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Wanted to hear first hand why some get excited about the 6L6G tube.
I've been a fan of the GL KT77's and got some RCA's to find out what the fuss is about. Perhaps they need to settle in, but I find the drier mids,less extended highs,a slightly smoothed over bass more pleasing in my system. Since the amp needs 8, the cost of "pedigreed" NOS wasn't in the cards. Found some that were the same cost as new production and quiet.Keepers.
Edits: 06/04/15Follow Ups:
The plate-to plate loading is different for the 6LGC and EL 34. One may sound better in a given amp, but that is not an indication that one tube is superior. The conditions change further when you change from triode, UL or pentode mode.
The EL34 tube is OK but there are better.
KT77 have more dynamics and extension.
KT66 are the same but more and better.
6L6GC Are a whole different animal,
rich, soft and creamy - great for Jazz or
a romantic evening with significant other.
DanL
"The EL34 tube is OK but there are better.
KT77 have more dynamics and extension.
KT66 are the same but more and better.
6L6GC Are a whole different animal,
rich, soft and creamy - great for Jazz or
a romantic evening with significant other."
I agree with your statements. KT66 huh? The only variant I haven't tried.
When I get bored fussing around with everything else. I see new production tubes are inexpensive.
The amp has UL/Triode switching. UL has a more dynamic presentation which is quite nice.
The way I describe it is ...
The 6L6GC brings them here
The KT66 brings you to them
The best 6L6GC is the TungSol
The best KT66 is the Genelex
The highs will astonish you
(Both Re-Issues)
DanL
Tre's comments on voltage and power are valid. A tube running over spec will sound stressed. Also, any differences you hear are within the confines of your amp.
All in all, if KT77s sounded best to you, those are the ones to use.
I had a 6l6g amp for a while till I gave it to a friend; there was a big difference in sound between all of the different variations of 6l6s. KTs were among the best. Most of them I liked a lot, even the ones I didn't like were still pretty good.
Iffa you a gonna compare 6l6s though, you need a dedicated 6l6 amp; Set up to the lowest power tube of the lot.
"Tre's comments on voltage and power are valid. A tube running over spec will sound stressed. Also, any differences you hear are within the confines of your amp."
Yes, I'm curious even though the manufacturer info claims their auto bias circuit is such that ANY tube(within specific types) is optimized.
Supposedly, as good as it gets?
I've been assured by the distributor years ago while owning the same brand, but a lower level model,such experimenting is okay.
"All in all, if KT77s sounded best to you, those are the ones to use."
Depending how my hearing/taste adjust to the sound, that may be the outcome. Using tubes as tone controls isn't as costly as cable madness.
The only type that really produced unappealing sonics were 6V6.
"Yes, I'm curious even though the manufacturer info claims their auto bias circuit is such that ANY tube(within specific types) is optimized.
Supposedly, as good as it gets?"
That's something that's sort of a possibility with fixed bias (adjustable with a pot), but quite unlikely with cathode bias (auto bias).
"That's something that's sort of a possibility with fixed bias (adjustable with a pot), but quite unlikely with cathode bias (auto bias)."
I'm not informed enough to know exactly what is going on with the particular circuitry and how it's done, but ANYTHING that is "auto"
makes me wonder-is there something that's missing?
There's certainly nothing wrong with cathode bias (auto bias), especially if your amplifier is class A and not push-pull.
A push-pull amp with cathode bias may struggle with balancing DC current through each half of the primary winding on the output transformer.
An amplifier with cathode bias that claims to work with a very wide variety of tubes will likely make some sacrifices on voltage and dissipation to do so. (Unless there's a way to adjust the cathode bias resistor)
What you prefer will depend on the rest of your system. There are quite a few excellent new production 6L6's. *I* would not waste time chasing used or NOS power tubes.
"There are quite a few excellent new production 6L6's. *I* would not waste time chasing used or NOS power tubes."
Yeah, if quality is good as I've experienced with the GL KT77, new is the way to go. It can get pricey and a set up for disappointment chasing used or NOS stuff.
You need to buy new production tubes from a dealer that does a good job of testing etc. You have a Prima Luna. Ask Kevin Deal about 6L6's.
Those look like 6L6ga?
The 6L6ga will only handle 360vdc on the plate and the Max plate dissipation rating in only 19 watts.
