amp shoot out

modular747 · « **Reply #20 on:** 17 Sep 2009, 08:14 am »

dupe post

rcag_ils · « **Reply #21 on:** 17 Sep 2009, 01:24 pm »

Ah.....what a nice late summer morning with music flowing out of the AE-25 Signature.

You are correct that the little AE-25 Sig. operates in push-pull, but the nice triode parameters designed for the amp, ultilizing the SET transformers used in other SET amps, that's what give the amp the SET like sound.

"The Super Amp is rich in second order harmonic, and that's one of the ingredients that make single-ended triode amps so wonderful to listen to. The level of the second harmonic is above that of the third harmonic, just as in a SET amp."

I don't know how it will measure up to the U70, but it'll be interesting to find out. I may build a Super Ultimate 70 Amp, after the comparison, who knows.

modular747 · « **Reply #22 on:** 17 Sep 2009, 04:34 pm »

Quote from: rcag_ils on 17 Sep 2009, 01:24 pm

You are correct that the little AE-25 Sig. operates in push-pull, but the nice triode parameters designed for the amp, ultilizing the SET transformers used in other SET amps, that's what give the amp the SET like sound.

Actually, there is no such thing as an "SET transformer", unless you mean one with a high output impedance. What purportedly gives SETs (and single ended solid state amps) their "sound" is the single ended design which is pure class A and very low proportion of odd to even ordered harmonics (though very high even ordered, which probably what the proponents actually like).

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"The Super Amp is rich in second order harmonic, and that's one of the ingredients that make single-ended triode amps so wonderful to listen to. The level of the second harmonic is above that of the third harmonic, just as in a SET amp."

I don't know who you're quoting, but this review found the opposite:

"The spectrum of a 50Hz sine wave at 5W into 8Ω is shown in
Fig. 3, from zero to 1.3kHz. The THD+N measured 2.1%, and the harmonics are distributed through- out the spectrum, with the odd harmonics slightly higher than the evens. The second, third, fourth, and fifth measure −51dB, −31dB, −50dB, and −45dB, respectively."

http://www.audioelectronicsupply.com/reviews/ae-25_super_amp.pdf

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I don't know how it will measure up to the U70, but it'll be interesting to find out. I may build a Super Ultimate 70 Amp, after the comparison, who knows.

Every decent push/pull tube amp I've seen has lower odd than even harmonics, and a fraction of the total amounts seen with the AES-25. The 550's have several orders of magnitude lower distortion products, as well as lower odd than even harmonics. What the AES-25 has, like SETs, is both high total levels of distortion and very high output impedance causing large frequency response fluctuations driving reactive speaker loads.

rcag_ils · « **Reply #23 on:** 17 Sep 2009, 05:13 pm »

There are "SET transformers" if you custom make them.

And no, these transfomers have output Z at 4, and 8 ohm.

The authur might have written the words in opposite with the graph.

"Some of the disappointment of many push-pull tube amps is that , by their very nature, they eliminate the 2nd harmonic, and allow the odd orders to be present. And the way you get rid of the odd orders is to add feedback."

It's not fair to compare the Super Amp with the Ultra550 due to the two different designs, but if Frank cloned the Ultra 550 sound signature into the U70, then it would be interesting to compare it with the Super.

avahifi · « **Reply #24 on:** 17 Sep 2009, 05:36 pm »

OK guys, lets quit carping over the specs, we have not even heard the AES-25 amp yet.

I will give it a decent listen in my reference system here and report back. There probably will be no disinterested listeners here and no double blind tests.

I will put it on the test bench and see what that tells me too.

Frank

Art_Chicago · « **Reply #25 on:** 17 Sep 2009, 06:01 pm »

Quote from: avahifi on 17 Sep 2009, 05:36 pm

OK guys, lets quit carping over the specs, we have not even heard the AES-25 amp yet.

I will give it a decent listen in my reference system here and report back. There probably will be no disinterested listeners here and no double blind tests.

I will put it on the test bench and see what that tells me too.

Frank

Frank,
I am wondering if you have or are going to send the UltraValve to The Absolute Sound for a review? It would be fun to see a comparo with "competitors" in the $2K range like primaluna and so on.

avahifi · « **Reply #26 on:** 17 Sep 2009, 08:23 pm »

I will think about reviews just as soon as we have the production metal parts available. We are still waiting for the third generation prototype chassis to show up. This one should be the final assuming no design screw ups. This has been a slower process than expected.

I will have two prototype Ultravalve amps at RMAF both a bit on the ugly looking side, but working just as we want them to. There will be other interesting new things to hear and see too.

