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Interesting amp measurements...


sfogg

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"Is it possible that the amp has a bit of very high frequency

oscillation as noticed on the scope traces when set to a higher freq.

time."

Could be, might be some form of crossover distortion too. I am not

exactly sure what is going on there, just noting the behavior.

" Also what are you using for a analyzer?"

Spectral Dynamics SD380.

Shawn

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Craig:

"Craig thinks the entire topic is a flame bait game as always."

Craig shouldn't worry about it then. Why does Craig always respond and contribute this way when other technically experienced forum members share ideas and experiments? Honestly! What is the deal with the 'flame bait game as always' proclamation, Craig?! Right, someone asked you about your opinion, but I don't understand the negative response. How is the sharing of this information flame bait?

Erik

Pretty simply Erik its flame bait because the amp in question identitiy is being hidden for some silly childish reason. Then to top it all off the guy testing it has never even listened to the amp. So this information has no reference point as to whether the amps sound good, bad. amazing or anything. IMHO this thread is just a big bait job.

Just like this post I quoted. You and shawn are feeling froggy once again. This time you tow are not dragging me into the anal analyzers pit of hell. Have fun!!!!!

Craig

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"Craig thinks the entire

topic is a flame bait game as always. " Then avoid the thread if you

think it is flame bait.

Has anyone else noticed that I am avoiding it? Someone brought me up so I replied specifically to the post.

Craig

Doing a fine job of avoiding it....

Shawn

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"My latest SET amp wouldn't even pass the Stereophile 1KHz square wave test. It's just awful. Nonetheless, it's the best freaking SET amp I've ever hooked of my Lamhorns. The "you are there" factor is present at the nth degree. In some way, that is interesting too..."

I'm curious. What kind of SET amp is this? I'm someone who can and does believe in the amazing sense of presence good single ended amps are capable of.

Erik

It's the Y.A.S.A., a 2A3 SET amp. This time the experiment was choke loading everything that could be choke loaded. I didn't expect much results fearing a "too much of a good thing" scenario. Much to my surprise, it was just freakin' incredible the first time around.

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"My latest SET amp wouldn't even pass the Stereophile 1KHz square wave test. It's just awful. Nonetheless, it's the best freaking SET amp I've ever hooked of my Lamhorns."

uh-oh...this sounds good...can you tell us more Jeff? schematic? Thanks, Tony

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"My latest SET amp wouldn't even pass the Stereophile 1KHz square wave test. It's just awful. Nonetheless, it's the best freaking SET amp I've ever hooked of my Lamhorns."

uh-oh...this sounds good...can you tell us more Jeff? schematic? Thanks, Tony

The schematic will be online at some point.

It is nothing revolutionary. Imagine a Horus without the first stage with an inductor loading a 5687 driver (instead of a plate resistance). This driver is cap coupled to a 2A3 (or a 300B) output stage. The output stage is in a parallel feed configuration. I tought I would spend a lot of time chasing ringing and oscillations because of the high number of inductors (3) forming resonnant LC circuits. I was lucky that every things fell perfectly in place the first time around.

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"My latest SET amp wouldn't even pass the Stereophile 1KHz square wave test. It's just awful. Nonetheless, it's the best freaking SET amp I've ever hooked of my Lamhorns."

uh-oh...this sounds good...can you tell us more Jeff? schematic? Thanks, Tony

The schematic will be online at some point.

It is nothing revolutionary. Imagine a Horus without the first stage with an inductor loading a 5687 driver (instead of a plate resistance). This driver is cap coupled to a 2A3 (or a 300B) output stage. The output stage is in a parallel feed configuration. I tought I would spend a lot of time chasing ringing and oscillations because of the high number of inductors (3) forming resonnant LC circuits. I was lucky that every things fell perfectly in place the first time around.

Don't you love when it goes like that! Problem is it rarely happens.

Craig

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Don't worry, one month from now, you'll be saying it sounds like a tin whistle in a Bathysphere....

Let me sell it before...
Ahhhhh... That brings up the next stage: Seller's Remorse, bringing the well placed, "Lord, I cant believe I sold those amps! They were the best amps I ever made. They make Horus sound like Man falling down stairs while wrapped in a copper robe! I am clown!"

Although it upsets me to place these beasts within a thread dedicated to measurements, especially since these amps appear to measure so imperfectly, here they are. The YASA. Special points will be awarded to anyone that can measure what the name stands for... (of note, the strange plugs in the front were to fill in a spot for a planned pot to be).

yasa_set_750.jpg

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"It is nothing revolutionary. Imagine a Horus without the first stage with an inductor loading a 5687 driver (instead of a plate resistance). This driver is cap coupled to a 2A3 (or a 300B) output stage."

This sounds like it could be very interesting. I had tried choke loading in the Horus (you might remember sometime back) but not with the 5687 -- which for me is among the best input/driver tubes around. I had purchased plate load chokes from Electra-Print (not so expensive but decent), and rewired the front end for a 6N1P, DRD-style. The choke was of course also on the grid of the 2A3 (coupling caps removed), and was fed by the voltage divider + cathode bias resistor on the output. It was a decent combination at first, but I honestly began to miss the Horus (with Ultrapath). I switched one of the monoblocks back to the former topology, and found on that side what seemed to be more air and clarity in the upper midrange and HF. Both are now back the Horus/Ultrapath. I also really preferred a cathode bypass resistor in the first stage, although I know some don't care for it.

I look forward to seeing the schematic when you have that available. I think it would be neat to try out, as well.

Erik

edit: I think part of the problem may have had to do with some Miller Effect issues, although we really liked the sound of the DRD 2A3 amps when they were here. Just not sure, but in this case I did prefer the AC coupling between the two sections of the 5687 and on to the 2A3. I think you would also quite like the sound of the Moth amp -- only some minor changes done to the power supply to extend tube life on the 5U4 (which I found to be fantastic in this amp). It's an instant-on tube, but I've installed a standby switch to warm things up before plate voltages are allowed in to take their seats. Shawn mentioned the GZ37, too, which might be a great candidate. Those were nice in the Moondogs.

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