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Parallel Single Ended EL84?

MickeySmile

MickeySmile

Well-Known Member
I am listening music from RH84 SE amp with the Cornwalls and the sound so good. :music: However, when I use it with other un-efficient speakers, around 89dB, the sound isn't good. Here my questions:
1. Can parallel single ended amp overcome this problem?
2. How more power the parallel SE amp deliver compare with SE amp with the same type output tubes?

Please educate me! Thanks for your knowledge and sharing!
 
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MickeySmile said:
2. How much more power will the parallel SE amp deliver compared with SE amp with the same type output tubes?
Click to expand...

Assuming you invest in the appropriate transformers, paralleled output tubes should be capable of exactly twice the power. However, due to the logarithmic nature of the human perception of sound, 2x the power is heard as one extra click on the volume knob. In most cases, you'd be hard pressed to appreciate the difference.

I'll quickly admit I don't understand why people pursue PSE designs. Good air gapped singled ended output transformers are difficult to design, and the quest for higher power handling capabilities increases the expenses exponentially. I don't want to turn this thread towards an argument of push/pull vs. single ended, so I won't discuss their virtues. I'll agree that SE has some very pleasant qualities, and I spend a lot of time listening to my single ended amps. You've already discovered for yourself that SE demands high efficiency speakers - why fight that?
 
Just a guess but PSE might provide some advantages in the lower effective rp which would make for lower turns ratio and higher damping for situations where the extra damping is desirable. Just a thought.

mike
 
Thank you Ty Bower and Mashaffer for the info.


Hi Ed, I have not hear RH34 before. Is it RH SE design for EL34 tubes?
 
Ty_Bower said:
I'll quickly admit I don't understand why people pursue PSE designs. Good air gapped singled ended output transformers are difficult to design, and the quest for higher power handling capabilities increases the expenses exponentially. I'll agree that SE has some very pleasant qualities, and I spend a lot of time listening to my single ended amps. You've already discovered for yourself that SE demands high efficiency speakers - why fight that?
Click to expand...

You make good SE iron sound uber expensive. For $84/each, Edcor makes SE iron capable of 20Hz-20KHz, with a 25 watt power rating. That power rating is more than enough for a two EL84s in parallel.


Even Magnequest is not unreasonable.
 
Oops, I meant the RH 807! I would think that with not much effort you could do a RH 6L6 using the exact 807 circuit, and a EL34 would be a drop-in at that point just about. If you didn't have a stash of EL34 or 6L6, might just as well make it with 807 if you don't mind the topcaps.

If there is another RH design out there, I'd be curious to see/build it, too!

RH807 schematic
 
ducati_EL34 said:
You make good SE iron sound uber expensive. For $84/each, Edcor makes SE iron capable of 20Hz-20KHz, with a 25 watt power rating. That power rating is more than enough for a two EL84s in parallel.


Even Magnequest is not unreasonable.
Click to expand...

Hammond has some very reasonable 30 watt single ended iron too. PSE makes perfect sense to me if you like single ended amps (like I do). The idea would be to get the same "sweetness" while opening up your speaker options a bit.
 
I have a plan for a parallel 6V6 SE amp running 4 of them per channel.
I picked up a spare pair a GTA SE-40 outputs which ran 3 6L6GC's in parallel.

But a design like that will take some tinkering to get right, not just slap tubes
together in parallel and call it a day, but I've ran parallel single ended in UL an
like what I've got from it that the plan for bigger is in the works. :)
 
Kegger said:
I have a plan for a parallel 6V6 SE amp running 4 of them per channel.
I picked up a spare pair a GTA SE-40 outputs which ran 3 6L6GC's in parallel.

But a design like that will take some tinkering to get right, not just slap tubes
together in parallel and call it a day, but I've ran parallel single ended in UL an
like what I've got from it that the plan for bigger is in the works. :)
Click to expand...

I am waiting to see your design in real amp. I also like to built it, too.
 
Kegger said:
I have a plan for a parallel 6V6 SE amp running 4 of them per channel.
I picked up a spare pair a GTA SE-40 outputs which ran 3 6L6GC's in parallel.

But a design like that will take some tinkering to get right, not just slap tubes
together in parallel and call it a day, but I've ran parallel single ended in UL an
like what I've got from it that the plan for bigger is in the works. :)
Click to expand...

My head starts to hurt when I try to figure out the driver requirments Keg.
 
jaymanaa said:
PSE makes perfect sense to me if you like single ended amps (like I do). The idea would be to get the same "sweetness" while opening up your speaker options a bit.
Click to expand...

I always assume that single ended magic is due to some kind of better "focus" - being as there is only one output tube, there are no imperfections in the matching between output tubes. In a push / pull design, one tube is pushing while the other is pushing, but what if they are ever so slightly out of sync somewhere along their respective curves? That can't happen in the single power tube case. Once you go parallel single ended, isn't it like holding two pencils in your hand to draw a line? They aren't going to go along exactly the same path.

Of course, my theory might be full of holes. Maybe it just doesn't work that way at all. Maybe single ended "sweetness" is just a predominance of even ordered harmonics. Even ordered harmonics tend to get canceled out in push / pull designs. Still, an amp designer could chose to build a circuit that leaned towards even harmonics through the careful selection of tubes in the portions of the amp that aren't balanced (12AT7 in the driver seat?).

I like them both, single ended and push / pull. Guess I need to build a couple PSE to see how I feel about them, too.
 
Ty_Bower said:
I always assume that single ended magic is due to some kind of better "focus" - being as there is only one output tube, there are no imperfections in the matching between output tubes. In a push / pull design, one tube is pushing while the other is pushing, but what if they are ever so slightly out of sync somewhere along their respective curves? That can't happen in the single power tube case. Once you go parallel single ended, isn't it like holding two pencils in your hand to draw a line? They aren't going to go along exactly the same path.
Click to expand...

As it has been explained to me (or maybe I should say, "As I understood, what was being explained to me"), The extra tube in the output is only providing additional current. It is not that the pair of tubes are working against each other, as in a PP output. The tubes must still be properly matched, to get the benefit of the output design.

Would this amp then be called a DET, "Dual Ended Triode? :scratch2:
 
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