Avantgarde Trios, SETs, and Impedance Curves

Has anyone ever seen an actual impedance curve plot for the Avantgarde Trios? I am about to acquire a 3 year old pair and need to find a great amp to drive them. I suppose conventional wisdom would be to use an SET of some kind. However, to perform their best, SETs really require a relatively flat impedance curve. So, I guess what I'd like to know is how badly does the Trio impedance fluctuate with frequency, and/or, empirically, what amps have Trio owners used that have rendered awesome performance?

How about it, Trio owners, any advice for a new Trio guy? Any feedback would me most appreciated!


I presume if you're buying Trios, your budget isn't too tight. With their 107dB/W efficiency, the ampifiers will have to have minimal circuit noise, or else you'll hear it in the quiet passages of the music. Some of the amps which I know work with Trios include
Audiopax 88
Tom Evans Linear A
TRON 300B (Cantata) or Jubilate amps

The Trons are designed to work especially with AG horns and are essentially bespoke amplifiers made in the UK to order. The US distributor is Jeff at Highwater Sound. If you can, have a listen to them. They may look expensive, but sonically they're a bargain.

Best wishes and good luck

Lamm ML2.2
Wavac's products do a nice job too. Suggest you check them out.
Try Croft (UK) if you can, not the last word on cosmetics but excellent sonics and one of the kind circuit approach. I have try many amps. Trio is not as easy to drive as I think it is, it require very powerful, linear and noise free design to perform.
Lamm ML2 or ML2.1, and the Art Audio PX25, as well as the previously mentioned Audiopax 88.
The Art Audio PX-25 amp also has a Avantgarde option (a low noise input version). A fabulous choice for my Duos and likely for your Trios. Startling black backgrounds plus many other desirable sonic characteristics make this amp unique.

I've also listened to the Audipax 88s and they are also good.
Gentlemen, I truly appreciate your suggestions, but the reason I bought used Trios was because I truly couldn't afford new ones. As such, I'm probably not going to be able to spring for power amps in the $20K to $50K range either.

Charlie, the Tron 300B looks like it would be fabulous, but I'm assuming it is above $20K. I've certainly heard good things about the Audiopax. And thank you for reminding me about the Shindo.

Good suggestions all around, gentlemen, if mostly a little rich for my blood at this juncture. Anyone had any experience with either the Atmashpere M60 MkII or the Wyetech Sapphire 300B with a pair of Trios.

Sebastian, I will check out the Croft. I think you make a good point about the Trio not being as easy to drive as one might think as I suspect that the impedance curve of the speaker probably fluctuates all over the place, though I don't know that for sure--was hoping someone might have that information.
You can find second hand Audiopax model 88's running between 5-6 grand.
Jim Smith the former Avantgarde USA distributer could have used ANYTHING to demo his speakers in Atlanta, but his personal choice was the Audiopax. I think there was a few good reasons for this. Synergy is one.
I have Duo/Omega's and the Audiopax Model 88 amps and am One Happy Camper! A bonus with these amps are tube replacement NOT being a financial ball buster. Plus they can be had in matching Avantgarde Laquer.
Good Luck;

The Tron 300B is about 15-20k USD. The TEAD Linear A is about 8-9kUSD

Look into Art Audio amps. Most are under 10k. I have Jota mono's and they match great with my 100db speakers. Art Audio is not talked about enough.
You can find second hand Audiopax model 88's running between 5-6 grand.
Jim Smith the former Avantgarde USA distributer could have used ANYTHING to demo his speakers in Atlanta, but his personal choice was the Audiopax. I think there was a few good reasons for this. Synergy is one.
I have Duo/Omega's and the Audiopax Model 88 amps and am One Happy Camper! A bonus with these amps are tube replacement NOT being a financial ball buster. Plus they can be had in matching Avantgarde Laquer.
Good Luck;
Gentlemen, thank you all for the additional suggestions.

Tim, you make a great point about Jim Smith and the Audiopax. I will look into these.

Richardmr and Tubes108, I have a local Art Audio dealer who has a PX-25, so I can borrow it just to get a sense of its flavor. Tubes108, since you've listened to both the Audiopax 88s and the Art Audio PX-25, did you actually compare them in an A/B comparison? Do you feel that you prefer the PX, or was your purchase based more on cost?

Charlie, thanks for the pricing info on the Tron and the Tom Evans. Wish I could swing the Tron, but that will have to wait for another day.

