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Changing to digital power amp

#9
I don't claim to be an expert in this amplifier topology, which is technically referred to as a class-D amp (as apposed to the most common class A, B, or AB amplifiers out there), but they do exist. Many of the amplifier manufacturers that have been using class-D amps have been marketing their amplifiers as "digital" due to their operation in which the output rails are switched in on/off states (hence the digital part) at an extremely high frequency to produce the output waveform and in some senses they are correct; however, it is somewhat of a deception to give the impression that it is a digital signal like your CD player, etc.. The waveforms are produced by using a few different methods of modulation (the most recent trend has been delta-sigma modulation but I'll leave it at that - you can investigate modulation schemes if you're really that interested.)

There is much promise in the class-D topology for a very efficient and light amplifier and this is really what it has going for it, not that it's "Digital". Distortion is a concern among some however I think that they've found ways to effectively eliminate the distortion problems. In addition, the electromagnetic interference can be severe due to the high speed switching that is at the heart of the amplifier. (similar to the EMI associated with switching power supplies that are popping up in everything lately - including your class-d amplifiers) but if the amplifier is made by a reputable manufacturer and if halfway good, I wouldn't worry about it. (I definitely wouldn't mount a wireless microphone receiver in the same rack as it though.)

I don't know what amplifiers you're looking at but almost all of the big name, reputable pro audio amplifier manufacturers (Crown, QSC, Lab-Gruppen) have class-d amplifiers (they just tend to avoid the word "digital" in their literature).

Sorry for the long winded reply, but someone out there might actually be interested in knowing what a "digital" amp really is.

There's a pretty good wiki on amplifier topologies here:
http://en.wikipedia.org/wiki/Electronic_amplifier#Class_D
 
#11
I promise, this is my last post in the same thread ... I just looked at the Markbass stuff. I know their stuff if great and by no means am I going to bash the quality of their amplifiers but their marketing is a little crappy and their manuals are worthless when it comes to technical details and specifications. All they say is that they are "digital" and that all of their amplifiers have "digital" power supplies. All that means is that the amplifiers are class-D and the power supplies are switching power supplies. No distortion specs are give which is really a shame, almost as if they have something to hide. :(
 
#14
jtallent said:
I don't claim to be an expert in this amplifier topology, which is technically referred to as a class-D amp (as apposed to the most common class A, B, or AB amplifiers out there), but they do exist. Many of the amplifier manufacturers that have been using class-D amps have been marketing their amplifiers as "digital" due to their operation in which the output rails are switched in on/off states (hence the digital part) at an extremely high frequency to produce the output waveform and in some senses they are correct; however, it is somewhat of a deception to give the impression that it is a digital signal like your CD player, etc.. The waveforms are produced by using a few different methods of modulation (the most recent trend has been delta-sigma modulation but I'll leave it at that - you can investigate modulation schemes if you're really that interested.)

There is much promise in the class-D topology for a very efficient and light amplifier and this is really what it has going for it, not that it's "Digital". Distortion is a concern among some however I think that they've found ways to effectively eliminate the distortion problems. In addition, the electromagnetic interference can be severe due to the high speed switching that is at the heart of the amplifier. (similar to the EMI associated with switching power supplies that are popping up in everything lately - including your class-d amplifiers) but if the amplifier is made by a reputable manufacturer and if halfway good, I wouldn't worry about it. (I definitely wouldn't mount a wireless microphone receiver in the same rack as it though.)

I don't know what amplifiers you're looking at but almost all of the big name, reputable pro audio amplifier manufacturers (Crown, QSC, Lab-Gruppen) have class-d amplifiers (they just tend to avoid the word "digital" in their literature).

Sorry for the long winded reply, but someone out there might actually be interested in knowing what a "digital" amp really is.

There's a pretty good wiki on amplifier topologies here:
http://en.wikipedia.org/wiki/Electronic_amplifier#Class_D
Click to expand...

Yup. All power amplifiers are analog, but some are more analog than others. :p Class-D is really more like FM radio than actual digital where sampling is involved.

