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Post subject: Interesting find- Tronix NOS 6L6GC for my upcoming amp build
Posted: Sun Feb 19, 2012 4:02 pm
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Well I just picked up this interesting old NOS tube for just a few bucks, I plan on giving it a try in my upcoming amp build which will use a single 6L6GC for output.

Anyone else ever seen or used these?

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Snowy


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Post subject: Re: Interesting find- Tronix NOS 6L6GC for my upcoming amp b
Posted: Sun Feb 19, 2012 6:40 pm
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These are Chinese made 6L6's. The give-away is the round mica top with the plastic "wings." One thing about them, they cannot really take the plate voltage and idle bias of an amp that had RCA 6L6GC's in them, Try to keep the anode below 425VDC & the idle bias wattage below 20 watts/tube (in Class AB1, push-pull mode).

If you are going to DIY a single-ended amp... keep the plate voltage around 350VDC and the idle bias no greater than 80% ("cold" Class "A"). Grid stoppers and screen resistor will be needed to prevent thermal runaway. Somthing between 6L6GB and 6L6GC ratings.

http://tdsl.duncanamps.com/dcigna/tubes ... 6gb-2h.gif

Good luck!

http://www.ebay.com/itm/Power-Vacuum-Tu ... 4162377435


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Post subject: Re: Interesting find- Tronix NOS 6L6GC for my upcoming amp b
Posted: Sun Feb 19, 2012 8:27 pm
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Bummer, I hoped it was something a bit more special than that. :lol:

I picked up another old NOS 6L6GC labelled a "Radiotron", I'll give that a try as well.

The amp will have switchable bias for using either a 6V6 as a 6W amp or a 6L6 as a 12W amp, so I'm just collecting any old NOS single tubes I come across.


Snowy


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Post subject: Re: Interesting find- Tronix NOS 6L6GC for my upcoming amp b
Posted: Mon Feb 20, 2012 12:05 am
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"Radiotron" is an old term for RCA made. Like Cunningham. Metal RCA made Radiotron 6L6:

http://www.ebay.com/itm/Vintage-Vacuum- ... 588f599cae


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Post subject: Re: Interesting find- Tronix NOS 6L6GC for my upcoming amp b
Posted: Mon Feb 20, 2012 5:55 pm
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Just an FYI... some of the finest 6L6GC type tubes ever made were the GE made pink or tan based 7581A. You can still find them at reasonable price, as many folks don't realize that these are the same as the famous STR-415. They are super tough tubes, last forever, AND can be biased hotter than RCA 6L6GC's. I bias them about 15-25% hotter. And they never overheat or show signs of distress.

http://www.ebay.com/itm/2-GE-7581A-KT66 ... 460109d9a4


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Post subject: Re: Interesting find- Tronix NOS 6L6GC for my upcoming amp b
Posted: Mon Feb 20, 2012 7:07 pm
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Thanks Beemer, I'll keep an eye out. One good thing about only needing odd singles is that the prices are mostly real cheap as most buyers are buying for amps that require at least a pair (matched) and then price jumps big time.

Snowy


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Post subject: Re: Interesting find- Tronix NOS 6L6GC for my upcoming amp b
Posted: Mon Feb 20, 2012 7:19 pm
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Those Chinese tubes will probably be just fine at higher Plate voltages, and also might sound great. The specs given above are for the GB, not the GC. My new Tweaker came with the same type, labeled by Ruby and Egnater, and the Plate voltage is about 470 volts, only biased to about 50% though. I also pulled a quad of them from a Carvin amp (exactly like the ones on the first eBay link above), two of which were still good, so I threw them in a HRDlx at 436 Plate volts biased at about 21 watts. Both sets sound great in each amp, I would hang on to them, they aren't bad tubes.

I would like to try some of the GE7581A, sounds interesting.

