Question about different tubes


I have a BAT VK30 tube preamp and a VK200 SS amp. The preamp has 6-6922 tubes and presently has upgraded tubes from upscale audio that say -Russian mill gray plate. The original tubes from BAT were Sovtek 6922's. I am driving a pair of Martin Logan SL3's, and the midrange is a little lacking.

My previous gear was Parasound, and the SL3's were so bright it could make your ears bleed!! From prior recommendations on Audiogon, I picked up the BAT equipment and the SL3's are so warm, its unbelievable. The midrange now however, is a pushed back or a little lacking, if you can understand what I'm explaining.

My question is: will a tube change to the original Sovteks or another tube improve my situation? or are there any other recommendations.

I am using a Nordost red dawn xlr between the amp & pre. Speaker cables are Innersound, coaxial biwire which consists of 2 separate runs to each speaker.

I was also wondering if the BAT amp rated at 100wpc @ 8 ohms / 200 wpc @ 4 ohms, and capable of driving to 1 ohm, is enough power for the 4 ohm Martin Logans. Before, I had two Parasound amps in a horizontal biwire doing 400 wpc.

sfrounds

Showing 2 responses by rayhall

You might try some NOS Mullard 6922's. They tend to push the midrange forward, but since I don't know your preamp circuit, I can only guess as to how they will sound in your unit. They may also brighter than the tube you are using now, so you might not get exactly what you are looking for.
Century,

Please don't assume that because you are having trouble with one tube preamp, that this means that all tube preamps will have the same problem. This is definitely not true. My experience is that there are really some top SS preamps as well as tube, and it is no longer correct to classify all tube products as having a "tube sound" or solid state products which have a "solid state sound". In fact, there are some of either stripe which come quite close to having no sound at all (neutral).

What your reputable friend said about tube gear is probably more appropriately said about tube power amps rather than preamps. It is true that tube power amps cannot supply the current to drive speakers particularly in the bass and at the high SPL's in the same way that solid state can. Sometimes this 'deficiency' will manifest itself as a "flabby" or uncontrolled bass. Additionally, a good many but not all tube power amps will sound rolled off in the extreme high frequencies compared to a good solid state amp. If you are am audiophile who prefers tube amps over solid state, chances are you are willing to give up some bass punch and/or control as well as maybe some high frequency extension and detail for the glorious midrange bloom which is available from tubes. Sometimes, the additional high frequency information that we hear with less than very high quality solid state is actually due to low level distortion products that we hear falsely as better high frequency extension. Tube amps tend to clip in a way which is much less unpleasant to the ear than solid state.

I have never really liked any BAT products (particularly preamps) which I have auditioned. I have generally found them to sound kind of flat and to lack dynamics. They have kind of always left me feeling "ho-hum" and that I don't know what all the fuss was about them.

That said, I wouldn't sell the preamp since you already own it before exploring whether through careful tuning and matching you can alleviate the problem. Perhaps with some good matching, you can bring out the beauty (hidden?) in these products. If I were you, I would start with the interconnects, as was suggested by Findoc. This is a more ideal place to make such a correction since the interconnect's effect on the sound is normally more dramatic than the tube. Acoustic Zen Matrix Reference will definitely push out the midrange at the expense of some deep bass and extreme highs. I don't know which Cardas he is recommending, but the Golden Cross, for example, is completely the opposite kind of cable from the AZ Matrix Reference. It is dark and not dynamic, a bad cable in my opinion and not what you are looking for anyway. Their reputation is to sound warm to dark, although some models sound more or less so. I do agree that the Nordost might not be ideal until you "understand" the balance of your system. In my mind, they tend to be bright, and to sound lean with a lack of deep bass. You might want to audition a neutral cable such as JPS Superconductor ($125-$150 for 1 meter single-ended, twice that price for balanced) first. It is an all-around first-class performer at any price and use of it will help you to get an unbiased idea of what your system truly needs. If you feel it still needs more midrange and immediacy, Acoustic Zen Matrix Reference would be a very good choice.

Once you are reasonably satisfied that the interconnects have improved the synergy, you can do some fine-tuning with the tubes. Keep in mind that the same tube can sound different in different preamps and some preamps are less affected by tube rolling than others, so weigh this in the recommendations (including mine) which you receive in this thread.

If you still can't achieve satisfaction and you are sure it is the BAT preamp that you want to replace, try auditioning some of the following SS and tube preamp products (ideally at home in your system, if possible). Additionally, some of these products are internally balanced and therefore should interface better with your BAT amp:

1. Either the Ayre K1, K3, or K1X or K3X (SS, balanced)

2. Hovland HP-100 (tube, single-ended)- most extended highs I have heard, very clear clean mids. Lacks deep bass and less than stellar dynamics.

3. CAT SL-1 (any model) (tube, single-ended) - great dynamics, bass and treble extension. Overall, the best preamp I have heard. The CAT's are also very sensitive to tube changes.

4. Lamm L-1, L-2 or LL-2 (hybrid, single-ended)

5. First Sound Presence Audio Deluxe Mk II (tube, single-ended) - great dynamics, bass extension and neutrality.

6. Pass X-1 (solid state, balanced)

7. Audible Illusions Modulus 3 or 3A (tube, single-ended)

Any of these will likely give any BAT more than it can handle. Synergy of any of these in your system is much more important than any measure of absolute quality which is way more important than engineering design. How they arrive at whatever sound quality you admire is not important and it doesn't follow that this quality couldn't be achieved using an entirely different design.

Good luck.