I have Trio 2.2 and tried an Atma-shpere M60 MK.II. The sound was very, very fast. The highs were rolled off and the sound was dead. I got board very quick. I suspect there must be an impedence drop in the top end. I use a pair of Viva Aurora monos. They use the 845. They sound very balanced and extended from top to bottom. They are alot of power for Trios and can play them at an insanely loud volume. I have only tried this a few times for a couple of minutes to impress my non-audiophile friends. I found the sound to be fast until I heard the Atmas. The Atmas I felt were maybe to fast, if that is possible. I will be trying a friends Wavac 300b next week. E-mail me if you would like to know my opinion on how it sounds.
Gotta check out the Mactone MA300, 22 watts, push/pull fast, dynamic, 3d soundstage, prefer this over ML2.
The Trio is tricky to set up because the impedance curve is very unusual for a horn- high in the bass and low in the highs, due to the design of the crossover, which is mostly capacitors. A lot of SETs have difficulty with the speaker as a result.

FWIW It is very easy to set up the M-60 to work with the speaker, by using the same technique that the designer used: negative feedback. The speaker is so sensitive that about 6 db of feedback can be employed in the M-60, solving any rolloff issues. This is easy to set up with an external jumper arrangement.

We don't regard the arrangement as ideal, but since the designer's amps used feedback, that's what you have to use. Neither the Duo or the Uno seem to have this requirement.
Why not solid state class A amplification, like Accuphase A-20, 20 class A. You can biamp or triamp the Trio's.

The problem is that really low output impedance amplifiers don't sound right on highly reactive/high efficiency speakers (like most horns). There are interactions that result in shrillness. So a tube amp is indicated...
I was using my Trios with Audio Note Kageki (really beatiful combination) then with EAR 834T, not as smooth as the Kageki, but no shrill and dynamic like hell then I am using an Altmann BYOB amp with the Trio and my REL Stentor II sub. The most musical combination I have ever heard, period. The battery driven Altmann amp is perfectly quiet absolutely no noise through the speakers at all, which makes all kind of music detailed, rythmic, smooth and flowing, quiteness is an important aspect when the speaker sensitivity is above 108 dB/W/m.
I guess I should check in here more often. I thought my thread was done in September. Thanks to all of you have responded here in November with some really helpful information and suggestions.

Ferenc, your comment on the Altmann amp is truly interesting. You're the first person I've seen report using the Altmann, and that you like it with the Trio tells me you are a man who listens and doesn't give one whit about the cosmetics of your amplification devices. I am also curious about your use of the REL Stentor II sub. I assume you have replaced the AG woofers, is that correct? Are you using one or two RELs? If so, at what frequency are you crossing into the REL? I didn't think the REL was able to go up high enough in frequency to mate with the Trio's lower mid horn.

711 smilin, the Mactone sounds very interesting as well, but given the inability to audition one with the Trios along with their cost, it probably isn't going to happen.

Atmasphere, it seems to me that you are saying that neither SETs nor solid state amps work properly with the AG Trios due to the Capacitors in the crossovers. Don't most speakers with crossovers use capacitors? Your comments seem to conflict with all the results of others who report very fine results with SETs and now Ferenc stating he is getting fabulous results with the Altmann amp, which to my knowledge (correct me if I am wrong) doesn't use any feedback just like most of the SETs that others have found favor with. Yet you claim that an amplifier with feedback is required in order to achieve proper results. It does make one wonder.
I think Atmasphere is saying that some SET's have trouble with the tweeters crossover. My 845 amps sound very extended on top. They are very powerfull for SET's though. I have heard from others that 300b amps have no problem also. Wavelength recommended to me there 300b Cardinal over their lower powered amps for trios. I will be trying a Wavac 300b next week and will give my comments later. It sounds like some of the flee powered SET's might have problems with trios. Many people use them though, so they should be auditioned first.
I would like to add one more thing that I forgot. I talked to Jim Smith last week on the phone. He no longer represents Avantgarde, but still answers the phone and gave me his opinion on amplifiers for Trios. I hope you don't mind me quoting you Jim. I was interested in maybe a ART px-25. He said that he thought the ART px-25 was a very good amp. I didn't ask him about the Audiopax which he also sold. I asked him about my amp, 845 Viva Aurora Monoblocks, which he did sell at first with Avantgarde. He told me that if he was stranded on an island and had to choose one amp for the rest of his life it would be the Vivas. It was a nice comment to hear from someone so respected in this industry. Jim says he has closed the distributorship business for good. I don't see any gain to make a biased comment. I still would like to try a low powered like px-25 or 45 tube. I have to hear it one day for myself. There must be other Trio owners out there with other amp comments. Also, anyone in the Vancouver, Canada area with a flea powered that would like to hear on Trios let me now.
A friend of mine was using the 45-based Kondo, which realistically makes about .75-1 watt. This ought to be enough on the Trio, but he was unable to run the amp so there was not a high frequency rolloff.

