Single-ended triode stereo amplifiers: SET-Amp Owners/Opinions?*

Playing Hampton Hawes Trio Vol. 1 through my new 300B (above) and my old Epicure 100V's and the piano sounds so nice. The bass is a tab bit flabby but still pretty good nonetheless.

 

A friend had a Wyetech Topaz. It is a terrific amp, usable with a wide range of speakers. I heard it on a horn system and on the 3.5 Maggies. The version of the Topaz he had used Audionote output transformers, not the transformers that are currently used.

 

Even though i had problems with my Icon Audio EL 34 Tube amp and returned it I must concur that the few hours late at night that they actually delivered full Stereo sound were magical and hard to forget. Like a barrier between the recording was removed and the artists seemed to come alive in my listening room - incredible !
So check those mono blocks out...Icon Audio builds good stuff.

 

Hi Inperson,

I saw the pictures you posted of the 300B amp you just got. That is an interesting looking amp. In an earlier post you said it was pushpull and had no rectifier. As far as I can tell, it has only two output tubes which would make it a SET (assuming it is a stereo amp). What kind of tube is at the far left? I would have guessed that that tube IS the rectifier. Also, it looks like the amp has two gas regulator tubes (the ones that are glowing). You don't see that many amps that use regulator tubes (I have a linestage that uses 6 gas regulator tubes).

It looks to me like you got a very serious, hardcore, SET amp.

 

I got into SET about 15 years ago and never looked back. I can't imagine not owning a SET amp. With the right speakers, both SET and OTL amps have given me more satisfaction than any other amp topology. I currently have a wide variety of SET's (45,2A3,300B,F2a,GM-70). While this is certainly overkill, it gives me great deal of system flexibility. For large orchestal stuff, I'll generally use the higher powered GM-70. For Jazz, I really like the F2a. For intimate vocals the 45 and 300B are wonderful.

 

I pulled out my Decware SE34 Monoblocks out for a final listen today, they're getting packed up and sent off to a new owner soon. Lovely amps! I love their fast single-ended sound and their only drawback is that they just don't get loud enough for my video sources in my living-room/dining-room area. If my room were 40 percent smaller, I'd have them in use all the time, the detail and the soundstage and the tonal balance are just so nice.

I've got my Decware Torii Mk III in place again and it really sounds very very much like these Monoblocks, with much more power and headroom. A fantastic amp.

 

Thanks! I am not the smartest guy when it comes to electronics but I do know I bought a single ended amp, haha!

Please read the post again. I was talking about two different amps. I was deciding which to purchase. One was this one, the single ended 300B, and the other was a Line Magnetic PP amp. Sorry if my post was confusing

For the 300B amp I bought, yes the far left tube is a rectifier. I prefer amps which have tube rectification.

About the regulator tubes, OD3's OD2's and such, how do they operate with the amp circuit? If most amps don't use them then why would this amp use them?

The two tubes between the 300B tubes are 6J8P tubes which are Chinese versions of 5693's or 6SJ7's. Those two tubes are connected to hum pots which are located behind the 300B tubes. I am not sure why they use these 6J8P tubes, any ideas? They are preamp tubes, right?

 

The OD3s, OD2s are generally used for voltage regulation. They control the operating points of the output tubes. My Torii Mk II amp uses either OA3, OB3, OC3 or OD3 (you can tube roll; I use OA3).
My Mk III also uses OC2 to regulate the input tubes. They're there to clean up the power a bit, sort of a power conditioning right up in the amp.

 

What the difference you find between the OA3, OB3, OC3 and OD3? Can they generally be tube rolled for any amp using one of these tubes?

 

Spent some more money today and upgraded the tubes. Nice to live in a city where I can take a 15 minute ride and get some mesh plate 300B's

 

I can't speak to whether they can generally be rolled in any amp that uses them. The maker of my amp designed it to allow tube rolling these types. Here is what he says about the use of the tubes in the Torii Mk III:

Voltage regulators can be ignored, or used to take the tube rolling experience to a deeper level. The four voltage regulator tubes below all modify the operating points of the output tubes they regulate. This in turn changes the way the output tube sounds. For example, you can use an OA3 which gives the highest grid voltage and usually the most low end performance. You can use an OD3 which gives the lowest grid voltage and usually the tightest bass. If you wished it to land somewhere in between, there is the OB3 and OC3.

