[audiotom]

I have an electronics guru friend who has brought over his 12 watt SET amp to try out on my Apollo 11s.  For music that isn’t too taking they sound just euphoric. A whole greater level of smoothness, resolution, etc. Bringing things out of the recordings left and right.
THe Apollos really sing.

Smooth revealing music is the most resolved.
Dynamic music that isn’t too complicated works too

However on more challenging loads - where there are a lot of things to resolve the amp can’t handle the load and restricts - losing tonal balance, frequency extremes, dynamics.

Just a little more amp control  and I would be in heaven

Has anybody had luck at a particular SET watt level? Tube design?

Thanks
Tom

[FullRangeMan]

I have an electronics guru friend who has brought over his 12 watt SET amp to try out on my Apollo 11s.  For music that isn’t too taking they sound just euphoric. A whole greater level of smoothness, resolution, etc. Bringing things out of the recordings left and right.
THe Apollos really sing.
And what SET amp was that?
This is the SET magic but if you dont liked better try a muscular Class D etc...

[Stercom]

The sensitivity of the Apollo 11 is 96db with 1 watt at 1 meter. At 10 feet away from the speakers you can drive them to over 100db with 12 watts. So, it's NOT the wattage of the amp. It's the quality of the output transformer and power supply in that amp that can't keep control during complex passages. There is a common misconception that MORE power means better sound. A lot of times it's how the amp is made. I would look for a 10-15 watt SET amp that weighs over 80lbs which usually means very beefy/stable transformers (just a very rough place to start) Here are the calculations:

[Maxboy]

I have a pair of Argos and drive them with a Viva Solistino 18W, class A,  SET IA. So far, I haven't experienced any compression regardless of the type if music. I also have a pair of RELs S/510 subs.

[jtcf]

I agree with Stercom. Another thing to consider is the amp will struggle with any impedance dips  in your speakers and run out of juice at those frequencies.

[mick wolfe]

Was the amp in question a true SET using a directly heated triode tube or an SEP? ( single ended pentode) Regardless, sounds like you can rule out that particular amp as your choice. If you want to stay in the true SET camp, I would suggest auditioning 845 based SET's. Aside from that, there are dozens of options in P-P amps in the 30-60 watt (or more) range that might fit your ear. Depends on your budget. Good luck.

[Rusty Jefferson]

It's the oldest dilemma in audio. "Love the sound of SET amplifiers but they run out of gas." 

Even really well designed/built 845 or GM-70 SET amplifiers are going to run out of gas with any speakers except very high efficiency speakers. That's why people most commonly use them with horn speakers.

[borism]

Audiomirror makes 45W mono blocks using Russian 6C33C tubes. They got favorably reviewed in AS.

[Stercom]

Here is an example of what I'm talking about - a 22 watt 845 SET integrated amp with 90lb transformers. This amp even has ELROG tubes which are some of the best made. I'm betting this would be a great match with the Apollo 11s and would not "run out of gas" .........  https://www.usaudiomart.com/details/649751071-melody-an845-set-integrated-amplifier/

[Rusty Jefferson]

You probably shouldn't imply that amplifier wouldn't have the same problem the OP is asking how to overcome. His friend's amplifier may have a better power supply and transformers than the one you referenced.  You don't know his room, or the music he likes to listen to and at what level. The difference in the extra wattage is only a 3db gain in level. Too many variables.

SET amplifiers are known for what he's describing. Transformers saturate, power supplies sag when you turn them up with complex music. Most don't control woofers well at high output. 

I'd suggest putting a couple notices up on the forums you frequent asking if anyone in your area would demo their SET amplifier like your friend did and see what some of the differences are like. Everything in this hobby is a compromise.

[audiotom]

Thanks for all the insight, I really appreciate it

I would clarify it as Restricted more than ran out of gas
The low end is very well retained and produces as low as my PP with authority in fact more body and natural warmth

The amp is pure SET based off of 4 UX250s and the transformers are massive
He typically works in the 5 -  8 watt etc variety for people with high end systems.
Great sounding amps.

