Pairing MLs with a Power DAC

[Trias]

The last couple of years has seen the advent of amplifiers that can be described as Power DACs, since they are essentially (multi-input) DA converters that can directly drive a set of speakers. The most well known is the NAD M2, but it has more recently been joined by more affordable options such as the NAD C390DD, the Wadia 151 Power DAC mini, the NuForce DDA-100, and this summer the NAD D7050 and NAD D3020.

The concept is interesting to me, as child of the digital age who has never owned an analog audio source, it makes sense to eliminate much of the intermediate analog circuits, which are essentially a source of noise and distortion.

The question (as with any amplifier) is, how will they fare driving a pair of Martin Logan hybrid electrostats. I have no doubt that the M2 would have any trouble. It is also way beyond my budget. (So is the NAD C390DD, unless I can find a good ex-demo deal).

Has anybody here had any experience pairing any of these to a set of Martin Logans?

 

[JonFo]

I have a NAD D7050 on pre-order, so hopefully soon I can fill everyone in on the results.

Like you, I'm a big fan of this concept, as I see it being incredibly effective with highly reactive loads like the MLs.

The challenge is getting an amp design that can flow sufficient current into the ESL system (capacitive panel with a step-up transformer ahead of it + whatever passive crossover in stock units). The M2 seems to get close, and I'm sure the 7050 will be lacking in that dept. so I'll not try and push it.
Just to be clear, my 7050 is for a dynamic speaker-based system in the living room, so it is NOT going to be used on the ML's. I'll just run a test and measure.

Have your read the technical briefs on DDFA? They are fascinating.

I have some ideas on this approach I hope to explore in the near future. But in any event, powerDAC's are the future of amplification, that's for sure.

 

[RUR]

I've had experience with another power DAC, the TacT S2150. When it worked, it was easily the best amp I've ever heard, bar none. Unfortunately, the TacT and the Summits didn't play well together and the amp would invariably give up after a week or three. ML and TacT politely asserted that the other party's design was problematic, and I never did get the issue resolved.

Having said this, I would absolutely encourage you to try NAD's version of this potentially great technology. Just make sure you have a warranty on the amp in case it doesn't work out.

 

[JonFo]

Hi Ken (RUR), that's right, the TacT's were the original PowerDAC amps, their first model had decent specs for current flow, but subsequent models like the 2150's like yours were engineered for normal dynamic speaker duties and to hit a lower price point (still spendy though).

I think the TacT design is not as comprehensive as the DDFA from CSR/NAD in terms of the feedback system. Assuming one engineers the rest of the circuitry for demanding low-impedance loads, it should perform nicely.

But good recommendation on the warranty if trying them out on an ESL.

 

[RUR]

Hi Jonathan,

Due to the "pure digital" topology, the TacT preamp controlled volume via Cat 5 connection while sending the amp a 0 dBFS signal via digital XLR. Will you be using the NAD in the same way i.e. FS from your AVP-A1, controlling volume via the NAD remote commands?

Ken

 

[Bevensee]

I listened to the French devaliet driving a set of Theos this summer. They did a great job. And they look amazing.

 

[RUR]

So called power DACs are designed to perform amplification at the very end of the signal chain so as to reduce amplification of distortions created in the analog stage. The enabling technology was pioneered by Tocatta back in the '90s, and the first commercial product AFAIK was the TacT Millenium ca. 2000. At some point, TI purchased Tocatta's technology and renamed it Equibit, where it was used in a very few high-end AVR's, and TacT products until their demise. Meanwhile, NAD developed their own version of the technology as used in the M2 and now other products.

The only other company I know of who produces a power DAC is Behold. Devialet's amplification approach is entirely different.

 

[bonzo]

Hi How is the NAD D7050 different from a Naim unitilite which has a built in DAC, streamer and Amp, or pairing an Audiolab M-Dac with Mpwr?

 

[Bevensee]

So called power DACs are designed to perform amplification at the very end of the signal chain so as to reduce amplification of distortions created in the analog stage. The enabling technology was pioneered by Tocatta back in the '90s, and the first commercial product AFAIK was the TacT Millenium ca. 2000. At some point, TI purchased Tocatta's technology and renamed it Equibit, where it was used in a very few high-end AVR's, and TacT products until their demise. Meanwhile, NAD developed their own version of the technology as used in the M2 and now other products.

The only other company I know of who produces a power DAC is Behold. Devialet's amplification approach is entirely different.

You re right. Devaliet is a combination of DAC, ADC class A and class D, so it is a bit different.

 

[Trias]

Hi How is the NAD D7050 different from a Naim unitilite which has a built in DAC, streamer and Amp, or pairing an Audiolab M-Dac with Mpwr?

The unitilite is a DAC combined with a conventional analog amplifier in a single unit. The D7050 (like the M2) is a DAC where the signal is amplified and reconstructed at the same time. (More precisely it is a class D amplifier that constructs a PWM signal directly for the digital PCM signal. The only the truely analog bit is the final low pass filter.

