Why is a 10 watt SET (single-ended triode) amp not bad?

[YaQuin]

Hello,

I am becoming more interested in tube/valve audio technology lately. As I understand it, SET audio technology produces "natural" even order harmonics during the amplification process which apparently makes music sound more "musical", "warm" and "natural".

The question I have is can one really enjoy the sound of an amplifier that only produces 10 watts RMS through a channel? Can speakers run on that? Why is it that a 100 watt RMS solid state system not sound as good as a 10 watt RMS tube amp? Is there more to this game than just watts? Should I be looking at something that has more amps as opposed to more voltage when calculating the wattage? Do any of these questions make sense?

Thank you in advance for your enlightning words.

[thegage]

It depends on what you mean by "enjoy."

10 watts is enough to drive many, many speakers to "reasonable" listening levels. If, however, you like to listen to large-scale orchestral works or head-banging rock on inefficient speakers you will not enjoy the performance.

OTOH, 10 watts mated with ultra efficient speakers can easily blow you out of the room, but when played at reasonable levels produces music that is very different--and to many people more seductive and involving--from that produced by high-power amps and inefficient speakers.

I have played around with very low power SETs (on the order of 1-2 watts per channel) and find much of what they do captivating. For my preferred speaker choices, however, they were not a perfect match.

John K.

[Jim Ricketts]

In the words of someone else, "it doesn't matter if you have 1,000 watts if the first watt sounds like crap". It is VERY important to insure that first watt sounds great cause they're not gonna sound any better. SET amps have the advantage in sonics by eliminating phase inversion and maintaining the signal throughout the circuit for a purer sound.

I agree with what John says about SET amps and speaker matching but that's true with any amp-speaker combination. SET amps are more concerned with a friendly impedance since their output impedance is typically much higher than push-pull.

Also, not all SET amps are "flea-powered" 1 and 2 watts. There are some extraordinary sounding SET amps producing 100 watts per channel that can drive a lot of average sensitive speakers to bone crushing levels.

And not all SET amps are created equal. Some have better circuits, some have better transformers (extremely critical to SET amps), some have better coupling capacitors and some have no coupling capacitors. Some are slow, soft, mushy, colored and rolled off and some are more neutral and fast in their presentation.

I would suggest looking for the speaker-amp combination that satisfies YOUR tastes and desires. Just keep in mind that all SET amps sound different and have different power levels just as all push-pull amps sound different and have different power levels. And no amp will fit every speaker and no speaker will fit every amp.

Just my 2 yen......

[Khorn]

Many might not agree but, I do think you pick the amplification to drive the speaker system and not the other way around. That's just the start of it. You could have the identical speaker system loaded into different spaces playing different music at widely differing levels in that case there could be multiple choices as far as amplification goes.

While a couple of watts can drive an efficient speaker to high SPLs the sound (dynamic headroom) might not be quite what you want. I have driven my Khorns with everything from low output SETs very to high powered SS amps and they all have their respective strengths and weaknesses.

In my particular situation running about 10 meters (33 ft) of speaker cable per side I find that a relatively low powered 60wpc SS class 'A' type amp combined with a tube SE pre-amp fits the bill. I'm sure that a high output tube amp would work also but I'm happy with what I have right now.

The only way you are really going to find out what is suitable is to actually try different combos out in your own system.

[Steve Hoffman]

Originally posted by Jim Ricketts
In the words of someone else, "it doesn't matter if you have 1,000 watts if the first watt sounds like crap". It is VERY important to insure that first watt sounds great cause they're not gonna sound any better. SET amps have the advantage in sonics by eliminating phase inversion and maintaining the signal throughout the circuit for a purer sound.



What Jim is getting at here, is that for a "modern" tube amp (let's say from the early 1930's on) to work correctly, two or more tubes have to work together to produce more watts. It's called "Push Pull". Most of these "Double Ended" amps sound fine; Marantz, McIntosh, Audio Research, VAC and many many more. Jim touches on phase inversion in his comments, and this means that the "sound" has to be torn apart as it enters these amps and put back together before it leaves; kind of like Mr. Spock transporting to the planet Zenon from the good ship Enterprise. In Mr. Spock's case, he can be put back together again quite nicely, but in reality, the audio signal does sometimes suffer from this approach.

The Single-Ended approach is that there is only ONE amplifier tube, so no push-pulling; the sound is not torn apart and put back together, it just IS. The result of this purity of sound is apparent in most single ended amps. Of course, the drawback, is that since there is only one tube, the power must be lower. With the right speaker, it can sound amazing.

The old Western Electric movie theater amps of the early 1930's (Westrex) used one 300B triode as the amplifier stage. Just one 8 watt tube to fill an entire movie theater! Big horn speakers only need a watt or two to really blast. When this equipment was junked by the theaters in the 1950's and later, it was discovered by the Japanese to sound quite wonderful in stereo systems. All of the WE gear is in Japan now, and worth a great deal of money. The Japanese and French audiophiles wanted more Single-ended directly-heated triode amps, so they were created (or recreated) from the old WE designs. This spread to America, where Dennis Had of Cary Audio jumped on the bandwagon with the first American made single ended amps.

The late Japanese master builder Nobu Shishido designed the WAVAC SET circuit, and this is what I use in my Hi-Rez work.

