Valve amplifiers

Wharfedale EVO4.1 Bookshelf Speakers

thevortex

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I have been thinking about going for valve amplifiers and building a music-only system. There are a few questions I have though...

Could people share some more information about single driver Fostrex speakers? Why should one choose them instead of other conventional speakers when it comes to valve amplifiers? Are there factors other than the high sensitivity? Where would you source them from? A mention of the cost outlay if possible? And if you were to pair these with a valve amplifier which one would you choose? SET or push/pull designs? Lastly the numbers that we see against each valve like 2A3, EL84 etc - what are they and what kind of difference do they make?

Too many questions I know...but I am sure you guys can point me in the right direction.
 

thevortex

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A small note before people pitch in. I have a NAD C372 powering EPOS M12.2 speakers powered by a HTPC with an ASUS Xonar D2X card. The objective is to take the system to the next level as far as music is concerned. And I am looking at valves to see if they fit the bill.
 

stevieboy

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hi vortex,

single drivers have paper cones generally or cones that respond very fast to signals. they also do not have a traditional crossover. the faster response means that even low level signals are reproduced very well and clearly and the no crossover means less of the signal is being lost as heat. no crossover also means the signal is not being split up hence is more 'whole'. the ideal partner is low power SET amps because these amps use one valve per channel instead of two like in a push pull amp. using one valve means an entire channel is being reproduced 'whole' instead of split and amplified by two valves and then recombined elsewhere in the amp. SETs also have fewer components and cleaner signal paths.

the negatives to single drivers is that extremes are not reproduced as well as multi drivers. also cone resonances exist unlike well/highly damped cones. thats the tradeoff for the superb coherency and palpability of a single driver sound.

viren makes two single driver speakers you can check with him about prices. mid 20s and 30s price points.

i'd choose a SET amp cos its far more involving than a push pull. more dynamic also.

2A3, el84 are valve types. each valve has a characteristic sound. there are direct heated triodes (used in SET amps) and pentodes (used in push pull amps). this is an oversimplification and is just a starting point for you to research online :)

if you're looking for a valve amp research the sound qualities of the valve type eg 2A3 or 300B and see if what reviewers are saying sounds like something you'd like. then see who makes the amp!

i'd recommend a SET from viren. he makes a 2A3 SET amp of about 3 watts and a 6C33C SET amp of about 15 watts. i've got the 2A3 SET and use the 45 tube instead of the 2A3 tube cos i like the sound of the 45 better.

regards
 

Asit

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Hi Vortex,

I cannot answer all your questions because of my lack of knowledge, but I can try to answer some of them.

I cannot give you the technical reasons, but the observation is that valve amplifiers are generally available as significantly less powerful (in terms of watts per channel) than SS amps. I think it is possible to build more powerful valve amps also, but it would be very expensive and also very heavy (heavy because unlike SS amps it has one transformer per channel at the output stage). A lot of the valve amp quality depends on the quality of these transformers, I am given to understand.

Now regarding SET and push-pull, both are class A and gets hot during operation, but a good implementation should be built to withstand that. But the user should ensure proper ventillation.

SET amps are typically a few Watts per channel (like 3 wpc for Viren's 2A3 that Stevie and Rajiv have, but Viren has another SET at 15 wpc that Nirmalprim has, and Mahiruha is about to get). The push-pull ones can be a few tens of watts (for example, my Leben CS300 is a class A push-pull design with 12wpc, arj's is CS600 at about 30 wpc).

My understanding is the full range speakers have high sensitivity. Can somebody explain the correlation?

Because the SET amps are low in wattage, one definitely needs high sensitivity speakers to get enough db at the listening position. Push-pull amps with their more wattage can drive normal speakers especially if the power vs frequency curve of the amp matches the impedance vs frequency curve of the speaker well. I think Nirmalprim has 90 db Cantons and He is reportedly having Viren's other SET amp (at 15wpc) driving them. For details, see the relevant pages of my amp thread. My little Leben CS300 has driven comfortably many speakers even around 85 db. Again, check my amp thread. If you cannot find the relevant posts, I'll help you.

Now about the sound. People say SET is very special, even better in principle than push-pull. I have never heard a SET (once Mahiruha gets his, I am going to invite myself, and am going to listen). But my Leben is simply wonderful, actually much more than I expected.