The problem is that the midrange unit is not rolled out when the tweeter rolls in. This is because there are only caps in the crossover- no chokes to kill the highs to the midrange. The result is that the midrange is in parallel with the tweeter. The big horn OTOH is 19 ohms, but with the midrange and tweeter in parallel with it, you have a low impedance at high frequencies.

To make this work you have to play with the taps on your output transformer. The issue is that if you have a zero feedback amp (really about the only thing that otherwise sounds right on a speaker like this), you will not get the proper loading of the output transformer at frequencies less than that for the tweeter. The result is ringing (harmonic distortion) which obscures detail.

The end result is while you get the speaker and amp to work, neither is presenting the best of what its capable of. If, OTOH, the crossover were dealt with, this would not be the case. I would be very interested to see what that speaker could do then!! Given the cost of really good tube amplifiers, it seems that correcting the crossover would be a relatively inexpensive way to create a transformation.
For my TRIO Omega with a pair of Basshorns, I am using a pair of Antiphon Monolith 300B SET monoblocks. The Antiphons produce 7.5 perfect watts with lots of current reservoir (its power transformer is 600 watt capacity) Due to its enormous power reservoir and huge damping factor, it can drive a speaker with a very difficult impredance curve. I have directly and indirectly tried many amplifiers for Avantgardes, but nothing comes even close to the performance of Antiphons when it comes to driving a highly efficient speakers with huge drivers (15 inches or larger)such as Tannoy Westminster Royal HE, etc.
One of my friend is also using the Antiphons to drive his pair of Wilson Watt/Puffy speakers(known as a very difficult impedance load despite of its good efficiency at 92dB). The Antiphons surprisingly replaced his former amplifier, Boulder 2060 stereo amplifier. My other firends are satisfactorily using the Antiphons for Avalon Eidolons and Rockport Technology Antares.
As you can denote from the above instances, the Antiphons are outstanding at driving a speaker with highly fluctuating impedance curve.
If you want more reference or photos, please let me know.
Tron 300B amps are ok match for avantgarde Trio,but you will clip 300B tube, 8 watts, not enoughpower for trios complex load, this speaker withdemanding music can easily handle 50 watt peaks.
With my Trio 2.2s, later upgraded to Trio Omegas (huge difference, btw, like removing stuffed cotton from the horns), and using a pair of 225 subs in an 18 sqm room, I have tried Jadis 845, Zanden 300B, Hovland Sapphire, Lamm ML2, and Audion 300B power amps. The Lamms sound by far the most dynamic and detailed with full top to bottom extension, all other amps sounded somewhat anemic/rounded off though perhaps richer/more musical in some aspects. I have yet to find the sound I am looking for, but am sticking with the Lamms while I continue to tweak the rest of my system.
Has anyone tried the ART PX-25 or Wavelength Cardinal with Trios. Anyone else have any comments on 45 SET's with Trios.
I have a friend with the ART PX-25- its not bad on the Trio at all. There are no 45-based SETs that can drive the speaker- try as you like, 0.75 watts is not enough...

Most people I know that are driving the speaker successfully use surprisingly large amplifiers given the efficiency of the speaker. This is probably due to the impedance curve, which is tricky for a lot of zero-feedback amps (which otherwise will be the best sounding on a speaker like this).
I should mention the Zanden 300B sound the best on many types of music from the midrange up - detailed and musical - but just sound anemic down below. If there was a way to biamp the speakers, or otherwise adjust the bass quality, I would stick with the Zanden. I tried biamping with Lamm and Zandens, and it sounded really wacky. I also tried left speaker with Lamms, and right with Zanden (ok, shoot me), and sounds surprisingly OK if I'm sitting in some off-axis position and don't mind the different sonic signatures - the brain somehow compensates after a while.
I have Trio Omegas with double and now I'm using triple 225 subs. At first I used a Berning Siegfried and it was wonderful except for the huge turn on and off thump it had. It's not sensitive to impedance like most OTL's or SE amps. Now I have some Butler Monads and they were as good as the Berning and dead quiet too so I sold the Berning. Now I have a Tube Distinctions 15watt SE amp that is outstanding but haven't had time to compare it to the Monads. It's way more engineered than the TEAD Linear A. I could be happy with either but one of these days I'll have to do a shootout. I'd love to try the First Watt F3 also and may do that since they have a return policy.
Hi Theloveman,

sorry for the slow answer.

I am using only one REL sub and yes it can go up enough, the REL Studio III can not do this but the Stentor can. My room is only twentysomething square meter with some tricky furnitures. My listening level is not too high, so I never felt I need more sub. The only amp which was as good to my music listening habit as the Altmann, is the EAR-Yoshino 834T integrated, which I was using between the Altmann and the Kageki for few months.