Regards,

Frank Van Alstine

modular747 · « **Reply #27 on:** 18 Sep 2009, 01:08 am »

Quote from: rcag_ils on 17 Sep 2009, 05:13 pm

There are "SET transformers" if you custom make them.

A transformer designed specifically for a single ended output would not be compatible with a push-pull circuit. Whatever transformer is in the AES-25, it couldn't have been designed for an SET.

Quote

And no, these transfomers have output Z at 4, and 8 ohm.

You're confusing rated output tap speaker matching impedance with output source impedance. Output impedance is in series with the speaker. If it is a significant fraction of the speaker impedance, it will significantly affect the frequency response into the speaker. Speakers are rarely resistive loads and the impedance varies widely with frequency. An "8 ohm" rated speaker may have an impedance variation from 2-32 ohms across the frequency band. If the amp output impedence is high, the result is large frequency response aberrations.

The ratio of speaker/amp output impedance is called "damping factor". To get reasonably flat frequency response into a real world speaker, minimum damping factor of 10 is needed. The AES-25 has a measured output impedance (at the 8 ohm tap) of 4.5 ohms (see the article i linked). This results is a DF of 1.8 for an 8 ohm speaker - truly poor.

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The authur might have written the words in opposite with the graph.

If you look at the graphs in that article, you'll see that's not the case.

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"Some of the disappointment of many push-pull tube amps is that , by their very nature, they eliminate the 2nd harmonic, and allow the odd orders to be present. And the way you get rid of the odd orders is to add feedback."

That concept is belied by the fact that SETs still have higher odd order than good push/pulls and hundreds times more than the 550s. It also overlooks the HUGE amounts of 2nd and even ordered harmonics which are 1000's times higher than in a 550. These are not inaudible.

In this case, the AES-25 has a distortion spectrum typical of a push/pull amp with little feedback, not an SET. Lots and lots of distortion, both even and odd, extending to very high orders.

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It's not fair to compare the Super Amp with the Ultra550 due to the two different designs, but if Frank cloned the Ultra 550 sound signature into the U70, then it would be interesting to compare it with the Super.

I'm not sure what you mean by that. As long as the comparison is made considering the power limitations of the smaller amp, (i.e. reasonably efficient speakers) "design" is irrelevant. You're comparing the sound, not the circuitry.

rcag_ils · « **Reply #28 on:** 18 Sep 2009, 01:41 am »

Quote

unless you mean one with a high output impedance.

Your word...Where did you say it was output source impedance? There's an article mentioned how the Super amp transformers were manufactured, but I have no time to type it out, and it's not on the web, it was also mentioned in the Super Amp instruction book. But skeptic like you probably wouldn't believe it anyway.

By the way, Super amp has no feedback.

The graph, I see nothing at -51db.

It's not fair to compare the AE-25 to the Ultra 550 due to different designs and speaker choice limitation, I don't want to talk about the sound, it would just piss you off.

gjs_cds · « **Reply #29 on:** 18 Sep 2009, 03:19 am »

Is it time to move this thread to the Super Amp circle? (If such a circle exists...)

Art_Chicago · « **Reply #30 on:** 18 Sep 2009, 03:37 am »

Quote from: gjs_cds on 18 Sep 2009, 03:19 am

Is it time to move this thread to the Super Amp circle? (If such a circle exists...)

yeah, it is called intergalactic waste bin... Oops!

simon wagstaff · « **Reply #31 on:** 18 Sep 2009, 03:45 am »

Um, without going into too many details I recently had the opportunity to compare my U70 for a somewhat extended period of time against a nicely built Aleph 30 clone.

No contest. I didn't even want to really listen to the Aleph 30. It did have a little more slam in the bass and perhaps just a touch more extension in the high end.

The micro-dynamics, especially in the cymbal splash and small drum percussion, the 3 dimensionality and all those ineffable qualities that make music live were there with the U70. I don't think there are measurements for some of that stuff.

I just recently upgraded interconnects and cables to Audioquest, those silly things with the batteries..

Even more transparent and 3-d. The interconnects really tuned up the bass, not what I expected.

Just as an aside my U70 is not bearing a big load in the bass. I have Infinity Intermezzo 4.1 with integral 850 watt subs. It was interesting to me though how the bass "character" of each amp was still clearly discerned. I also have a pair of VMPS subs with a 250 watt per channel amp helping out in the bass department. I KNOW what room lock sounds like.

