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Good day Keepers of True Sound,
Yer previous help has had my jtm45(w/Crate V50 iron) running quite sweetly.
Became aquainted with a local HiFi gent who's been tapping into his old stash
of vintage tubes for me. Recently "gave" me a pair of RCA 6L6gc blackplates for a
C-note. He didn't have time to use his lab testor, so he used his Eico for emission,
transconductence, and somethin else, I forget. Said to try em out, and if something was
funky, he'd do another pair on his lab testor for me.
I think something IS funky.
Split Cathode Biased Siemens STR EL34s were running at:
B+: 412 / Plate: 407(actual 379) / Cath: 28 / Grid(pin4): 362 - heavenly sounding.
Switched cath resistor to Shared Cathode 300R & 100uF/100v as per one of your previous posts,
fitted the 6L6s, and hooked up my meter using ShuntMethod. Both tubes read:
B+: 454 / Plate:433(actual 400) / Cath: 33 / Grid(pin4): 452 - YIKES!?
On top of that, Current Draw reads 60mA on one tube, 40mA on the other.
(w/ fillament-cathode glowing very brightly on the 60mA, much dimmer on the 40)
Love the sound way more than ELs, but not as clean as I expected, in fact (nicely) gritty
at only 3vol. Guessing it's comin from that HOT@60mA tube, but also wonderin if it's added to by
the mismatched current draw. My two sets of ELs were only off by a mA or so.
So,
1) Is this mA mismatch way out of the ballpark ?
2) Is there an obvious problem with one tube or the other ?
3) What the heck made my B+ voltage jump ?
4) Oh my GOD! What is with the crazy voltages on my GRIDs !!!???
Still lovin the mysteries, appreciate the generous community,
and keep drowning out dis-harmony with the sweetness of True Sound!
Thanks.
Yer previous help has had my jtm45(w/Crate V50 iron) running quite sweetly.
Became aquainted with a local HiFi gent who's been tapping into his old stash
of vintage tubes for me. Recently "gave" me a pair of RCA 6L6gc blackplates for a
C-note. He didn't have time to use his lab testor, so he used his Eico for emission,
transconductence, and somethin else, I forget. Said to try em out, and if something was
funky, he'd do another pair on his lab testor for me.
I think something IS funky.
Split Cathode Biased Siemens STR EL34s were running at:
B+: 412 / Plate: 407(actual 379) / Cath: 28 / Grid(pin4): 362 - heavenly sounding.
Switched cath resistor to Shared Cathode 300R & 100uF/100v as per one of your previous posts,
fitted the 6L6s, and hooked up my meter using ShuntMethod. Both tubes read:
B+: 454 / Plate:433(actual 400) / Cath: 33 / Grid(pin4): 452 - YIKES!?
On top of that, Current Draw reads 60mA on one tube, 40mA on the other.
(w/ fillament-cathode glowing very brightly on the 60mA, much dimmer on the 40)
Love the sound way more than ELs, but not as clean as I expected, in fact (nicely) gritty
at only 3vol. Guessing it's comin from that HOT@60mA tube, but also wonderin if it's added to by
the mismatched current draw. My two sets of ELs were only off by a mA or so.
So,
1) Is this mA mismatch way out of the ballpark ?
2) Is there an obvious problem with one tube or the other ?
3) What the heck made my B+ voltage jump ?
4) Oh my GOD! What is with the crazy voltages on my GRIDs !!!???
Still lovin the mysteries, appreciate the generous community,
and keep drowning out dis-harmony with the sweetness of True Sound!
Thanks.
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