Unbeknownst to me he wanted to hear this prototype on my Apollo 11s (he loves their sound and high efficiency) using a lower end garden variety  tube first and get my fair assessment after a week. He dropped it off and I have been exploring tougher material as well as ideal rich acoustic music.

In the next week I will hear what a much more refined and authoritative NOS tube will do
He says I will be pleasantly surprised as he has applied this to his lesser watt amplifiers

My other amps are Uesugi 55 watt PP Monoblocks.
EL 34 and ax7 au7 based. Telefunken and Mullard 60s NOS. They are a wonderful match with my Apollo 11s. I also have Doshi 80 watt pp Golden Lion NOS 6550 mono blocks. Both very dynamic. but the lure of SET draws me in, and in

My room is 27’ wide 14 1/2’ deep 8’ ceilings. Speakers on long wall and effective sound treatments.   I am typically an 85 db peak listener. Rarely 90

[Jarbs]

I’ve had a good number of tube amps driving my Apollo 11 during the last 4 years, ranging between 1.5 watts and 100 watts. Three of them were true SET. Generally 20watts drive them well. Examples of these 20w amps are - LTA Ultralinear, Allnic M2500 PX25, and Lampizator GM70 SET. All very different topologies.

But regarding only the SET variety, I’ve heard the following results. My overall room is about 1100sf, but plays smaller, maybe like 600 sf in the upper frequencies.

Thomas Mayer 45/2a3 - Beautiful, coherent, detailed sound, especially from the 1.5w 45. Tango transformers. But dynamics were less than ideal on all but acapela vocals. The 2a3 had a bit more punch at 3.5watts, but some of the magic disappeared. I can’t recommend 3.5 watts.

Line Magnetic 845 Premium - Rated at 30 watts. This thing is heavy. Sounds like 100 watts. Can drive the Apollo 11 hard. Led Zep anyone? But despite the macro dynamic heroics, micro detail was poor. I couldn’t live with it. Missing too much content. Maybe upgraded tubes would have helped, but the iron core EI transformers were likely the limiting factor.

Lampizator GM70 monos - Rated at 20 watt. Latest 2022 version. Last pair produced. Copper plate GM70 output with WE300b drivers. Best of the SET’s I’ve run as the macro and micro dynamics are in good balance. Good bass drive. Nice stage. This is enough power for most any program material IMO.

Best results are likely in the 211 or GM70 range. Dropping to 300b might be limiting in the low end for most applications, unless in the Uber end of the price spectrum and the iron that comes with it. Maybe there are some 845 applications worthwhile too. PX25 is probably the very bottom to consider at 6watts. I’ve really liked the PX25’s I’ve had.

[Stercom]

Great post Jarbs. Excellent equipment and advice based on using his exact speakers. That's what AudioCircle is all about!

[Stercom]

**

[genjamon]

Jarb's experience with the Line Magnetic 845 Premium is interesting - and maybe not fully representative of the Line Magnetic 845 sound.  I haven't heard that particular amp, but I own a Line Magnetic 518ia and had it paired with Daedalus DA-RMa V2 speakers for about three years.  Didn't find the microdetails lacking, and the 22 watts were able to fill my 25' x 30' x 10' listening room as loud as I would ever want (near concert rock levels if desired).  The system was loafing at 85 dB peaks. 

Used with Psvane WE845's, Mullard 1958 metal base 5ar4 rectifier, Genalex new production KT88's, and some nice NOS 12AX7's.  The stock Chinese tubes were absolute trash.  I would only use them to test if the amp was functional. 

A good friend also has used the LM 218 845 amp he has used for a decade in his much more intimate small room vinyl setup.  Paired with a Shindo preamp, that system is truly magic on every speaker I've heard him use in that room.  Not at all lacking in the SET micro-detail magic.

