The Truth About Digital (Class D) Amplifiers

[Sleestack]

Yeah, after reading up some more on this, I came to the same conclusion. It appears that as long the damping factor is 50 or more, it really makes no difference. TacT's 45 should be just fine. (It appears the high damping factor in ICEpower et al. is more of a sales pitch really).

Peter

After spending more time modifying my target curves this past week, I noticed that using the same target curves with the Bel Cantos that I had used with prior amps, my 2 channel system does sound less bright. In my case, this is something I was trying to achieve, as I have found that all of my systems benefit from target curves with slight high end roll off. In most case, at least 2-3 db by 20kHz.

 

[rollinrocker]

Why is a high damping factor, as opposed to a low one, considered an attractive sales pitch. Define "damping factor".

[Edit: I'd suggest a new topic for this one - Admin]

 

[Peter Nielsen]

Why is a high damping factor, as opposed to a low one, considered an attractive sales pitch. Define "damping factor".

Here you go:

http://www.audioholics.com/techtips/audioprinciples/amplifiers/dampingfactor.php

Peter

 

[Peter Nielsen]

After spending more time modifying my target curves this past week, I noticed that using the same target curves with the Bel Cantos that I had used with prior amps, my 2 channel system does sound less bright. In my case, this is something I was trying to achieve, as I have found that all of my systems benefit from target curves with slight high end roll off. In most case, at least 2-3 db by 20kHz.

Hmm... I had a DEQX with reference mic and measured my Maggies in my room with the fully linear JC-1 amps. I have a very clear drop in the curve starting at ~10kHz with a ~4dB drop at 20kHz. This is obviously caused by the room and/or speaker. Since my speakers/room naturally drop, I think I have reason to worry if the amplifier causes any additional drop....

However, the TCS could easily correct for this? It does do room correction all the way up to 20kHz, right?

BTW, is the TCS good for 2 channel music too? I don't have a separate 2ch setup, so this is important to me.

You're probably right about Lexicon's room correction. It might not be mature enough. However, what about Meridian? They've been in the room correction business just as long as TacT, maybe even longer ?!...

Peter

 

[Sleestack]

Hmm... I had a DEQX with reference mic and measured my Maggies in my room with the fully linear JC-1 amps. I have a very clear drop in the curve starting at ~10kHz with a ~4dB drop at 20kHz. This is obviously caused by the room and/or speaker. Since my speakers/room naturally drop, I think I have reason to worry if the amplifier causes any additional drop....

However, the TCS could easily correct for this? It does do room correction all the way up to 20kHz, right?

BTW, is the TCS good for 2 channel music too? I don't have a separate 2ch setup, so this is important to me.

You're probably right about Lexicon's room correction. It might not be mature enough. However, what about Meridian? They've been in the room correction business just as long as TacT, maybe even longer ?!...

Peter

I don't think the Meridian room correction does it all either. I just spoke to a Meridian owner who is switching to TACT for that very reason.

The TCS is good for 2 channel as well. You can store up to 9 corrections, so I use independent measurements and corrections just for 2 channel. You can also assign different crossovers (or disable them) for 2 channel if you don't want to use your sub. You'll have plenty of verstaility when it comes to setup options.

Despite your measurements, I think if you use room correction, you'll find yourself drawing curves with slight rolloff. If you need to add a bit of high end extension, you can do that too. Your target correction curve is drawn up to 20kHz.

 

[ar-t]

Damping factor, eh?

Apart from being one of the most misunderstood specs pertaining to amps, it is also perhaps the most useless.

(OK......most specs are not of much help to the consumer when you get down to it. None will tell you how an amp will sound. Nerds like me who design amps love specs, but only when used as evaluation aids.)

You realise, of course, that it rarely stays flat across the audio band. Apllies to ICEpower, and just about every "conventional" amp ever made.

 

[Peter Nielsen]

I don't think the Meridian room correction does it all either. I just spoke to a Meridian owner who is switching to TACT for that very reason.

You're right, Lexicon, Meridian, DEQX, and maybe others only do automatic room correction up to ~250Hz. This was a disappointment with DEQX really.

Makes you wonder, why can't the other brands to what TacT is doing? Is TacT really that unique...

Peter

 

[rollinrocker]

Peter,

My question about damping factor was a little ornery i guess, sorry. I do know what damping factor is, I was trying to determine why you thought a high number would be desirable for a sales pitch as opposed to a low number. Why do you think the public would find a high number attractive?

 

[Peter Nielsen]

My question about damping factor was a little ornery i guess, sorry. I do know what damping factor is, I was trying to determine why you thought a high number would be desirable for a sales pitch as opposed to a low number. Why do you think the public would find a high number attractive?

I've seen several manufacturers claim how greatly improved their latest digital amps are. Statements like "First generation digital amps had damping factors in the tenths. Second generation amps in the hundededs. Our new improved third generation of amplifiers now have a damping factors in the thousands..."

I was baffled to see that the $21,000 Boz system only has a damping factor of 45... Which promted my question... Of course, that was quickly straightened out with a little research.

Now, figure what would happen if a customer goes to a store and lets the saleman get into his sweet talking mode. In this situation a sales pitch like the one mentioned above could sway the customer to choose another brand claiming that TacT is a first generation amp and is outdated (you can't get farther from the truth, but not all customers are educated or have a chance to find out all the hairy details).

And it WORKS! For a brief moment that little piece of FUD did scare me away from Boz. Fortunately, after furthter investigation I now know better. Anyway, it's pretty safe to assume this sales pitch does harvest a few customers

Peter

 

[Peter Nielsen]

Latest info regarding TacT vs. Bel Canto's ref 1000:

"I've compared the BOZ to the Ref 1000s and I think the Boz amps are much better, and there is definite synergy using BOZ amps with the TCS"

Who am I going to believe?

