[brj]

Hello!

This might get a bit long, but I just started researching digital amps, so let me take a crack at defining them so the more knowledgeable out there can clear up any misconceptions I might have...

A true digital amp accepts a digital signal encoded via Pulse Code Modulation (CD's, etc.) and converts it to a digital signal encoded via Pulse Width Modulation.  Thus, we go from representing the amplitude of an analog signal using variable voltage measured at a constant sampling rate to representing the amplitude of an analog signal using constant voltage with a variable pulse width.  Final conversion to analog prior to hitting the speaker is handled using "simple" filters.  Benefits include the ability to make smaller, lighter amps that have high (>85%) input to output power efficiencies, and to maintain a digital signal throughout more of the audio path.  Challenges include providing enough bandwidth and switching speed to handle the high frequency portion of the audio spectrum.  These devices are labeled "Class D" devices and, while they have been around for many years now, have finally started to come down in price as the required chip count per amp started to drop.  Volume is controlled digitally, with historically variable results in terms of sound quality.

So how did I do?


Ok, with that out of the way, my actual question is... are "affordable" digital amps finally competitive with their tube and solid state cousins in terms of sound quality?

To bound the question a bit, let's call anything under $2000 USD "affordable" - and the lower the better!  I guess I should also point out that by "sound quality," I'm thinking about distortion, accuracy, etc. and the not personal preference usually seen when comparing "warm" tube sounds with "analytical" solid state sounds.

Ok, if you managed to stay with me this far, can you offer any insights into the current state of the digital amp?

Many thanks!

-Brian


By the way, I found the following digital amp manufacturer list while googling this topic:

   http://www.digitalamp.com/DigitalAmpCompanies.htm

I don't know how complete it is, but there were more companies there than I was expecting.

[ABEX]

I wrote a little here about what you are asking.
http://www.audiocircle.com/index.php?topic=7542&start=40

I would not read to much into specs as it's the sound that counts. There are many examples as to things having great specs ,but not sounding great and vice-a-versa. Tube amps measure with high distirtion yet sound beautiful with the right source matrial and setup.  

Some folks are replaceing their ultra expensive gear and getting the Modified Panasoinc that Wayne of Bolder here at AC is doing which is a mighty big statement.

It also comes down to personal taste ,how deep your pockets are and associated equipment, most importantly your speakers, as to  what shall determine weather or not they can replace standard Class A\AB amps in ones system. Nothing is as simple as to weather one is going to get away with using a certain type of amp in all situations to get the best performance.

Personaly I think the new Digital amps give great or better performance than one would expect from an ultra cheap component like the Panasonic Digital Amps.  

AS far as the state of Digital amps:
We are just seeing the beginning and I would look at the manfs. like TI,TacT and the others news. Manfs will be getting more units out also.Surprisingly Bolder Amps are using Digtal also and they make great stuff.  

If it were me and I had $1K right now I would get the Panasonic unit through Wayne of Bolder because he is taking the 2nd rate parts that panasonic is using and replaceing them with Audiograde parts. I learned a long time ago that you get your best bang for the $$ by getting modified equipment rather than pay exuberant prices for SOTA stuff.Wayne does good work and the price is reasonable after taking into account what he has to do in order to do the mods,the parts used etc..

If you want to go seperates there are a few options. There is Solar Hi-Fi here at AC and Kevin will help you out. It would be a way of tailoring the amp to your system I think.

It's Panasonic or Solar Hi-Fi for my taste in Digital amps at this point.

Hope that helps and good luck!

[JohnR]

Your definition seems OK to me, except that this business about "true" digital amps is, IMO, mostly marketing. All switching amps are Class D.

[brj]

Thanks for the replies, guys!

ABEX -

I was looking at separates, and I've stumbled across some of the companies you mentioned.  My problem is that since I'm planning what will be my first real audio system, I don't have an existing system in which to A/B components.  Research can only do so much, but I'm trying to do as much as possible - and most of that is focused on bang-for-the-buck and where the various audio component technologies are going.

JohnR -

My reference to "true" digital amps was more geared to the use of digital inputs (vs. analog) rather than the class definition.  It wouldn't surprise me in the least if this label is marketing driven...