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Post subject: Re: Interesting find- Tronix NOS 6L6GC for my upcoming amp b
Posted: Mon Feb 20, 2012 8:15 pm
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Beemer, thanks for the Ebay tip! Snagged those GE 7581's tonight. Let you know how they play out. Art

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Post subject: Re: Interesting find- Tronix NOS 6L6GC for my upcoming amp b
Posted: Mon Feb 20, 2012 9:30 pm
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I hope those GE 7581A work out well for you. I have 3 quads of GE pink based 6CA7 heading my way. Really nice tubes for Marshall units that originally had Mullard EL34 in them.

BTW... JiangXi Electronic labeled 6L6GC were made by Shuguang, from 1990-2000. They have redone the data sheet to more of a 6L6GA or GB standard.

http://analogmetric.com/goods.php?id=367

The only Chinese made 6L6GC that I'd recommend for amps pushing 425-450VDC & 30-40 idle watts of dissipation is the 6L6GC-STR sold by TAD. These are also made by Shuguang, but to TAD standards.

http://thetubestore.com/tad6l6gc.html


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Post subject: Re: Interesting find- Tronix NOS 6L6GC for my upcoming amp b
Posted: Mon Feb 20, 2012 10:44 pm
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Still no specs showing low Plate voltage for these tubes. Where is this redone data sheet, or any data sheet for these tubes? None of the links have specs. :?:

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Post subject: Re: Interesting find- Tronix NOS 6L6GC for my upcoming amp b
Posted: Mon Feb 20, 2012 11:20 pm
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Chinese are notorious for not printing data. Or data that they print is overly optimistic. I'm just passing on hi-fi ppl's information, who have these tubes in their units. I'll will post on those boards & get back to you.


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Post subject: Re: Interesting find- Tronix NOS 6L6GC for my upcoming amp b
Posted: Mon Feb 20, 2012 11:46 pm
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That would be cool. Until then I'll keep trying to melt the ones that I have. :lol: Both the Egnater and Carvin put 470 volts on the Plates, and not a glitch so far. Although, both amps come biased on the cold side from the factory, I bumped them up to about 50% (15 watts). But the ones in the HRDlx are idling at about 21 watts. :shock:

I didn't have any better luck trying to find specs on the 6L6GCMSTR. I think that they are a copy of the Philips STR, but no specs. :?: Definitely used in amps with at least 470 Plate volts though.

Dang it, now you've got me watching my tubes with a mirror while I play. :shock: :lol:

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Post subject: Re: Interesting find- Tronix NOS 6L6GC for my upcoming amp b
Posted: Tue Feb 21, 2012 12:20 am
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Shimmy, prolly as long as the idle watts of dissipation is around 19-20 watts per tube (regardless of plate voltage)--- you'll be ok. Grid stopper & screen resistors may help keep them from thermal runaway.

Most ppl on hi-fi boards are running UL tapped 6L6GC at 40+ watts per tube (cold Class AB or B). Sometimes, even hi-end Chinese amps come this way. And the inevitable happens. Will get back to you on any data sheets.


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Post subject: Re: Interesting find- Tronix NOS 6L6GC for my upcoming amp b
Posted: Tue Feb 21, 2012 1:28 am
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Shimmy, Check on page 31 of link (about half-way down).

http://analogmetric.com/download/Shugua ... imited.pdf


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Post subject: Re: Interesting find- Tronix NOS 6L6GC for my upcoming amp b
Posted: Tue Feb 21, 2012 8:36 am
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I was looking at that last night, especially the extra letters on the end, this one being "R". If that is the same tube as the GC, it is rated a 360 Plate volts and wouldn't be a good choice in any amp that required 6L6GC.

40 watts idle for one tube?! WTF? Yeah, if you run a tube that far over it's max rating, few tubes would survive. I think that there will be no problem with higher Plate volts and a 15 to 21 watt idle in a guitar amp for these tubes, whatever the tubes actually are.

Hard to believe that the GC, GCJ, GCP, GCR, and GCMSTR, would all have the same tube specs, or that manufacturers would use them in amps with Plate volts of 470 volts, without the tubes being able to survive. :?:

I also have a copy of an old Shuguang Tube manual from '73, the Chinese is a little hard to read though. :lol:

Just wondering, since the OP tube was relabeled, what version those actually are? I didn't see any original label or markings. :?:

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