[EVOLVIST]

I guess the title says it all, or maybe not. Is there any such thing as a Class A digital amp? I guess that's to say Class A topology that takes digital input and spits out wire to your speakers.

[RDavidson]

You're mixing your mashed potatoes with your peas. Note there's no such thing as a digital amp. That's a misnomer. Class D doesn't stand for "digital." https://en.m.wikipedia.org/wiki/Amplifier

[EVOLVIST]

You're mixing your mashed potatoes with your peas. Note there's no such thing as a digital amp. That's a misnomer. Class D doesn't stand for "digital." https://en.m.wikipedia.org/wiki/Amplifier

No, no...I don't mean a Class D switching amp. Class A topology with digital inputs from a digital DAC.

Chord Electronics is said to be working on a line of amps in this "class," which takes the digital signal, and without adding distortion amplifies the sound. They say the first one will be 20 WPC.  So, I'm wondering if this is a whole deal, or has it been done before.

Google pulls up nothing but Class D, but I guarantee a switching amp is not what they are talking about.   

[G Georgopoulos]

Chord Electronics is said to be working on a line of amps in this "class," which takes the digital signal, and without adding distortion amplifies the sound. They say the first one will be 20 WPC.  So, I'm wondering if this is a whole deal, or has it been done before.

Google pulls up nothing but Class D, but I guarantee a switching amp is not what they are talking about.

yes it has been done

[Armaegis]

So... basically you're just looking for an amp with a built-in dac??  I'm sure they exist, although the only ones coming to mind for me right at this moment are A/B.

[RDavidson]

Oh. OK. Hmmmm.....nothing really comes to mind. Maybe the Parasound Halo integrated puts out a few Class A watts, as most Parasound amps do. But, you're probably talking about high bias class A, like 20-30 wpc I'm assuming? In that case, I know of none.

[EVOLVIST]

yes it has been done

Like what?

[G Georgopoulos]

Like what?

hahaha, since the begining of digital audio most dac's employed class-a buffers
now suppose you have a world class class-a amp
putting a crap dac in it won't make it better than other pure (non-dac) world class class-a amps

btw, i don't like class-a,it sucks (power)...

[santacore]

The recently released Exogal Ion is going in that direction, although not a class A amp. They sell it as a power dac, and not just a power amp.

http://www.exogal.com/index.php/products/ion-power-dac

[EVOLVIST]

The recently released Exogal Ion is going in that direction, although not a class A amp. They sell it as a power dac, and not just a power amp.

http://www.exogal.com/index.php/products/ion-power-dac

That's very curious. Interesting.  I have one of these coming in for audition from Chord, but it's an AB design.

http://www.chordelectronics.co.uk/product/ttoby/

It's not quite the technology I'm looking for, but the specs are nice (for what that's worth).

[skunark]

Devialet merges a class A with a class D amp with DAC.   I went to a presentation where the bird-eye explanation was the class D amp provided the current and the class A mosfets provided the voltage, they have some patents on this approach.   Sadly they paired it with a brand new speaker that I haven't heard before so it was hard to say what did what and what was lacking.
https://en.devialet.com/expertpro/#technologies/

Audio Research has an integrated class A tube amp with a dac:
http://www.audioresearch.com/en-us/products/integrated-amplifiers/gsi75

Pathos has a Class A amp with dac:
http://www.pathosacoustics.com/index.php?option=com_content&view=category&layout=seminyak:features-intro&id=2&Itemid=318&lang=en


Jim

[roscoeiii]

Some other examples of the digital amp the OP may be referring to are the TacT 2150, which is what I use with my DEQX HD-4 sending it a digital signal. The NAD M2 is another example and I think NAD has used this in other amps in their line as well (but not all).

But the M2 and the TacT 2150 are not Class A. Not entirely sure if the traditional amp typologies (Class A vs Class A/B) apply to this type of digital amp. But they put out a lot more power than you'd expect from a Class A design (or rather a Class A design that isn't massively heatsinked etc like the Pass big boys).

[KLH007]

The recently released Exogal Ion is going in that direction, although not a class A amp. They sell it as a power dac, and not just a power amp.

http://www.exogal.com/index.php/products/ion-power-dac

The Comet/Ion combo never converts digital to analog, so there is no D/A process, PCM to PWM directly driving the outputs, simply a power supply that drives speakers.

[roscoeiii]

The Comet/Ion combo never converts digital to analog, so there is no D/A process, PCM to PWM directly driving the outputs, simply a power supply that drives speakers.

Yup. Same for the amps I mentioned.

[G Georgopoulos]

The Comet/Ion combo never converts digital to analog, so there is no D/A process, PCM to PWM directly driving the outputs, simply a power supply that drives speakers.

PWM is class-d,where is the digital?

[srb]

It there was no analog conversion somewhere in the circuit stages before leaving the amplifier, there would be no music to listen to.

[EVOLVIST]

Some other examples of the digital amp the OP may be referring to are the TacT 2150, which is what I use with my DEQX HD-4 sending it a digital signal. The NAD M2 is another example and I think NAD has used this in other amps in their line as well (but not all).

But the M2 and the TacT 2150 are not Class A. Not entirely sure if the traditional amp typologies (Class A vs Class A/B) apply to this type of digital amp. But they put out a lot more power than you'd expect from a Class A design (or rather a Class A design that isn't massively heatsinked etc like the Pass big boys).

The Tact 2150 is a very curious amp. For the time it was very cutting edge, outputting to 24/192, but by today's standards if I'm playing DSD (which I rarely do) the signal will be truncated. It's pretty close, in theory, to what I'm describing.

After reading the manual, though, not only isn't it clear about what class amp it is, but also a THD of 0.01 is quite a bit of noise after going through the rigors they describe in coming to their product.

This outfit isn't around anymore, but when they were, it would take 5k to take one of these home.

[KLH007]

I misspoke about PCM to PWM, apparently Exogal doesn't use PWM to drive their outputs, they won't actually disclose the method they use, too much time & effort in R&D to give away, anyway the Comet/Ion power DAC sounds spectacular.

[G Georgopoulos]

I misspoke about PCM to PWM, apparently Exogal doesn't use PWM to drive their outputs, they won't actually disclose the method they use, too much time & effort in R&D to give away, anyway the Comet/Ion power DAC sounds spectacular.

[AmpDesigner333]

I couldn't resist....  Tommy O here, owner of Digital Amp Co, a.k.a. "Cherry Amp".

There IS such a thing as a digital amp.  Misnomer and all.  At some point, the control signal (audio) is represented as a digital value (by the modulator).  An upcoming article in POF about the Golden Cherry Maraschino Amplifier will contain more detail on this.

Direct digital amps ---- those that perform modulation in the digital domain and take a digital input (typically PCM) don't perform sonically as well as a D/A converter driving a high performance ANALOG input "digital amp" such as the Maraschino.  The difference is about 20dB!  Why?  Well, most of such efforts have been open loop, and that makes high performance very difficult.  Attempts at wrapping such an amp with feedback (using an A/D) to reduce noise and distorion tends to produce that "too much negative feedback" abrasive sound of the 1990s style Class-AB amps, like Adcom.

In case you don't know me, I've been designing amps for 30+ years.  It can be done.  AND, I've done it.  The results are simply in favor of analog input Class-D.  Unfortunately, most analog Class-D these days is pre-fab module based ---- amp manufacturers too lazy or greedy to design their own amps....