#3711
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The copper V-Caps will be a revelation. Be sure to re-visit your 6V6's after they settle in. Do you have a 5R4GY rectifier?
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#3712
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5U4-G - 5.0 - 3.0 - 44 - 225 - 450 - octal 5Z3 (274) 5AR4 - 5.0 - 1.9 - 17 - 250 - 450 - low Vdrop 5U4/5Y3 5Z4 - 5.0 - 2.0 - 20 - 125 - 350 - low drop 5Y3 80 - 5.0 - 2.0 - 60 - 125 - 350 - 4pin 5Y3 5R4-G/GY 5.0 - 2.0 - 67 - 250 - 750 - high voltage 5U4 Any technical concerns / risks with it? Here's a quote from poster wyatt at another forum explaining the effects of these specs in an amp: "The Vdrop is the voltage drop across the rectifier, those numbers (-17, -20, -44, -60) are over-simplified, the actual Vdrop will depend on the actual incoming AC voltage becing rectified. The 5AR4/GZ34 has the least Vdrop, then the 5Z4, then the 5U4G and finally the 80 (5Y3)." "A side-effect of the voltage drop is the sag it adds. The more Vdrop, the less efficient the rectifier is, meaning it takes longer to supply the current. This adds Sag. When you pick a note or strike chord, the amp demands more current and the less efficient rectifiers can't supply it right away, so you're note/chord sort of drops in volume before ramping back up again. The more the amp is cranked the prominent the sag." I adhere to these observations because I have always preferred the sound of low Vdrops in my rig. The goto 274B in my case is an intermediate Vdrop (44) so it's a tradeoff and it sounds great with smaller output tubes. The preferred 5AR4 is ideal with larger (more current demanding) output tubes (6550 / kT-88) and this rectifier limits sag. "Higher voltages mean more headroom and tighter feel. Because the plate voltage changes, you should check bias after swapping rectifiers." The last statement may create a problem since our amps are self-biased. Should this be a consideration? Last edited by Musica Amantem; 05-14-2017 at 12:51 PM. |
#3713
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No concerns. I wonder what the voltage drop of the Sophia 274' is? I can't find the answer.
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#3714
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The goto 274B in my case is an intermediate Vdrop (44) so it's a tradeoff and it sounds great with smaller output tubes. The preferred 5AR4 is ideal with larger (more current demanding) output tubes (6550 / kT-88) and this rectifier limits the corresponding sag. In addition, I remember Dennis saying the 5U4G (274) works better with 6V6 / 6L6 and the 5AR4 with 6550 / KT-88 relative to the 2nd order harmonics released near clipping. Last edited by Musica Amantem; 05-14-2017 at 01:16 PM. |
#3715
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These 7581A's are even better sounding after some time on them. The dynamics are really good. Bass drums kicks have incredible impact. |
#3716
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A for sale ad says the amp can use 300B tubes?
Dennis Had Inspire KT88 tube amp. This amp will use KT88, EL34, 6L6, 6V6, and 300B power tubes. With 6V6 tubes it makes about 7 WPC. With the KT88 it makes 12WPC. Off white powder coat with faux wood front Something in not adding up for me. Any insight? Thanks. |
#3717
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#3718
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BTW, I came across a paper from Steve Deckert (Decware) which addresses differences between true triodes and pentodes strapped as triodes. Here's a quotation that called my attention: "In a pentode such as the EL34 where the screens are not tied together internally, it is possible to wire it as a "true triode". It is the only pentode I know of that is. The other ones have internal connections on the screens that can't be changed so you end up with a "Pseudo triode" as I've heard it called." In my Triode-strapped amp, the KT-77 sounds best. I know this tube is a far relative of the EL34 and its a tetrode, but makes me wonder if anyone has got a better result with the EL34 than with the KT-77 in his Triode-wired Inspire, OTBE. I remember someone mentioning a Mullard EL34, but I cannot tell if that poster had a Triode-wired Inspire amp. I guess the only way to find out is trying one ... There goes my determination to stop chasing down new tubes Last edited by Musica Amantem; 05-14-2017 at 04:22 PM. |
#3719
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Amp was made on 9-30-13; seller claims "I once asked Dennis if I could put a tube in, I can't remember which, and he said stick it in. If it works, yes, if it doesn't, no." and "I have used the 300B output tubes, and have a set of Valve Art tubes to go with it."
I thought 300B requires totally different circuit/voltages. Seller gives pentode power ratings for other tubes. |
#3720
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