From my readings, my amp thread and experiences with my Leben, I am inclined to tell you that there may perhaps not be a typical tube sound or a SS sound. It probably depends on the proper implementation. You would not believe in the dynamic range my Leben has. Highs are very detailed. The usual complaint about valve amps is the lows. Although Cranky is still not completely pleased but that is more due to my speaker positioning, the bass is a lot more present and well defined than most SS at the price point.

So A well implemented tube amp can have in principle everything that a good SS amp can have, and all that surprisingly at a much lower wattage. In addition it can have wonderful tonality, and music to me is mostly tones and microdynamics. In addition, huge soundstage, seperation etc can all be there. Smoothness also can be incredible as can a very good SS amp have.

You have a decent SS amp in Nad C372. I would say if you have to have a valve amp, you have to do a good job of it, otherwise you may not be satisfied. I do not mean high price. Viren's amps for example are very very popular and he has reasonable prices, but I have never heard them and so cannot comment. But barring that to improve on your existing amp, you have to look at very good tube brands.

Regards.

PS: After my post I find that Stevie has also posted, and has some explanations of high sensitivity of full range speakers.
 

gobble

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Someone please post a brief comment on the sound characteristics of SET vs a Push-Pull - if there can be a generalization at all ? ... :)

Vortex, please listen and find something you like before you dump that great SS amp for a valve. I like the slam of a SS for sure. Maybe a tube pre might give you enough to be content with .. barring of course the perceived lack of coherency with two-way or three...

Regards
 

Asit

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Someone please post a brief comment on the sound characteristics of SET vs a Push-Pull - if there can be a generalization at all ? ... :)

Vortex, please listen and find something you like before you dump that great SS amp for a valve. I like the slam of a SS for sure. Maybe a tube pre might give you enough to be content with .. barring of course the perceived lack of coherency with two-way or three...

Regards

I would not think one can make generalizations. A push pull amp can sound 'better' than many SET amps. And I can bet my bottom dollar that my push-pull Leben would beat many badly implemented or even average SET amps. It depends on implementation. Also, it is true that people having valve amps usually do tube-rolling, i.e., change to different tubes for their different sound signatures. But again, it's not as simple as that. For a given amp, this method makes sense. But I do not think its prudent to buy an amp because it has a particular valve. The whole implementation has to matter, and I think it does in a major way.

I would rather not go into a SS vs valve discussion. In the usual implementations up to a budget, there will be strengths and weaknesses on both fronts. I would rather go for an amp (irrespective of tube or SS) that is GOOD.

One thing I forgot to mention in my last post. Many people have the notion that tube amps may have a bloated or colored sound that is somehow more involving. Actually in my Leben, the sound is crystal clear, if there is such a thing with very very little noise floor. The musical involvement in my opinion comes from tonality and microdynamics, and a good amp will give you those.

I agree with gobble on his suggestions ( I also voiced similar concerns in my previous mail) except that a good valve amp can also give you the slam, really.

Regards.
 

thevortex

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Thank you Stevieboy and Asit for the lovely responses. Very interesting and thought provoking. And thanks Gobble for chipping in as well.

Stevieboy - I did look very closely at Viren's website. Tonal clarity, musical involvement, micro-dynamics (insofar as I understand them) and intense detailing are what I enjoy. And my hope is that valves can get these factors to a higher level than what I am enjoying right now. My concern really is whether the Lyrita amps can take the music to a higher level than my NAD C372. I will be researching the various triode numbers you gave - thank you.

Asit - It appears we both enjoy many of the same things in our music. My concern is exactly as you put it. I want a valve for those typical characteristics that are being spoken of while at the same time I want for the experience to transcend what is available to me right now. All this at a reasonable price point to boot.

Are there any specific valve amplifiers that you would recommend given that I love the NAD C372 sound? I must warn you though that I have not enjoyed the NAD BEE amplifiers that I have heard. The C372 though has been massively impressive and soulful.

Gobble - I am not looking at throwing away the NAD or the EPOS speakers. Just looking to see if the entire music experience can be improved upon with the same chain. If not then the upgrade might have to be put away. Hence the question on the possibility of valve amplifiers driving my EPOS speakers. However I wanted to learn how exactly these full range speakers are different from conventional ones.

I am aware that there are sensitivity differences, a lack of crossover and a simplicity of design that make a full range driver what it is. Can anybody put it in words as to how this might differ (in practice) from the smooth, soulful and natural sound that EPOS speakers produce. Or any other good conventional speaker produces?

