| Re: Open-Loop and Tone [message #27212 is a reply to message #27211] |
Sun, 05 February 2006 16:03   |
Damir
Messages: 1005
Registered: May 2009
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Illuminati (2nd Degree) |
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Huh, one of the my "must build" projects is a small quality practice guitar amp, probably 8" combo. Front end - ECC35/6SL7 or noval 5751, maybe 12AY7 or even "maybier" 12AX7, two stages with tone controle(s) in between. I`ll certainly try EF86, and some other pentodes I have, say EF184 and E180F. EF86 is suprisingly good sounding in "Matchless" DC30 amp I`m familiar with. This, pentode ch is maybe better sounding then 12AX7 channel.
Output tube - two "standard" candidates, EL84 and 6V6GT - maybe to use them both, haha, (cathode switch - 6V6, EL84 and BOTH position), if possible...IME - EL84 overdriven sounds softer and warmer ("VOX" sound), and 6V6 a little cleaner and more dynamic ("Fender" sound), but it`s a subjective experience:-). I have one 2k5:4 Ohms SE OPT, it can be 5k:8 Ohms without problems, with few other primary taps - I`ll try a SE UL, not a "traditional", pentode ("Champ") style... 
Triode+triode (k2) distortion for the guitar isn`t high on my list, some odd harmonics "roughiness" is essential here, IMO.
Power supply - EZ80/81, maybe "traditional" 5Y3 or totally "odd" solution from little AZ... stash I have. CLC + LC, with good (probably MKP) capacitors...B+ about 270-300V.
Tweaking with feedback loop in some "Fender" amp gives me the impression that the "level" of NFB is well thought out here, for the "semi-clean" sound they want. When I decreased NFB, sound improves in "openess" and harmonic structure, more "alive" sound, and better, smoother overdrive. But, it can be less controlled, more "boomy" on the LF and amp can be too sensitive. With small speakers/boxes low DF "boomy" sound probably isn`t a problem...Huh, just a few subjective points... Hey, possible interesting new "Group Build" project?
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