Adding tubes to SS system-Tube Preamp Amp or Int?


After reading up on tube gear, I am intrigued to try out tubes for the first time in my 2-channel system. As of right now, it is all solid state - I recently got hold of a Parasound JC2 preamp and A21 amp.

I'd like to incorporate something 'tubey' in there just to see for myself what the sound will be like. I am totally new to this, so I dont know where to begin. But I know that I only want to buy a single component for now, so...

Do you folks have an opinion on whether it would be 'better' in any way to use a tube preamp connected to the Parasound A21 amp vs a tube amp connected to the Parasound JC2 preamp? For those of you that love tubes, which method do you think would give you more of the 'tube sound'?

Another consideration - my JC2 is setup with an HT bypass, but since I am not using HT in this system yet, I am thinking it might be a neat option to find a tube preamp, send it through the JC2 bypass directly into the A21 amp. That way, there will be no needed movement of cables (connecting/disconnecting) in order to utilize both the solid state and tube components.

If those are both just bad or suboptimal choices, maybe I'll just look for an integrated tube amp? But again, I want to leave it at one component for now. Just want to start limiting my choices to one of the 3.
nnck

Showing 4 responses by larryi

Nnck,

All of the subject areas you touch on are complex, so, at best I can offer only some very general advice.

I would start with looking for speakers. By far, speakers define the basic sound of the system. Find what you like and then look for a compatible amplifier. Because of compatibility issues, certain choices of speaker will eliminate certain amplifiers as contenders, so it makes little sense to choose the amplifier first. This is particularly the case with tube amplifiers which tend to have more limited ranges of compatibility.

Speaker efficiency and impedance characteristics MAY determine what is compatible. A lower efficiency speaker will mean a greater need for power. A speaker with a low nominal impedance (e.g., a 4 ohm rated speaker) MAY mean it presents a difficult load (again a bigger issue with tube gear than solid state). But, such a single number hardly tells it all. I would suggest looking at a Stereophile magazine test report on speakers. One of the first charts shown shows how the impedance changes with frequency. Even an 8 ohm rated speaker will have certain frequencies where impedance dips well below that number. Not only is how low that points important, but WHERE that dip occurs. If it occurs at around 60-150 hz (it is a bigger deal than if it occurs elsewhere because there is a lot of musical energy in that frequency range. The graph also shows another plot of "phase angle." Because of the characteristic of the load (the speaker) delivery of power and current do not go up and down in lock step so they end up being out of phase with respect to one another. A high phase angle, combined with a low impedance at a particular frequency, would make for a "difficult" load. I know this sounds very complex, but, at least Stereophile technical reports do give a subjective analysis of how difficult a load is a particular speaker under test.

For all of the technical arguments, ultimately, it does come down to personal trial. Whether or not you will "need" high power or a solid state amp to handle a difficult load will depend on personal practice (how loud you play the system, how big is the listening room) and personal priorities (compared to comparably priced solid state amps, tube amps rarely do bass with as much impact or tightness, but whether that is important is purely subjective).

When trying out different amps with the speakers that you like, don't overlook combinations that may seem incompatible. A lot of people, including dealers, overestimate the amount of power that is needed for a particular speaker. Often, a lower powered amp can deliver adequate power while also delivering qualities that a higher powered amp cannot. I know a local dealer that sells mostly low-powered tube gear that has several high-powered solid state amps to use for comparisons. Often, customers comment that the low-powered tube amp sound more powerful than the solid state amps. That is not really the case, but, what the listener is hearing is how good the sound can be at LOWER volumes when the amp sounds good. I know that my system is moving in the right direction when I find myself listening at lower, not higher volume.

I generally don't like the sound of most higher-powered tube amps (more than about 60 watts or so). If I truly needed that kind of power I would concentrate my search on solid state amps. The one notable exception is OTL (output transformerless) design. I like the sound of OTL amps for both high and lower-powered use. So, if I needed more power I would look first at OTL amps, then solid state designs (OTLs put out a lot of heat and have other operational issues that may rule them out).

I think that in most home listening rooms, and if listening levels are not too high, there are very few speakers that truly demand an amp bigger than 60 watts. In short, don't rule out lower-powered tube amps. I find that many otherwise fine audiophile-approved speakers suffer from being somewhat lifeless and dull sounding (particularly in comparison with horn and single-driver systems). To compensate, a lot of people play their systems quite loud. In that case, one may profit by not increasing power, but going with tube amplification, which tends to sound more lively at any given output. This is particularly the case with OTL amps.
NNck,

As I understand your setup, you need a tube linestage (instead of a buffer) because you need the volume control. Does the signal then get passed back and through the JC2 circuitry so that the HT passthrough is acting sort of like an external processor loop?

I think you could have some interesting fun trying different tube gear in such a loop, but, it is hard to predict the result with ANY given component and, while you might get some idea of what tube gear sounds like, the reasonable conclusions you could draw from that experience would be somewhat limited.

