New 6L6GC Project. DC -> LTP

[sorenj07]

Not sure I follow..? We have a CCS here so even with no signal, a 3.3mA draw per tube is inevitable, so the plate resistor must drop that voltage? Or am I missing something? It really has been a while :\

[sorenj07]

newest iteration. neglected to draw 1K grid stoppers on the 6N1P inputs. also haven't sorted out the protection diode, everything else seems pretty solid.

[20to20]

Just curious, what is the cost of the 2 additional chokes you have in the PS?

[sorenj07]

they're some triad models. probably not more than $30 total from allied.

[sorenj07]

got 'er built. all is well except those 72K plate resistors on the 6N1P are dropping way too much voltage, I'm reading like 180V on the anode. looks like it's back to 47K as planned. that said, it doesn't distort audibly and there isn't any audible hum, so i'm happy so far :)

overall wiring


bias supply


outside


inevitable glow shot

[20to20]

That's art work.

Congrats.

20

[sorenj07]

aw, thanks. after scraping the old orange paint off the transformer bells with a razor and painstakingly sanding them back down to bare steel, and 3 coats of dark chestnut stain on the side panels, it had better sound good. so my brain says it sounds good :)

now my next reasonably serious question: should a tiny bit of redplating on these Shuguang 6L6GCR's worry me? i'm apathetic about buying a new set of JJ's or EH's, especially since with my luck, one of them always arrives crooked.

[Blair]

Beautiful work Soren!

Oddball question, but what are your octal sockets?

I hope school went well, and you are on your way to a great career!

Blair

[EWBrown]

Under normal / safe operating conditions, the 6L6GCs should not have any red-plating, and I suspect that the shuguangs are of a lot "lighter" internal
plate structure than most other (REAL) 6L6GCs. Try reducing the idle current with them, just so that something doesn't unexpectedly go "kaboom"

REAL 6L6GCs can handle 30W PD, these Shuguangs are probably good for about 20 W maximum... I'd SWAG that they are more akin to the older 6L6Gs or 6L6GBs.

(Just like the infamous "Sino" "Made in Chian" 5AR4 "Election Tube", which barely has the voltage and current handling capabilities of an average 5Y3GT).

The Russian-made 6L6GCs are just about nuke-proof, they are as tough as old army boots, as they were designed around guitar amp usage,
which can subject them to a lot of electro-stress..

Interesting design, I really like it, and your craftsmanship is excellent

/ed B

[sorenj07]

Beautiful work Soren!
Oddball question, but what are your octal sockets?

Thanks! They're the teflon ones on Partsconnexion. I really like them!
As for the career, I'm a techno dj/producer so fat chance of that! :)

[sorenj07]

Thanks Eric! I'll probably just shell out and pay for the real deal soon. Pity it's really hard to find the coke bottle Shuguang's, seems like everyone caught on to how good those were for the money.

[sorenj07]

One of the Chinese 6L6GCR's blew. Now I've got a quad of JJ/Tesla 6L6GC's singing along and all is well. Still contemplating some global feedback but things are sounding pretty Ok without.

final schematic, using 1.5a slow blow fuses

[EWBrown]

Those Shuguang 6L6Gx's look very similar to some Russian made 6L6GB equivalents that I have, and those are rated at 19-20 W max PD, at best, and I'd
call that rating as being overly optimistic, after looking at their plate structures, and relatively "light" construction.

I'd rate them as being slightly hefty 6V6GTs at best... The 6L6GCs from J/J, Sovteks, EH's, etc would be a LOT better, they are made for hard use as in guitar amps, as well as for audio. The Sovteks and EHs are, as they say, "as tough as the proverbial army boot", they can take a lickin' and keep on tickin' like the old Timex watch ads from the '60s and '70s

FWIW, I have a quad of "Sino" EL34s which also have a similarly wimpy and undersized plate structure, they came from a Chinese-made PP amp which I repaired / upgraded for a friend a few years ago - I replaced the EL34s with Svetlanas, and the original Sino branded 6N4 (12AX7 equivalent) and12AU7 driver tubes with J/Js, and the improvement was amazing, it made a truly sick and sad sounding amplifier sound "almost" very good, considering the overall cheap construction and components used in it.

/ed B in a warm and rainy NC.

[noahtheviking]

I would run another 22uf 500v in parallel with the other 22 uf 500v you have plenty of transformer for that matter