-Brian

[KevinW]

Hey, Glad to see that my amp makes the cut on 'affordable' cost by $1. That's luck, plain and simple

My take on the different flavors of Class D amps is a little different than most opinions.  A class D doesn't care whether the signal it amplifies is analog or digital, it just amplifies it and then that signal is low-passed into analog.  

What sound quality boils down to is the quality of the input signal, which is a direct function of the quality of the input circuitry controlling the PWM conversion.  Using a direct digital control reduces the number of expensive components needed to make good sounding control circuitry in the digital domain only.  However, the engineering needed to make direct-digital control is tricky, and appears to be only just now implemented in a decent manner.  But this is what allows the Panny receiver to be so cheap... ignoring any attempt to spend money on analog.

Regarding analog, well hasn't making good sounding analog circuitry been the name of the game for 50+ years?  This takes good engineering and quality parts to do it right, just like it always has;  and don't expect that to change with so-called 'true-digital' amps.  That is a misnomer.  If you like to listen to vinyl or tuners, there is no other choice than a good quality analog-controlled class D.  

One final observation is that there is nothing inherently superior in a digital-only class D amp regarding sound quality.  This depends on many other factors.  However, digital-only class D amps can be cheaper than an amp that also does a good job with analog signals.  This is certainly a different kind of advantage to those who are willing to compromise or sacrifice their analog sources.

[Tyson]

I believe kevin is correct.  If you don't listen to analog, the digital amps are a godsend.  Since I don't have a turntable, and VCRs & tuners are interently low fidelity, the direct digital input amps are a godsend of quality sound for digital inputs for very cheap.

What I want is a wireless antenna that takes an over the air digital signal from a PC based music server (or even a 400 CD changer or 2 or 3 from another room), keep it purely digital until the output to the speakers, and thus be able to have a huge library stored and programable from the server.  I'd never have to put in or take out another disc in to a transport again

[JoshK]

Tyson,

They is an enterage (sic) of 801.11g devices that will do just that. Look in the Square circle under music server projects and you'll start to see what I am referring to.

[Brad]

Like Josh says...

The Slim Devices Squeezebox seems to focus the most on sound quality though  

[brj]

Kevin and Tyson, thanks for the replies!

I guess I should state that I personally don't expect to use any analog sources, so while a given amp may handle an incoming analog signal as adeptly as an incoming digital signal, the avoidance of all D/A and A/D conversions upstream of the amp itself seems like the primary benefit (to me).  Basically, digital amps seem like a great way to save money at a given performance point, reduce power usage, device size and overall system complexity.  What I don't know is whether class D amps have evolved enough to compete sonically with those analog competitors that have "50+ years" of head start (to quote Kevin).

I would like to pursue the higher resolution SACD or DVD-A formats at some point, but until they approve a means digital output, I think I can continue living with standard Redbook CD's.  This would be especially true if something like a modded Panny could replace everything but the speakers and source for about $1k!  Heck, I could use my existing nothing-special DVD player as a source, start with a base Panny and then divert a much larger chunk of my budget into the speakers.  Would this be perfect?  Of course not, but since upstream components seem to be evolving faster than speakers, this approach would seem to protect the value of my system the longest.  Mod the Panny and DVD player a bit down the road for a relatively low cost, and then enjoy my system for a few years while letting the multi-channel format wars, digital evolution and other growing pains sort themselves out.

Gee, it sounds like I know what I want, doesn't it?  You wouldn't know from reading that I've changed my plans 30 times since I started reading this outstanding forum a couple of months ago!!    I like doing my comsumer research up front and saving for the "right" product at the beginning... but the audio industry is proving more challenging to sift through than any other I've seen!

Kevin, is your base amp still under $2k with shipping and taxes?     (By the way, I'd like to play with active crossovers someday, which would require separate components instead of a single receiver, so that enters my equation too.)

Thanks again for the enlightenment!

-Brian

[brj]

*laugh*  Great, now I've got another option to go research!  Thanks guys!  

Of course, that offers a completely different solution to my previous question about the quality of multidisc players...

http://www.audiocircle.com/index.php?topic=7586

-Brian