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Ok, I am writing to get everyone's thoughts and opinions on what the best amplifier would be for K-horns. I have heard quite a bit of praise for SET amps, but have never heard one. The 2A3 SET's seem to be favored over the 300B's. I currently own an Audio Research VT-50 tube amp and love it. Of course, if there is something that would sound even better with K-horns, then I would like to look into it. For the 2A3 amps, I hear that Cary makes a top-notch amp. Are there any others out there that could be even better? Another amp that I have considered is the BAT VK-60. I just want to hear what the rest of you think. Of course I will let my own ears decide, but thought I could get some good suggestions from the rest of you Klipschaholics.

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I myself am looking for best amp! The Mcintosh is great, but tubes cost thousands and id need 2 amps!!

That is why i just jumped the reciever i have, the pre out and main ins,to run my Mcintosh solid state along with it!!

With my 2 pair of cornwalls!

Regards Jim

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If you ever have a chance to listen to a $10,000 amp, take it!

I, however, have a pair of 300B SETs that set me back $1600, good tubes and very high quality internal parts included (Black Gate caps, silver wire, etc)

Do they sound good? Is a bear Catholic? Does the pope sh*t in the woods?

I imagine 2A3 is good too, but I can't imagine it being WAY better. I'm not sure you can GET way better than this.

And twice the power helps juice it up a little, although it takes 10x the power to sound twice as loud.

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Thanks for the feedback guys.

mdeneen: I love the VT-50. I have not found anything I don't like about it. In fact, this is the best overall sounding amp I have had in my system. As most of us do, I was just wondering what out there would be even better. At 45 wpc, there is no shortage of power. Since this is the only tube amp I have tried, I want to get other people's opinions on other amps (and even how this amp would compare to other ones). The SET's have been getting great compliments. The VK-60 has received great reviews, and one of the things that sounds appealing is the auto-biasing feature.

Hubert: I have never seen Futtermans, but I have heard of them. Maybe someday I will be able to audition them.

Randy: What kind of 300B amp do you own? I don't think the 2A3's would be "way" better, it just seems that everything I have read slightly favors the 2A3 over the 300B. Of course, there are some areas where the 300B is better, and of course this is all subjective. You have to have the right speakers to use the lower powered 2A3's.

I'm just trying to get more thoughts on amps from people who have direct experience with them. With SET's, the word "Magic" seems to be used quite often.

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jmon, I have Welborne Labs Laurels, and if you want good stuff, they have it.

They also have 2A3's, but all they sell anymore is kits.

After hearing the 300B's I can't imagine the 2A3's being significantly better. I can't imagine ANYTHING being significantly better.

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Nothing personal y'all, but I thought the question was about amps, not distortion generators. biggrin.gif

OK, OK now, everybody just settle down. To each his own, and whatever floats yer particular boat, and all that other live and let live baloney. But you simply can not deny the fact that most of the devices mentioned are not high fidelity by any stretch of the imagination. If you don't believe me, go read the December Stereophile review of the $40,000 per pairs> Cary CAD-1610-SE monoblocks.

-Disco Betty

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Disco Betty? Uh, okay...

Anywho, welcome to the fray...

As to tube amps being "distortion generators", well, when it comes down to it, ALL amps are distortion generators. The only argument is what TYPE of distortion, and HOW MUCH, and how the different amounts of different types are perceived human hearing. Solid state amps produce (uh, seemingly) miniscule amounts of harmonically related distortion products, in most cases predominently 3rd order harmonics, and the level of distortion vs output level tends to reach a minimum value someplace just short of the clipping level, that percentage of distortion to signal increasing slightly with lower output levels. They also produce small amounts of transient intermodulation distortion and low levels of noise. Tube amps, particularly single ended triode amps, produce much higher harmonic distortion. However, the distortion characteristics are different - the se tube amp is predominantly 2nd order, and DECREASES with dropping output levels. This distortion may be much HIGHER that a solid state amp when measured at an output level of 5 or 10 watts, but can easily be much LOWER than the solid state amp's when measured at a fraction of a watt.

So which distortion is more annoying - the odd order distortion whose percentage contribution decreases with increasing power levels to almost immeasureable levels, or the even order distortion which has a very, very low percentage contribution at very low power levels then climbs to significant levels with increasing power?

