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In Reply to: 800w tube amps posted by Keith Tan on September 17, 2004 at 10:57:29:
I would love to hear the VTL Siegfried. It is said to be a great amp. If you have some big Soundlabs before the new mod, or big Maggies 20.1's this would be the ticket. It is a big ticket though.Here is a link to an IAR review.
Follow Ups:
If the info on the website is correct, this amp runs the output tube extremely hard. Retubing all the time will be the result.Too bad the audio rags don't do some very simple analysis and state these sorts of things in the reviews. With only (12) 6550 output tubes producing 800watts, each 6550 is required to produced 66+ watts. Well beyond the design of the tube. These tubes will smoke very quickly.
By comparison, ARC Reference 600 which produces 500watts, uses (16) 6550 for output as I recall. This translates to 31.25watts per tube. Much more conservative approach and well within the limits of the tube.
Ridiculous that VTL designs such an amp at that price point that is so poorly executed, if it only uses 12 output tubes. And it is even more ridiculous that the audio rags hide this sort of nonsense.
That gets you down to a better watts per tube measure.The s-400 has 12 tubes total for 400 watts output.
Yes I read the site a bit more carefully. The actual rated power is 600watts into 8 ohms, so 12-6550 is a bit better. However, this is right on the edge of rated output, not a good way to design anything IMO. But hey if folks are having good luck with the product, what do I know? It will require retubing more frequenty that something that was designed a bit more conservatively.
has no means to bias each tube. likely drives them with some 12AU7 variant at six grids per plate or some rubbish as that, in AB1 as well. Single-pair output stages, at that power level *IS* difficult and expensive, and nearly impossible to do w/o fans in class A.None of this says anything about how they sound, or how much better they could...
live long and prosper,
Douglas
!
Beware the man who behaves deceitfully towards others, for there is nothing else to save you from his deceiving you
If you can buy those damn things you can afford a few tubes don't you think?
Oh agreed. Problem is you are going to be retubing all the time.My output tube count could be wrong, or VTL's site is wrong.
But if (12) 6550 is what they are using to produce 800watts out, then I would consider this a very poor excuse for an amp no matter how it sounds. At that price they should be able to get things right.
This thing is ONLY about the sound. So what if it's practical? None of those big tube amps are for the faint of heart. I used to use a CJ Premier One. That this stressed tubes BAD. Way too much B+ I think? Sounded great! Made for a nice space heater as well! Cozy up by the fire.
Oh I get it. Most certainly.Poorly designed products that are unreliable as hell, with huge price tags. Questionable that they sound any better than a correctly designed similiar circuit. I don't believe for a moment that a 6550, or any tube for that matter, sounds better when it is run well beyond its design limits. Kind of like a car engine runs best when it is way into the red and is about to blow! Not many folks would buy into this nonsense, but for some reason when it comes to audiophiles and their toys, they do. Amazing really.
But the audio rags extoll the virtues of this junk, and the dewy eyed guys with more money than common sense buy into this nonsense and just has to have this amp!
All part of the audiophile nonsense that keeps many a company going. High maintenance is one thing. Retubing an ARC Reference is not going to be cheap. But at least you are not required to do this every few hundred hours.
High end audio is one of the few rich boy sports where customers are sold unreliable, poorly designed garbage, and walk out the store with a smile on their face! The fact that the client is rich seems to be the excuse for ripping the guy(or gal) off!
First off the IAR is not your typical "audio rag". This sounds like the first time you have ever heard of it. No advertising. The IAR has a very long history. It ain't Stereophile. OK? Have a bit of respect and learn who it is you are spouting off about.Second, as big a fan as I am of Audio Research, the REF series amps are going to be the least reliable in the line by virtue of the sheer number of tubes employed. These are not a shining pillar of reliability. Tubes arc, fact of life. Every time you add a pair of output tubes you increace the problems that can occur by my guess a factor of about four. So you don't like the VTL design because of some preconception. What the hell do you really know about this amp other than the review I pointed you to(and then you bitch about)and what is on VTL's web site? This amp isn't aimed at your segment of the market. Get over it. If you want reliability and high power buy a solid state amp. If you want reliability in a tube amp buy a small one with one pair of outputs per channel. Perhaps the VTL people know something you don't? Could that be?
Seems you have never used or listened to an amp like these. Calling the VTL garbage with the small amout of info you have is closed minded.
Again, you are reading words into what I said and making many assumptions.First, I have been reading IAR for better than 20 years. Don't really place anymore value in what Peter has to say than any other publication. Way too many 1A products over the years, soon to be displaced by yet another, you got it 1A product, for me to take him too seriously.
Second, you are assuming that I do not have the means to afford such a thing as VTL Reference products. If I wished to own such a product, I could and have many times in the past.
Third, I never said the VTL amp was garbage. What I said is there are many products in the market place that have huge price tags and are nothing more than garbage. Whether or not the VTL falls in this camp, I do not know since I have limited exposure to the VTL product.
Forth, running additional tubes in the output stage certainly is not less reliable than an amp with a bit fewer tubes that runs those power tubes rated at or beyond rated output. The VTL Reference amp does run the 6550 right at rated output after looking a bit more carefully at their spec. Not beyond their spec.(6550), but right at the limits. Given the choice of 4 more tubes, ala ARC Reference 600 to produce 500 watts, or the 12 in the VTL at 600 watts? For my money I would go with the ARC. Running power tubes at rated output is not a recipe for long term reliability. Not all of VTL's products run the output tubes that hard. This amp does. ARC did this same thing years ago and learned a valueable lesson. A couple more tubes run more conservately for the same output produces a far more reliable amp. Sure your chances of having a bum tube are greater with more tubes, but that is about it. One could be really conservative and state that anything more than a pair of power tubes it too much.
I confirm...he really is an ARC Fan. ARC @ sixteen tubes...hmmm.
ARC fan no question about it. There are also many other fine makes of tube and solid state equipment in the market place. Just as good as any ARC product for the right system and the right owner.Now seriously. 12 output tubes or 16 output tubes? Either way you slice it, that is a whole lot of output tubes! Any amp with that many output valves it bound to have some issues. Just way too many power valves to get working in harmony. But given the choice of 12-6550 running at full output or 16-6550 running at 70% output? All things being equal I will go with 16. Tubes that have an easy life in the circuit generally perform and last much better than tubes that are running full tilt.
The first you do is to swap tubes around to see if it follows the tube. What a giant pain in the ass that would be.
Agreed with that, I would prefer tube amp using four power tubes only, working with high efficiency speakers. Also, quad set of old stock tubes are easier to find.
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