I've had a couple of "audiophile" class-D power amps on my bench that spewed out enough EMI to completely mask AM radio stations on a radio 10+ feet away...
 
#17
Like the AMPEG SVT-8PRO I haven't had the chance to try one. It uses a SWITCHING POWER SUPPLY. Switching supplies take the AC line and instead of rectifying the 60 cycle they spin the stuff up to several hundred KHz and then rectify it there. The IRON in the power supplies become VERY small. All computer supplies big and small are going switchers. Well guess what? The things fire off EMI like no tomorrow like MArk mentioned. They need to be sheilded and filtered like crazy. I say what are the serious estoteric audiophiles doing? Are they jumping all over switching supplies or are they buying 200# transformers? Bob Carver is the proponant of switching. They are doing what we usually do, they are buying tubes and iron.

In addition the SVT-8PRO uses a class D amp. The technology is proven. But how does it really sound? The amps are 22# instead of 40 like my 4PRO's are. Maybe AMPEG will send me 4 8PRO's to try? BOB
 
#18
Bob Lee (QSC) said:
:D

I've had the Duke Ellington quote in my sig since I joined TB! Do you ever listen to Schickele Mix on the radio?
Click to expand...

no, I don't think my NPR/PRI station here in Philadelphia ever played it but it looks really interesting. It would definitely be right up my alley. In my only minimal searching, it doesn't seem as if there is a way to find old recordings of the show. I'll keep looking though. :) Thanks.

I'm not sure where I first saw the Ellington quote (I'm sure it was some pro audio related thing) but it's a good one!

Sorry for the thread hijack. :ninja:
 
#19
jtallent said:
no, I don't think my NPR/PRI station here in Philadelphia ever played it but it looks really interesting. It would definitely be right up my alley. In my only minimal searching, it doesn't seem as if there is a way to find old recordings of the show. I'll keep looking though. :) Thanks.

I'm not sure where I first saw the Ellington quote (I'm sure it was some pro audio related thing) but it's a good one!

Sorry for the thread hijack. :ninja:
Click to expand...

From the first time I heard Peter Schickele describe his show as "dedicated to the proposition that all musics are created equal, or as Duke Ellington put it, 'If it sounds good, it is good'" close to 20 years ago, that quote has stuck in my head. I've used in my sigs on TalkBass, ProSoundWeb, and other forums.
 
#20
I had a Carver PM1.5 many years ago.
I am not an amp expert but i have experienced a wide selection of them for about 35 years..The Carver was my first experience with a switching power amp.. Switching Power (SMPS) should not be confused with a Class D amp... Two different sections of the amp as you most llikly already know. And I am sure the Carver was NOT class D but AB with a SMPS

I was young and had a road crew so weight was not an issue at that time.I was using a Crown PSA2 on my bass rig which was amazing!!!!!!!!:bassist:
That amp was stolen so i got a BGW 750B. Also a great amp but had different sonic properties and did not seem as clear as the crown and was slightly darker.

I left that playing situation and was them moving my own gear so i sold the BGW and got one of the first lightweight Switching amps of the time by getting a Carver PM1.5.
Big mistake.
That amp had almost NO booty at all compared to the Crown or BGW.. The carver was not good for a bass player that was used to something much bigger...



rbonner said:
Like the AMPEG SVT-8PRO I haven't had the chance to try one. It uses a SWITCHING POWER SUPPLY. Switching supplies take the AC line and instead of rectifying the 60 cycle they spin the stuff up to several hundred KHz and then rectify it there. The IRON in the power supplies become VERY small. All computer supplies big and small are going switchers. Well guess what? The things fire off EMI like no tomorrow like MArk mentioned. They need to be sheilded and filtered like crazy. I say what are the serious estoteric audiophiles doing? Are they jumping all over switching supplies or are they buying 200# transformers? Bob Carver is the proponant of switching. They are doing what we usually do, they are buying tubes and iron.

In addition the SVT-8PRO uses a class D amp. The technology is proven. But how does it really sound? The amps are 22# instead of 40 like my 4PRO's are. Maybe AMPEG will send me 4 8PRO's to try? BOB
Click to expand...
 

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