Granted, the tube amp, because of it's high output impedence, is going to have frequency response anomolies that will be huge in comparison to a low output impedence solid state amp, but are these more or less important ti

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Ray and All,

Yeah, BUT...it seems to me that a good ss amp even at it's worst, is going to have distortion components that are below the threshold of audibility for the overwhelming majority of people. Whereas tubes distortion are typically orders of magnitude higher, not to mention the often rolled off frequency extremes and susceptability to response variations relative to output impedence. (As you mentioned.)

Still, I would not deride anyone who prefers "tube sound". But it just seems to me that euphonic distortion and frequency abberations are just not what "high fidelity" is supposed to be about.



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>>Which "frequency response errors"? How does the impedance of the speaker affect a tube amp different than say, an SS amp? << A solid state amp with feedback will have an output impedance of less than 0.1 ohms.A push pull pentode with feedback will be about 0.5 ohms.A push pull triode with feedback will be about 1.2 ohms.This figures out to .75dB for the pentode and 1.7dB for the triode compared to the solid state amp driving the impedance curve of a K/B/LS/C.A Heresy as a load would half the difference.A SET with no feedback will have huge errors.This is not entirely bad.The Klipschorn has a 108dB peak at 250hz that correlates with its minimum impedance.A SET with no feedback will deliver about 3dB less than a solid state amp at this frequency range.EQ where it is needed without buying an EQ? A SET with no feedback will vary about 6dB driving a K/B/LS/C compared to a solid state amp.Totally a function of the output impedance vs the load impedance.>> I have a Tandberg 150 watt solid state powering my Cornwalls and I love the sound. << I sold my Tandberg 3008 150W amp to a friend to drive the low end of his 'Super Cornwalls'.Dual K33 bottom with a modified Rane AC22 + B&K ST202 on the top.An ST120 or ST140 would have been enough but I couldn't find one used.The Tandberg sounded better than the B&K on top but the B&K sounded like mush on the bottom.

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The tube amp vs. SS amp debate is still alive. I still believe the best way to decide is to let your ears be the judge, and forget about the results from test measurements.

There is an interesting article in the May/June 2001 issue of Listener Magazine that discusses this very subject. The conclusion of the article is that for audio use, tubes SOUND better than transistors. Of course you still have to have speakers that work well with tubes.

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courtesy of Stereophile...

Mark Levinson No. 383 Integrated Amp:

"The power-amplifier output impedance was very low at approximately 0.055 ohms across most of the audioband, this rising to a still negligible 0.065 ohms at 20kHz.

Because of this very low source impedance, there was virtually no change in frequency response as the load varied (fig.1)."


An unusally good tube amp, the McIntosh Labs MC2000 power amplifier:

"The output impedance measured a maximum of 0.4 ohmquite high in comparison with solid-state amplifiers but admirably low for a tube amp.

Fig.1 shows the MC2000's balanced frequency response. (The unbalanced response is essentially identical.) Note that the response into a simulated load is relatively flat for a tube amplifier: approximately ±0.25dB over the audible range."


A typical tube amp, the VTL IT-85 integrated amplifier.

"The IT-85's output impedance was moderately high, at 0.85 ohms across the audioband. (The ST-85's source impedance was slightly lower at 0.75 ohms, which probably explains the slight difference in gain.) As a result, there will be a mild, ±0.6dB interaction between this impedance and the manner in which the partnering loudspeaker's impedance changes with frequency, which can be seen in fig.1 (top trace at 2kHz)."


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What about the music?

Are we in this to read charts or enjoy ourselves by getting lost in the beauty of a breathy blues solo from Lester Young or Ben Webster or WHATEVER?

I've been into "hi-fi" for more than a couple of decades now and I gotta tell you, I've never heard a solid state amp that was "musical." Call it tube distortion if you like, but I'm in this for what's inside those grooves, not what some scope says.

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I am just as interested in the "why" and "how" as most of you--it's just that it drives me crazy when people pull out "specs" to defend or trash the merit of any kind of gear. I know people that hate my old MAC tube gear and bully for them, but don't trash it based on any kind of measured performance! There's all kinds of solid state crap from the 70's and 80's that measures close to "pefect" (remember Phase Linear and the early Bryston stuff?) and sounds HORRIBLE! And I was lucky enough to audition a pair of 2A3 SE monoblocks that retailed for 5 times the total amount I have invested in my rig that measure like crap but sound like magic.

Like Yogi Berra said, "statistics remind me of the guy who drowned in a river with an average depth of 2 feet."