Been a lot of bickering and carping on this thread. I don't really see how one or two people going over Frank's place and spending an afternoon checking things out will resolve anything, one way or another. Maybe. Since the simple mod the U70 still remains an amazing amp, projecting music in a 3-dimension bubble into my room. Whether it is better or worse than another amp all depends on your criteria. I would be surprised if any other amp could do what the U70 does.

Like the Grateful Dead, it is not the best at what it does, it is the only one that does what it does.

Well, I just had to get that Grateful Dead reference in there. Maybe there IS another amp that sounds like the U70. I haven't heard it though.

AmpDesigner333 · « **Reply #32 on:** 18 Sep 2009, 05:40 am »

Do you know anyone with a DAC4800A or Cherry amp? It might be well worth the listen, especially considering micro-dynamics and imaging... Thanks.

rcag_ils · « **Reply #33 on:** 18 Sep 2009, 10:05 am »

I don't understand why there's all the bickering either, time to put this topic to rest, good day.

avahifi · « **Reply #34 on:** 18 Sep 2009, 03:46 pm »

So when do you want to bring the amplifier over? I have all day Sunday open.

Regards,

Frank

rcag_ils · « **Reply #35 on:** 18 Sep 2009, 07:43 pm »

Frank, you have PM.

Thank you

avahifi · « **Reply #36 on:** 23 Sep 2009, 07:49 pm »

Well rcag_ils was here this afternoon with his AES-25 tube amplifier.

On my test bench it measured about 10.5 watts per channel into 8 ohms. High frequency square waves (1K and 10K at 2V out) showed some slew rate limiting and partially damped overshoot and ringing.

Sweeping it, we noticed a significant underamped resonance at about 30KHz and another at about 60KHz.

In the system driving a set of Nathen Fields fantastic little and low priced ($899 a pair) mini monitors, it really was no contest. The AES is a really nice sounding amp, pleasant, with a sweet midrange, nice extension both high and low, a nice big image. However it has nowhere near the dynamic range, transient response, bass control and power, or purity as the Ultravalve amps. Its about 20 watts shy in power too.

I am sure rcag_ils will have more to say. He brought over some very nice sounding CDs for the listening session.

Regards,

Frank Van Alstined

Wayner · « **Reply #37 on:** 23 Sep 2009, 08:32 pm »

Glad you had company and played together nice!

Did he want to trade his amp in?

Wayner

Art_Chicago · « **Reply #38 on:** 24 Sep 2009, 01:55 am »

Quote from: avahifi on 23 Sep 2009, 07:49 pm

The AES is a really nice sounding amp, pleasant, with a sweet midrange, nice extension both high and low, a nice big image. However it has nowhere near the dynamic range, transient response, bass control and power, or purity as the Ultravalve amps.

Regards,

Frank Van Alstined

Frank, how is Ultravalve's sound stage in comparison with the AES? I am asking because that was one of rcag_ils reasons to have that audition.
Thanks,
Art

rcag_ils · « **Reply #39 on:** 24 Sep 2009, 02:23 am »

I have to thank Frank for the bench time, As always, I've learned a few things on testing. The original AE-25 was rated at 15W in triode mode, obviously the manufacturer "cooked" the spec a bit.

I didn't switch it to ultralinear mode to see the output power (supposed to be higher), since I wanted to stick with it's original design. The overshoot that we witnessed was relatively small, about 2-3 cycles, and not big swing. Too long of hook-up wires could have contributed to this oscillation, and of course, circuit design could have played a part on this too. The bright side on the underdamped resonance we noticed is that they are well above the basic audio band, I am not sure how much impact they have on the sound, Frank probably would be a better person to explain this.

The sound, in the given environment, Ultimate 70 has very fast, tight, clean, punchy and detail bass, the trademark of the AVA amps, very dynamic indeed. In comparison with the U70, the AE-25's bass performance appeared to be loose, relax, low freq is there, but less dynamic than the U70.

I compared the same mid/high passages when the artist plucked his guitar in both amps, for that the AE-25 has a more exaggerated edgy tone, and stands out more than the U70, Frank said it might have been due to the brightness from the amp's output overshoot condition, it didn't sound bad too me, I said that not to defend the AE-25, but it was similar to the sound when I saw the artist played live in concert at a much louder volume. Frank thinks that the female vocal in his demo CD sounded better in the U70 than the AE-25, but the male vocal and the background female vocal from my demo CD sounded fine in both amps in my opinion. We only used three tracks from three difference CDs for the audition. The listening test result is the U70 wins in the bass/dynamic department, the AE-25 didn't do poorly for what it is.

Frank's cat didn't participate in the audition.