The 6L6gc will do 500vdc and 30 watts dissipation.
The EL34 will do 500vdc (or more) and 25 watts plate dissipation.
I don't know the voltage of your amp but you might want to check (if you haven't already) the plate to cathode voltage and the plate dissipation you're subjecting those tubes to.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
The amp is self biasing. So for a little audio excitement, changing the flavor when desired is simple. The only thing preventing me from trying the KT150 is price. At $800 a set, a bit much for my wallet.
Maybe its a little early to judge, initially the softer overall presentation took getting used to. The KT77 on both ends is noticeably more detailed, but the 6L6 has a smoothness(for lack of a better term) not heard in the KT77?
I will leave them in for awhile and let my ears dictate which tube will prevail.
You still need to measure the operating point when switching tube types. Careful of the high heater draw tubes like the KT120/150 as your amp may not be able to supply the heater current without stressing the power transformer.
"You still need to measure the operating point when switching tube types. Careful of the high heater draw tubes like the KT120/150 as your amp may not be able to supply the heater current without stressing the power transformer."
Thanks, the manufacturer and distributor say the transformer specs are up to the task.The distributor demos my amp with the KT150. Doubtful I will ever try them. At $100 a bottle, too pricey to use bottles as tone controls. Kinda like cable madness.
The only tube that produced really undesirable tone was the 6V6.
"The only tube that produced really undesirable tone was the 6V6."
Which should tell you the problem with the claim that you can plug anything into the amp and the amp will optimize itself. The 6V6 is the best sounding tube of the bunch within its power limits if it is used correctly. There is a combination of current, plate impedance and output transformer reflected impedance which can be optimized for one specific setting. Your "best" tube is going to be very specific to how your particular amp is set up. Using the tubes as tone controls is just adding distortion, you are not getting the best out of any of the tubes except for the one specific tube the amp was designed around. See if you can get them to tell you what that tube is.
"The 6V6 is the best sounding tube of the bunch within its power limits if it is used correctly."
I have read more than few comments about the 6V6 magic. Also raves of the EL84. For whatever reason, maybe the limitations of "auto bias", the amp will not show the 6V6 in its best light.
I play a 6V6 guitar amp and have a shoebox full of assorted glass, so I popped some in to just see what the happens. Dull.
'For whatever reason, maybe the limitations of "auto bias", the amp will not show the 6V6 in its best light. '
As Chip said, the idle current, idle voltage and load impedance has to be adjusted for each type of tube to get the best out of it.
The answer to the question "can your amp do this" is no.
No amp can do that, not yours not anybodies, and be running each tube type correctly.
You really need to check the plate voltage and idle current in your amp before you damage those nice 6L6ga tubes you're using.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
"you really need to check the plate voltage and idle current in your amp before you damage those nice 6L6ga tubes you're using."
Fortunately, the tubes were cheap($36)in relative terms? They were probably $.75cents when new! And they aren't part of a "premium" batch.
For this excercise, based on published info and distributor adivice, no NOS tubes of significant value/performance were harmed.
As mentioned in original post, so far I do like(or getting used to)the somewhat "dry" presentation. Everything the KT77 does is there, except the dial is turned maybe a notch or two down.
"For this excercise, based on published info and distributor adivice, no NOS tubes of significant value/performance were harmed."
How do you know that is true?
Published info and distributor advice could very likely be wrong.
Until you measure the current and plate to cathode voltage and then calculate the plate dissipation in watts you do not know how hard the circuit is running the tubes.
Voltage times current = watts.
Those are very nice 6L6ga tubes you have there. There's no point in torturing them.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
"How do you know that is true?"
Just like ANYTHING, I wouldn't be surprised if there is a touch of EMBELLISHMENT? Maybe a tiny bit of SSSTTTTRRREEETTTCCHHIINNGG the truth?
Reality, I don't know, and simply place my trust in what I've been told by the distributor. I would think he has a reputation to uphold. And based on my dealings including warranty concerns, no issues.
You're right, measuring is the only way to know. I won't be poking around with a multimeter, so I will just rely on my ears for now.
I do however, believe ANY "auto" design is subject to limitations.
"Reality, I don't know, and simply place my trust in what I've been told by the distributor. I would think he has a reputation to uphold. And based on my dealings including warranty concerns, no issues."
