Tube Power With VR4-SRs

catastrofe · « **on:** 5 May 2010, 09:31 pm »

What type of tube power is recommended for the VR4 SRs? I'm thinking of 80W/channel for a medium sized room (2200 cubic feet).

ceedee · « **Reply #1 on:** 6 May 2010, 12:58 am »

Hello Catastrofe,

You can think about the VA 880 of KR Audio.

I use them to drive the VSA's for more than 15 years now.

Just look at the picture from the Munic Show.

Have fun.

Cor

McTwins · « **Reply #2 on:** 6 May 2010, 06:47 am »

Hi
I am using McIntosh MC275 with great results, or better with two of them in mono.
Thanks

McTwins · « **Reply #3 on:** 6 May 2010, 07:37 am »

Hi
Cor....
I just read the specs of the KR Audio amps. Is it true that all the amps have 3% THD, isin't this too much

, or is there some printing error in the specs.
Thanks

varsharun · « **Reply #4 on:** 6 May 2010, 08:56 am »

Quote from: catastrofe on 5 May 2010, 09:31 pm

What type of tube power is recommended for the VR4 SRs? I'm thinking of 80W/channel for a medium sized room (2200 cubic feet).

The VR4 SRs have high sensitivity (90+ I think), so a moderately powerful tube amp would do. I would highly recommend the Primaluna tube amps.

-Arun

ceedee · « **Reply #5 on:** 6 May 2010, 10:54 pm »

Quote from: McTwins on 6 May 2010, 07:37 am

Hi
Cor....
I just read the specs of the KR Audio amps. Is it true that all the amps have 3% THD, isin't this too much , or is there some printing error in the specs.
Thanks

Well this is just a number used already for a few years.
Now adays KR amps. are very quiet and clean.
Q.: can you hear a difference of 3 % ? I can't and most people either

CorI

McTwins · « **Reply #6 on:** 7 May 2010, 11:51 am »

Hi
Ok, I see.
Maybe I hear it or not is not the issue. The number (THD 3%) tells me everything about this amplifier.

catastrofe · « **Reply #7 on:** 7 May 2010, 12:14 pm »

Guys, please keep this thread on track. I'm interested in what type of tube wattage would be required to drive VR4s. A debate over the audibility of 3% THD belongs in another thread.

Thanks!!

es347 · « **Reply #8 on:** 7 May 2010, 01:06 pm »

Distortion figures are meaningless for tube amps or at least not as significant as with SS.

hometheaterdoc · « **Reply #9 on:** 7 May 2010, 01:36 pm »

as with anything, it's those bass drivers that need the juice. The mid/tweet combo is relatively benign. VSA's big floorstanders, even with their higher rated efficiency, still like juice and lots of it... the steeper crossovers and parts needed to do the crossover point to the bass driver soak up some juice.

You can run them with more flea powered amps. But they won't open up as much and come alive like when there is more juice behind them. I've run 4SRs with bridged mono Butler 2250s for ~1300 watts into 4 ohms and they loved it. I've run them with 20 watts of monoblock tube power, 30 watts, 35, 40, 50, 60, 75, and >100. They liked more power than less. But a lot of that was room size (16 X 23), music material, and volume chosen.

Depending on your room size, you could easily get away with 60 watts if you're not trying to rock out at concert levels. A used BAT VK-60 with some good NOS 6SN7s in it and you're good to go for half nothing (used F series boards on audiogon go for less than $2K). I picked one up recently to play with it because I'm curious about the 6C33C tube. It's a surprisingly good sounding amp. Not absolute control of the bottom, but a very intoxicating sound with the right differential amp and driver tubes. It also is rated at 60 watts at 3% distortion.... it's much less at lower power ratings... but they are trying to get maximum power for specs out of it... which is likely what KR is doing as well...

BobRex · « **Reply #10 on:** 7 May 2010, 01:56 pm »

Quote from: McTwins on 7 May 2010, 11:51 am

Hi
Ok, I see.
Maybe I hear it or not is not the issue. The number (THD 3%) tells me everything about this amplifier.

Actually the number tells you nothing about the amplifier. All the spec tells you is the output power at 3% THD. The 3% figure is frequently used to define the clipping point of a circuit, aka: the full output. Below clipping the distortion is reduced by a magnitude or 3, and may even be at the noise threshold, depending upon power levels.

So if Cori says that he uses the KR amps successfully, it's because he is using them well within their performance envelope and isn't approaching clipping.

How large is your room and how loudly do you expect to play? Oh, and what type of music? It's quite possible that unless you are a headbanger you'll only be using a few watts anyway.

catastrofe · « **Reply #11 on:** 7 May 2010, 02:24 pm »

Bob,

Room is 12 X 23. . .all types of music other than C&W. Volume 85 - 95DB. It sounds like 80W - 100W would be fine.

msm_1 · « **Reply #12 on:** 7 May 2010, 02:29 pm »

Hi

I've been playing with switching amps for awhile now. I have a Rogue 88 Magnum that I've used with good results running both highs and bass units ( 70/channel )

I did however like the sound better running the tube on the mid/tweeter and using a good SS amp driving the bass unit ( Classe DR-9 @ 100/channel + )

I am experimenting with the spectral amp, but still may use the tubes on mid/tweeter especialy using a tube Pre

Thanks

Mike

BobRex · « **Reply #13 on:** 7 May 2010, 03:54 pm »

Quote from: catastrofe on 7 May 2010, 02:24 pm

Bob,

Room is 12 X 23. . .all types of music other than C&W. Volume 85 - 95DB. It sounds like 80W - 100W would be fine.

