For tube sound, which is more important: preamp or power amp?
I have always loved the “tube sound” - warmth, midrange, soundstage. Through the years (since about 1975), I have owned many tube and solid state amps and preamps, in various combinations. Presently, I have a tube amp and a solid state preamp. But like most of you, I am thinking of making changes, again. Not to cloud the discussion, the specific brands are not important. I also listen to acoustic music, females vocals, love mini monitors, EL34s, NOS tubes, and don’t care that much about bass. So you can see that my taste fits the tube sound very well. But I have had systems that are too warm, not enough dynamics or details, and fat in the low end, too.
okay, now to the discussion. To produce the tube sound, which is more important: the preamp or the power amp? Let’s talk in general, and (if possible? May not be) not tied to one specific piece/brand/model of equipment. I know there are exceptions to any general rule. Not sure if it makes a difference to your comments, but I have no phono and am running line stage only.
As an attempt to prevent the conversation as going in a big tangent, let’s assume equality of price/quality. i.e. not comparing a $10k power amps contribution to a system to that of a $1k preamp. Let’s also assume that the amp (tube or solid state) can drive the speakers just fine, such that compatibility does not limit the decision. And ignore mono blocks versus stereo amp differences.
two follow ons: I have the perception that preamps give you more bang for the buck - meaning that it takes less money to get a great tube preamp compared to a great tube amp. Agree/disagree? And second, I have never owned a tube dac or CD player, and will assume that tubes in either of these is less critical than in a preamp or power amp. Agree/disagree?
Since getting new speakers, I am going to retract what I said earlier. I said preamp , but mainly because I have always held the preamp as the most important electronic component.
I have been experimenting with tube compliment in my amps and am struck by how revealing my speakers are of any changes made at the input and also how different output tubes sound.
They both contribute to the flavor, so careful matching is the key.....sometimes it's just trial and error and has more to do with luck than care. So YMMV
Very late to this party but an interesting read. Which is more important? I could not figure that out so I bought a Raven Integrated Reflection MK2 tube amp that right now generates around 65wpc. Having an integrated tube amp provides me everything that I want and I could not be happier with the power, performance and the sound. I also like that I am able to play with tubes. I have 4 power tubes. I have tried 6500's, Vintage GE, KT 88 and now KT 150's. You do get slightly different sound with each one. I also have 12aT7's, 12AU7's, and 6922's. I like the convenience of one component as opposed to two. It is a showcase piece and everyone who comes into my house wants to know what it is.
I agree with mofimadness. The preamp will give u the tone u want; the power amp will amplify that sound. IMO, u can't have a power amp that's too powerful. Class A bias is the way to go, if u can swing it. 600-1200 watts is good, depending on your speaker efficiency. U want something u can weld with. No clipping; good tight bass. Tube preamps👍 Some tube preamps have a bit of tube rush. They require low noise matched tubes. If you're in to quiet classical music, they may not be for u.
I have been using a Conrad Johnson PV9a pre into a Quad 306 Solid State to drive my B&W DM70’s. The speakers are a Hybrid Electrostatic that are not the easiest to drive, so I thought that this would be the best combination. In fact it sounded great and gave great pleasure.
However just recently I got hold of an Art Audio Quintet power amp. This has taken the system up to a whole new level. The soundstage has opened up and the sound is much more dynamic.
These particular power amps allow switching from Triode mode to Ultralinear plus feedback switching (.5 to 6 db I think). I now find that I prefer Triode mode and minimal feedback whatever music is being played. Is it possible that one of the reasons that Valve amps sound so good is that they tend to use much lower amounts of feedback that most transistor amps? I have noticed that the sound seems to open out as I select lower amounts of feedback.
Anyhow, I am shocked as to how well these amps drive my B&W’s even in triode mode with just 15 watts. I would not want to go back to using a transistor power amp on my main system. If I did upgrade in the future, it may be to a single ended triode, but for now I am more than happy.
