SET amp recommendation

Recently made the switch from Cary 805 AE to Atma Sphere OTL pre-amp and amp. The OTL dynamics and sound is where I live now, but still looking back over my shoulder at SET. I still have a Cary SLP 05 preamp with no one to play with. Can someone give me a recommendation for a good used SET (any configuration) amp for $1,500 or less. See a lot out there, but could use some guidance.

Yet another thread with too little information.......

You had a 50 watt SET so I'm thinking a 1 Watt SET might not work well for you but just a guess with so little info.

What speakers do you have, how efficient are they, what kind of music do you listen to, how loudly do you listen?

Look into the Almarro A318B amp. Google it and you'll see a 6 moons review.
Speakers are Vienna Acoustic 91db sensitivity, I increase their impedance to about 12 ohms using zeroformers so I am not afraid of lower wattage amps. My listening room is small so what I hear is direct energy from the speakers. Music I listen too is not too crowded or heavily orchestrated, mainly vocal, acoustic and the like. Anticables connect everything together balanced or not. I guess what I am looking for is SET configuration that is not overly colored or muddy. The Carys were nice, but just say I am glad I didnt pay full price for them.
I hear ya, some SET amps are colored and others are crystal clear, much variation is available.
In your price range a used Grant Fidelity 300b (with the Shuguang Black Treasure 300b) would fit your needs, Reviews say it`s a quiet amp with good transformers(crtical for SET sound quality).
Best of Luck,
The 2 most important components of an SET amp are the power supply and output transformers.

If you have a high quality source and resolving speakers, I don't believe there is much available for $1500 you'd be happy with long term.


You don't really have an SET friendly set up at least for your typical 2.5 watt 2A3 or 8 watt 300B amp. Doesn't your speaker manufacturer recommend at least 50 watts?

If your speakers are 91 dB 4 ohm and you multiplied it up to 12 ohms the trade off is you get less power delivered to the speaker. The maximum voltage output of the amp is what it is but the autoformer divides this down so less gets to the speaker.

Fine if you have power to spare but starting with a low power amp and a medium sensitivity speaker you do not. I don't see any advantage to the autoformer if you choose a tube amp that has a 4 ohm tap.

Certainly no harm in trying.

Based on your speakers and price point, I think a used 300B is probably the most likely candidate for you. I don't think you will be happy driving your speakers with lower powered SET amps 45/50/2A3.

Another potential option is to keep checking ebay as periodically Sean Casper offers F2a amps in that price range. The Siemens F2a tube (made famous in German Klangfilm amps in the 1950's) has about the same power rating as the 300B but has a completely different sonic signature. It is a much more dynamic sounding tube with better bass. It also has a wonderful presence to it - it comes across as a much more powerful tube. What it does give up to the 300B is some midrange sweetness and a bit of nuance. Both would be very good alternatives to your OTL.
Great information! Thank you
If the 12 ohm load of the zeroformers remains relatively flat a 300b amp would love this load. If the amp has "good" quality transformers and P.S. as audiofeil mentioned earlier, I believe 91db speakers in a smaller room at normal listening levels will be fine. 1500.00 budget does limit choice to some degree(good transformers and P.S. are`nt cheap).

I have used my 300b SET amp with 89 db speakers(8 ohm) in a friend`s system(large room) without any promblems what so ever.
If the 12 ohm load of the zeroformers remains relatively flat a 300b amp would love this load.

As long as you can live with the loss of power. I believe these calculations are correct.

from 12 to 4 ohms is 3:1 for the impedance ratio

take the square root of 3 to get the voltage ratio = 1.7

If you have an 8W 300B amp you have 8V at the 8 Ohm tap (8V squared divided by 8 ohms = 8W)

divide that 8V by 1.7 to get 4.6V which will get you a little over 5W max.

maybe, but that's not a lot to drive a speaker with a recommended power of 50W.

This much I know, my speaker is a 14 ohm load(94db efficient) and it is a splendid match with my 8 watt amplifier, sound levels usally 75-85db(in a 14x26x8ft room)If his speaker is truly 91db efficient and he listens at modest levels(his stated preferenc)i.e. around 60-75db range the speakers are only drawing fractions of a "watt" of power.
He says his room is small, With a good quality 300b amp he will be fine.

It`s my understanding/experience that tube amps like a higher ohm load that`s relatively flat.
12-12-11: Herman
As long as you can live with the loss of power. I believe these calculations are correct....
Not that it makes much difference, but the power loss will be a bit less than what you calculated. Since the output impedance of a SET amp is significant, it will be able to put more voltage into 12 ohms than into 8 ohms. Output impedances that I recall seeing for 300B SET amps range from around 2 ohms to around 5 ohms, corresponding to damping factors of 4 to less than 2.

