Tube/amp ?

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khenegar

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I have a pair of summits and would like to know what u people recommend for power output from a tube amp to drive the stat panels without any loss of hi freq?
 

Rich

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Someone more versed than me in the technical aspects of tube amps will have to respond to your specific question, but I will give you my experience. I am driving my Summits with my Conrad Johnson Premier 140 tube amp, which provides 140 wpc to the panels and has a beefy power supply. I couldn't be happier with the sound and I'm not missing anything in the high frequencies that my fifty-one year old ears can notice. And this is coming from using Sanders Sound 800 wpc SS monoblocs for years on the same speakers. Get a quality tube amp with a fair amount of wattage output and a beefy power supply and you will be pleased.
 

MPS

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I have a pair of summits and would like to know what u people recommend for power output from a tube amp to drive the stat panels without any loss of hi freq?

Generally I would recommend choosing from (semi) high powered tube amp, such as ARC VT-1XX, REF-1XX . (Semi)High power amps have bigger output transformers with lower output impedance.
Optimally you should try it in your own system first.
 

Spike

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My 50-watt SixPac monoblocs are powering the ReQuest panels just fine. No loss of high-freq.
 

sdolen

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60 Watt Rogue Eighty Eight on EM-ESL. Also used in Triode mode at 40W just great. Sounds much better than some of the 120-200W Solid State Amps I tried from Parasound and Rotel.
 

roberto

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Hola Ken, I do love my CLXs with tubes...I am using a VT-100MLIII, with excellent results. There is a kind of high frequency roll off, normal in tubes. Transistors are too bright for my liking. I assure you that everything is there, and I do not miss anything from the signal applied. Happy listening!
 

twich54

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60 Watt Rogue Eighty Eight on EM-ESL. Also used in Triode mode at 40W just great. Sounds much better than some of the 120-200W Solid State Amps I tried from Parasound and Rotel.

While my Spire's are no longer in the mix, when they were my Rogue M-180 Mono blocks did a wonderful job, their wide bandwidth provided plenty of good high freq reproduction for these 62 year old ears.

As for the Parasound amps, I thought Anthony (asindc) had a pair of their monblocks and was quite pleased with them ..................
 

Pneumonic

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Hi, khenegar

I have a pair of summits and would like to know what u people recommend for power output from a tube amp to drive the stat panels without any loss of hi freq?
A few things to keep in mind.

Stats present a mostly reactive (ie capacitive) load to an amplifier and, therefore, operate on volts and not watts. You have to be very careful when looking at an amp’s wattage rating when it is being used to drive a stat panel. Watts is far less important than the amp’s power supply voltage rating! An amp with an inadequate power supply voltage performance will easily clip when hooked up to a stat …. despite its wattage rating.

Also keep in mind that a stat’s highly reactive behaviour means that it has weird phase angles and sends electrical current back to the amp (when signal reverses polarity). Many amps tend to be unstable under such conditions so you need to make sure the amp is stable with reactive loads.

Furthermore, because a stat acts like a capacitor, its impedance is inversely proportional to the frequency it sees. So a stat will have a high impedance (say a couple hundred) at low frequencies and a very low impedance (say around 2 ohms) at high frequencies.

Note that come time for an amp to perform, you want it to be ideally impedance matched to the speaker load it is asked to drive. This will ensure the amp performs with a flat frequency response and delivers maximum power. We know that impedance matching is a severe challenge for tube amps due to the impedance variations a stat load presents to it. In order to help remedy this the vast majority of tube amps use output transformers which have impedance (1, 2, 4, 8, 16 ohm) taps on them to allow for a better impedance match. Though helpful, such taps are still a compromise due to the fact that stats do not have constant impedance across their full frequency bandwidth.

As an example. A tube amp will be able to drive the high impedance frequency bandwidth - the midrange and lower highs - of a stat with a flat frequency response. However, at higher frequencies – when the impedance of the stat drops to below the impedance taps used on the amp - we will encounter rolled off the highs to some degree. To minimize this impedance mismatch, one generally uses a lower impedance tap on the amp.

However, there is a problem when you use a tube amp’s lower impedance tap …… the amp’s drive voltage drops proportionally. The lower the tap value the lower the drive voltage.

We know from previously that (when driving a stat) voltage is the #1 key for an amp. So, when you use a lower tap on the amp - to better match the impedance of the speaker – you will have less output voltage to drive the stat speaker properly. That may become an issue if you listen loud enough and run out of voltage drive and clip the amp.
 
