Which tubes? My amp can except El34, 6L6, KT88, an

I can say that the Electro-Harmonix 6550 outperform both the Svetlana 6550 and Svet KT-88 in both my Rogue Tempest, and in the Cary SLI-80 Signature. They sounded cleaner top to bottom. The Svet KT88 had a bit more warmfuzzy in the mids, but you definately heard the fuzzy.
Based on the Super sound of the Electro Harmonix 6550, and the stellar review of their EL-34 in Vacuum Tube Valley, I picked up a matched quad from the the tube store for less than $50...
EL 34 tubes are supposed to have less bass than their big-bottle counterparts, but I gotta say, these things sound GREAT. Note, that my Rogue is auto bias, and is made for the 6550/kt88, so the EL-34 tubes are being run much hotter than is ideal for tube life, which certainly affects sound, but if they sound this good run hard, I can only imagine what they might sound like properly biased.

If you're going to try 6550s, the Svetlanas are super cheap, sound most neutral. I prefer the ElectroHarmonix, and hadn't heard of the aforementioned compatability issues, but I digress. Svetlana KT88s are pretty good, too.
Come to think of it, Svet El34s are cheap and good, too. As I said, I prefer the EH tubes...

HOWEVER
I can't believe, even though you didn't ask for it, that I'm the first one to suggest that the smaller tubes in your amps are much more likely to affect sound quality than the output tubes.

THis thread has pretty much covered the bases, regarding power tubes... what kind of "little tubes" does your amp use???

Kana813, I have been wondering the same thing about the Vandersteen you are talking about, I though it was called the Reference Monitor. We will have to wait and see.

Using a high pass filter before the main amp with the 5's(and with the 2Wq, which I have) gives you the true benifits of bi-amping, since the main amp has the low bass filtered out. Using the speaker signal from the amp lets the built in sub amp take on the character of your main amp so that they don't sound like two distinct and different things, and keeps the blend more seemless. That's why Rec can get away using the amps in triode for 50watts. Same reason I can use a 45 watt amp and the 2Wq with 2Ce's(which are rated at the same 87db sensitivity as the 5)to get fairly realistic levels

Rec, seems the most info that can be found on the update from the Model 5 to the 5A, is in the adds in both the latest Stereophile and TAS. The add states,"a switch-mode power-factor corrected amplifier supply, a proprietary woven-cone midrange with high-efficency magnet assembly,a new tweeter utilizing a more aerodynamic magnet structure and die cast alloy chassis, and the requsite refinements in the crossover.."

Maxgain- agree with the benefits of taking the low bass out
of the main amp. My SF P1SE sound much better(cleaner/faster) without having to deal with the bass from 50 hz down.

I think the V5s are a true classic design that will hold their value(like the other Vandys). I hope Mr.Vandersteen
brings the Signature One/Reference Monitors to market, for those of us who have smaller rooms or want to roll their bass.

Mahalo for all the info.

Aloha & an early Mele Kalikimaka.

To answer some of the questions,

I am using the vandersteen 5 crossover.

I am currently using in each mono amp 6 Tesla el 34's they came with the amp along with 1 - 12AU7 and 1 - 12FQ7 .

So as I take it the 34's are better on mids and highs but cheap and the KT88 is good bass and good mids and highs but expensive 6550 is between the two including price?

I have been reading and finding out that the Mullard NOS 12AU7 is a worthy upgrade to the sound of your amp?

What does the 12fq7 tube do and why is it such an oddball?

I have also read that the new Svetlana KT88s are really good as well as the EL34's. Are the Svetlana type tube the ones to buy for new production?

One last question, the NOS output tubes worth all that extra money I have read that some of the new production sounds quite good?

Thanks for all the reply's, I look foward to hearing your answers.

Ras

I know the NOS guys will scream bloody murder, but I think that the current crop of Svetlanas and some of the Electro Harmonix tubes are they way to go. A dozen output tubes can be expensive, NOS output tubes are down right precious. El34's will end up costing as much as KT88 since you will chew them up twice as fast and still get 1/2 the power while doing it. I still say Svetlana 6550c's are the way to start for what I feel is the least flavoured sound of the lot,or if you like a more romantic (classic tube) sound get the KT's. Check out www.thetubestore.com, they have some good info on the site and they may be able to steer you the right direction. They have some NOS small input/driver tubes like 12AU7 but I didn't see that they had any 12fq7's at all. If you give them a call, they may have feedback from other users of your amp and what works best.(did you ask Quicksilver?) The guys at the tube store are great people to do business with and have fair prices. I got driver tubes from them that one of my old amps didn't get along with and the exchanged them for me, which I thought was great! If you really want exotic NOS talk to Andy at Vintage Tube Services. Have fun!