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Post subject: Re: GE 6L6GC Snake Oil or worth it?
Posted: Tue May 03, 2016 6:18 pm
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$200 for a matched set is steep even for NOS. I like the TAD short bottle 6L6's. Tone similar to the old GE bottles and at $50 for a matched set you could go thru 4 sets! I have a set of them in my '66 Bassman, good tone and it's crankability is just fine!

T2

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Post subject: Re: GE 6L6GC Snake Oil or worth it?
Posted: Wed May 04, 2016 3:15 am
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jackhammer wrote:
I thought the GE connection was interesting. I can only offer another option.
These new tubes are supposed to be like GE 6L6 tube. I'd try these first.


http://www.musiciansfriend.com/power-tu ... ower-tubes


They are very much like the originals. I compared an original set of GE with the GT Reissue version in a '68 Bassman, and actually preferred the GTs, they sound great, and I left the GTs in that amp. The difference was very slight, the GT were just a tad more clear than the GE. I also put a set of the GT Reissue in an Ibanez amp and they sound wonderful in that amp also. I liked the GT so much, I bought the company.......OK, would you believe I bought a truckload.......OK, I bought a few sets anyway. :lol:

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Post subject: Re: GE 6L6GC Snake Oil or worth it?
Posted: Wed May 04, 2016 11:32 am
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Are they still making those GE Reissues, or are these left over?


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Post subject: Re: GE 6L6GC Snake Oil or worth it?
Posted: Wed May 04, 2016 5:04 pm
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AFAIK they are still being made, in China. TAD has a version of these that seem like the same tube, getter flash on the side.

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Post subject: Re: GE 6L6GC Snake Oil or worth it?
Posted: Thu May 05, 2016 7:50 am
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I'm running the TAD short bottles in a Peavey Triumph 60 from the eighties and i have real deal NOS GE's in my vintage Super Reverb, both sound amazing.
I'll bet ya the original GE's outlast the the TAD but they both sound excellent so.....................

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Post subject: Re: GE 6L6GC Snake Oil or worth it?
Posted: Fri May 06, 2016 6:10 am
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I started this thread because I wanted to order these NOS GE 6L6GC's (just to have for my next tube swap).
The tubes I have now are the new Tung-Sol 7581A's (bigger plate).
After reading the following from another forum....maybe I'll just stick with the Tung-Sols.:

With these tubes being new on the market, there has been quite a bit of buzz about them, from how they look, to their size, and how they sound -- all of which has received positive press. Of course, any long term dependability results will simply take time to prove out, but in the mean time, tests can still be run to see how they stack up against the original American pieces, and the other current production versions of this tube. Therefore, an order for a matched quad of these tubes was placed with Jim McShane, who quickly got them to my doorstep.

From the stand point of size and appearance, these tubes are for all intents and purposes virtually the same size as the original full base American 7591 (non A version) tube -- even though this new tube is identified as a 7591A. Therefore, this new tube is slightly taller than the button based A version of this tube as last produced in America, with that tube being slightly shorter than the non A American version as well.

The internal structure has detail differences as well, with the most notable difference being that the tooling holes in the plate are round in this new tube, versus square in the American versions. But don't just give these tubes a casual glance, or it would be quite easy to assume that they are an American product! A dead giveaway however is that the classic Tung Sol stop sign identifying the tube type appears to be painted onto the top of the tube, rather than etched.

Overall however, the size and appearance are very positive, with this new tube looking like it was actually born out of the original American device.
So onto some initial testing.

I have not run all the tests I plan to yet, as I wanted to get some initial findings out there to the community. Therefore, at this point, I have only been able to validate the match as provided by Jim, the power output capability, and simply how the tubes reacted to the test events. The results are significant.

From a standpoint of matching under quiescent (no signal) current draw conditions, 3 of the 4 tubes were matched within better than .5%, while the forth tube was still well matched, but deviated from the rest of the pack by 3.3%, which then set the overall balance achieved for the quad. By itself, this is very good matching, with the matching of the three tubes being beyond exceptional. With this level of quiescent matching -- particularly with high Gm tubes like the 7591 family of tubes represents -- you can expect the output tubes to be well balanced in equipment that offers limited or no ability to adjust individual output tube current draw.

Understand that while the tubes MAY be manufactured to a good tolerance level, the high degree of quiescent matching achieved in my quad is entirely due to the vender used. Therefore, the few extra pennies paid for a quality vender not only culls out the rejects, but also produces a superior match. I have no business connections with Jim, but when his service, culling, and matching are all considered, his reputation and value are well deserved.

With these being new tubes, and my sample so small, it is hard to establish what a norm is for their power capability. However, I can state that as judged against a nominal American device, the group as an average produced nearly 87% of the power that quality American devices can produce. On an "English" scale, this places these tubes as solidly GOOD as compared to what the American pieces can do. That scale has any tube producing 81% or better of what a nominal American piece can produce as being GOOD. Within the group, two of the tubes were dead on the 87% average, while one was weaker at 82%, and another being an over achiever at nearly 92%.