The smaller seven pin regulating tubes clean the power for each input stage. There are also four tubes you can use here, starting with the stock OC2 also know as VR75. This gives the input stage the highest gain. Changing to a VR150 lowers the gain of the input stage.

With the stock tubes we ship in the amp, you get ideal performance in most applications.
It's just that you CAN tweak a TORII to a very fine level if so motivated.

From this page: http://www.decware.com/newsite/TORII.htm

I find that there are differences with these tube types, even differences within the same tube types between straight-sided and coke-bottle shaped versions. I've played around with a few brands of each type and an RCA straight-sided OA3 works best for me in the Mk III amp, it has the most dynamic sound and the lowest bass output to my ears. This amp can really be fine-tuned to tailor your taste and needs. I'd suggest sending an inquiry to the manufacturer to see if you can "roll" these sockets.

 

I will ask them. Thanks for the idea!

 

Hello Everyone ... I am a new member.
Has anyone read this very informative pdf on the contrast of push-pull and single-ended designs?
www.passdiy.com/pdf/seclassa.pdf ... a very excellent read.

I believe why single-ended HiFi has sonically always have been desireable is because of:
When you make a sound ... the characteristic nature of that sound through air as the medium is single-ended ... not push-pull ... not stereo and also, the sound is typically the "result of its single-ended nature, the harmonic content of air is primarily 2nd order, and most of the distortion of a single tone is second harmonic. Air's distortion characteristic is monotonic, which is to say its distortion products decrease smoothly as the acoustic level decreases."
Thus, the "natural life-likeness" of single-ended HiFi.

 

Buy a pair of Air Tight ATM-211



and enjoy the tunes.

 

Wow!

jeff

 

You could build an AM transmitter with six of them, two Class C RF finals, two push pull audio modulators, two rectifiers for High B+. You'd sound good on 160 or 80 meters.but they won't let you play music. If you were in the middle of nowhere you could probably get a broadcast license for a low power daytimer, but you wouldn't make any money.

Get free stuff though.

 

Well he can just sell them at around $1500 a pair, or even more since they seem to be really nice with original cartons and all that jazz.

 

Nice bit of info! It is rare that I get to talk shop with someone who knows the Wyetech stuff so well. The Audionotes were $1000 each at the time. There was a retired NASA engineer who contacted Wyetech and indicated he could do one better (since he apparently designed the Audionote ones Audionote was decreasing production, thus raising the price and Wyetech was interested in at least sourcing out a possible replacement for the long term. In the end he went with this gentleman (out of California somewhere) but it wasn't until the monoblocks that he was able to introduce them. In the interim, he had to go with a solid transformer but from memory, not as thoroughly enjoyed by the Audionotes. The new Ruby monoblocks (211 and 300b) use some outrageously pricey transformers, hand-wound and custom built just for the Ruby. Again, designed by this NASA gent. $2k/unit I believe. Takes a while to build them.

 

The Coincident Frankensteins mated to their Triumph speakers. These over built monoblocks have been a musical delight for five years and counting. They sound so pure with such beautiful details and have more than enough to push my current Coincident model with double passive subs containing four 10" nomex woofers. I have upgraded everywhere since but the amps.
Never going back.

Coincident also has just the amp for those wonderful 211's

 

My buddy here in China bought about 50 or so, not sure if they were RCA's though, from some military guys. They were just sitting around out in the west of China, used for radar equipment or something like that. But I think he paid more than $5.00 each.

 

I have a SET 300b mono,s with horn system , and another system with large P/P amp ( Audio Research Ref 600MkIII mono,s) which both sound very good .

System matching is more important with SET amps, but very rewarding.

When retubing amps , the 300b amps are a lot easier and cheaper too.

Cheers Victor.

 

It is important to compare apples to apples so to speak.

Directly heated triodes tend to be very expensive, despite their being easier to manufacture than popular beam power tubes. This may be because of volume-guitar amps drive the manufacture of power tubes-gullibility, or whatever. But it is a fact. You can buy many 6550s for the price of a single 300B.

I have built SETs and listened to others. I have also built single ended amps and converted them from triodes to beam power tubes strapped as triodes, and back, and the differences were minimal. This was using good Tango output transformers, choke filtered power supplies, in amps that were swooned over by triodephiles but I sneaked in the beam power tubes and they swooned the same until I told them.

The really extreme triode guys reject the 300B as a matter of fact and will only listen to 45s, 10s, _single plate_ 2A3s or 845s in bigger amps.