You might be surprised by your real power needs. Don't restrict yourself, you may be very surprised at what 40 watts can do! Look at Prima Luna, Cayin, maybe even going esoteric with an Atma-Sphere OTL. There are a number of amps that may work for you.

Have you heard the 4s with a tube amp? You will gain in transparency and "palpable presence", but you may not be happy with the difference in bass - you'll get more texture, but lose impact. And the impact loss is pretty endemic to all but the most powerful tube amps, even then, the amps still don't match comparable SS (for impact only, tubes will almost always have superior tone.)

When Cori recommends a KR amp, he's probably willing to give up bass slam for tone. I'd agree with that decision, but you may not.

Can you borrow any tube amps?

satfrat · « **Reply #14 on:** 7 May 2010, 04:04 pm »

Quote from: catastrofe on 7 May 2010, 02:24 pm

Bob,

Room is 12 X 23. . .all types of music other than C&W. Volume 85 - 95DB. It sounds like 80W - 100W would be fine.

Well I guess that depends on what tube amp you might be going with but regardless, I'm going to highly disagree with you from the 1 and only time I've had the opportunity to hear the VR4-Jr's with a 100wpc VAC tube amp and VCR tube preamp. I heard very little imaging or sound stage depth and quite frankly it wasn't a very lively experience for me. I would recommend you PM the system's owner, MFSOA and talk to him about his experiences. For me that day, that system didn't come alive til the VAC tube preamp was connected to a Digital Amplifier 4800 which at the time was pumping out I think something like 350 wpc. When this amp was connected to Mike's VAC preamp, magic happened, the imaging was rock solid and there was a ton of sound stage depth.

So I'd highly agree with Shane that your speakers need the power regardless of what volume you're listening to, and 95db isn't low volume by any stretch of the imagination and neither is 85db really. You'll wants lots of clean power and unlesss you're willing to byamp tube amps for the tweeters, I'd leave the tubes for the preamp and get yourself lots of clean power overall. Talk to mfsoa!

I own Butler tube hybrid amps (150wpc) so I'm partial to them myself but then again I haven't heard them on the VR4's either,,, but maybe mfsoa has?

Cheers,
Robin

hometheaterdoc · « **Reply #15 on:** 7 May 2010, 05:02 pm »

Robin,

The points you are making are very valid regarding VR-4jr.... just know that the VR-4SR is a very different animal than the VR-4jr.... especially depending on what iteration of VR-4jr you have.... if you have one of the first couple hundred pairs, they have a completely different requirement than later ones sold...

Is the 95dB mark average level or peaks? 8 foot ceilings or 9 or ???? Room open up to other areas of house of self contained room with standard door?

The thing I love about VSA is that they are so darn good off axis that you can get your speakers a bit wider usually without hurting center fill. I often liked them along the long wall when I set them up... do you currently have them along the long or short wall? with only 12 foot depth in your room with a long wall scenario and the depth of the speakers themselves, not likely very practical for you...... just wondering... What's your listening distance?

Edited to add:

BobRex's point about bass is very valid as well. I've heard a LOT of tube amps. They just will not slam like a sand amp with very few exceptions. The texture and tone will be there, but they don't have the grip. That might be an ok compromise for you. But you have to hear it to decide one way or the other. Hybrids kind of bridge the gap. Aesthetix makes a very nice one, Moscode as well. But they're both a bit pricey at >$6K new and neither sounds like an all tube amp...

catastrofe · « **Reply #16 on:** 7 May 2010, 06:02 pm »

Thanks Shane.

95DB is close to peak. . .normal levels are low to mid 80s. The room has 8' ceilings and is pretty much a rectangle with the entry at right rear.

Speakers will be (haven't even settled on VSAs yet but am leaning that way) on the short wall, and since this is a dedicated room I can sit wherever I need to.

I'm interested in trying tubes with whatever I purchase, so I don't want something that's completely tube unfriendly or that requires a fortune in amplification to reach its potential.

ceedee · « **Reply #17 on:** 7 May 2010, 11:00 pm »

Well,

This is a nice discussion about the tubes to fitt the VSA's.

Tubes are not the easy part of amplification, but they are moving emotional us at most.
They are very individual performing as we can see and hear here.
Single ended designs are the closest to reality as many of us discovered already.
It depends of speaker sensitivity, roomsize and roomacoustics what type of Tube amplifier you can use at best. Remember one basic rule; The more you invest the more music you get, but beware, 'less is more often, so you will be satisfied at most after all'.

You can enjoy music very subtil from a 2A3 tube.

Just discover the one which fitts at best in your situation.

Good luck

Cor

It is just a matter of sence and tast which will fitt at best.

mikel51 · « **Reply #18 on:** 8 May 2010, 01:01 am »

I have VR5 anniversaries. Originally, I was powering them with a BAT VK75SE (75 w/ch) tube amp, and I was very very happy. I switched to a modwright solid state amp (150w/ch). I felt like the solid state amp gave much punchier bass and tighter control....overall superior to the VK75SE. I still haven't tried biamping with the tubes on top and the SS on bottom--but for a single amp, I have to say that the SS Modwright amp has won me over from being a tubeophile.

satfrat · « **Reply #19 on:** 8 May 2010, 02:04 am »

Quote from: mikel51 on 8 May 2010, 01:01 am

I have VR5 anniversaries. Originally, I was powering them with a BAT VK75SE (75 w/ch) tube amp, and I was very very happy. I switched to a modwright solid state amp (150w/ch). I felt like the solid state amp gave much punchier bass and tighter control....overall superior to the VK75SE. I still haven't tried biamping with the tubes on top and the SS on bottom--but for a single amp, I have to say that the SS Modwright amp has won me over from being a tubeophile.

What have you paired with the Modwright? Thanks.

Cheers,
Robin