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MPS

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These are all good points, for this reason I did recommend looking into (semi) high wattage tube amps. Higher wattage means higher voltage swing capacity and allows you to use lower impedance tabs without easily clipping your amp. High watts means high power handling transformers which generally means lower output impedance (there will be exceptions as usual).
However my experience and that of others indicates that some success can be had even with 8 ohms output tabs, especially with CLX. Each amp model even from same manufacturer will have somewhat different output characteristics so best option is to go and try by yourself or otherwise find a reliable source of information.

Semi high wattage tube amp meaning in 100W-200W, more can be useful if needed.
 

khenegar

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Amp

Hola Ken, I do love my CLXs with tubes...I am using a VT-100MLIII, with excellent results. There is a kind of high frequency roll off, normal in tubes. Transistors are too bright for my liking. I assure you that everything is there, and I do not miss anything from the signal applied. Happy listening!
Roberto: do U know where it is possible to find one of the audio research vt100 mklll amps that u use? Thanks
 

Pneumonic

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Semi high wattage tube amp meaning in 100W-200W, more can be useful if needed.
Like with watts, more volts is always better. Especially when volumes are needed to produce live levels. For such demands, 100w will only get you into the 1,400v stator range (using 1:50 step-up) and will almost certainly be troublesome. 500w gets you into the 3,200v range which should be fine for almost all home applications.

Of course, not everyone needs or desires live level volumes so, for them, they might be able to employ a somewhat lower voltage amp. Unfortunately, the great challenge for most is actually figuring out if they are using an amp that is clipping or not.
 

Bernard

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Roberto: do U know where it is possible to find one of the audio research vt100 mklll amps that u use? Thanks
US Audiomart has a MkII version for $2,200. Roberto's is highly modified, IIRC. I read claims way back when that the MkII was better than the MKIII, but you read that with any product.

I'm using ARC VTM 120 monoblocks. They drive my SL3s very well.
 

TDIMike

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60 Watt Rogue Eighty Eight on EM-ESL. Also used in Triode mode at 40W just great. Sounds much better than some of the 120-200W Solid State Amps I tried from Parasound and Rotel.

That's pretty bold considering my Parasound is the best amp I've heard in person including much more expensive McIntosh equipment.

Does anyone have any familiarity with Vincent amps? I've seen a pair of monos in Audio Advisor that are pretty interesting.

http://www.audioadvisor.com/prodinfo.asp?number=VISPT700
 
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MPS

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US Audiomart has a MkII version for $2,200. Roberto's is highly modified, IIRC. I read claims way back when that the MkII was better than the MKIII, but you read that with any product.

I'm using ARC VTM 120 monoblocks. They drive my SL3s very well.

VT100 and VT100 mkII are pretty much the same, VT100mkIII is much closer to REF110
 

roberto

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The VT-100MK2 uses the 6922 tube, four on each channel. The VT100MK uses the 6H30 tube and are 2 on each channel. This is a new design and the tubes are not interchangeable.

http://www.arcdb.ws/VT100/VT100.html

Here you can read more about the differences between them. Right now, mine is the version MK3 and I am using the KT-120 output tubes, and also did change the bias resistors for metal film 1 ohm, and the 100 ohms metal film, both rated at 3W. Also did change the 1uF coupling capacitors, for 2uF rated at 400V polypropylene MusicCap. I do like a lot the change...and also I am running the bias, at 60mV, a little bit lower than the factory recommendation. Its a good quality sound what I am getting from this power amp. I do know that there are a huge possibilities regarding capacitors, and also the price for them...but, this is what I did, and worked for my ears...

Happy listening!
 

PaulRS

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I recently called John Atkinson a numbskull (Mikey was not happy) because he implies that a speaker's frequency response will follow its impedance curve when used with an amplifier with low damping factor. This is not true. Speakers, even electrostatics, operate on power. Sure, put a voltmeter across the terminals of MLs and it would show decreased high frequency response. Put an (ideal) ammeter in series with the speaker it would show a rising HF response. Correct? I have done this with mine (Montis, tube amps w/ 0.7Ω output impedance, compared with solid state): put a microphone in front and measure their response and there is little or no difference.
 

RonR

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Different people will have different subjective preferences for sound pressure levels and for dynamics. As a result different people will find different amplifier power requirements for ML speakers.

To satisfy my preferences I think Prodigys require at least about 150 watts. Summits, with their actively powered woofer cones, can get away with less.
 
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