Thanks again for the meaningful and detailed responses.
 

viren bakhshi

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Hi vortex,

Let's see if I can clarify a few things for you.

Did you know that the Epos M12 speakers that you have come quite close to approximating a full-range system? The mid-woofer covers the range from bass to 5 kHz, which is the critical midrange. The woofer is coupled directly to the amplifier, without an external crossover, just like a full-range is. That's because the woofer rolls off smoothly on its own, based on the design of the surround and spider. The catch is, that to get that smooth natural rolloff, the cone had to be designed with lossy materials (probably polypropylene) with inherent damping. Heavy weight of the cone and surround leads to a low sensitivity of 87 dB.

So, you already have been listening to a full ranger. But, what you get with a purposeful designed single driver full-ranger is full frequency capability, absolutely no crossover (because of no tweeter), much lighter cones, with subsequent high sensitivities. There is an inherent quality in high sensitivity speakers, of vastly improved dynamics, and of portraying micro detail.

That is where realism in music lies - in the micro detail. In the capturing of the rise and fall of notes, of the harmonics, and their relationship to each other. If this time and phase relationship is disturbed, a sense of artificiality comes in. There goes your involvement in the music - for if there is a turnoff, it is in the sense of it sounding artificial.

And that's where tube amplifiers shine. And single-ended tube amplifiers in particular. In the reproduction of micro detail, in vivid dynamics, in the natural relationship of the harmonics. The less you process the signal, the lower the chance of harming that relationship. It's time and phase errors. The single ended amp does not split up the signal at all. The push pull amp does, regardless of whether it's running in class A or not. The single ended amp maintains the delicacy and clarity of the signal much better. Sorry, it's here that solid-state just does not cut it!

Regards,
Viren
 

thevortex

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On the subject of SET vs push/pull amplifiers I found this post on the ecoustics forum. With apologies to the original poster and with belief that since it is on the WWW it is OK to reproduce:
---------------------
Most people have assumed that a 2 to 8 watt per channel SET amp wouldnt have the balls to get out of its own way. It couldnt possibly have any real bass, but we hear the midrange is to die for.

Most people would also assume the only way to hear any dynamics from a flea powered amplifier is to use big nasty horn speakers so really what is the point?

All of these assumptions are probably a side effect of the general direction that high-end audio has taken since the 1960s. Solid state has made high power affordable for everyone so the loudspeaker industry responded by making speakers less efficient to both reduce their size and flatten their response.

Despite popular belief, you do not need horn speakers to use or enjoy a SET amplifier. You can also find many horn speaker designs that sound wonderful, better than wonderful in fact, so the question then becomes this:

What are the advantages are to using SET amps with high efficiency speakers?

To answer this, lets start with the advantages of a SET amplifier over any other type. A Single Ended Triode is the simplest circuit design there is, using the least number of parts. Typically this is a driver stage coupled to a single output device. Triodes do not require negative feedback, something found in most all push-pull circuits, solid state or tube. Negative feedback is used to lower distortion specs and in the case of solid state devices it is often the only thing keeping the transistors from exploding all over the inside of your amplifier. Feedback a problem? If you dont mind the time smear it creates and the resulting 2 dimensional sound stage, then no I guess its probably not.

Aside from the amplifiers superiority by simplicity, there is a more profound reason for using SET amplifiers. The magic predominately lies in the first watt. By magic I mean inner detail and most of the dynamics. For example, a pair of 96dB speakers playing with one watt of power against the average noise floor in your listening room (55dB) is 40 dB of dynamic range. (96 55 = 41 dB) Adding a second watt increases the dynamic range by only 3 dB. For every additional 3 dB you need to double your power. This should clearly illustrate that there is over 10 times the dynamic range in the first watt as there is in the second.

This brings us directly to loudspeakers. A typical loudspeaker today is 86 dB efficient with 1 watt. It also usually has a complex crossover that attempts to keep the frequency response and impedance flat. The crossover alone will usually dissipate a significant portion of the first watt as heat before it even reaches the drivers. To reach the same loudness level as the 96 dB speaker will with 1 watt requires over 8 watts on the 86dB speaker. If we used 2 watts on the 96 dB speaker the other would require 16 watts to keep up. If we used 4 watts on the 96 dB speaker the other would require 32 watts to keep up.

The problem here is resolution. If you cant hit a listening level with the 1st watt, youre not likely to hear whats happening in that 1st watt. For a driver to achieve a high efficiency its moving parts must be low in mass. That makes it dramatically faster or more accurate than a speaker with heavier moving parts. If you like inner detail and want to hear all of the textures and layers of a good recording you need fast, efficient and coherent speakers.

