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

I am not a power tube guru so will defer to others for details of tube maintenance.

I think it safe to say power tubes tend to be the most shot lived and must be replaced periodically.

I do not believe one tube going bad requires others be replaced in general, but finding the bad or lesser performing tubes can be a challenge without the right equipment and know how and desire. That is always the key.

Personally, I am used to dead quiet background noise and maintaining this with tubes just n the pre-amp can be a challenge a times.

Also, replacing tubes, particularly larger power tubes, is not an inexpensive endeavor these days like it once was in their heyday.

Thanks again guys. I am understanding the graphs much better now.

My question now is concerning both of your comments that the impedance and phase shift graphs or specs I choose as examples are maybe not "tube gear friendly speakers". I understand what you are saying about only using the measurements and numbers as guidance and not the end-all answer, but if you see things in the graphs or specs that specifically lead you to believe this, I'm interested in what it is. In at least 2 of those 3 examples, the reviewer actually commented the the speaker would be an easy load to drive. So if there are things that are not tube-friendly, I'd like to know more about it.

Larryi- Thanks for the mention of the Prima Luna. That looks like another nice piece of equipment. And it also has an HT bypass that looks like it would give me the same option of using my SS preamp with just the tube amp in the circuitry. The only concern is for roughly the same price point the Cayin A100T has alsot double the power, uses similar tubes (but more of them) and had many of the same functions (although the Prima Luna has an auto-biasing) function that the Cayin does not). I was looking at the Ayon earlier this week, and it looks excellent too. There dont seem to be many reviews online though.

Mapman- Could you also offer a little bit of info about tube maintenance. It is one thing I have not considered at all yet. Approximately how often will the power amp tubes need replacing (roughly speaking)? What is an approximate cost for similar tubes? If one tube goes out, do thay all need to be replaced? Thanks again.

Agree with larryi in general.

I would not assume any of those are "tube friendly".

That's not to say they might not sound perfectly good to you running off a tube amp.

The thing is that at least on paper, which as said is only an indicator, I would expect tonal colorations at certain frequencies and possibly challenges with dynamics and loudness as well with the less efficient models.

The end results may still sound very nice or even quite good, but I would be willing to bet not optimal and that a better matching for better balance, dynamics and ability to go loud is possible at the same price poit.

You might want to start a thread to ask specifically about user experience with Vandersteen speakers and tube amps. I am not very familiar with that combo so I cannot comment. I would expect challenges with dynamics and loudness and perhaps some coloration due to impedance related issues however off the cuff based on specs. I think Vandys and SS are a common pairing and I would personally probably lean that way.

Also keep in mind that the down side off tubes is that power amps in particular require some maintenance of the tubes over time. Poorly performing tubes can be a pain in the but, especially when there are a lot of them. I like the sound of the half dozxen or so tubes I use in my pre-amp and DAC, but even this results in time spent making sure things are in good working order that I would not have to deal with if all SS.

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.

Larryi and Mapman-

Thanks for that info. More things slowly starting to make sense here. I'd like to go over a couple of specific examples if possible to explain further.

I should just start with my current speakers - the Vandersteen 2Ce. Specifications pulled from the manufacturers website (http://www.vandersteen.com/2cesigii_specifications.pdf) show the following:

IMPEDANCE: 7 ohms nominal 4 ohms minimum.
SENSITIVITY: 86dB with 2.83 volts of pink noise input at 1
meter on axis.
RECOMMENDED AMPLIFICATION: 40 to 160 watts per channel into 8 ohms.
FREQUENCY RESPONSE:
29Hz to 29kHz 3dB
32Hz to 21kHz 1.5dB
By FFT step function.
DISPERSION: 29Hz to 16kHz 3dB 30 degrees off axis.

The first page of the Stereophile measurements (http://stereophile.com/content/vandersteen-audio-2ce-loudspeaker-sidebar-3-measurements) show the graph I believe you are referring to. I cant say I understand everything completely here. But I think the set of curves that is generally lower might be the impedance since it tends to stick around 6 or 7 and then falls to around 4. Both sets of curves fluctuate wildly at the lowest frequencies, and then stabilize somewhat before gradually drifting up (phase) or down (impedance). I hope I got that much right. But other than that I cant say much about anything that would need to be addressed in terms of the amp needed to power these. As you say, the reviewer does indicate that this would be an easy speaker to drive.