Iscm, As the level of negative feedback (NFB) is increased the output impedance decreases and damping factor (DF) is increased. Depending on the speakers involved the additional NFB can be beneficial up to a certain point. Generally speaking I believe that the less NFB utilized he more natural and open the sound quality becomes so I understand your listening observations. Some speakers are intentionally designed to work very well with low and even zero NFB amplifiers.
I use a DAC, line stage and power amplifier and all 3 of them are zero NFB designs. The result is a very organic, lively and emotionally engaging sonic character. Charles
I went all tube- pre, amp, phono - more than 30 years ago, when SS amps were harsh and consequently, I had lost interest in recorded music. Solved that problem! Amps and preamps are equally important. As many above have noted, there are many ways to skin a cat. I think tube maintenance issues are exagerated. Yes you have to change them every few years, and they cost a bit. It’s trivial compared to what most here have spent on gear. We all have had to nurture some trouble shooting skills, and occasionally, soldering. No big deal. You can make an argument for ss amps based on less heat and power useage, and sometimes these can be controlling factors; I live in Houston, there are times I am not inclined to run all those tubes - but I’m not convinced that class D amps will compare. the electric bill (power and a/c costs) is a relatively minor consideration when you’ve spent tens of thousands on gear and content. Tubes are more musical. I really see no reason to use a SS pre.
Regarding tube maintainance, one can select a power amp that is not so high powered and uses output tubes such as EL34 or el86. These sound good and do not break the bank when they need replacing. Of course the amp still needs to be well designed and have good output transformers.
I am amazed just how powerful some low output valve amps can sound.
If I could only chose to have a valve pre or power I would still chose a good valve pre first with the intention to change the power to tube later.
charles1dad, I now find that even though I have Triode and feedback switching on my power amp, I nearly always keep the amp in triode mode with minimal feedback.
The maker of the amplifier said that these days most of his amps are fixed in triode mode with low feedback. He suggested that if I ever wanted to upgrade that I should try one of his single ended pure triode models. He thought that triode amps can often drive speakers better than ultra linear anyway if they have well designed output transformers.
For now, even thought I rarely use it, I still like the option the switch modes and change feedback.
Is it possible that one of the reasons that Valve amps sound so good is
that they tend to use much lower amounts of feedback that most
transistor amps? I have noticed that the sound seems to open out as I select lower amounts of feedback.
You can either run high amounts of feedback or very low amounts; in between (about 6db up to about 15db) its application can be really detrimental.
Feedback, while suppressing distortion, also adds some of its own, and the type it adds (harmonics 5th and up) is pretty audible. Even though its a very small amount, its audible because the ear uses those harmonics to sense sound pressure, so it has to have a 130db range!
Tubes (triodes in particular) are very linear so it is possible to build zero feedback tube amps much easier than it is to do so with solid state.
So, quite often, yes, this is one reason tubes can sound better than transistors.
atmasphere I am curious that you suggest that over 15db of feedback need not be detrimental. Perhaps I miss-understood.
My understanding is that one of the reasons that low feedback may be beneficial, is that the feedback is very slightly out of time with and that the human ear is extremely sensitive to this. Like all things, I am sure that the selection of feedback is a compromise, as is everything concerning the design of an amplifier right down to the quality of components and build quality.
Some things, I am sure, are just down to plain old fashion.
My understanding is that one of the reasons that low feedback may be
beneficial, is that the feedback is very slightly out of time with and
that the human ear is extremely sensitive to this. Like all things,
I am sure that the selection of feedback is a compromise, as is
everything concerning the design of an amplifier right down to the
quality of components and build quality.
Its not a timing issue so much as a matter of distortion generation (while suppressing feedback, it adds some of its own). But the ear is indeed quite sensitive to this, because the distortion generated are higher ordered harmonics and the ear uses those to sense sound pressure. Combine that with how music energy is distributed over frequencies and that's about as sensitive as it gets due to the Fletcher-Munson curve!
I prefer zero feedback, but 20 db of feedback is easier to listen to than 10 db or so. There's a sort of 'in-between' hump where a moderate amount of feedback results in audible problems that lower or larger amounts don't have.
