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Bob Cordell
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HE2007 Listening and Measurement Workshops

For those interested, I've posted a detailed show report covering the HE2007 audiophile workshops that Peter Smith, Darren Kuzma and I presented. The report is posted at www.cordellaudio.com. The workshops included:

Amplifier Listening Comparison
Loudspeaker Listening Comparison
The Peak Power Demands of Well-recorded Music
Amplifier Measurement Clinic
Speaker Measurement Clinic
Active loudspeakers - An Example

These workshops were jointly sponsored by Stereophile and Ray Kimber, and we are grateful for their generous support. John Atkinson loaned us his own Ayre CD/SACD player for use as a source - what a seet machine! Thanks, John.

Bob

jkalman
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Re: HE2007 Listening and Measurement Workshops

Hey Bob, was it you I ran into at Duane Reade on Saturday? I asked whoever it was were to find the Tums?

Anyway, great workshops. I wish I could have attended all of them. The three I attended were educational, especially the A/B between tubes and solid state amps. It was quite a difference in the sound, one I didn't expect to be so obvious (and one that might end up being very costly for me down the road, OUCH!).

Thanks to everyone who did the workshops. Most importantly, thanks to Stereophile and Kimber for sponsering the event, it was excellent!

Elk
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Re: HE2007 Listening and Measurement Workshops

Fun stuff.

Thanks!

Bob Cordell
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Re: HE2007 Listening and Measurement Workshops

Hi Jeff,

Thanks for the kind words about our workshops. The tube vs solid state listening comparison seemed to go back and forth this time, with some people, such as yourself, being more able to readily hear the difference than was our experience at the RMAF. We have found that the level matching is very important in this test, and it can influence the results one way or the other. We also had a lot of cases where people clearly seemed to hear a difference, but thought that the solid state amp was the tube amp. Finally, what you heard may also have depended on what day you attended the listening test. On Friday, we were using Peter's floor-standing three-ways; on Saturday and Sunday, we were using his two-ways on speaker stands. The two speakers have different impedance curves, so the way they interacted with the tube amp may have been a bit different as well.

We certainly had a lot of fun putting on those workshops, and indeed learned a lot ourselves in putting them together and presenting them.

Bob

jkalman
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Re: HE2007 Listening and Measurement Workshops

I was standing off center and to the side, so I couldn't hear how the two amps imaged or soundstaged, but I definitely heard a tonal difference, a richer sound and more detail (especially in the trailing end of the notes) from the tube amp. I wish I had more time to see what other differences I would notice in the center position with more familiar recordings and a more unlimited amount of time, as I noticed those differences in only the minute or so that the music was being played while one of the other participants was switching back and forth between amps.

It really changed my thoughts on tube vs. solid state. I never thought the differences would really be that noticeable and the amps weren't driven into clipping at all, so the tube wouldn't have been suffering from soft clipping sound anomalies to make it sound different either. It definitely changed my thoughts on those two types of amps (I've never had an opportunity to compare them that directly before like I did on that Saturday morning!).

Good stuff! Thanks again for doing it. I hope I get to experience the other three workshops at the next event I can attend.

Elk
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Re: HE2007 Listening and Measurement Workshops


Quote:
It really changed my thoughts on tube vs. solid state. I never thought the differences would really be that noticeable...

Odd, isn't it?

There is nothing in the measurements or the specs that would predict that SS sounds so different than tubes.

It's one of the things that makes this hobby interesting.

CECE
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Re: HE2007 Listening and Measurement Workshops

Cool. MOSFETS baby. Dave pioneered a revolution when he came out with his MOSFET amp. Wasn't Hafler teh first to use them Hitachi devices in audio amps? And his ST70 Tube amp is still in use...40+ years later. Hafler was a real visonary, inovative aduio guy. totaly new concepts, cool. His kit products got so many involved in home audio at a quality level, not mass fi at the time. No such dudes around today is there? There are more marketeers than true audio inovators. Lotta repackagers of the same ideas, into freaky expensive boxes. 3 box pre amps!!!! 3 box CD players.

Bob Cordell
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Re: HE2007 Listening and Measurement Workshops

Hi Jeff,

There were actually two other tube vs solid state experiments that we could have done at HE2007, but did not have time for. Both would have attempted to take the amplifier-loudspeaker impedance interaction (damping factor) out of the picture.

In the first experiment, we would have done the tube-solid state amplifier listening comparison using my Athena active loudspeakers. Since they have their own built-in tri-amplification, they present a purely resistive 8 ohm dummy load at the speaker terminals. This would eliminate any coloration differences between the tube amp and the solid state amp due to the usual speaker impedance variations as a function of frequency.

The second experiment would have pitted my Super Gain Clone (SGC) amplifier against the tube amp. This would be a closer comparison for three reasons: first, the SGC is only rated at about 55 wpc, closer to the tube amp's power rating; second, the SGC incorporates soft clipping, again making it act more like a tube amp if clipping ever happens; and third, the SGC deliberately incorporates a small amount of series output resistance to knock the damping factor down to about 20, more like that of a tube amp.

Cheers,
Bob

CECE
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Re: HE2007 Listening and Measurement Workshops

Isn't the "tube sound' bloated uncontrolled effects due to it's poor damping factor. No control, loose bass. More control over the drivers makes for a better sound? Hybrid tube pre amps, use only the best of tube/SS? High voltage swings can be handled by the tube, current via Mosfets...same idea for the amps? Low damping factor is not a good thing is it? Or high power capabilty, is hardly a tube amp either? Some high end guitar amps are just 60W or so, but they are being used to produce one spectrum, guitar tonality. A hi fi amp is trying to reproduce the entire spectrum of instruments on playback. No? Exagerated uncontrolled bass blurs the detail in the bass patterns, well controlled bass, lets you easily hear the well recorded bass line in some great music. these high end guitar amps are around $5K for a mere 60W head...they are built to survive road rigors, and keep on going. But they have their own tone, used to make the music not reproduce it with nutrality. They do make a great combo on a Les Paul, great amp, and the only time magic is real is in the fingers working the strings on the Les Paul.... All tubes for "reproduction" seems to alter the sound too much. Hybrids seem logical, even though they appear to be great energy wasters, in HEAT!!!!

Colnmary
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Re: HE2007 Listening and Measurement Workshops

I do like the best of both worlds.

My gear from CDP to Pre and Power Amps are hybrid. JFets, MosFets and Tubes all in class A. Until the power really kicks in.

I like, DUP, believe in bi-amping and giving my woofers some grunt behind them. (Power amp can put out a kilo watt into 1 ohm load per channel)This is where I personally believe a big woofer needs Power to grab those suckers and make them start and stop on a dime while cranking out concert level dynamics in my room at home.

The other Power amp puts out even more grunt, but has a more delicate sound and drives my midrange and ribbon tweeters. The tubes give the vocals the warmth I need, the Transisters give my woofers the kick, drive, and power they need...

CECE
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Re: HE2007 Listening and Measurement Workshops

Yupper, watts and hybrids...you da' man....Sound like Bell Labs STILL does audio right, since they discovered and pioneered most of the ideas and discoverys way way way back when. Cool. Do you know www.mattoree.com Local dude.

Colnmary
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Re: HE2007 Listening and Measurement Workshops

Do you know www.mattoree.com Local dude. Hadn't heard of him until now, but from the listening to the music from the web site, he sure can play.

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