A good SET amp combined with a single full range driver with no crossover or a simple 2-way using minimal crossover parts on the tweeter only, has a purity and depth that you simply dont find in more conventional systems. It is a benchmark for coherency, and noted for its ability to create hauntingly real holographic sound stage. Bass and dynamics with this combination sound more realistic in part from the tremendous speed and in part from the coherency.

Ive consulted many people about their audio systems, and the most common complaints include dry somewhat fatiguing sound with a fairly boring soundstage followed by the realization that it simply doesnt connect you to the music emotionally like it could. Experience has taught me that by far the easiest way to get a liquid sound that becomes holographic with stunning clarity and detail, something that excites the listener, is to set him up with an SET and simple pair of efficient speakers. It also usually ends up being the least expensive solution.

The biggest conformation of this is reports from audiophiles who used to have several hundred watts and many thousands of dollars invested in show winning audio gear, but now report that even a good 2 watt SET on efficient speakers has better dynamics and weight which they find simply amazing. If youve ever observed how audiophiles rotate through audio gear during their lifetime you might also find it interesting that the ones who finally land on SET amps and good speakers seldom find anything they like better.

The bigger is better mentality that is directly connected to more expensive the better is certainly the handicap that stunts most audiophiles from discovering truly high fidelity sound. Will the guys at the audio salon laugh yes the will. Will your fellow audiophiles laugh when they hear you sold everything and got a 2-watt amplifier yes the will. Is this important to you? Only you can decide, but I would suggest it has little to do with high fidelity.

In closing, remember this It is dangerous to place amplifiers, speakers, cables etc., into neat little categories in an effort to make some sense of it all. Not all tube amps sound good. Not all solid- state amps sound bad. With the Internet audiophiles have been set free to research things in a far more unbiased way then ever before. Before the Internet there were only trade magazines, and manufactures literature to educate us all and it goes without saying fairly biased sources. Of course the Internet is full of misinformation, some intentional, some out of ignorance, but at least you can find all sides and make your own determinations.
-----------------------------
 

GeorgeO

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Bottom line is that with efficient speakers flea powered SET is possible, with others(87db, for example) PP is the way to go, since they need the power of PP. My 87 dB does not sound good when driven with 9wpc, but sound very nice with 28wpc.
 

thevortex

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Any Valve amplifier recommendation which would be better than a NAD C372? Yes I know they are chalk and cheese - but still!:)
 

thevortex

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Hi vortex,

Let's see if I can clarify a few things for you.

Did you know that the Epos M12 speakers that you have come quite close to approximating a full-range system? The mid-woofer covers the range from bass to 5 kHz, which is the critical midrange. The woofer is coupled directly to the amplifier, without an external crossover, just like a full-range is. That's because the woofer rolls off smoothly on its own, based on the design of the surround and spider. The catch is, that to get that smooth natural rolloff, the cone had to be designed with lossy materials (probably polypropylene) with inherent damping. Heavy weight of the cone and surround leads to a low sensitivity of 87 dB.

So, you already have been listening to a full ranger. But, what you get with a purposeful designed single driver full-ranger is full frequency capability, absolutely no crossover (because of no tweeter), much lighter cones, with subsequent high sensitivities. There is an inherent quality in high sensitivity speakers, of vastly improved dynamics, and of portraying micro detail.

That is where realism in music lies - in the micro detail. In the capturing of the rise and fall of notes, of the harmonics, and their relationship to each other. If this time and phase relationship is disturbed, a sense of artificiality comes in. There goes your involvement in the music - for if there is a turnoff, it is in the sense of it sounding artificial.

And that's where tube amplifiers shine. And single-ended tube amplifiers in particular. In the reproduction of micro detail, in vivid dynamics, in the natural relationship of the harmonics. The less you process the signal, the lower the chance of harming that relationship. It's time and phase errors. The single ended amp does not split up the signal at all. The push pull amp does, regardless of whether it's running in class A or not. The single ended amp maintains the delicacy and clarity of the signal much better. Sorry, it's here that solid-state just does not cut it!

Regards,
Viren

I just saw this post from you Viren. Thank you for weighing in on this. What you say makes a lot of sense. I selected my EPOS speakers after almost 6 months of auditions and after almost driving Raghu of Decibel crazy:). To his credit he was always patient and he has always pointed me gently in the right direction when I tended to dither.