First, more than solid state gear, I think there is a HUGE difference between different brands/types of tube gear. My system is currently tube-based and I suppose I would be considered a tube person, but, MUCH of the high end gear I least like are tube-based. There is a truly striking difference in sound between, for example, the VTL/Audio Research/BAT sound and the sound of Audionote/Shindo/Kondo gear. There is nothing much in common between the sound of low-powered single-end triode tube amplifiers and a pushpull pentode amp using 6550 output tubes.

To add to the complication, compatibility is harder to achieve with tube gear. On paper, it is much harder to match a tube amp to a variety of speakers (power needs are harder to meet, low speaker impedance may not work well with high output impedance of many tube amps, etc.), it would seem to make sense to do what you are proposing, which is to introduce tubes at the line level. But, in my own experience, even when a tube linestage is supposedly electrically compatible with a particular solid state amp (i.e., low enough output impedance from the linestage), the actual practice is quite wildly unpredictable. So, it comes down to actually trying a combination--I would never try to predict the results. I have gotten more predictable results with solid state linestages feeding tube gear than the other way around. I am not saying tubes feeding solid state doesn't work, I am saying the results are unpredictable, and more often than not, you will not get "the best of both worlds" but something disappointing. If that happens, don't give up or draw any conclusions about tubes.

I do like your idea of at least trying tube gear in the chain. If by chance or by experimentation you hit upon a nice sounding combination that would be great. But, by no means can you then conclude you are enjoying what others consider the "tube" sound. It would be just one of many aspects of "tube" sound.

Be forewarned that it may then set you on a path to trying other tube components, and perhaps, trying different tubes in each tube component. Again, there are vast arrays of different sound that one can get by changing tubes.

At least here, it does not seem to be a minority opinion that a tube power amp is the preferred way to sample tubes. I agree with that, with the caveat that it is quite important to consider power requirement as well as output impedance match. I tend to think that most people OVER estimate how much power they really need, but still, with certain speakers, one cannot consider certain amps because of power limitations. Likewise, I think a lot of people over estimate the importance of amplifier damping factor, but, there may be certain speakers with too highly reactive impedance for use with certain amplifiers.

I am a fan of low output single-ended amps (2a3, 45 tube in particular), but, frankly, these are highly specialized amps for use with high efficiency/high impedance speakers. I've also heard, and liked some higher power single-ended triode amps using 211 and 845 tubes (Wyetech and Viva amps for example), but these tend to be expensive because of the demand placed on having very high quality output transformers and power supplies. For higher power needs, my first preference are output transformerless amps, like those made by Atmasphere (very dynamic and lively sounding).

Good luck on your search. Searching for the right tube gear is either a lot of fun or a major source of frustration-it depends on your inclination to experiment, and a lot of LUCK.
NNck,

It really isn't possible to say what works just from numbers; even looking at the published curves only gives one an inkling of what may be troublesome, but, even then, actual experience often contradicts the measured statistics. Still, to read the curves, the most important thing is the lowest point on the impedance curve (the solid line in Stereophile). At that particular frequency, look to see where the other curve lies. On the right hand vertical axis, you will see the phase angle that that point represents. If it is plus or minus 30 degrees or more, that would be a difficult combination of low impedance and high phase angle.

Several years ago, I got to help someone with Wilson WP 7 speakers. These were reported to be easy to drive, and the manufacturer claimed something like 95 db/w efficiency. In fact, the manufacturer would show them being run by an ipod feeding a really cheap amp to demonstrate the primacy of speakers in the selection process. In a really high end system, I found this speaker to actually be a "difficult" load to work with tubes. Sure, it is pretty efficient, but, it must otherwise be difficult to drive because it did not work well with a lot of tube amps, though even low-powered solid state worked well with the speaker. In the end, a Hovland (medium-powered solid state amp) was employed to drive the speaker.

I am not familiar with the particular speakers you mentioned above, but, their stats suggest that they are not tube gear friendly speakers. Even so, tube gear, even medium powered tube gear, could be used with such speakers as long as you can accept certain limitations -- cannot be played at head-banger level, might be somewhat challenged in bass response.

I have only limited experience with Cayin amps (I believe it was a KT88 model). For the money, I thought it was a very good sounding amp and I was surprised to see how well constructed the amp appears to be (neat soldering, decent parts). The Prologue amps, also from China, are another decent sounding alternative that is not a bank breaker. If you can spring for more, I think that the integrated amps from Ayon sound decent.

For something completely different look at OTL amps from Atmasphere or Joule. These are power amps, not integrated amps, but, they offer speed and immediacy that will make you sit up in your chair like no other kind of amps. These are sort of the antithesis of what some people think of as tube sound (not as warm, lush and relaxed sounding), but everyone should experience OTLs.