You are correct that there is a bit of compromise with the use of feedback, and frankly most designers fail to get it right as there are more variables than the old school formulas suggest!
I have not auditioned any tube preamps, but purchased a pair of ARC Classic 120s from here last year. Prior to that I had a single Parasound HCA 2200ii and then a 2nd running them in mono. This took me to 750wpc SS with a very well respected pair of amps with all the specs for great bass and dynamics. I have 86db floor standers. The ARCs at 110 wpc outshined them in every aspect....including bass! The output level was higher, more dynamic and more detailed. The smoothness of the sound is where I think the lack of ear fatigue comes in. I'm only listening to vinyl. Fast-forward 9 months and I'm wondering about SS again so I just picked up a B&K 200.2 and it sounds fantastic. It reminds me a lot of the Parasound. I listened for a day and then reconnected the CL120s and it was the same transition as before. I think I got very lucky in my choice of tube amp for my first experience since they each have 8 6550s as output tubes. Newer amps have fewer with a higher output/tube and maybe thats why they are so strong....not real sure. I would love to compare my ARCs to another tube amp, but that's not in the plan for now. I encourage anyone who hasn't had a tube amp in their system to figure out a way to make it happen.
Avanti1960 mirrors my own findings. Tube power amp definitely makes a bigger imprint on the overall magic than a tube pre-amp. Not only that, it is much easier and less fussy for a solid state pre-amp to drive a tube power amp. Not so the other way around. Tube pre-amps, even good one with strong output, will choke if asked to drive SS amps with input impedances much lower than, say 50 kohm or so. That basically rules out half of the SS power amps out there. BTW I like all tube for classical and jazz, but for rock you gotta have that SS pre-amp in there to drive that bass.
I utilize my massively powerful 12 watts per side Firebottle amp into 99db Klipsch Heresy III speakers (which, I might add, is plenty of power for these speakers), helped along with 2 REL subs adding 250 watts to the party. I like tubes for jazz and classical, and I also like tubes for rock, mumblecore, EDM, reggae, test tones, screechy animal sounds, and Harry Shearer's podcasts. The Freya's ability to go passive or FET provides an instant "what if I bag the tubes" reference, and I have a second SS Mosfet amp hooked up to the Freya outputs for extension speakers (Concentric tweeter KEFs, and I stick those in the windows to play to my deck...works great) that I can use as a SS reference if I wish as they're in the room also (sort of hidden generally but can be pointed into the room).
BTW I like all tube for classical and jazz, but for rock you gotta have that SS pre-amp in there to drive that bass.
That's pretty subjective- I find that my tube amps can play bass better than any solid state amp on my system. I play a lot of rock too. My speakers go to 20Hz and are 16 ohms so tubes play them easily. On top of that, my amps are full power to 2Hz, so no hint of a rolloff at any frequency the speakers can play.
Preamp - it's all about the signal. The preamp feeds an output signal to the amplifier, which in turn sends it to the speakers. The amp just provides a higher voltage to drive the speakers.
If the preamp distorts the output signal, the amp can't fix that.
So true Al and This is why for quite some time I've subscribed to the "weakest link" concept in regard to audio components/signal chain. Every link along this chain is simply important. Screw up any part of this signal path and you can't make up for it elsewhere. Charles
Preamp for tubes, solid state for the power. It isn’t purest way to use tubes, but the cost of a high powered tube amp (100% amp) or a power amp is prohibitive for most buyers. I’ve always had solid state amps, but on a hunch I bought the Monoprice 50 watt hybrid and have been surprised just how much the tubes make in defining the instruments, voices, and widening the sound stage. It doesn’t hurt the output amp is clean. I do believe my next new amp will be the Rogue. It won’t break the bank, and it gets high raves for a hybrid amplifier.
tube character will sound more obvious with a tubed power amp. Selection of tube type will also dominate the effect (EL34, 6550...). On the other hand less character is more desirable.
You must have a verified phone number and physical address in order to post in the Audiogon Forums. Please return to Audiogon.com and complete this step. If you have any questions please contact Support.
