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In Reply to: RE: Single End Parallel Class A amps. posted by Cougar on February 12, 2014 at 16:18:31
A KT-120 is not a triode, even when wired as a triode.Parallel tubes should give more power but IMO the whole point of SET has been thrown out with the bath water when you use triode wired beam power tubes (paralleled or not).
Direct Heated Triodes are very linear compared to triode wired beam power tubes.
IMO the term "SET" means only one thing, Single Ended Direct Heated Triode.
Here's what's wrong with push pull IMO.
You're counting on the two tubes being perfectly matched.
You're counting on the drive signal to be perfectly out of phase at all frequencies and having the exact same amplitude.
You're counting on the two halves of the primary winding of the output transformer to be perfectly matched at all frequencies.
When any of the above are not matched the signal gets degraded to some degree or another.
I know you're not talking about push pull but unless the two tubes in a single ended parallel amplifier are perfectly matched some of that same type of degradation will occur.
You won't have the purity of a true SET amplifier. (not to mention the lack of purity of a triode wired beam power tube to begin with)
If you want a SET amplifier, build or buy a true Single Ended Direct Heated Triode amplifier. That's the only way you'll know what all the fuss is about.
End of rant.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 02/13/14Follow Ups:
Truer words may never have been spoken.
Aren't transistors alien technology?
About a biscuit away from being done with these "Soloist 88s", Push-Pull KT-88 mono blocks from Diyaudio.com. Mullard 5-20 designed by Tubemack, breathed on by Johan Potgeieter, Eli Duttman, Steve Brown, et. al. Professor Brown is showing me, by e-mail, how to build the schematic.
I currently alternate between a direct-coupled 45 SE (Schmalle/Tucker) and a triode wired, KT-88 SE (George Anderson). The purity of tone of the 45 is undeniable but the larger muscles of the KT-88 are seductive too. Listening to Steve Brown's Allen Wright inspired Push-pull a few years ago convinced me that a push-pull belongs on my shelf.
Going from 1.8 to 6 to 50 Watts is an eye-opener!
...I love the sound of a 45 ,,,, but I'm seduced by the sound of an 845..
JMHO..
Have fun
Willie
I'm with Willie and Tre in principle. Unless speakers demand high damping factors or simply need to be played at a SET-precluding volume. I'd opt for a higher power SET amp in preference to PP.
Interestingly, over the years I have read comments suggesting that despite their high-ish efficiency and over-damped bass response, the 4Pi speakers used by Bill seem to benefit from more oomph than one would usually expect.
Cheers.
“As long as we have any intention to be right… we should be wary. So long as words have the slightest ego attachment, they are dishonest.” Charlotte Joko Beck
....you hold the test leads to check the 1200 Volt B+
running about 700v plates and pulling 80ma..
Like a 45 on steroids..!
Have fun !
Willie
.
“As long as we have any intention to be right… we should be wary. So long as words have the slightest ego attachment, they are dishonest.” Charlotte Joko Beck
I understand the rant but....everyone who really loves the sound of reproduced music has their own idea and taste of what sounds good to them.
Not everyone can afford an SET that can drive the average speaker...or can they always afford a speaker that works well with SET amps that might have a more palatable price....with that said, there is definitely a range where we would all agree...maybe this discussion should happen on the DIY venue.
At this very moment, I'm listening to an EL84 triode strapped RC coupled power amp driven by a 5687 parafeed preamp with LL1674 opt all DIY driving DIY back loaded horns using Tangband drivers that cost 30 bucks apiece.
My IT coupled 50 mono blocks are down stairs and I'm happy to sit a listen to the EL84 rig..upstairs...
Hat's off to anyone willing to put the time into a design and build what makes them happy...
amioutaline? put your stuff on the DIY forum...
Stuben
You mean the one with Clocks, Crystas and Telephone Calls? That one?
maybe i'm missing the humor, or I just don't get the reference.
It is my understanding that the SET forum is for commercial SET amps, not diy discussion primarily. There is a TubeDIY forum for diy amp builders. Yes, it has been polluted by capacitor and low-DCR power supply babbling but I think most people can sort thru that stuff. I'd rather just browse thru one diy forum on AA then have to sort thru the SET and DIY areas, personally.
Nice looking amps there!
With two 97db speakers and 1 watt going into each you have 100db in the room. I doubt you are using any more than that.
Any differences you hear between the 1.8, 6, or 60 watt amps is the difference between those amps in the first watt or damping, etc.
Did I mention my first post was a rant? :-)
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
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