I would take what your dealer says with a "grain of salt". He wont make any money telling you what are the limitations or point out the deficiencies in the product he is selling.
Regarding the ability of your amp to use the various types of 6L6 tubes, that is true to a certain extent because all those tubes have the same pinout. That means it will work but the amp and the power tube will not be optimized for each other. I have built a 6V6/6L6 amp that is single ended and has a switch to adjust the cathode bias resistor that corresponds to the correct current consumption for each tube type. In this case the power difference between the 2 types is most obvious but the sonics are little nicer with the 6v6.
One thing to check when running higher power output tube like kt90, kt120, etc. is the heat from your power transformer. I noticed in my amp that when running the 6L6 tube the PT was much hotter. If that is the case with your amp when you are tube rolling you better buy the "extended warranty" for that amplifier . good luck, Dak
about them being 75¢ that is. My February 1963 RCA price list shows 6L6's selling for $8.60 each. That's $66.50 each in today's money.
I really had no idea.Nevertheless,$8.60 went MUCH further back then!
My exaggeration went too low!
I never understand why people get upset with the idea that you change your system to fit your taste. They use this pejorative term "tone controls" as if that is the absolute worst thing a person could want from his music making system. I think a lot of use NOS and new production small signal tubes to fit our preferences . So what? I have been very happy listening to a lot of different systems with different cables and many many tubes. I have mostly enjoyed the pursuit I call my hobby. In fact I was just thinking about how nice a particular 12AU7 tube I had collected somewhere along the way compared with the stck tube in a small 1 tube headphone amp. At first I thought the stock tube sounded really good and what was the point of collecting and spending money on esoteric tubes it won't mak a big difference. Wel, you guessed it -it did matter, and the sound of this remarkable little amp was that much better. (End Of Rant)
Steve
I've been convalescing for the past week. 2 separate surgeries on the SAME arm. Plenty of down time to listen...and fuss around.
As a music lover and a gear nut in denial, I "get" the hobby aspect of audio. Wouldn't bother wasting time HERE if it wasn't the case.The more I listen, my adjusting period is starting to notice the positive traits of the old bottles. Bass notes are "rounder" the initially dry mids aren't as dry and highs aren't as distant/pushed back like before.
Haven't decided on vocals yet. Both sound amazing.Update:after replacing the KT77's and listening back to back against
the 6's, in my system,the 6's sound more natural!
This is based on a listenings thru the preferred method-mono record thru tubed phono. I played a very clean 61 Ella Fitzgerald CLHC and 60 LNMWME. WOW! System dependent as always, I use the humble AT OC9III on a VPI Classic. Nothing special, but it delivers the goods.TUBE HEADS: I have an odd ball among the 8. This tube is made by Sylvania and a worn sticker on the glass indicates it was a "select" lab
equipment tube or something to that effect. Also stated its an "experimental" tube. Its about 1/4" taller with stuff going on there.
Any info on this thing?
The rest are like the top pic
Edits: 06/05/15
I have had a few selected tubes which were replacement tubes for lab equipment, that were either not used, or were working pulls. Today with all the hype over the S variants like ECC803S I would imagine that a selected tube would be pawned off as an S. I can't remember what I did with the last one which was a smooth plate Telefunken (not an 803S).
Your odd shape must have been a trial run of the type you are using. As I said, perhaps prototype? I don't know what tube type you're using, what are the small tubes and are they preamp tubes of an integrated or input tubes to a power amp ? What are you using in the phono section/stage?
Steve
"Your odd shape must have been a trial run of the type you are using. As I said, perhaps prototype? I don't know what tube type you're using, what are the small tubes and are they preamp tubes of an integrated or input tubes to a power amp ? What are you using in the phono section/stage?"
In those days a few of those companies did OEM tube stuff for driven instruments, so nothing unusual. Poked around sites and haven't found that exact configuration. Just curious. It's a very cool looking tube
and would imagine a set of monoblocs would heat your house in the winter!
The small tubes on the integrated are AU7's. Mine are a mix of RCA's and Mazda.
Phono is the last edition Fosgate. For the money, I've found it to perform way beyond my expectattions. Tubed with GE,Raytheon,Phillips. RCA tube rectifier.
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