Anybody ever hear one of these things? They use 4 KT88's per channel and supposebly put out 100wpc.
http://www.caryaudio.com/reviews/may97.shtml
http://www.caryaudio.com/reviews/may97.shtml
KT88 100wpc Monoblocks
- Thread starter DanTana
- Start date
Never heard that one but I have this one http://www.audioresearch.com/VM220.html
Rockmonton
Infected with Altecitis
probably push pull paralell
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Here's another one I found, made by BEZ :
http://www.bezdz.com/images2/T9B.jpg
Very slow site, from China.
http://www.bezdz.com/images2/T9B.jpg
Very slow site, from China.
tubino
A guy with too many tubes
The Dynaco version
The Dynaco Mk VI used four 8417s for a monoblock.
More Info Here
OPTs were A-451s. I had a pair of homebrew amps using 4 KT-88s (clear genalex) for a channel, and Dynaco A-450 OPTs (same as 451 but without a 4 ohm tap, IIRC)
Bauhausler has the OPTs now. If I weren't all into SET amps, I'd be hot to do something with them. 23 lbs each for that SERIOUS statement.
The Dynaco Mk VI used four 8417s for a monoblock.
More Info Here
OPTs were A-451s. I had a pair of homebrew amps using 4 KT-88s (clear genalex) for a channel, and Dynaco A-450 OPTs (same as 451 but without a 4 ohm tap, IIRC)
Bauhausler has the OPTs now. If I weren't all into SET amps, I'd be hot to do something with them. 23 lbs each for that SERIOUS statement.
tubino
A guy with too many tubes
Whoa, hey, I never BUILT a Mk VI clone, and I never even listened to the 4-chassis (giant separate power supplies for each channel) homebrew set. It was a long way from plug-and-play!
So I'm only talking about my personal preference for single-ended.
My view is that PP is difficult to do really well because of the phase inverter problem. But when PP is done really really well, it's great.
I just knew that I'd never get around to getting those amps going -- though I may recycle the great power supply parts. I have a thing for UTC commercial grade chokes and transformers. And when I build that 813 amp...
So I'm only talking about my personal preference for single-ended.
My view is that PP is difficult to do really well because of the phase inverter problem. But when PP is done really really well, it's great.
I just knew that I'd never get around to getting those amps going -- though I may recycle the great power supply parts. I have a thing for UTC commercial grade chokes and transformers. And when I build that 813 amp...
NOSValves
Super Member
Nothing hard about doing a phase splitter that does a great job. It's just that Dynaco never did it. All the Dynaco amps hand one huge strong point which is the Iron. The rest of the circuit was a engineering feat is simplicity to meet a price point. Of coarse anytime a price point enters the picture compromises follow.
tubino
A guy with too many tubes
A good job, maybe, but you say nothing hard about a GREAT JOB without asymmetric and/or freq-dependent distortions, or bandwidth limitations (transformers), steady over time?
I thought this page from TubeCAD was a good brief description of pros and cons of various phase inverters.
Some truly balanced ones have been done -- by the oscilloscope gods at HP and Tek, for example. But how often do you see that quality in an audio amp?
NOSValves
Super Member
Tubino,
Your falling for the tube lore here. Lets compare THD numbers watt for watt of output of your SET amp to my Push Pull I bet there very similar at low output and as the output rises but before the SET amps rated output the SET distorts by a extreme percentage more the my PP. The time that most distortion becomes prevalent in the PP amp is way above all but the most robust and expensive SET amps could even think of reaching power wise anyway. It is not at all hard to make a great phase splitter that will easily perform up to distortion specs of SET amp. Now show me a SET amp that is absolutlely flat from even 20hZ to 20 khz I yet to have see one cross my bench that isn't extremely rolled off above 12 Khz on up. I also have not seen one that doesn't end up with near 3 to 4% distortion at there rated output measured with a Sound Technologies distortion analyzer. Now I have not tested a boat load of these types of amps but I have tested a few of the more popular and pricey brands.
I'm not at all trying to trash SET amps because the distortion they do produce is a very mild sounding type. But to say what you said above IMHO is just not true. The problem with most phase splitters is they just simply build them to simple and without AC balance adjustments. Hence the word needs "tweaking" in there discription. The tweaks are easy !
Craig
Your falling for the tube lore here. Lets compare THD numbers watt for watt of output of your SET amp to my Push Pull I bet there very similar at low output and as the output rises but before the SET amps rated output the SET distorts by a extreme percentage more the my PP. The time that most distortion becomes prevalent in the PP amp is way above all but the most robust and expensive SET amps could even think of reaching power wise anyway. It is not at all hard to make a great phase splitter that will easily perform up to distortion specs of SET amp. Now show me a SET amp that is absolutlely flat from even 20hZ to 20 khz I yet to have see one cross my bench that isn't extremely rolled off above 12 Khz on up. I also have not seen one that doesn't end up with near 3 to 4% distortion at there rated output measured with a Sound Technologies distortion analyzer. Now I have not tested a boat load of these types of amps but I have tested a few of the more popular and pricey brands.
