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Post subject: EH 6L6GC's
Posted: Sat Oct 04, 2014 9:40 am
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Just got my blues deville back from handwired circuit, and tube driven reverb.
The builder had it outfitted all EH tubes, including EH 6L6GC's.........one of which i believe blew out within 1/2 hr of use.... (when i dimed it for about 5 minutes). Volume cut way down after hearing loud clicks on low lower notes. I immediately shut down.
Builder told me he had bias set at 43 ma @ 480vdc plate voltage (70%).
I already ordered JJ 6L6GC's, assuming the EH's cant take the high plate voltages..........
Anyone else had problems with EH 6L6GC's when used at this high a plate voltage?
I'm hoping thus is just a fluke/tube related.


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Post subject: Re: EH 6L6GC's
Posted: Sat Oct 04, 2014 10:32 am
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EH 6L6GC's are usually good tubes. However, like other modern made output tubes --- selection can be important. Perhaps, the owner happened to get a bad set of tubes.

I haven't heard of anyone having a bad set of the new Tungsol 6L6GC-STR. Though, it is still best to buy of a reputable dealer that tests each tube and culls the good ones from the bad. Plus, stands behind the tubes he sells.


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Post subject: Re: EH 6L6GC's
Posted: Sat Oct 04, 2014 10:46 am
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BMW2002Ti wrote:
EH 6L6GC's are usually good tubes. However, like other modern made output tubes --- selection can be important. Perhaps, the owner happened to get a bad set of tubes.

I haven't heard of anyone having a bad set of the new Tungsol 6L6GC-STR. Though, it is still best to buy of a reputable dealer that tests each tube and culls the good ones from the bad. Plus, stands behind the tubes he sells.

Yep. Got Ruby screened JJ's coming from Dougs. He thinks those will handle the higher plate voltages better..........if that's what the problem turns out to be in the end. Surfing the net does seem to indicate that the EH's seem to crap out more often......hoping that's simply the case given my higher than norm. plate voltage of 480v.


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Post subject: Re: EH 6L6GC's
Posted: Sat Oct 04, 2014 11:38 am
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Ask a refund for the tube from the builder .He must warranty is job and the parts he put in the amp .


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Post subject: Re: EH 6L6GC's
Posted: Sat Oct 04, 2014 11:58 am
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I personally wouldn't use EH on output stage...JJ's always seem to work well and last every gig out.

However the best preamp tube i use is an EH12ax7 as it is warm,clear and has more gain than most others. (IMO)


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Post subject: Re: EH 6L6GC's
Posted: Sat Oct 04, 2014 12:15 pm
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I see many amps with EH on outputs tubes working well and for long time .

Bad tube ; it could happen with any brand


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Post subject: Re: EH 6L6GC's
Posted: Sat Oct 04, 2014 1:28 pm
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At this point i'm going to concurr that it happened to get a bad tube. Builder says they were'nt matched....but looked close with respect to the two bias adjustment pot positions.
Usually matched tubes are also screened further.
If i find the same problems with the Ruby JJ's at the 480pv, i'll prob. need to look at other causes.....maybe screen voltages?
btw.....the two long plate EH 12AT7's he used ARE my favorites for drivers. They've held their output and sounded better than any other current or nos AT7. recommended
http://www.parts-express.com/Data/Defau ... 0_HR_0.jpg


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Post subject: Re: EH 6L6GC's
Posted: Sat Oct 04, 2014 1:30 pm
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I never bough matched tubes since I learn that better sound is with 5 to 10 Ma between each tube.

And all tubes from good tubes saler are with in these specs


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Post subject: Re: EH 6L6GC's
Posted: Sat Oct 04, 2014 1:40 pm
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stratele52 wrote:
I never bough matched tubes since I learn that better sound is with 5 to 10 Ma between each tube.

And all tubes from good tubes saler are with in these specs

Good to know.


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Post subject: Re: EH 6L6GC's
Posted: Sat Oct 04, 2014 1:45 pm
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Yes .

Perfect match , 0 ma = sound may be sterile.


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Post subject: Re: EH 6L6GC's
Posted: Sat Oct 04, 2014 9:56 pm
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Yeah Louis, I've done that with my amps. But 6ma is the biggest difference I've tried(just my preference). With other folk's amps, they're within 2ma. Because that's what they want!!! Hey, What do you think about using matched(balanced) phase inverter tubes??? Art

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Post subject: Re: EH 6L6GC's
Posted: Sun Oct 05, 2014 12:53 am
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aclempoppi wrote:
Hey, What do you think about using matched(balanced) phase inverter tubes??? Art



I never try or do a listen test . Do you do some test yourself ?


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Post subject: Re: EH 6L6GC's
Posted: Sun Oct 05, 2014 4:20 pm
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Been using matched PI tubes for 15+ yrs, in all the amps that I retube. So, I will have to try a test !! To be honest, the power tubes in my amps, at this time, were NOS matched pairs(2ma) when installed. The RCA (6L6GC & 6V6GT) and Tung Sol(5881) tubes have been in the amps for 1-2 yrs. So, they may have drifted a bit by now. I'll try the PI test next week!!! Art

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Post subject: Re: EH 6L6GC's
Posted: Sun Oct 05, 2014 4:42 pm
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This is a little above my knowledge as to why....but i recall hearing from my tube vendor that balanced phase inverters are'nt necessary in long tailed phase inverter circuits (my drri).
I however, still ordered them matched and high output because i like the dynamics of a strong power tube driver. I figure even with matched phase inverter, there's still plenty of imbalance left in my output tranny windings anyway.
My logic says that i can keep from going overboard with an imbalanced circuit by having balanced pi tube......but then again......what's a long tailed pi circuit?


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Post subject: Re: EH 6L6GC's
Posted: Mon Oct 06, 2014 1:29 am
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Thank's for the answers . :D


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