Use of Digital Amps: Need serious help

Hi i recently got out of the audio deal and sold my entire system. It was too much for me. While randomly scouring the net i came across an interesting product the Spectron Musician II. This amp essentially has a dac built into it. Apparently all digital amps take the analog signal that you send it and use an A/D converter to digitize it, then amplify it digitally and send the signal to the speakers. The Spectron (along with the new Tact 2150) allows you to never covert the signal to analog ever, and i mean never, the signal is digital (which makes no sense actually) when it reaches the speakers. So in effect all you need is a transport because the Spectron and the Tact both have built in volume controls. So now this allows me to have a potentially extremely very good system, (I know the tact and spectron are both incredible amps when fed analog signals) for next to nothing. In my old system my cd player, an audio aero mk II which was jaw droppingly good i might add, alone would cost me far more than my entire new system. So now the question is... after all of this... does anyone have any experience with running a purely digital signal versus digitizing an analog one with any of these amps? How good is this technique and how important is it to have a good transport, cost is no object really. I won't reenter the audio world if my new system will not be comparable to my old one. So if anyone knows let me know if this is a good technique. Thanks in advance for your help.
No, the signal is not digital when it reaches the speakers unless the speakers have built-in D/A converters to convert the signal back to a useable analog form. There may be a few speakers like that on the market (maybe Snell, Meridian, etc.) but my guess is that the amp has to convert the signal back to analog before it gets to the speaker or your system will pretty much sound like a fax-machine's data stream. And I can't listen to that very long. :) It has to be converted back to analog somewhere for you to hear it as "music".

My guess is that such an "all-digital" system (using currently available technology) will not be the eargasm you might think. There will be almost no euphony and the sound will likely lean toward the clinical or dry. I doubt that you would characterize it as "sweet". And what about adding an analog source, I mean, if you wanted to?

Of course I could be wrong. This is only my best guess as I haven't heard such a system myself. It sounds good in theory but in actual practice I'm not so sure it would live up to the hype...

That said, the amps you've mentioned are supposed to be very good sounding units. If you bought it and found you needed more of what analog delivers then you could always add the analog somewhere upstream. As I see it, there's not much risk in trying it. Perhaps others have done this and will write in with their impressions...

Then again, some things will sound quite good -- at least until you make a comparison to something better.
I heard an all digital TacT system at a show. As such take this with those limitations in mind. I really liked it. Plato, it was not dry, if fact I would describe the sound as liquid. Others found the sound a tad bright. If one thinks in terms of a digitaly propelled electrical signal, then it is all digital. The signal converts PCM to PWM, not to traditional analog. I have great hope for future developments of this technology.
My friend Lordgorian,

[Who I think made a big mistake by liquidating his system, but alas he is young and has a lot of life ahead of him.]

I think the big question you have is: Does the Spectron or Tact regulate the volume of the signal in the Digital or Analogue domain?

If they do it in the digital domain (which my gut tells me they do, else they would probably be called integrated amps), the odds you are going to get the kinds of perfomance that you had before with your Capitole II are pretty slim. All sorts of information is lost when you start manipulating the digital signal to regulate volume.

Now if the amps regulate the volume in the analogue domain you could be in good.

I fear though these amps take in a digital signal -> process it digitally for volume -> send it the switched amplification. This would make the most sense if these amps truly could take in a digital signal. Else the digital signal would have to go through a D/A process then be atenuated for volume then through a A/D process and then to the switched amplifier. This would not make a lot of sense.

Thus, I would be willing to bet that these amps regulate the volume in the digital domain. And unless they have some revolutionary digital volume technology (which is doubtful), I doubt you will get better sound than you previously had.

Nevertheless, I would love to hear some folks who have experience with this situation come forward and report their findings.

Always remember: Sometimes the shortest signal path is not the best signal path. The parts and processes that a signal goes through many times matter a lot more than the actual distance of the signal path.


I can't say that I have heard the Spectron with purely a digital signal but, I have used a passive line stage with it and it was a bit dry. Since then, I have used a tube preamp that sounds fantastic, a giant killer, the MiniMax. It added the warmth and liquidity that made the system more capable of reaching me emotionally. I did not have to break the bank to buy this preamp either. It lists for $1195.