[rbbert]

...My overall room is about 1100sf, but plays smaller, maybe like 600 sf in the upper frequencies...

A bit nitpicky perhaps, but cubic feet is a far more useful measure than square feet in this context.

[Jarbs]

Additional thoughts on this.

First, the Apollo 11 have been a great amplifier evaluation tool. Real chameleons. Exceptional HF extension and phase. Coherent mids. Decent low end dynamics, but not quite pipe organ territory. An easy load and not too sensitive to damping factor.

The LM 845 Premium is an enjoyable amp and certainly a great value. My wife liked it best and looked at me cross-eyed when I sold it, LOL. I upgraded the driver tubes and ran it as an amp from my Allnic L9000 preamp. The front end at that time was an Antipodes K50 server into a Lampizator Pacific dac. Very capable. It’s a lower mid centric in presentation, and I liked that. Upgraded outputs would have helped. I bought the unit from a local friend who had upgraded 845’s. His comment to me was that upgraded outputs would help, but not significantly alter the presentation.

I had a number of good amps to compare to at that time. Allnic M2500 PX25, VAC 200iq, and shortly after the Thomas Mayer. These were the “direct compares”. It wasn’t close. Either of the push pull amps went way beyond what the LM845 could do in the HF and resolution department. But this is something I really hone in on for certain types of music which are rich in this content. Vocals? No. 1950’s jazz? No. Electronic stuff with engineered sound stages. Yello, Kraftwerk, Radiohead, Can.

IMO, SET amps are best for vocals, jazz, and similar. The coherent, unconfused, midrange is the best there is. Natural and 3D. But there are compromises at the frequency extremes. Other amp types have better resolution and dynamics. I love the SET tube distortion flavor. Better than the SS amp distortion flavor. All amps have distortion.

When I got the Thomas Mayer and VAC 200iq in the same room, the two heavy weights knocked each other out. The TM exposed the VAC for having a contorted confused midrange, and the much higher powered VAC dynamically blew the doors off the TM and the bass and HF were much better. In the end I couldn’t live with either with their limitations exposed.

Pick the right tool for the intended job. I still haven’t found one amp that does it all. It’s ok to have a few.

[Jarbs]

A bit nitpicky perhaps, but cubic feet is a far more useful measure than square feet in this context.

Fair enough. 9 ft. Ceilings

It’s an odd shaped space. A cross shape with the rig in one leg which is 17 ft. Wide x 9 ft. Height. The speakers see a depth of 52 ft. 22 ft. Out from the front wall, the room expands to 38 ft. Wide. Not much bass reinforcement going on in this room.

Generally listen in the 70db range. But do have a 200w SS amp when appropriate.

[Jarbs]

Ok. One more comment.

Before stumbling onto the Lampi GM70 monos. I was working with Oliver Sayes on an amp spec. that I would consider ideal for the Apollo 11.

211 SET with 10y driver, Lundahl interstage, custom wound permalloy 50watt rated output transformers. Separate power supplies tube rectified. 4 chassis. 12 watt rated output. It’s a lot about the power supplies and the output transformers.

This borrows heavily from the Thomas Mayer cookbook. The 10y driver is the secret sauce.

I should have followed through with this.

[genjamon]

Thanks for sharing the additional context, Jarbs. I have a much better sense of what you found lacking in the LM now. I certainly wouldn’t claim the LM 845 sound is the ultimate in resolution or in frequency extension. My Odyssey, Folsom, and now ClassDAudio amps each outperform the 518ia in terms of absolute resolution and frequency extension. But there’s still a rightness and realism to the LM 845 sound that is completely different than any of these solid state solutions, even when paired with my Don Sachs tube pre. And with top quality tubes, you do get ample details and nuance to be holographic and not warmed over/fuzzy - that inner light of the music that good SET reveals, along with the excellent macro dynamics of those 845 tubes.