Class D with high efficiency speakers

@tweak1 no the Voyager is not stock it has the EVS mod.

A quick update. My AGD Audion monoblocks have now been in my system for over a week. They arrived in a very robust plastic flight case and fit/finish of the amps is first rate. The amps are comparatively light so installing them was very straightforward.

On power up the Gantubes glow with red LED’s. I was slightly concerned that this would be too bright but it’s quite subtle and tasteful in my opinion. I like the idea that if there is an upgrade in future I can change the Gantube rather than the whole amp.

The first thing to say is that the amps do benefit slightly from a few days break-in. However, they seem to require no ‘warm-up’ when switched on. My Atma-Sphere S30 needed 30 minutes before the magic happened!. The first impression was that the soundstage has widened and instruments at the back are more defined and easy to follow. But wow! the vocals are super-clear and form a fantastic central image. There’s so much detail that instruments each seem to have their own space. The bass is very tuneful and, again, easier to follow. A really important thing for me is the sound of cymbals and snares being hit and these amps really do bring a ‘live’ quality to their sound.

I had a concern over connecting my REL S812 to the amps as REL warn that ‘most’ Class D amps can overload their input due to floating ground i.e. the -ve terminal is not ground. I started to follow AGD Production on Instagram and was surprised to get an answer to my question within an hour from the designer himself (Alberto Guerra). He confirmed the -ve terminal is ground on this amp so I was able to connect my REL at high level across the speaker terminals.

I think these new Class D type amps are going to change the audio scene over the coming years. Particularly for people like me that don’t have a dedicated listening room, it’s great to have equipment taking up less space (and energy).

I drive Lansche 4.2 with Starkrimson full range.

My impression of Starkrimson is very positive.

But amplifier and speakers need to have synergy due to impedance and frequrency aberration.

Thus the best way is to do audition it yourself.

I will send my tour unit to the person in next line tomorrow.

Efficient amps and efficient speakers, sounds like a fabulous combination and it is.

I've decided to try the AGD Audion monoblocks. I have them on order now and will give some feedback once they arrive.

@orchardaudio 

Leo I haven't switched back yet. Good combo with the Zu's

@evank thank you.

I just hooked up my Zu Omen MKII's to my Orchard Audio Starkrimson Ultra GaN FeT amplifier. I use Audio Physics classic 20's with the Orchard amp. These are just my thoughts listening for about 20 minutes right now. Preamp is Schiit Freya +. The Zu's are 97db 12 ohm. I usually use my Zu's with the Willsenton R8, 25 watts in triode mode. They sound pretty good so far. Bass is more impactful but not sloppy. Overall, the music has more authority.  No problems handling the power of the Starkrimson amplifier. Zu says their speaker can be used with all types of amps, low power or high power. I would probably have to fiddle around with speaker cables to properly tune it 100% to my liking.

Few more minutes gone by. I'm digging it. I'm not an expert but I can say go for it.  Whichever brand you decide to go for you should be fine.

@orchardaudio 

Not yet. I'm demoing some new cables right now on the Zu's and my tube integrated. Soon I promise.

@evank have you had a chance to try the Starkrimson amp with the Zu speakers? I am interested in hearing your thoughts.

I have quite a number of customers that use my GaN amps with 95+ dB speakers.

Atmasphere - thanks for an informative answer, as always. I am not sure about the Dream Maker speakers

You might ask Duke.

Atmasphere - thanks for an informative answer, as always. I am not sure about the Dream Maker speakers, but it may be that they are designed for high output impedance from the amps (like your speakers) so that class D might sound a bit lean, compared to more beefy OTL sound from the MA-1s. Not sure, have never compared. My gut feeling would be to try class D first in a smaller system.

I am sure class D can sound great and it would be great to try, with my sensitive Dream Maker speakers (16 ohms, efficiency:  92 dB/1 watt, Voltage sensitivity:  89 dB/2.83 volts). If class D can lift these even further I am all ears.

I want to correct an impression I may have given in my post above. I have not heard many class D amps in my audio  circle. Mostly, solid-state amps at a lower price level than my MA-1s. So - I really don't know.

One  thing I do know, is that running the passive speaker in an active speaker combo from an MA-1 amp instead of the active speaker amp, can result in a big lift of performance. This includes Audioengine and Elac active speakers. They sound much better.

Only combo like that I have heard is Atmasphere Class d running Classic Audio Design at Capital Audiofest this year and the Class D sounded spot on  and hung in there with the OTLs.

Give the PS Audio M1200's a trial. Class D using a long lasting tube for the input stage. 

I am sure his new class D sounds good. But I would guess it is a case of plus and minus?

