Tubes v. SS: can you mix and match?

OK, I'll put my unqualified neck on the chopping block...

Webnick: It's the ratios, not the absolute values involved, that matter most. Convention says that there should be a factor of at least 10X between the output impedance of the soucre component (the lower of the two) and the input impedance of the load in order to minimize LF frequency response roll-off (keep in mind that in actuallity, these impedances will vary with frequency, which is usually not specified). Again, the vast majority of preamp/amp combo's will satisfy this criteria. (The other thing that should be watched for if one is using a tube preamp having a highish output impedance, say more than a few hundred ohms, is to avoid long runs of highish-capacitance interconnect, the combination of which can cause premature HF roll-off.)

Philojet: Simplistically speaking, the differences between tubes and transistors that people talk about as far as distortion spectra go has a lot to do with the way they behave when driven into or near clipping (tubes behave more 'nicely', meaning higher overall levels of THD can be less objectionable with tubes). Below clipping, the main differences between distortion spectra have as much to with circuit design as the type of active device(s) used, although tubes will usually display higher overall distortion and noise levels. Simpler tube designs (triodes) are usually considered to display 'nicer' distortion properties than the more powerful tetrodes and pentodes, and a similar characterization is often applied to FET's as compared with bipolar transistors.

As for the distortion spectra themselves, low-order products (mostly the 2nd and 3rd harmonics) are considered less undesirable ('nicer') than higher-order harmonics, a smoothly descending harmonic series (from low-order to high-order) is considered preferable to an unevenly descending/ascending series, and even harmonics tend to be surpressed by typical push/pull amplification circuits (yielding a harmonic series that emphasizes the odd-order products, which by definition are higher-order than the even-order products, and results in an uneven roll-off of the harmonic series). This description ignores a lot of other considerations and types of distortions, including the questions of distortion levels vs. distortion qualities vs. other considerations (such as higher power capability) that may come into play as design trade-offs. (EE's forgive me...)

Wow, that was a mouthful Zaikesman. I didn't understand all of that, I'm sure. Hmm . . . I'm a little long of tooth, now, but I listen to rock a lot, yet enjoy classical on occassion. The speakers are currently Energy A5+2s, but I'm searching for Energy Veritas 2.3s. I want to bail on my faithful SS Adcom 500II preamp and 545II amp, and try a SS preamp/tube amp scenario. No phono here; simple line staging. So passive SS preamp coupled to a tube amp capable of 50 watts and up should do it. I'm looking for a more musical, warmer sound in my Blue Oyster Cult to U2 rock; my reggae's bass will take care of itself. Any thoughts?

Oh, and I'm prety sure my interconnect action is fine. (.5 meter Audioquests)

Webnick, are you sure you meant to say "passive" preamp, not linestage? The two are different (though not mutually exclusive) things. You probably know this, but "linestage" just means there's no phono pre-preamplification included. "Passive" means the inputs and outputs are not actively impedance-buffered and the 'preamp' offers no gain, just attenuation. Going passive *could* offer a theoretical advantage in ultimate transparency under ideal conditions, but there's the rub - it can be very condition-sensitive. I'm guessing that for a relatively non-tweaky audiophile and bass-enthusiast like you seem to be, an active linestage preamp might be the safer bet, especially if you listen at a wide range of volumes.

(My presumptive description of you as a listener and audiophile - if correct - could also point towards SS power amplification over tubes, which generally won't give quite the bass or carefree operation that SS can. This is why many audiophiles who want to incorporate some tubes go the tubed preamp route, but that's another kettle of fish, and as a tube-lover myself I don't want to discourage tubed experimentation. In any case though, you should be able to improve greatly on the Adcom stack, whether you go all-tubed, all-SS, or a combination of the two.)

For your proposed combination of SS preamplification and tubed power amplification, I've found this can work very well, provided of course the gear is up to snuff. In particular, forgoing tubes in the preamp can eliminate some potential hassles with tube noise and finding decent tubes, while I feel that a tubed power amp is the main contributor to providing the greatest traditional strengths of tubes (as well as some weaknesses, but in areas I don't value as highly; I should note that this assessment is probably a minority view). Impedance concerns won't be a factor here: SS preamps (active ones, that is) have low output impedances and tube amps have high input impedances, so the minimum 10X ratio differential rule of thumb will be handily exceeded and no roll-offs will occur. Your options are pretty wide-open, but the way I'd approach it personally would be to get your speakers first, then find an amp that works well with them and your room and tastes, and save the preamp for the crowning touch (well, relatively speaking...next you'll start itching about your source, cables, power... :-)

I'll throw my two cents in the mix, I have a Jolida 1501RC, and have had everything else (SS), well, not everything else (would like to try Pass), but with my Triangles, my current system, is the best I have ever had in 20 years of this obsession, and I am truly pleased..

Hey, Zaikesman. Thanks for your input. Let me address your insights in the order presented.

I thought passive meant 'no tone controls.' Active meant otherwise. My bad. I'm just looking for the cleanest warm sound I can get.

I'm not really a bass enthusiast (even if I seem to be), but rather one who likes sharply defined bass (I don't like it loud, just accurate). So I don't need 'punch' for my music.

So you like the tube amp route? After filing my last post to this thread, I second guessed myself and began to wonder if a tube preamp/ss amp might be a better route. Listeners seem to be dumping a lot of ss amps on the market right now (for example, I've noticed a lot of Adcom 565 monoblocks on the market for relatively cheap). Conversely, seems that the new tube amps on the market in my price range have very low power ratings and the ones that specify the requisite power are older. And as related side questions, do you leave your tube amp on all the time? And is it a relatively new feature that some preamps and have have a power-on standby circuit?

Tunes4me: have you replaced the stock tubes in your Jolida? What did you give for it, if you don't mind me asking, and what did you have before it?

Thanks folks.