Taking as an example an output impedance of 4 ohms (damping factor 2), I calculate that the 8W capability into 8 ohms would be reduced to 6.75W into the 4 ohm load through the autoformer's 3:1 impedance transformation.

Best regards,
-- Al
Thanks Al,
I knew there was some definite advantage for tube amps driving higher ohm loads. Higher voltage output, I`ll remember that now.
Hi Charles,

An additional reason stems from the fact that if speaker impedance is higher, amplifier output impedance becomes a smaller fraction of speaker impedance. That will decrease the magnitude of frequency response variations that will result from interaction of amplifier output impedance with variations of speaker impedance that occur as a function of frequency.

Also, the very low damping factor of these kinds of amplifiers will increase in proportion to speaker impedance.

Finally, higher load impedance means that less current (although more voltage) is required to deliver a given amount of power.

All of those are reasons why, as you said, "tube amps like a higher ohm load that`s relatively flat."

Best regards,
-- Al
Al, you are the man when it comes to clear technical explanations.I don`t have an engineering background but my ears sure told something very good is happening with the higher ohm speaker loads and tube amplifiers(particularly
SET amps).
Best Regards,
12-12-11: Erfranke
I guess what I am looking for is SET configuration that is not overly colored or muddy. The Carys were nice, but just say I am glad I didnt pay full price for them.
I had a similar Cary experience with the Cary SEI 300B. Lush, intimate, involving, but too much of each for my taste.

As Zmanastronomy suggested above, the Almarro A318-B is a terrific choice. You get almost every last bit of the SET "magic" without the coloration. And it is 18wpc. That extra ~3dB in output makes a difference sometimes.
The assumption that 300b SET are all lush and colored is as inaccurate as stating all solid state or all push-pull tube amps sound the same.
There`s such a wide assortment of character among the many 300b amps available, slow.fat and syrupy to fast,tight and lean.
What circuit/Parts quality?Level of transformer and power supply?Cary,Wavelength,Yamamoto,Coincident,Tron or Art audio, they`re all different.
Which 300b tube? Generic chinese,JJ,Sophia,EML or W.E.?
What driver tube? Capacitor,interstage transformer,choke or direct coupled signal path?
Far too many choices in amp design/implementation to stereotype the resulting sound quality.
I am hearing some good comments regarding Asian made/assembled 300b/318 SET amps. Have not considered them before; believed they were built with profit in mind, substandard components and transformers. Should i be thinking different if it is going to be a throw-down amp anyway playing second fiddle to my OTLs? Or, wait for a good used domestic?

Mixing apples and oranges, I am curious about the sound profiles of other non-SET amp configurations, such as McIntosh, PrimaLuna, Integrated amps using EL34,EL84, 6550s, the list is endless. Has anyone had a good experience with any of these they want to share?
I think you are all over the map and don't know what you want. You might as well put solid state amps in the mix and class D as well.
You may not know this but Ralph has built for his own use a 45 SET amp. He has mentioned it before in some threads here. You might want to chat with him about the sonic attributes of SET vs. OTL.

We have a 45 amp that we sell too, in addition to a 300B. I also own Music Reference EM-7 12v SET amps. After significant listening with all three, I have to say my S-30 has easily heard advantages in overall dynamics, as well as, lower end frequency extension, while not giving an inch in the midrange and upper frequencies.

If you are just looking for a different flavor to have on hand you could do a lot worse than the Almarro 318 that a couple people recommended here. especially given your price point.
I forgot to add this to my previous post.

If you really want to rock your world pick up a Music Reference RM-10 MkII. I can almost guarantee you will rethink what high-end audio means to you.
I would`nt bother with a 300b SET amp if it s not quality built, it will just disappoint you. Poor parts,transformers etc. won`t get you anywhere.

Personally I`d take a premium made SET over an OTL amp but of course individual preference rules.
Hi Jwm,
I agree with your observation.
I gotta agree w/Clio09 the Music Reference RM10 MKII is the most satisfying piece of gear I've ever owned on many levels. Someday when my economics improve I hope to have a nice stereo SET or S30 just to play with alternatively. great fun when you know what you like isn't it?
Yes I agree with JWM, I am all over the map which is precisely why I am gleaning advice from the experts; so many amps so little time. My focus is quickly narrowing, and I am avoiding many a disappointing mistake to be certain thanks to this forum.

I am a big fan of the OTL and do not see that changing anytime soon, based upon the economics of listening room size, discretionary income, time I can devote, and subjective listening taste.

The endorphin/enkephalin release from tubes keep me addicted to experiencing different flavors and to that end all of your inputs are highly respected and valued with selecting another flavor to savor.