Switching / Class D Amps: The Technology & Issues

[gene]

<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN style="FONT-SIZE: 10pt; mso-bidi-font-family: Arial"><FONT face=Arial><A href="http://www.audioholics.com/techtips/audioprinciples/amplifiers/SwitchingAmplifierIssues.php"><IMG style="WIDTH: 125px; HEIGHT: 85px" alt=[amp] hspace=10 src="http://www.audioholics.com/news/thumbs/amp_th.gif" align=left border=0></A>Switching power amplifiers (aka. Class D) have a distinct advantages over linear power amplifiers most notably in two particular areas – efficiency and cost.<SPAN style="mso-spacerun: yes">&nbsp; </SPAN>In a market predominantly driven by price point, these types of units will continue to gain in popularity. <SPAN style="mso-spacerun: yes">&nbsp;</SPAN>But do they live up to the performance standard set by classic linear amp designs?<SPAN style="mso-spacerun: yes">&nbsp; </SPAN>Read the article to find out what hurtles manufacturers must jump through to ensure good amplifier design and the parameters we will be looking for improvements upon as this technology evolves.</FONT></SPAN></P>
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<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN style="FONT-SIZE: 10pt; mso-bidi-font-family: Arial"><FONT face=Arial>[Read the Article]&nbsp;&nbsp;&nbsp;&nbsp; [Switching Amp Basics]</FONT></SPAN></P>

 

[mike c]

so .... do you have plans of reviewing a switching amplifier?
hint: Rotel RMB1077

here's an idea for an article:
Switching Vs. Analog (primarily subjective) -> since AH already has a review of the RB1095

I have a question too re:
"Audioholics would like to see switching amplifier performance improved in a few areas, such as reduced out-of-band components, lower output impedance, and most of all, improved grounding techniques. "

is the high out of band component a result of the technology, or just the quality of the receiver dropped off to you?

 

[gene]

is the high out of band component a result of the technology, or just the quality of the receiver dropped off to you?

It is a function of bad amplifier design practices including:
1. Lack of good board layout
2. Lack of good grounding scheme
3. Lack of Post Filter Feedback Stage

We plan on reviewing more of these type of amps after we establish a solid test procedure since they are very challenging to accurately measure.

 

[mike c]

thanks gene.

 

[bgrounds]

Any review of the PS-Audio G series of amps would be great.

 

[3db]

good circuit board layout is not that cheap

It is a function of bad amplifier design practices including:
1. Lack of good board layout
2. Lack of good grounding scheme
3. Lack of Post Filter Feedback Stage

We plan on reviewing more of these type of amps after we establish a solid test procedure since they are very challenging to accurately measure.

I used to layout circuit cards and found that the highger the frequency content involved, the more difficult the layout was and the more copper and shielding was required like embedded ground planes etc. I'm curious to see if the manufacturers are willing to do the extra work and design it properly or are they too much in a hurry to put out a so so product for profits sake. Call me old fashion but for now I'll stick to good old inefficient analog designs for my amplifier and power supplies. yeah they be heavy and inefficient but they are clean.

 

[Sleestack]

I used to layout circuit cards and found that the highger the frequency content involved, the more difficult the layout was and the more copper and shielding was required like embedded ground planes etc. I'm curious to see if the manufacturers are willing to do the extra work and design it properly or are they too much in a hurry to put out a so so product for profits sake. Call me old fashion but for now I'll stick to good old inefficient analog designs for my amplifier and power supplies. yeah they be heavy and inefficient but they are clean.

The digital amps I use (TACT BOZ 216/2200) are cleaner than any of the SS amps I've used (Classe, Meridian, Parasound, etc.). They are more expensive than the pieces used in the article (and many SS amps) and I'm not sure about the specifics of their design, but I know they cause no interference issues for me. More importantly, they have my systems sounding better than they ever have. Nothing wrong with being old fashioned, but I don't think one poorly designed amp should make you draw conclusions about all the available amps out there.

 

[ichigo]

Not to mention most of the noise issues were fixed with the Panasonic SA-XR55. It's just sort of unfortunate an older model got reviewed--maybe like the B&W 600-series in the shootouts?--and then the final score is not indicative of what the current model can do against current competition, rather than see an old model falter against current competition.

 

[W_Harding]

There is a review on this website that says very good things about a class-D amplifier. The review:
http://www.audioholics.com/productreviews/avhardware/IntegraDTC-9.4Review_01.html

 

[ichigo]

It's also more expensive than most analog flagships. By a mile

Kind of goes against the "cheaper to build" axiom heh.

 

[zildjian]

Halcro's new digital switching amp also got a great review in last months Stereophile (despite the reviewers low class tone/language he raved about the amp). However, it's just another example of a great switching amp that happens to be the price of a car that will start reliably in the winter!

 

[3db]

throw enough money at anything

The digital amps I use (TACT BOZ 216/2200) are cleaner than any of the SS amps I've used (Classe, Meridian, Parasound, etc.). They are more expensive than the pieces used in the article (and many SS amps) and I'm not sure about the specifics of their design, but I know they cause no interference issues for me. More importantly, they have my systems sounding better than they ever have. Nothing wrong with being old fashioned, but I don't think one poorly designed amp should make you draw conclusions about all the available amps out there.

and you make anything happen. How much did you pay for TACT amps? Can you proove that they are cleaner than Classe. Meridian, and Parasound or is this just your subjective opinion?

When I look at those curvers and I see that noise burried in the signal, it kinda worries me, ya know? I'm not say Class D amps are bad. What I am asking is will the manufacturers anty up and desin them properly to get rid of the associated high frequency switching noise or will they maintain mediocer design philosphys for purely profit reasons?

 

[Sleestack]

and you make anything happen. How much did you pay for TACT amps? Can you proove that they are cleaner than Classe. Meridian, and Parasound or is this just your subjective opinion?

When I look at those curvers and I see that noise burried in the signal, it kinda worries me, ya know? I'm not say Class D amps are bad. What I am asking is will the manufacturers anty up and desin them properly to get rid of the associated high frequency switching noise or will they maintain mediocer design philosphys for purely profit reasons?

The TACT gear is not cheap. The pre/pro and amps for my HT ran well over $30K (although I am b-amping 5 speakers). That being said, the other gear I had wasn't exactly cheap either. I also haven't done any objective testing, but I'm not looking to prove anything to anyone except myself. I have done side by side comparisions with some of my gearhead friends and feel very comfortable stating that the TACT BOZ amps sound better than anything I've had. In addition to exhibiting no distortion at dangerously loud volumes, the TACT amps provide significantly more resolution at average and lower volumes. Also keep in mind that the TACT amps only accept a digital signal. Most other "digital" do an AD conversion and only accept analog inputs.

I'm not sure when all companies will get their act together, but I don't think you can just lump all the companies together because of one Audioholics article that looks at a very limited range of products.

 

[gene]

Not to mention most of the noise issues were fixed with the Panasonic SA-XR55. It's just sort of unfortunate an older model got reviewed--maybe like the B&W 600-series in the shootouts?--and then the final score is not indicative of what the current model can do against current competition, rather than see an old model falter against current competition.

This was NOT A REVIEW! It was a tech article on Switching amps identifying potential issues with their designs. The Panasonic was used as an example. Regardless few of these amps use the proper post filter feedback in their designs b/c they are mostly cookie cutter designs bought from chip manufacturers. Implementation is key to getting these right, which few companies invest the time/effort or have the proper staff armed with the math skills to do it correctly.