Now on to the Dali Helicon 800 since this is one of my top choices for a replacement pair. Manufacturers website (http://dali-speakers.com/display_content.php/USA/speakers.html/179/1061) indicates the following:

Frequency range (+/- 3dB) [Hz]: 31 - 27,000
Sensitivity (2,83 V/1 m) [dB]: 89.5
Nominal impedance [ohms]: 4
Maximum SPL [dB]: 113
Recommended amplifier power [W]: 50 - 400

I unfortunately cant find the Helicon 800 impedance graphs. But just to use the Dali Helicon 400 review from Stereophile instead (http://stereophile.com/content/dali-helicon-400-mk2-loudspeaker-measurements) There may or may not be much correlation between these 2. But the impedance fluctuates wildly again at the lowest frequencies and then stabilizes and drifts between 4 and 6 or so. The reviewer again says they are easy to drive. Anything else to note?

And now Monitor Audio PL300. Again from the manufacturers website (http://www.monitoraudiousa.com/products/platinum/pl300/specification):

Frequency Response: 28 Hz - 100 KHz
Sensitivity (1W@1M): 90 dB
Nominal Impedance: 4 Ohms
Maximum S.P.L(Per pair in room): 118.6 dBA
Power Handling (RMS): 300 W
Recommended Amplifier Requirements (RMS): 100 - 300 W

Again no graphs at Stereophile, but for the PL200 (http://stereophile.com/content/monitor-audio-platinum-pl200-loudspeaker-measurements) the impedance fluctuates MUCH MORE throughout the frequency range. But also with a VERY high sensitivity. I dont know how this would differ in terms of the tube amp you might want to choose?

I just want to use these examples for the sake of discussion about what sort of ratings in a tube amp you might want with my current speakers and some of my options for new ones. I can go through several other speakers on my own to see how they compare as well.

And so far, my favorite contender for an integrated tube amp is something like the Cayin A100T. Mainly because I like the option it has of using the full integrated tube amp vs using the pre-in input terminals on this component, that would allow me to use this as a stand-alone power-amp with my Parasound JC2 as the pre. And for the sake of completeness, the specs on the Cayin are as follows:

Frequency response: 10Hz - 65kHz
Total harmonic distortion (THD): 1% (1kHz)
Signal-to-noise ratio: 89dB
Input Impedance: > 100 Kohm (RCA)
Vacuum tube: KT88 × 8, 12AU7 × 2, 6CG7 × 2, 12AX7 × 1
Input Terminals: Aux, Tuner, CD, pre-in
Circiut: Class AB PP
Sensitivity: 480mV, 900mV (pre in)
Output Impedance: 4 Ohm, 8 Ohm
Power Output: 50w Triode - 100w Ultralinear
Consumption: 280 W

I know this is a lot of reading. Thanks for following along and helping me out here. :)

Tube power amp is "tubiest". You have to make sure your speakers are tube friendly for this to work optimally though.

I use a tube pre-amp. That introduced a healthy dose of positive tube attributes without sounding overtly "tubey". That is good because I want my music to sound natural, whatever that means, not like the technology used. I'm sure different tube pre-amps will sound significantly different from each other and not all present the same results, especially if compared by swapping into the same system.

If you use a tube pre-amp, impedance matching to an appropriate power amp is important to optimize results, especially if a SS power amp is used.

I also have and use both SS and tube DACs. The tube DAC can also provide an audible dose of tube like sound. It can vary to quite SS like to distinctly "tubey" depending on the specific tube used and teh rest of the system, so tube rolling can be done to tweak the sound significantly in some cases.

I've used different tube makes in the pre-amp and have heard little difference in the sound there to-date from one type to another, other than background noise perhaps which can vary greatly from tube to tube, depending on health and quality.

For a tube integrated, again the main thing is to make sure the speakers are tube friendly and that the amp has enough power to truly drive them well.

Also, expect with a tube amp that is well matched to speakers that less power may suffice to deliver good sound at higher volumes than with SS amps. The reason for this is that tube amps tend towards soft clipping while SS amps tend towards hard clipping.

