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Bieworm wrote: ↑

Fri 04/02/21 1:11 am

TriodeLuvr wrote: ↑

Thu 04/01/21 10:10 pm

Bieworm wrote: ↑

Thu 04/01/21 9:46 pm

Merely out of curiosity. I will be trying el34 too

6L6 and EL34 need output transformers with different primaries. It's not really possible to compare the two types unless the transformers are changed with them.

Jack

is that so? If I look for output transformers there is always the tube type specified in the datasheets. It always says both 6L6 an EL34.
I have a 36W OT with 4k prim...

The 4K primary (sometimes 3.5K or 3.8K) is suitable for a pair of EL34s. 6L6 variants perform best with a higher impedance primary, typically 6.6K.

The chart below is from the 6L6WGB datasheet. The loss in output power when the two tubes drive a lower Z transformer is typical of all the 6L6 series. Whose datasheets are you reading that don't make this distinction?

I was referring to the datasheets of OT's with 4k prim. I'm not worried about the loss in power because it will still be plenty powerful. And like I aready stated, the 6L6 adventure is merely out of curiosity.. ofcourse there will be put in EL34 tubes eventually
but who knows I might like the 6L6 's so much I won't even bother to go the EL34 route

TriodeLuvr wrote: ↑

Thu 04/01/21 10:10 pm

Bieworm wrote: ↑

Thu 04/01/21 9:46 pm

Merely out of curiosity. I will be trying el34 too

6L6 and EL34 need output transformers with different primaries. It's not really possible to compare the two types unless the transformers are changed with them.

Jack

That's not accurate. As your other post shows, the output level changes with 6L6, but that doesn't matter unless you're trying to target a specific wattage. With a 4K primary, he can hit the 36W to 40W range with either tube set pretty easily.

I'm not out on a specific wattage. I'm only wondering how the extremely sublime preamp of the tremolo TMB combines with the 6L6 power after it. Josh has the EL34 area covered...I think this design deserves the research and expansion. 6L6 tubes tend to beef things up in their own way, different from an EL34. I know it robs some marhalliness in the end, but that isn't per se a bad thing. And I'm convinced Josh is going to look at the new born tremolo TMB with parentlike pride

What can I say? You can use any tube with any transformer if performance isn’t important. Operating 6L6s in AB1 with a 4K load is inefficient, and the power lost in the mismatch is dissipated by the anodes. This means the tubes run hotter for a given output, and their tone will be different as well. Can you compare the sound of a properly terminated pair of EL34s to improperly terminated 6L6s? Of course, but that’s not what I think of when someone says they’ll compare two tube types. It’s like comparing a 4 ohm speaker to a 16 ohm speaker without changing the transformer taps. Josh, extracting more power from a pair of 6L6s mismatched with a 4K transformer is only “easy” if higher B+ voltages are available and higher anode dissipation can be tolerated. Let’s be clear - I’m not attempting to tell anyone what they can or can’t, or should or shouldn’t do in this matter. I’m only pointing out the facts of operation as they pertain to these two tube types.

Jack

You're right. But as I don't have a reference or any particular sound in mind I'm not expecting something ...

Bieworm wrote: ↑

Fri 04/02/21 1:48 pm

You're right. But as I don't have a reference or any particular sound in mind I'm not expecting something ...

I understand that now. And hopefully you'll hit on a combination that works really well. One other thing worth mentioning is that the higher Ra of the 6L6 might adversely affect damping. That could result in "incoherence" caused by speaker overshoot and/or ringing (similar to what happens when a series resistor is added in order to reduce sound levels). If you feel that this is occurring, it might be worthwhile to temporarily install a more robust feedback network. Replacing the typical Marshall value of 100K with something like 33K would be a good start for experimentation. Of course, NFB can produce other effects when the various stages are overdriven, so this might or might not work out.

Jack

TriodeLuvr wrote: ↑

Fri 04/02/21 2:56 pm

Bieworm wrote: ↑

Fri 04/02/21 1:48 pm

You're right. But as I don't have a reference or any particular sound in mind I'm not expecting something ...

I understand that now. And hopefully you'll hit on a combination that works really well. One other thing worth mentioning is that the higher Ra of the 6L6 might adversely affect damping. That could result in "incoherence" caused by speaker overshoot and/or ringing (similar to what happens when a series resistor is added in order to reduce sound levels). If you feel that this is occurring, it might be worthwhile to temporarily install a more robust feedback network. Replacing the typical Marshall value of 100K with something like 33K would be a good start for experimentation. Of course, NFB can produce other effects when the various stages are overdriven, so this might or might not work out.

Jack

There is no NFB in that amp, nor should there ever be. The stiffness that would add, would kill the character of the amp.


Just a side thing... About a decade ago I modded a Traynor YCV80. It came stock with 6L6 tubes in a quad. But it could run with 2 or 4 tubes...and my mod was to add a switch to change the bias to allow use of EL34 or 6L6. The OT was a 1.6K primary into a 4 ohm speaker.

https://youtu.be/_pM1KmdKPHE

Thanks,
Josh