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I'm in total agreement with both you and Mdeneen. I'm in it for the music, but I'm a techie by nature (I'm the CTO for an internet B2B site) so when I'm listening to my stereo, and I try changing something (different amp, for example) and I find myself thinking "Way cool! That sounds WONDERFUL!" I can't help wondering, "why?" Not out to prove tubes are better / worse than solid state, or cables do / don't make a difference, or horns are better ( biggrin.gif ) or less accurate ( tongue.gif ) than direct radiating speakers; I'm just incurably curious. The discussions here regarding different output topologies and the analysis of the differences between tube / bipolar / MOSFET output stages are more along the lines of "Gee, look at that... wonder what THAT means?" than anything else.

Mdeneen, here's the discription of the "simulated load", again stolen directly from the Stereophile site (geez, hope they don't get ticked off that I use so much of their stuff... URL to original is http://www.stereophile.com/fullarchives.cgi?60 and be sure to tell them I sent you...)


"Real-Life Measurements

By John Atkinson, August 1995

As mentioned by two readers in this month's "Letters," amplifiers are used to drive loudspeakers but are almost exclusively measured into resistive loads. The reasons for this are twofold: 1) real loudspeakers both produce neighbor-annoying sound levels and tend to break when driven with typical amplifier test signals; and 2) the question as to which "standard" loudspeaker should be used is impossible to answer---at least the conventional resistive loads are consistent and repeatable.

However, the general point that an amplifier should be measured into a load similar to that of a real loudspeaker is a valid one. Loudspeakers can be much more demanding than resistive loads, as evidenced by Eric Benjamin's 1993 AES paper, "Audio Power Amplifiers for Loudspeaker Loads." We had been thinking about how to implement this for some time, when, as a result of a chance conversation, Ken Kantor of NHT and International Jensen sent us a speaker simulator he had been using.

Its circuit diagram is shown in fig.1. Combinations of resistors, inductors, and capacitors produce a load with an impedance magnitude and phase plot (fig.2) intended to represent a typical two-way, sealed-box, 8 ohm loudspeaker. (The small-value resistors shown are the measured series resistances of the coils.) The impedance peak in the bass is the equivalent of the woofer's enclosure resonance; the peak in the low treble is identical to that produced by a crossover filter. The phase angles are also typical; note that the worst-case phase never coincides with the lowest magnitude.


Fig.1 Circuit of Ken Kantor loudspeaker simulator, intended to represent a two-way, sealed-box minimonitor with a nominal impedance of 8 ohms.


Fig.2 Kantor speaker simulator, electrical impedance (solid) and phase (dashed) (2 ohms/vertical div.).

However, the rising impedance above 5kHz, coupled with a positive phase angle---intended, I assume, to be equivalent to the tweeter voice-coil inductance---is almost never found in a real speaker. I modified the Kantor circuit by adding a Zobel network---a resistor and capacitor in series---across the input terminals (fig.3). The impedance magnitude and phase of the modified simulator are shown in fig.4---the load is now moderately demanding but not untypical. All Stereophile amplifier reviews will now include measurements made with this load. We shall see if significant differences emerge.

" TARGET=_blank]http://www.klipsch.com/ubb/uploads/circuit2.jpg

Fig.3 Circuit of Ken Kantor loudspeaker simulator, modified to include Zobel impedance compensation in the treble.


Fig.4 Modified Kantor speaker simulator, electrical impedance (solid) and phase (dashed) (2 ohms/vertical div.).

Letters in response:


Why did you add the Zobel network? It has a cut-off of about 10kHz. Did you want to provide an ever-increasing capacitive load to the amp at high frequencies or just limit the spurious responses of all the other Ls and Cs?


If you look at the impedance plot of the Kantor load, which is intended to resemble a small two-way sealed-box speaker, it is much kinder to amplifiers at high frequencies than any speaker I've measured. All you have above 5kHz is the rising impedance above 8 ohms due to the simulation of the tweeter's voice-coil inductance. I added the network purely on an empirical basis to make the impedance magnitude and phase look more like that of the speakers I have measured. It is not quite what is needed, but I only had a small selection of suitable component values in my surplus parts box. It is close enough, however.---JA "

End of quote

Units of measure on the vertical axis are in relative dB. That is, for the Levinson amp, the response is down approximately 0.5dB at 50kHz. The reason the scale on the verticle axis is different is because the magnitude of the frequency variations on the three amps varies widely, and using the same scale for all three would result in the Levinson having a perfect response curve ( wink.gif ) or the VTL not fitting on the chart.

Please check out the stereophile archives on their website for much more information.

We now return to your regularly scheduled program.



Music is art

Audio is engineering

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