 

[JonFo]

Hi Jonathan,

Due to the "pure digital" topology, the TacT preamp controlled volume via Cat 5 connection while sending the amp a 0 dBFS signal via digital XLR. Will you be using the NAD in the same way i.e. FS from your AVP-A1, controlling volume via the NAD remote commands?

Ken

That NAD is also a streaming player, so I'll use its own internal DLNA renderer to play back some high-res FLACs of the test tones and sample music.

I could never integrate this with the current big rig. So I'll just drive one of the panels (the smaller center channel one) with one output channel to measure / test.

But yes, a challenge in a pure PowerDAC amp is external gain control.

My ideal chain is a pre-pro like the AVP but with digital outs and one gain control channel output, then I can string speaker processors and other items between the pre and some PowerDAC amps and still be able to have uniform gain control across all 15 or whatever amplification channels I happen to use at the time.

 

[RUR]

But yes, a challenge in a pure PowerDAC amp is external gain control.

My ideal chain is a pre-pro like the AVP but with digital outs and one gain control channel output, then I can string speaker processors and other items between the pre and some PowerDAC amps and still be able to have uniform gain control across all 15 or whatever amplification channels I happen to use at the time.

Same boat I'm in, though only six channels. In theory, I can do it with the Trinnov, but it's an expensive experiment and the idea of trusting the NAD remote to simultaneously and accurately adjust gain on multiple power DACs makes me very nervous.

TacT was onto something with their hard-wired and daisy chain-able gain control signal from preamp to power DAC(s).

 

[Bevensee]

Just to clarify: TacT is still alive and kicking. They just changed the name to Lyngdorf Audio. The Millennium powerDAC is now in 4th generation.

 

[JonFo]

...
TacT was onto something with their hard-wired and daisy chain-able gain control signal from preamp to power DAC(s).

Yes, them and Meridian long before, as they have always transmitted full level digital audio streams with separate gain & command signals to their DSP speakers. So the speaker is told it's gain offset from reference is X as a command, then as the user manipulates the 'Volume' for the system, all speakers are told the target level the user selected. This is how all amps or powered speakers should operate.
It's silly legacy to vary gain before the final amplification step. Tons of noise and or distortions creep into systems because of this.

So yes, future PowerDAC amps need to have separate gain control channels, understand notions like gain offsets, etc.

 

[JonFo]

Just to clarify: TacT is still alive and kicking. They just changed the name to Lyngdorf Audio. The Millennium powerDAC is now in 4th generation.

Thanks Bevensee, it's easy to forget others might not know that. They also create some pretty amazing (and uber expensive) stuff as Steinway-Lyngdorf

If I wanted to switch to TacT PowerDAC amps, I'd require three Milleniums, and four SDA2175's so about 36,000 Euros or over $50,000

I think I'll stick with the Sanders ESL amps for now.

 

[Rich]

I think I'll stick with the Sanders ESL amps for now.

For the money, they are hard to beat. Love my Sanders monoblocs.

 

[RUR]

Just to clarify: TacT is still alive and kicking. They just changed the name to Lyngdorf Audio. The Millennium powerDAC is now in 4th generation.

I understand the confusion, but the story is a bit more complex. The original TacT was formed last century as a partnership between Peter Lyngdorf and Boz (can't recall his full name). Peter and Boz had a falling out in the early 2000's, which ended with Boz owning the TacT name and Peter continuing as Lyngdorf Audio. Peter retained the rights to sell the Millenium and continues to sell and improve it - now Mk IV IIRC.

The "new" TacT, now owned solely by Boz, developed some terrific new pre-pros and amps, including the 2.2XP and S2150 I once owned. Unfortunately, he closed the doors early last year and sales and service of TacT product have ceased. There were plans to license the technology to Emotiva for a new pre-pro, but that, too, fell apart and Emotiva now plans to use Dirac's software in that product.

So, no more TacT.

 

[bluenote56]

Tact / Lyngdorf

As I am seriously interested in switching amp technologies, I dropped an email to Lyngdorf, if any problems may arise driving my Summits.

This is what they responded: they can't make any statements about former TacT products, but the actual SDA 2175 will go well along with ML electrostats. Even, if the summit may be somewhat demanding, there is plenty of power and there will be no issue with low impedances.

Their SDA2175 appears to be a bargain. Worth for Evaluation. I will give it a try.

Best regards
Johann

 

[bonzo]

Hi, for those who mentioned Devialets, there are reports on the internet that Devialet does not do well when impedance level drops below 4 ohms. How do I test that? I am auditioning them with Logans probably this weekend, so while playing a song, how do I test a drop in the impedance

 

[JonFo]

^^ To test the low-impedance scenario, play tracks with lot's of high (>10Khz) content.
So instruments like the violin, that have harmonics in the upper regions, picolos, and if on rock, anything from [insert whinney high-pitched singer here] ;-)

If the amp doesn't blow, or audibly distort, then maybe it passed. but it will be hard to tell if it will survive long-term.