@o_holter Its been a year and a half now and I've not heard any tradeoffs. But if your speakers are designed for amps with a high output impedance (and mine are, FWIW...) things might be different. If you are dealing with a speaker like that you might find the class D to be a bit leaner in the bass because it will make less energy into the impedance peaks that are in the bass region of the speaker.

I would certainly try it. It might make for a good match. 

I would not sell the OTL - wait until you’ve tried other types of amps, and give it time. I have Atma-sphere MA-1 v 3.2 monoblocs, mainly fed by the Io Eclipse. They are a daily joy in our system, with top level NOS driver and output tubes and clean power. I am on regular visits to my friends in our local audio circle, some of them with class D amps, but I always come back thinking that I love the tube OTL sound at home.

I was surprised that Ralph / Atma-sphere - post above - wrote that he didn’t miss it (M-60). I am sure his new class D sounds good. But I would guess it is a case of plus and minus?

Thank you for th replies so far.

I've had the DUO's since 2007 and agree they need thorough set up and matching equipment. I found Jim Smith's book invaluable in getting my listening position and speaker position just right.

The AtmaSphere OTL's are a very good match (I've tried a number of amps) and I really like the sound I've been getting for the past 10 years+. But I've been intrigued by Ralph Karsten's views on Class D and the fact that he prefers his Class D amps to his own OTL's!

Ralph will know more about amplifiers and systems than I'll ever know so it was him that has set me off on this exploration!

I've also been in contact with another Avantgarde DUO owner who is using a NAD Class D amplifier very satisfactorily. 

I like trying things that are a bit different and I'll update this thread as I experiment.

The Avantgarde Duos have self powered sub woofers so low bass performance of any amp will not be a factor. They are amongst the most revealing, most dynamic speakers ever made & until you actually listen to them properly set up with top quality ancillary equipment, most will not truly understand what they can do & how great they can be.

I powered mine for years w/ an Art Audio PX 25 tube power amp (5 watts / side) & it was truly magical at any volume. They will be a real test for a class D amp & any shortcomings it might have. I’m very curious to hear how that all turns out.. please keep us updated. Thanks

@jaymark 

Is your Voyager stock?

Take a right turn.  Try a Pass XA25.  I will never sell mine!

I know, it is Class A.  I have left it on for days and didn't notice any electricity use increase.  Class D will be detailed but so is this one.  This unit is single ended only, no balanced output.  It is very quiet(S/N).  A demo from Reno HiFi would be about $4k.

I know your question was about Class D but with the efficiency of your speakers you can get away with very little wattage, either tube or solid state. Have cou considered a very low wattage tube amp, like 5 watts or less? Alternatively, maybe a firstwatt from Pass? I'm about to try some MA-1 amps from Atma-sphere but part of the issue is that to do that transformer less you need A LOT of tubes which makes tons of heat. A 300b or 845 amp will run significantly cooler. Just a thought 

Duos with class D? But...why?

I ran the LSA Voyager GAN class D amp into Spatial X3 high efficiency speakers.  This pairing sounded great.  The top end extension may be a tad better than the superb Coda#16 class A amp that replaced it.  However, the midbass and low end was not as good as the Coda.  

I would consider the PS Audio s300. I like the sound of the M700s on my ML electrostatics.

To try, best is go for Aiyima's offering(official store) in Aliexpress they are below 100 USD and has got very good reviews at ASR testing.

I am running Peachtree Nova 300 and Harbeth 30.1 24/7 with no probs at all and electric bill is almost un impacted. With a little effort -cords, ethernet- it sounds really good.

I'm using a Peachtree GaN 400 with Tekton Double Impacts (98 db/4 ohms), and I'm really liking the sound, especially with the addition of a tubed Rogue preamp.

My question is, does anyone have any experience of running a new Class D GaNFET amp into high efficiency / high impedance speakers?

@rocketiii My speakers are 98dB and 16 Ohms. I've been running our class D GaNFET amps on them the last year and a half or so. They replaced a fully optioned set of our M-60s. I don't miss the tubes at all.

I'll let you know after the weekend. I have an Orchard Audio Starkrimson which I can hook up to my other system which consists of Zu Omen mkII. Give me a few days.

I ran a desktop mini amp with a Tripath TA2024 chip (10W) through my 91db speakers (Closer Acoustics OGY). Yeah it works just fine. No complaints. I only upgraded to a typical 40W class A/B amp for more power. 

One thing I would be concerned about is the noise floor of some of these cheaper class D amps. The Tripath amp is very mediocre by all standards and the noise floor is noticeable when you put your ear against the driver. I experience the same thing with my class A/B amp. It's hardly a bother.  

If the Topping PA5 measures well then by all means get it. The convenience of having a book-sized amp which runs cool is a huge plus. 

Ralph recently introduced his own class D amps. He says he likes them even better!

You can buy and try the Topping PA5 amp ($349). Advanced Class D 55wpc. It measures exceedingly well!