each - 6.3 VAC filaments also present (of course).
Any direction or advise is requested!
Respectfully, Steve Z.
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Hi SteveZ616
I think Hoffman's project is fine as is (my be I like more cathode biased amps than fixed biased)
however if you want to "study" about the possibility to transform a cathode biased amp in a fixed one
give a look here
https://taweber.powweb.com/store/6d30_schem.jpg
https://taweber.powweb.com/store/6d30_layout.jpg
the Weber 6d30 has both abilities
so you can have an idea about differences and how to modify the circuit
Have nice Holidays :smiley:
Kagliostro
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Wow! That was quick!!!! Thanks for the material.
Design/graft/tweek/dance...here I go...
You have a great holiday also!
Respectfully, steve z.