One of the primary aspects behind my selection of the EPOS was their simplicity in crossover.

Having got that out of the way would there be any particular SET amp that you would recommend given my requirements?
 

viren bakhshi

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Vortex,

With the sensitivity of 87 dB of the Epos, you'll have to go with the Lyrita 6C33C SET amp (15 watts per channel), if you want to go the SET way.

A suggestion - research will only get you so far. Just go listen to any tube amplifier setup, either with a dealer, or a friend, or a fellow forum member. Listening will tell you right away if it's for you or not!

Viren
 

thevortex

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Vortex,

With the sensitivity of 87 dB of the Epos, you'll have to go with the Lyrita 6C33C SET amp (15 watts per channel), if you want to go the SET way.

A suggestion - research will only get you so far. Just go listen to any tube amplifier setup, either with a dealer, or a friend, or a fellow forum member. Listening will tell you right away if it's for you or not!

Viren

Thanks again, Viren. Any suggestions or pointers as to whether anybody in Chennai might be using that amp and whether I might be able to go have a listen there?

And yes, I do plan on listening to a tube amplifier pretty soon.
 

Asit

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Hi Vortex,

I did not see any SET vs push-pull in the write-up you dug up. Did I miss anything?

However, a very relevant and important part is the closing segment that I have quoted in the following:

In closing, remember this It is dangerous to place amplifiers, speakers, cables etc., into neat little categories in an effort to make some sense of it all. Not all tube amps sound good. Not all solid- state amps sound bad. With the Internet audiophiles have been set free to research things in a far more unbiased way then ever before. Before the Internet there were only trade magazines, and manufactures literature to educate us all and it goes without saying fairly biased sources. Of course the Internet is full of misinformation, some intentional, some out of ignorance, but at least you can find all sides and make your own determinations.
-----------------------------

I have underlined the parts which are the least controversial, easily understandable by common sense and also the most important. And these echo the sentiments I expressed before.

All I can say is I am NOT ready to be forced to accept over-simplification and accept unfair and completely subjective statements. Neither should you. You have a pair of ears and just use your musical sense to judge music and equipments, no bars for SS or tube or SET or anything else. The secret is NOT to have a SET mind :). People will have different views, but after all it's your purchase and you should be able to do it with a free mind. Only you can say what cuts it for you.

Regards.
 

thevortex

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Hi Vortex,

I did not see any SET vs push-pull in the write-up you dug up. Did I miss anything?

Asit - I ought to have marked that line up especially as that was the only line throwing light on that aspect:) Here it is from the original post:

A Single Ended Triode is the simplest circuit design there is, using the least number of parts. Typically this is a driver stage coupled to a single output device. Triodes do not require negative feedback, something found in most all push-pull circuits, solid state or tube.
However, a very relevant and important part is the closing segment that I have quoted in the following:



I have underlined the parts which are the least controversial, easily understandable by common sense and also the most important. And these echo the sentiments I expressed before.

All I can say is I am NOT ready to be forced to accept over-simplification and accept unfair and completely subjective statements. Neither should you. You have a pair of ears and just use your musical sense to judge music and equipments, no bars for SS or tube or SET or anything else. The secret is NOT to have a SET mind :). People will have different views, but after all it's your purchase and you should be able to do it with a free mind. Only you can say what cuts it for you.

Regards.

Believe me I am very happy with the sound of my NAD C372. Being a lover of classical and vocal based music, I would just like to exhaust the valve option and confirm for myself as to the aptness of the choice I have made on my audio system.

In that regard I will definitely go hear music on a Valve system before I take any further step. When it comes to my audio system I am anything but quick to make a decision as many audio dealerships here in Chennai have probably experienced:).

I would love to learn more on this list about valves and solid state amps and the perceived difference/similarities between the two. I am definitely not interested in finding out which one beats the other. Because I am a strong believer in the horses for courses policy. And I trust that with the combined expertise of the members here, we can get somewhere near that objective.

Thanks for weighing in, Asit. Your inputs are valued.
 

mahiruha

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Hello Asit,
you are most welcome to visit me when the Lyrita setup arrives. I guess it will still take couple of weeks. It will be my pleasure to have your company and gain some understaning of critical music listening. In the meantime I am keeping myself busy by playing lot of video games so that I don't get too much impatient about the amps arrival.Howz your stands coming up?
Mahiruha.
 
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