Call Galen Carol Audio,, in San Antonio. He has both the Spectron and the MiniMax. Plus, he is a super guy to deal with and will give you a fair deal along with the experience he has in running the Spectron using a digital signal. Tell him I sent you. Good luck.
I had the Musician II in my system and while it was one of the cleanest sounding amps I heard, I did not select it for my system. My old Kinergetics just sounded better. Note that there was not that great of a sonic improvement with the comparison of the twelve amps I auditioned, just slight differences in most cases.

I use a Tact M2150 digital amp with a modified Theta Data Basic II CD transport. Speaker are Vandy's and the cables and power cords are Omega Mikro and Silent Source. I'm very happy with the sound. It is not the least bit dry or analytical, but rather smooth and extended. I've had several systems throughout the years and this one's my personal favorite. Tact also has an optional ADC that can be installed by anyone in just a few minutes. This is a very simple and cost effective setup that has saved me money and honestly I'm more than pleased with the sound.

I just want to share my understanding of how digital amps work - derived from the PS Audio page for the HCA-2 (a Class D digital "switching amp"). In your entry, you note that:

"Apparently all digital amps take the analog signal that you send it and use an A/D converter to digitize it, then amplify it digitally and send the signal to the speakers."

That is generally true, but I think it's important to recognize that the HCA-2 doesnt' digitize the analog signal into a digital pattern such as that found on a CD. Instead of trying to simulate the wave form that represents the music, what it is doing is giving the amp instructions to pass 100% of its power generation through or to cut it off, and the timing of those "ons" and "offs" is modified by circuitry to then create the wave form. So, the pattern of "offs" and "ons" the amp generates is different than the digital waveform shown on a CD. Perhaps the Spectron and the TacT work differently, but this is my understanding of how the HCA-2 works. If this is correct, "all" digital amps are not the same.

Clarification welcome! I hope this is useful. Peter
You might want to talk with John Ulrick at Spectron.He is very friendly and informative.He could explain how the direct digital input works and how digital volume control is achieved.Contact information can be found here
The volume control in both of these amps are digital. But none the less there appears to be no loss of data because the volume is regulated differently, while the data is PWM and not PCM anyways, digital amps in my experience sound like a mix between tubes and SS they are liquid but extremely clean, a great combo but could use better depth. None the less, im looking for experience and not oppinions about what this might sound like. Im hoping someone with experience with the Tact components can help me. Thanks.
The greatest advantage of digital technology (in general, not just for audio amps) is much lower cost for the same performance. And regarding performance (sonic quality in our case) it can be anything you want it to be with the right software, or other means of digital data processing (eg: firmware).
I didn't realize that Spectron had released the digital input option. They have been talking about it for quite a while. They do have remote sense speaker cables that a lot of people like. Spectron was working on speakers that had a digital amp for each driver. Kind of like the waveform speakers that have since gone out of business. But at one of the trade shows they couldn't get a prototype working. The other digital amplifier is the Tripath module which is used by Bel Canto and some new products coming out in Europe. It calls it's technology Class T becuase the output frequency is variable spread spectrum up in to the megahertz range. Spread spectrum supposedly eleminates digital noise at a sigle frequency by speading over a frequency range giving a cleaner output.
Spectron has not released the digital input option, yet.

Some other interesting digital amps are the Carver Pro ZR
It is possible that a new paradigm is created whereby digital input feeds such as PCM (analog level represented by magnitude of digital code at 44KHz/nyquist) can be directly converted to PWM (average loudness represesented by a dgitally derived "on" interval...the duration of this interval has the analog loudness information)via computation. Similar to a single bit DAC (or DSD) with the filtering done right at the output via a inductor. This would be very DIRECT and maybe this is what people mean by direct digital.

However, if the analog input is cleaner, then it means that the digital siganl is converted by onboard DAC to analog. This intermediate signal would then need to derive the "fixed interval duration" via an analog to digital process (ADC) to set drive the class D output stage. For the case of analog inputs, the "extra" DA conversion needed by digital inputs would not be needed.

If you ask the above theorectical question to the designer, it should indirectly answer the question about how things are done.