I'm not at all trying to trash SET amps because the distortion they do produce is a very mild sounding type. But to say what you said above IMHO is just not true. The problem with most phase splitters is they just simply build them to simple and without AC balance adjustments. Hence the word needs "tweaking" in there discription. The tweaks are easy !
Craig
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tubino
A guy with too many tubes
If by "tube lore" you mean the engineering textbooks of the 40s and 50s, then yeah, I fell for it.
THD is not the figure of merit here. I don't have time at the moment to do this right -- I'll try to come back to it. Tweaking to balance the AC signal is not just a one-time thing, is it? Which do you pick as a great phase inverter?
BTW, I still happily listen to PP amps. I'm just a bit happier with a fine SET. Maybe that's the difference between good and great?
Thatch_Ear
Addicted Member
I have heard the AudioResearch 8 6550 amps too. On a pair of Lynns and it sounded damned good.
Heard some monsters over at a guy's house that had 8 per ch with a separate power supply chassis so they must have weighed in at at least 200 lbs per channel. I'll take notes next time I go over. He had one of those compressed air cushioned TTs with an 80 lb platter, hair thin silver wires in the tone arm, yada, yada. He was in between speakers so a pair of Cambridge 2 ways were on milk crates, sounded good but wasn't a real test of the system.
How about 3 separate power supplies for the preamp?
About the lack of phase inverters in Dynas, maybe that is why I was never wild about the ST-70s. Liked them but liked Fisher better.
You want to do PP right do the modified Williamson you can find instructions for at <www.chimeralabs.com>
Heard some monsters over at a guy's house that had 8 per ch with a separate power supply chassis so they must have weighed in at at least 200 lbs per channel. I'll take notes next time I go over. He had one of those compressed air cushioned TTs with an 80 lb platter, hair thin silver wires in the tone arm, yada, yada. He was in between speakers so a pair of Cambridge 2 ways were on milk crates, sounded good but wasn't a real test of the system.
How about 3 separate power supplies for the preamp?
About the lack of phase inverters in Dynas, maybe that is why I was never wild about the ST-70s. Liked them but liked Fisher better.
You want to do PP right do the modified Williamson you can find instructions for at <www.chimeralabs.com>
Thatch_Ear
Addicted Member
I'll be down there today and there is a Manley Stingray on the bench I will get to look at, which by the way Dennis told me has a Williamson Circuit which is now around 60 years old. So much for great gains in circuit topology over time. It seems the greatest improvements in sound have come from the better materials that can be used (mostly by DIY) like Vampire, Cardas and custom caps.
I am going to quit using Orange Drops, at least in my gear. I picked one up with a magnet the other day, so the leads are made with inferior metal.
I am going to quit using Orange Drops, at least in my gear. I picked one up with a magnet the other day, so the leads are made with inferior metal.
NOSValves
Super Member
I enjoy listening to all topologies at times. I just feel you picking out phase splitters as the evil of push pull isn't a fair statement. I could pick out many different flaws to the SET topology also. The perfect amplifier doesn't exist and never will. All topologies have compromises in one respect or the other.
Craig
PS
reading information from the 40's and 50's is a pretty narrow way to garnish a complete opinion. Your leaving out the hay day of tube Hi Fi. Oh and by the way during the hay day of tube Hi Fi the late 50' and 60' almost no manufacturer even made a SET amplifier. hmmmm wonder why?
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tubino
A guy with too many tubes
Craig,
I think you misunderstood me. I'm not talking about "evil", just the difference between good and great PP amps, which -- to me – seems to require some care with the phase inverter. I never heard a GREAT PP amp that didn't take care with the phase inverter (though I listen pretty happily to merely GOOD PP amps, and regularly!). As for learning about things like tube inverter topologies, I linked to a 1999 publication, but honestly I would be happy if I really understood everything in the RDH4, and everything in that TubeCAD piece was old news by 1960. Personally I can't name a single development in tube inverters after the 50s, other than the differential pair refinements I alluded to with the 'scope designers. But if you can, I’d be happy to learn about it. I don’t doubt they could exist, I just can’t name them.
How about this: the heyday for tube THEORY was the 40s and 50s, but the manufacturing heyday was a bit later. What can you point to in tube theory from after 1960 that wasn't a minor refinement of previously published stuff? Maybe IMD and crossover distortion? I haven't thought much about this timing and history issue. Counterexamples welcome!
