I just read in RDH4 the 6L6 is very low in 3rd harmonics, and pentode have higher 3H. Why 6L6 seldom get mention in DIY build?
6L6 and other tubes
Hmmm,
I thought it was one of the American mainstays of power tubes
for the 40 to 190 watt amp range (multiple tube designs)
for mono blocks, stereo, to music instrument.
Then for lower power applications there is the 6V6 12 - 40 watts
for multiple amplifier and tube designs.
Heck for "ultra low" performance 2 - 12 watts there are some
12AX7a designs. We could probably design even lower good
sounding stuff using lower gain pre amp tubes, using them as
power tubes for mini amps. There are even transformers for
them too. Thinking out side the box helps.
Kind of like when people ask whats wrong with the
5U4GB...nothing at all they are good rectifier tubes.
Hmmm,
I thought it was one of the American mainstays of power tubes
for the 40 to 190 watt amp range (multiple tube designs)
for mono blocks, stereo, to music instrument.
Then for lower power applications there is the 6V6 12 - 40 watts
for multiple amplifier and tube designs.
Heck for "ultra low" performance 2 - 12 watts there are some
12AX7a designs. We could probably design even lower good
sounding stuff using lower gain pre amp tubes, using them as
power tubes for mini amps. There are even transformers for
them too. Thinking out side the box helps.
Kind of like when people ask whats wrong with the
5U4GB...nothing at all they are good rectifier tubes.
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Good quality new old stock 6L6s are now pretty expensive, due to Fender guitar amps burning up the world's reserves of them. Chinese and Russian new production tubes are available, but when you are building a DIY tube power amp, it is tempting to use weird unpopular tubes so you can get NOS ones cheap.
I built my tube hifi amp to accept most octal based power tubes, and I just use whatever I can get a reasonably matched quad of. I'm currently running GEC KT88s salvaged from a pair of scrapped lab power supplies. If I had 4 6L6s I would happily use them.
I built my tube hifi amp to accept most octal based power tubes, and I just use whatever I can get a reasonably matched quad of. I'm currently running GEC KT88s salvaged from a pair of scrapped lab power supplies. If I had 4 6L6s I would happily use them.
That's a funny question to ask since the 6L6 is probably the most popular power tube of all time.
Are you asking why it is not more fashionable to tube snobs today?
Are you asking why it is not more fashionable to tube snobs today?
The reason I ask because it seems like more people talk about EL34 for pp and the few schematics that use pentode or tetrode are EL34. That's the reason I have the impression the EL34 is the way to go!!!
Particularly Fender and a lot of other brands using 6L6 for guitar amps!!! Requirements of guitar amp is a stark difference from audiophile amps. They glorify odd harmonics!!! They want distortion!!! Some use switch triode connection to lower the power and it is not well received because it just doesn't have the "Oops" for guitar amp. So I have the impression whatever good for guitar amps are not good here!!!
So my question is If I use 6L6 and go either triode or UL, I should have little to no odd harmonics?
Particularly Fender and a lot of other brands using 6L6 for guitar amps!!! Requirements of guitar amp is a stark difference from audiophile amps. They glorify odd harmonics!!! They want distortion!!! Some use switch triode connection to lower the power and it is not well received because it just doesn't have the "Oops" for guitar amp. So I have the impression whatever good for guitar amps are not good here!!!
So my question is If I use 6L6 and go either triode or UL, I should have little to no odd harmonics?
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I will admit that amongst beam tubes and power pentodes I do prefer the EL34 in triode connection. I'm mostly in DHT land these days and use 6L6/6550/KT88 as pass elements in power supplies..
Good for you Alan.
An acquaintance of mine was going to give me an old amp with
GEC KT88s in it as he didn't use it. He also had a spare quad
to give. Unthinkingly I mentioned that to one of my "friends"
who weaseled his way into it and took the amp, tubes, and more.
Have a great new year ya'll.
An acquaintance of mine was going to give me an old amp with
GEC KT88s in it as he didn't use it. He also had a spare quad
to give. Unthinkingly I mentioned that to one of my "friends"
who weaseled his way into it and took the amp, tubes, and more.
Have a great new year ya'll.
Directly Heated Triode (such as 300B)
Some people prefer it in triode, some like other tubes. It mainly depends on the tone you are looking for.
Personally I like the 6L6. 🙂 🙂 🙂
Some people prefer it in triode, some like other tubes. It mainly depends on the tone you are looking for.
Personally I like the 6L6. 🙂 🙂 🙂
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There's a graph around somewhere, I think it's in the RDH4, showing how different loading changes how much power you can get, and how much 2HD, 3HD and THD you'll get from a push-pull pair of 6L6. Or maybe that's from the Mullard book about EL34...
IIRC, lower impedance loads raise the THD quite a bit, but that is mostly 2HD, as 3HD goes down with lower impedance loads. As load impedance is raised, 2HD goes down, but 3HD goes up. On that chart, for 6L6 the highest power output and lowest THD is reached with around a 6k6 ohm load, but at that point 3HD is actually higher than 2HD. At about 4k5 load, power output is a little lower and 2HD is higher than 3HD, but since in push-pull the 2HD will be reduced, you might end up with lower distortion overall.