But that's not the whole story. There are details of the testing that show the very notable improvement that these tubes represent over the other current production 7591 tubes I've tested:

1. The bias setting is VERY stable in all four tubes. Other examples of non-American 7591s I've tested tend to be lazy in reaching a final resting point, or, will change with short term large signal (power output) excitation tests. The stability noted with these tubes was impressive.

2. The tubes performed very well with the heaters operating at 6.300 vdc. Many Russian tubes actually require a heater voltage that is about 5% high of spec to achieve a reasonable level of performance. With the Tung Sols, not only was the performance very good at the design center of 6.3 volts, but it only slightly improved with the heaters operating a +5%.

3. Most importantly, the power readings at maximum power output were quite stable!! This is huge, with a stability that is reminiscent of quality American pieces. Other examples of these tubes all too often either increase from a lower power level during testing due to internal heating of the tube, or actually sink in power, because the cathode simply cannot keep up. That these tubes -- all of them -- held a stable power output reading during testing represents a significant improvement over previous foreign efforts to manufacture this tube that I've tested, which should bode will for tube life. It speaks directly to the quality of cathode construction and activation, which is everything towards that end.

All in all then, these tubes are still somewhat short of the best American pieces produced. But in my opinion, they represent a major improvement over previous modern efforts to manufacture this tube. These tubes represent a significant effort to actually replicate the original device in terms of size, appearance, and performance. My testing is clearly and obviously limited to a four tube sample. But based on the results I'm seeing, versus that which I've all too often seen in the past, the results are very positive. I am very heartened by the development of this tube. I look forward to the experience that others can provide as well!

Happy tubing!

Dave


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Post subject: Re: GE 6L6GC Snake Oil or worth it?
Posted: Fri May 06, 2016 8:34 am
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The new Russian made Tungsol labeled 7581A seems to be good tubes --- provided you do not run them at the output levels of the original GE 7581A (some 1970s amps push these to nearly 40-watts/tube). Ppl sometimes push these GE tube to nearly 50 watts (STR varieties) --- and the tubes just laughed at the current & voltage.

Run the Russian TS 7581A at around 30-32 watts max and you'll be fine. Idle bias of around 22-25 watts/tube for the Class AB1 Fender push-pull will give you nice tone and good life.

AFAIK, there are NO vacuum tubes made in the US anymore. This includes fluorescent and microwave bulbs. The GT GE 6L6GC were leftover from the old Owensboro, KY GE plant (1980-early 90s). These are really mil spec 7581A. Relabeled 6L6GC, for consumer market. Very good tubes. Tough and great tone. But, gone the way of the dinosaur. :(

Russian made mil spec and certain Chinese tubes seems to be the best output types, now. With the JJ EL84 also being a good, tough tube. I would buy from a good dealer that sorts their stock for quiet, well-balance tubes.

Good luck, with those TS! :)

http://www.mif.pg.gda.pl/homepages/fran ... /7581A.pdf


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Post subject: Re: GE 6L6GC Snake Oil or worth it?
Posted: Fri May 06, 2016 9:29 am
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BMW2002Ti wrote:
The new Russian made Tungsol labeled 7581A seems to be good tubes --- provided you do not run them at the output levels of the original GE 7581A (some 1970s amps push these to nearly 40-watts/tube). Ppl sometimes push these GE tube to nearly 50 watts (STR varieties) --- and the tubes just laughed at the current & voltage.

Run the Russian TS 7581A at around 30-32 watts max and you'll be fine. Idle bias of around 22-25 watts/tube for the Class AB1 Fender push-pull will give you nice tone and good life.

AFAIK, there are NO vacuum tubes made in the US anymore. This includes fluorescent and microwave bulbs. The GT GE 6L6GC were leftover from the old Owensboro, KY GE plant (1980-early 90s). These are really mil spec 7581A. Relabeled 6L6GC, for consumer market. Very good tubes. Tough and great tone. But, gone the way of the dinosaur. :(

Russian made mil spec and certain Chinese tubes seems to be the best output types, now. With the JJ EL84 also being a good, tough tube. I would buy from a good dealer that sorts their stock for quiet, well-balance tubes.

Good luck, with those TS! :)

http://www.mif.pg.gda.pl/homepages/fran ... /7581A.pdf


Yea....I biased my 7581A's at 60% of a 30 watt rating. I just liked the idea of a larger plate running cooler and possibly lasting longer.


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Post subject: Re: GE 6L6GC Snake Oil or worth it?
Posted: Fri May 06, 2016 10:31 am
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ckmckool wrote:
Yea....I biased my 7581A's at 60% of a 30 watt rating. I just liked the idea of a larger plate running cooler and possibly lasting longer.


Biasing at 60% to 65% of max plate dissipation is a prudent decision IMO. The tone is not likely to suffer significantly but it may extend the service life of your tubes.

Arjay

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