I just got a DEQX digital crossover/room corrector and planning to try a multi-amp, digitally crossed system where one amp (Altmann BYOB with Altmann Attraction DAC from the digitalout of the DEQX) drives the Trio less sub and the other, sub way is driven by the DEQX as well through another Altmann DAC to the line level input of the REL. This way an almost perfectly timed integration is possible between the Trio and the REL sub. I hope so :-)
Hi Ferenc,

Thank you for your response.

Given that your listening level isn't very high, I can understand you're not needing the additional sub, but I am convinced that there is a lot of ambient information in the low frequencies that can only be reproduced in stereo. This element can lend a lot towards realism.

Obviously from your prior posts, you've had considerable experience with tube amplification on the Trios, so I am curious if you find the Almann to be the equal of the tube amps in terms of instrumental weight, body, timbre, and harmonic richness? These are the areas that I typically find solid state amps fall short of a good tube amp.

My room is similar in size to your own, so perhaps the Altmann BYOB would provide adequate power for me as well, though I may listen a bit louder than you on some occasions. I am surprised that since you like the Altman so much, you didn't decide to triamp the Trio with the DEQX providing the crossover and EQ for each of the three drivers. In my mind, the phase and timing errors between the three horns could be completely corrected with the DEQX, and I would think that since those timing and phase errors occur at frequencies where the human ear is considerably more sensitive, they would be far more audible than the ones between the Trios and the woofer.

Of course, you'd have the added cost of two more BYOB amps, but even the cost of three of them isn't as much as most SETs. I do wonder if you could run 3 amps without compromise on one large car battery? If these amps sound as good to me as they do to you, I'd love to try that myself.
I have the curve if anyone is interested. It has two peaks of 38ohms at 90hz and 65ohms at 950hz. It's about 9ohms at 10K hz and is faily flat from 8k out to 20k.
Hey Jls3, after all this time, someone with an actual impedance curve. Is the impedance plot you are describing coming from the older 8 ohm version or the newer Omega series rated at 19 ohms? I can't even begin to comprehend the 65 ohms at 950Hz as that frequency is well above the lower cutoff of the midrange driver's operating range--no low powered SET or solid state amp will be able to drive it at that frequency. If I may ask, how did you obtain this impedance plot? Was it derived from information published elsewhere or did you perform actual measurements?

If you have an actual graphic display that could be sent via e-mail or posted here on the forum, I'd love to see it. Thanks for the information.

My experience is limited to the Duo, not the Trio, but the speakers are enormously revealing. I used them the first year with a pair of Audiopax 88's and they were delicious. However, the move to the Lamm ML2 was noticeable in a variety of ways.
The speakers also benefitted from Apex footers, and very good wire- the jumpers that came from the factory pale by comparison to the aftermarket choices.
I have never been completely satisfied with the bass from the Duo though. Maybe it is me, or my room, but the problem isn't lack of bass, it is a discontinuity in the sound between the horns, which are very open, and the monkey coffins, which sound like amplified speakers. Perhaps in a large room- large enough to get the distance you probably need to let the Trios converge properly- the bass can be sorted out. I know AvG now offer a smaller horn-loaded woofer other than their monster bass horn, but I have not heard it. Jim Smith is a very good guy and quite knowledgeable.
Hi Theloveman,

actually you are quite right regarding the active multiamp setup. I was thinking of it a lot, but I definitely would like to use the digital output of DEQX to drive 3 Altmann Attraction DACs plus 3 Altmann BYOB amps and the active sub. However in the meantime I realized that soon we will have to move to a new home and in the new home there will be not enough room to take the Trio over so I probably will be forced anyway to change (sell) it, and I am looking for the Zu Definition Pro as an ideal replacement candidate. In case of the Zu two ways for the active driving would be enough, one for the sub section and one for the rest, as a kind of compromise.

Regarding the Altmann BYOB amp, it is very difficult to compare it to any tube or SS amp. It just sounds right and to be honest I can not explain what is the reason. It does not have a real signature on the sound just let the music flows. Since I own the Attraction DAC/BYOB amp I am just spending my money buying all the different music on different media like CD, DVD and LP. If there is anything in the music to entertain you and grab your attention, this combination will give you the best part of the music. It shows the quality difference between recordings, but does not require your attention to deal with it, you have to deal with the music content only. To be really honest after owning $100k plus amp and CD for some 6 years I can not imagine to find anything which suits me better. On ANY price and I am talking about $2k for the amp and the DAC plus a Macbook against $100k plus amp and CD. I am hooked.