I know... The best bet is to go and pick up a sub $1k receiver and be happy. Leave the money in the bank!

Peter

 

[nbourbaki]

So Peter have you decided what you're buying to replace the JC-1s? What digital amps have you auditioned? What were your impressions?

 

[dack]

Hi audiophiles, your thoughts about JVC hybrid feedback digital amps that are in same range as panasonic xr?

JVC’s entire receiver line features the company’s Hybrid Feedback digital amplifier that is compact, highly efficient and able to generate high power output with low distortion levels. This technology uses two digital feedback loops to generate a precise signal and two analog feedback loops to ensure that the final signal is identical to the original. It is this digital amplifier technology that allows JVC’s receivers have a significantly lower profile than traditional receivers.

Usually, digital amplifiers are compact and lightweight because the process of digital amplification combines high efficiency
and reduced transformer and power supply than analogue amplifiers. But analogue-digital conversion of signals generates
digital noise, and fluctuations in the power-supply voltages and power-supply noise can also cause analogue noise.

The Hybrid Feedback Digital Amplifier Eliminates these noises by using two feedback systems: a digital feedback to significantly improve the precision with which the PWM (Pulse Width Modulation) signals are generated, and an analogue feedback that further 'brushes up' the signals to ensure the waveform of the analogue signal at output is identical to that at input. Combined, the two feedbacks are extremely efficient, which results in higher sound quality.

All in all, JVC has achieved not only the compact size, but also high power and low distortion — 1/10th that of conventional amps.

 

[nbourbaki]

The JVC technology sounds a lot like Halcro.

[Stereophile]
And in addition to the switching noise that you'd imagine is part and parcel of a system such as this (think of a class-D amp as an audio-frequency switch-mode power supply), he's identified a distortion that, in his words, is mathematically intrinsic to a class-D amplifier with pulse-width modulation: The shape of the triangular carrier wave becomes distorted—is actually rendered asymmetrical—while the amplifier is in use, resulting in a nonlinear phase advance in the final output. Which ain't good.

Halcro developed a circuit that actively modulates the carrier wave and corrects its symmetry during amplification. The Halcro company has appended the trade name Lyrus to this distortion-canceling circuitry, but you could also call the technique carrier-symmetry modulation

 

[Peter Nielsen]

So Peter have you decided what you're buying to replace the JC-1s? What digital amps have you auditioned? What were your impressions?

Unfortunately I don't have the opportunity to audition any of them. Furthermore, I'm of the opinion that an amp needs to be auditioned in the actual room with the actual speakers its going to drive. Speakers are different, and auditioning an amp with a different speaker does not say a lot...

I've pretty much set my mind on going with TacT Boz. The news about the new TCS Mk III (or whatever it will be called) with builtin HDMI v1.2 (for digital SACD playback) was pretty much what convinced me that I want a complete all-digital TacT system, although it is very expensive. OTOH, all is relative. A Mark Levinson setup would actually cost me the same...

Peter

 

[dack]

Sounds cool, is Audioholics gonna check out JVC digital amps?

 

[Peter Nielsen]

So Peter have you decided what you're buying to replace the JC-1s? What digital amps have you auditioned? What were your impressions?

Today I pulled the trigger on the $30,900.00 TacT setup (TCS Mk II and Boz 216 with five 2200 modules). Now the waiting begins...

Peter

 

[nbourbaki]

Peter, that's fantastic! I'm sure the wait will be worth it. Now that the weather has cooled a bit (at least in Cinci), I was wondering if you missed your JC-1s

 

[Sleestack]

Today I pulled the trigger on the $30,900.00 TacT setup (TCS Mk II and Boz 216 with five 2200 modules). Now the waiting begins...

Peter

I've had that setup for the last year. You'll love it.... but make sure you go through setup carefully. I've blown a tweeter or two learning how to use the TACT gear.

 

[Peter Nielsen]

I've had that setup for the last year. You'll love it.... but make sure you go through setup carefully. I've blown a tweeter or two learning how to use the TACT gear.

What caused the tweeter to blow? The automatic calibration? (Fortunately the tweeter and midrange on my Maggies are protected with fuses).

BTW, did you hear about the TCS Mk III that is suppsed to be released later this fall? It will supposedly have HDMI v1.2 and allow us to run SACD and DVD-A in digital all the way. I'm going to upgrade as soon as it's available...

Peter

 

[Sleestack]

What caused the tweeter to blow? The automatic calibration? (Fortunately the tweeter and midrange on my Maggies are protected with fuses).

BTW, did you hear about the TCS Mk III that is suppsed to be released later this fall? It will supposedly have HDMI v1.2 and allow us to run SACD and DVD-A in digital all the way. I'm going to upgrade as soon as it's available...

Peter

I eagerly await all new TACT products... but yes, I did know about the TCS MKIII. Im not sure how SACD and DVD-A is going to be run digital all the way unless Denon iLink is also incorporated. Nevertheless, make use of your ADC6 for now, b/c listening to 5.1 audio through that setup is already amazing.

When I first got my TACT gear, I did not know what I was doing and made extreme corrections that added significant gain. I also had my tweeters separately amped. I also made the mistake of picking "yes" for digital amps when I was using solid state amps... this sends a max signal to the amps. The result was a few blown tweeters. That's what happens when you think you can figure things out without reading the manuals.

Just make sure you use a reasonable level for your impulse response during testing and that your corrections don't add significant gain. I tend to have my corrections attenuate the signals by 1 or 2 dB compared to bypass mode. If you setup properly, this won't be an issue.

Do pm me with any questions you may have during setup. I know the end results will give you the best listening experience you have had with your speakers, but I don't want you to get frustrated with the learning curve, which is steeper than what you experience with most gear.