I've read in a lot of places that 6L6, like 807, yields higher 3HD than EL34 or KT88.
It seems there are a lot of contradictory statements floating around about the relative merits of 6L6 vs EL34 vs KT88 or 6550.
Even I managed to build a relatively pleasant sounding PP 6L6GC amp for hi-fi. Since I managed, I figure someone who knows what they're doing could make something pretty darn good out of PP 6L6's. 🙂
Are you interested in a guitar amp or a stereo amp?
For guitar, the EL34 is preferred due to it's greater power output.
For a stereo amp, I will ultimately go with 6L6s (6P3S).
Right now I'm still building lower power (mostly SE, Single Ended ) Stereo Amps.
At one time I measured distortion of several output Pentodes and Beam-Tetrodes in and found the 6L6 to be very good. However I also found that each tube required re-biasing to optimize it's distortion. If you simply try swapping tubes you will be disappointed and not truly see what each can do.
For guitar, the EL34 is preferred due to it's greater power output.
For a stereo amp, I will ultimately go with 6L6s (6P3S).
Right now I'm still building lower power (mostly SE, Single Ended ) Stereo Amps.
At one time I measured distortion of several output Pentodes and Beam-Tetrodes in and found the 6L6 to be very good. However I also found that each tube required re-biasing to optimize it's distortion. If you simply try swapping tubes you will be disappointed and not truly see what each can do.
I have used 6L6GCs by the dozen simply because they are more efficient than EL34s, although the difference is not impressive. Over here, price is also a factor. And rather than KT88 or more powerful, I have used two 6L6GCs in parallel: 60W plate dissipation, better heat spread etc. (Also, Pa of EL34 = 25W compared to 6L6GC of 30W, etc. etc.)
Regarding comparative distortion EL34s do quite well at about 0,7% in UL. But what quantities are actually produced depend heavily on circuit design, effect of variable load (loudspeakers) etc. One must remember datasheet figures are for constant loads with zero phase shift; quite some way removed from practical loudspeaker loads.
Yes, off the top of memory I seem to recall rather greater popularity of EL34s, but I am not at all convinced that this has to do with higher fidelity per se. Perhaps more with fashion or economy? Not sure of costs in other countries. The KT88 is also popular perhaps because of a little edge in power dissipation. .And both these for higher gm of almost twice that of the 6L6.
I recall days when KT66s were the craze of the time (they did look rather impressive!) - no longer! (In fact the 6L6 is within 10% of KT66 specs, which is within the manufacturing tolerance for either tube. This to the extent that several Russian manufacturers simply put 6L6 innards in a glass tube, label it KT66 - and charges 60% more!)
Regarding comparative distortion EL34s do quite well at about 0,7% in UL. But what quantities are actually produced depend heavily on circuit design, effect of variable load (loudspeakers) etc. One must remember datasheet figures are for constant loads with zero phase shift; quite some way removed from practical loudspeaker loads.
Yes, off the top of memory I seem to recall rather greater popularity of EL34s, but I am not at all convinced that this has to do with higher fidelity per se. Perhaps more with fashion or economy? Not sure of costs in other countries. The KT88 is also popular perhaps because of a little edge in power dissipation. .And both these for higher gm of almost twice that of the 6L6.
I recall days when KT66s were the craze of the time (they did look rather impressive!) - no longer! (In fact the 6L6 is within 10% of KT66 specs, which is within the manufacturing tolerance for either tube. This to the extent that several Russian manufacturers simply put 6L6 innards in a glass tube, label it KT66 - and charges 60% more!)
I too like the 6L6 for an audio power tube. I have a simple single ended amplifier that uses 6L6 for power tube driven by a 6SL7. The sound is open and easy to listen to. I do have some old stock Sylvania that I like very much but I also like new JJ tubes as they sound very nice too. Just my two cents.
Lower power. But yes, even easier to drive. And there's the EL84, a bit lower in power but even lower drive requirements. There's a good case to be made for using paralleled EL84 rather than 6L6 or EL34.
So there is a lot of virtue to use low plate voltage and low primary impedance to get lower 3rd harmonics?
The question is how come I have people suggesting me to get even over 5K primary for EL34 with 400V plate voltage? I was going to get 4K primary only. Sounds like 3.3K is even better!!! 2nd harmonics is not that bad and they got cancel in pp stage. Hell you guys go all the way to single end to get more 2nd harmonics!!!! I can even put a switch to switch between triode or UL and have more power than the single end.
The one from Lundahl that looks good is LL1620 3.3K:4ohm. So even when speaker go higher impedance in higher frequency, it's still low enough impedance.
The question is how come I have people suggesting me to get even over 5K primary for EL34 with 400V plate voltage? I was going to get 4K primary only. Sounds like 3.3K is even better!!! 2nd harmonics is not that bad and they got cancel in pp stage. Hell you guys go all the way to single end to get more 2nd harmonics!!!! I can even put a switch to switch between triode or UL and have more power than the single end.
The one from Lundahl that looks good is LL1620 3.3K:4ohm. So even when speaker go higher impedance in higher frequency, it's still low enough impedance.
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And then there is the argument for parallel EL34 PP with 100W out.
(we are talking Guitar amps here. eg Marshall JCM800)
(we are talking Guitar amps here. eg Marshall JCM800)
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