If you want to read a descriptive review of the SET "sound", the late Harvey Rosenberg wrote a good one here:

http://www.tmhaudio.com/new_page_3.htm

Of course, I'm a supporter of SET's and a WAVAC endorser. Matched with the right speaker, the results are musical in the extreme!

Have fun, and experiment!

[RDK]

Gamma, you can learn a lot about "flea-powered" SETS here at Decware.com. I have the basic Zen and like it quite a bit. It constantly surprises me that it only outputs a couple of watts...

http://www.decware.com

Ray

[pigmode]

Jim & Steve,
Thanks for the great explanations.

[akshobhyavajra]

Originally posted by RDK
Gamma, you can learn a lot about "flea-powered" SETS here at Decware.com. I have the basic Zen and like it quite a bit. It constantly surprises me that it only outputs a couple of watts...

http://www.decware.com

Ray


The Zen is quite amazing - esp for the money. One of these little amps (1.8 watts) drives my pair of Reference 3As in a small room and sounds fab with Jazz and even classical.

It is not necessary to use a pre with it, but I find that the right pre does compliment the Zen.

In short, though it's a good place to start without investing too much money. Retubing and rolling is inexpensive - no need to bias...

Also interesting - and certainly worth a look are the Bottlehead amps - both DIY and assembled available.

Regards,

~Michael~

[YaQuin]

Steve, when you say "double-ended" do you mean "push-pull"? Also, are you saying that "horn" speakers are really an ideal match for tube amplification for the fact that they are more efficient?

Mr. Ricketts, does "impedance" have anything to do with speaker "efficiency"? Do SET amplifiers need a nominal 8ohm load or would a 2ohm load be better? What types of transformers should I look for?

I thank each and every one of you deeply. Your explanations and viewpoints will give me a great basis to go start experimenting. However, if I had the money I think I would just go straight for a pair of the top-of-the-line Wavac HE-833 mono amps. But hey, I don't make that much money yet.

Again thank you all for your knowledge and input. This board is truly a treasure. :)

[akshobhyavajra]

Originally posted by GammaSpace
if I had the money I think I would just go straight for a pair of the top-of-the-line Wavac HE-833 mono amps. But hey, I don't make that much money yet.

Again thank you all for your knowledge and input. This board is truly a treasure. :)



GammaSpace,

FWIW, you don't necessarily have to spend a lot of money to get quality sound in each and every instance.

I recently went to a well-known local Cary dealer / guru and advised him that I was considering a pair of CAD-300SE Signature amps ($5K). He said not to waste my money and purchase a ASL TULIP 2A3 instead ($1K).

He added that the ASL "smoked" the Cary and after all these years of selling Cary (10 years) he was questioning how the company justifies a $5K pricetag...

Sometimes we (collectively speaking for audiophiles) want the "label" on the amp for the sheer prestige of it - when in reality a set of tricked out Bottlehead amps may well have a superior sonic signature.

Just a thought from someone who used to go "label" shopping....:rolleyes:


Regards,

~Michael~

[Jim Ricketts]

Originally posted by GammaSpace
Mr. Ricketts, does "impedance" have anything to do with speaker "efficiency"? Do SET amplifiers need a nominal 8ohm load or would a 2ohm load be better? What types of transformers should I look for?

I thank each and every one of you deeply. Your explanations and viewpoints will give me a great basis to go start experimenting. However, if I had the money I think I would just go straight for a pair of the top-of-the-line Wavac HE-833 mono amps. But hey, I don't make that much money yet.

Generally speaking, SET amplifiers have a higher output impedance than push-pull so a bit more care must be taken when choosing the matching speakers. Typically, the higher the speaker's impedance the better. As long as you choose speakers with 4ohm or higher, you should be fine. The more powerful WAVAC models can deal with lower impedance speakers better than say 10w 300b amplifiers.

WAVAC use customized versions of Tango transformers that are noted for being one of, if not the best sounding trannies with ultra wide bandwidth. Nobu Shishido mentioned in an interview that to do transformer coupled SET amplifiers correctly, one must use very high quality transformers as it is so critical to the final sound.

As a note in passing, the HE-833 100w/ch monos are extraordinary albeit a bit costly. The new MD-805m monos with 55w/ch give a lot of that same purity at ~ a third of the price. Affordable ultra-high end, relatively speaking of course.

Hope that helps - feel free to contact me directly.

[Steve Hoffman]

Originally posted by GammaSpace
Steve, when you say "double-ended" do you mean "push-pull"? Also, are you saying that "horn" speakers are really an ideal match for tube amplification for the fact that they are more efficient?



Yes, push-pull. I was making a little play on words.

The reason horn speakers still exist in the world is because they run loud on one watt. Perfect for SET amps.

HOWEVER, a horn speaker (if used) must be chosen carefully; some "honk", some have no bass, or no top end, or bad imaging, etc.

If a Tannoy with a 15" woofer and horn (that goes up to 13, 000 cycles on a good day) is matched with the correct low power amp, it can sound like real music. When you consider that most audiophile speakers are around 85 db efficient and that most horn speakers are around 106 db efficient, well you can understand the difference in power needs. (This means that with one watt of power, a speaker can be driven to a certain db level without strain). The higher the number, the louder the speaker can go without clipping.

On the other hand, a 100 watt solid state amp mated to a pair of Tannoy horns is overkill in the extreme, although the sound will be decent, because Tannoy speakers are very un-horn like (they don't honk and have a rather mellow sound with a magic midrange and full deep bass).