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.

I should also have said that every 3 db variance in a speaker's efficiency results in either a halving or doubling of the power required to maintain the same volume level.

There are many members who can better answer your question, and I hope they will. That being said, you would like your tube amplifier to see as flat an impedance curve as possible, preferably remaining above 6 ohms and definitely not dipping below 4 ohms. Keeping your efficiency above 90 hz or more, depending on your amp, will also help. These are very general guidelines.

Ok. Then what is considered a 'benign' impedance? Also, are there any other general rules I should be aware of? What about the sensitivity of the speakers vs the power of the tube amplifier?

I know there wont be any 'absolute' rules. But how about some places to start for someone that really doesnt know much about it.

"could someone explain in a bit more simplistic terms what I need to look for in order for it to match with the JC2 preamp and whatever speakers I eventually choose?"

That's a sensible question. Unfortunately, it just doesn't work that way. Trying to match a tube amplifier with whatever speaker you eventually choose is impractical at best. Speakers range widely in their compatibility with tubes. Above all else, try to narrow your choice of speakers to those offering a benign impedance. You can save a bundle on your tube amplifier by doing so.

Agree 100% with The Doctor and the gentleman who introduced us, Sufentanil.

I don't care where you put tubes in the system, in how many places, or how many tubes you have, you won't get that tube sound unless and until you have tubes in the power amplifier section.

Wow! Thanks everyone for the comments, and it is obvious to me that I have lots to learn! Some of what you are saying I understand, some things I am not entirely clear on.

Looks like opinions pretty much cover all the options. I suspected as much really, but it is still somewhat overwhelming. However, it does seem that there is more of a preference for tubes in the power amp for the fullest 'effect'.

I hadn't thought much about tubes in the source components, DACs, or 'buffers'. I'm not convinced I want to go that route yet. But it is early on still and things may change.

Honestly, my idea of tubes in the preamp was driven mainly by it's perceived simplicity in connections. Seems like I could simply add a tube preamp to the system and connect it to my JC2 preamp via the bypass input, which would send the signal passed the JC2 untouched directly to the amp. I wouldnt need to switch around any speaker cables since I would have only the single SS amp. Any sources I wanted to hear via tubes could be connected to the tube preamp, and any sources I wanted to hear via SS could be connected to the JC2. However, in practice, I suspect I would still be switching the source cables back and forth as I would probably experiment with any single source with both preamps.

If I go the route of the tube amp instead, I am now thinking about components such as the Cayin integrated amps (A88T, A100T) which could be used as a standalone all-tube preamp/amp, while at the same time it is able to be used solely as a power amp using the preamp inputs it has that bypass it's preamp section. So I would have an all-tube integrated, with an option to be used as a tube power amp only. Is this a norm for tube integrated amps? Are there others like this?

So I have to ask a few more questions about the method of connection if I use a tube amp. The JC2 preamp has 4 pairs of outputs (balanced, unbalanced, etc) that are all active simultaneously. So could I connect the JC2 out to the SS amp via one output and to the tube (integrated) power amp via another output? I would have to switch speaker connections between the 2 amps dependent on which I wanted to use? How would this work out?

Yes, I deliberately left out the part about the speakers, although I am aware that it is a very important part of the equation. The reason for this is that I plan to upgrade speakers soon. Right now, I am using 20+ year old Vandersteen 2Ce speakers. And I am still unsure of which speakers I will be getting. I'm not sure whether to even bring it up here as I dont want this to turn into a discussion of speakers. But I realize it is important, so some of the contenders for new speakers would be: Dali Helicon 800, Monitor Audio PL300, Focal 1037Be, B&W 803D, Vandersteen Quatros or Model 5.

If I go the route of the tube amp, could someone explain in a bit more simplistic terms what I need to look for in order for it to match with the JC2 preamp and whatever speakers I eventually choose?

To get the benefit of tubes, it is probably best in the amp.

I agree completely with Charles1dad, Mechans and all the rest who are advising a tube amplifier if you want to experience tubes. While upstream tubes will influence the sound of your system, they will not give your system a tube sound. In other words: tube source + tube pre + SS amp = SS sound, IMO.

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.

