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modifying kt88 pp ul amp

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Thanks.
I didn t know they were THAT bad...
Actually i m a bit surprised cause i read no one saying they re bad, and i ve read a bunch now.
So i m a bit upset and I need to read more now.
rondo muller is in German 🙁 so I can t really get anything on their web page
this is a pity 🙁
 
Don't get me wrong, Edcore isn't bad. They are just not good. There is a difference.

I know for a fact that Jan Wüsten has regular customers all over Europe. Its gonna be an extra 19€ though for shipping. I don't know if there are any winders in Spain, I only know some in Germany, Netherlands and eastern Europe.
 
ok.
then, compared to the mullard amp discussed in the other post, which one would you advise?
I mean, this pp3 one you modified would cost like $1200.
And the mullard one? it s 2 monoblock and it sounds like really complete and prof. something outstanding. What about price?


i m still considering Bruce's one turned on a stereo chassis from on of his friends. I m really lost again. No idea where I should go towards now...
 
That's basicly something everone has to go through: There are a zillion different schematics out there and you basicaly can't tell how good they are until you have build them. I can't tell you about the Mullard, it's brand new, so I can't possibly know anything about it. Only thing I know is that the people working on it are highly competent, so it's propably gonna perform well. Like many do.

I like the interstage coupled approach because of several reasons:
Firstoff it's realy as simple as it gets. Less to do wrong, just a good way to combine high quality ingredients. Secondly an interstage xformer is a very good phase splitter. Referring to Stan White again, no tube can ever split that equaly. You buy in bandwith problems, which are no problem when using really high quality iron like Lundahl, Hashimoto, Tamura, Onetics or such. Further you save a lot of parts including the couling caps, which are known to alter the signal. Although one could build a directly coupled amp to achieve this too, this gives you DC current at the o/p grids, which people like Olsen or Sakuma hold responsible for other audible problems.

In short: If using high quality parts I currently believe this to be one of the best solutions sonicaly and it has the big advantage of being realy simple.
Call it KISS or Ockham's razor (entita non sunt multiplicanda praeter necessitatem .. or something) or quote Einstein ("Things should be made as simple as possible but no further"), it all boils down wo the fact that simple solutions often give equal or better results than complicated ones.
 
If I were you, I would start looking for something with Ultralinear taps in the range of 40 to 43% and not 33 like the suggested Lundahl. That didn't matter to the designer when he specified the LL1663, because he planned it only using triode mode. And for the power transformer and chokes you are really free to buy anything that fits the same specifications (VA rating, secondarys). And I would, because Lundahl chokes are very expensive (about three times what I pay for a choke). The power transformers aren't that expensive, but still no bargain. I'd rather choose a toroid from Rondo-Müller (sourcable via askjanfirst.com), they have a higher efficiency, are more compact and have far less magnetic stray field AND are wound to your exact specifications without being any more expensive.
SOWTER PUSH-PULL OUTPUT TRANSFORMERS
well it seems the sowter are not in your range advice.

the mullard like are going to be more expensive than 1100 €?

you also mentioned earlier that the PSU was not completely convincing you.
I would need a psu for a stereo chassis. > you seem to say this one hasn t been properly or enough studied.
am i wrong?


night,

i.
 
Sowter definitly belongs under the "or such" category. They have a very good reputation. As do Amplimo, AE Europe and Tribute, although Amplimo doesn't make interstage transformers.

The Mullard is going to cost about the same as the interstage coupled approach, i guess. You are saving one complete tube for phase splitting + two pairs of coupling caps + parts. Think about the fact, that you'll never have to replace this tube either.

Which PSU did I think not to be perfect? The one from the Ciuffoli?
Yes, I would make a little more efford on the PSU, which would reflect in implementing an extra filter stage and a tube rectifier.
You can basicaly reduce the main transformer to one big one in a shared PSU, but most chokes aren't rated for as much current as two KT88 pp op stages need (500mA), so you'll propably end up with two filter chains after all.
 
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