Mechans,
Very well said.

I know that for me there was no contest. The tube power amp provided the tube magic . I had tried the tube front end solutions but none of them did what the tube power amps did. Not a tube preamp, nor a tubed CD, player could came close to the effect that a tube power amp had. I understand that the real purpose of a tube buffer is to improve impedance matching and not to introduce a tube "signature" on the sonic.
Except for Micheal/Sufentenil, I am in that minority opinion but I am emphatic about that position. I am inviting your disapproval but I think anyone who has actually tried a tube power amp instead of just noting that their tube preamp made some difference would immediately realize that the tube power amp is far and away the most important factor in achieving the tube difference.
If the OP really wants to get the exaggerated droopy sluggish rolled off tubeyness typical of the unrefurbished golden age HI FI tube amps, then all he need do is buy one- for relatively little I might add. That sound is still incorrectly held by many as being the essential benefit of using tubes. It is not. The modern tube amp does not limit top end but conversely "sparkles" as my friend Trelja would say. The reason it appears to sound smoother is that it does not suffer the edgy, hashy, or gritty distortion which is more typical of SS. I am told the SS distortion is odd order whereas the tube distortion which while greater, is even order and percieved as pleasant. The real benefit however the incredible dimensionality that modern tube power amps yield, it is really 3D magic.
I agree that the tube amp bass can be looser and that low impedance highly reactive loads work well with every tube amp. Some will not be a good match with every speaker. However there are enough good speaker manufacturers aware of the popularity of tube amps that offer compatible products.
End of rant.

What Tgrisham said.
If you have speakers that would do well with tubes, I would recommend a tube amplifier. IMO, this is where more of the 'tube sound' comes from, but by no means is it that cut and dry.
If your speakers are designed for SS then I would recommend a tube preamplifier.

The question asked by the OP was which method would provide more of the tube sound/experience. In my experience the tube power amp will have the greater impact of imparting tube character given the critical mating with the choosen speakers. I`ve found that a tube preamp tends to be more chameleon like within a system unless it has overt sonic colorations(which the better ones don`t)

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.

Hello Nuck, I can only speak to my system and my tastes in music and all of the above comments have merit. I have a pair of Parasound JC-1s fed by a Herron Audio VTSP-3A tube preamp and a Herron Audio VTPH-2 tube phono stage and the synergy between the preamp and JC-1s is excellent. I have always preferred a tube pre in front of a SS amp. Just my tastes and opinion.
Violin

Getting a tube pre-amp is almost independent of the speakers but a tube amp is very dependent on the speakers. Which speakers will you be using? Which tube amp you get will depend on the efficiency and impedance characteristics of the speakers. The pre-amp on the other hand simply has to match the input impedance of the amp, a much easier match to make. I also like the idea of the Eastern Electric Tube DAC, which I own. I also own a Modwright tube pre-amp. The EE is a great way to get into tubes for digital sources. The other decisions about a pre-amp are about features-which tubes, HT bypass, number of sources, remote, etc. The types of tubes you choose will give you more or less "tubiness". The Modwright is not very "tubey", and that relates to the type of tubes it uses. I think you will enjoy a tubed pre-amp for starters. If you really like it you can then experience a tube amp. I agree with all of the opinions above, they all have merit. Buy used and try things out first. It will take the sting out of buying-selling something that doesn't work out.

Pre-Amp tubes are alot cheaper and last longer

Preamp.

Another solution might be to find one of the tube buffers that were sold for CD players (Musical Fidelity X-10) and try that. They still come up used here from time to time and I'm sure that somebody is still making new ones (not the X-10). This is probably the least expensive way to try out tubes. If you have a processor loop, you could even try it there to "add tubes" to all of your source components.

What about getting the Eastern Electric Minimax Tube DAC? You'll get a great flavor with one tube thrown into the mix. $770 brand new delivered to your door. The EE dac exceeded the quality of another dac that I owned at more than triple the price.

I feel I might be in the minority, but I think that you generally get more of the benefit of tubes by having them in the amp section, rather than the preamp section. That said, having both tube preamp and amp (or an all-tube integrated) might be optimal.

But to start, I would go with a tube amp. Just make sure the tube amp will mate well with your speakers.

Michael