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In Reply to: Re: QSC Amps - Audiophile Quality?? posted by Bob Lee (QSC) on December 6, 2004 at 12:23:35:
Yep, some certainly do add colorations to the signal. Although in the hi-end world it's not always about accuracy (flamesuit on). For the most part I've found class "A" amps like my Forte' tend to be slightly more accurate than class "AB". The Belles was advertized, if memory serves, as class "A" up to 20 watts, then class "AB" from there to the 150 rms. I always questioned that as it ran pretty cool unless I pushed it hard, whereas the Forte' (and Threshold) are HOT all the time. It will certainly keep my room warm in the winter!Now that we've entered into this discussion I wish I would have kept an MX1500a when I sold the sound company a few years back. Always a day late and a dollar short...
Al
Follow Ups:
A class AB amp has separate banks of transistors for the positive and negative voltage swings, and they are biased to have a nominal amount of overlap so that the transitions between positive and negative are smooth and not discontinuous. Thus, a class AB amp is essentially operating in class A when the output voltage is ± a few volts about the zero crossings, and it tapers to class B as the voltage goes beyond that. So your Belles is apparently class AB.What's your methodology for evaluating an amp's accuracy?
My methodology - wow, guess i need to put my flame suit on!Seriously, as a fellow electrical engineer I certainly should have some sort of procedure or method to determine how accurate a piece of hi-fi gear is. Unfortunatly, measurements do not fully explain how a piece of gear sounds. I've used the SIA Smart software to compare the incoming waveform vs. the reproduced waveform, you can measure impedances and so on, but in the final analysis, it is my belief that your ears need to be the final determining factor.
So I listen to acoustic instruments, specifically guitar, to help me determine how accurate an amp is. I know what a Martin, Ovation, Gibson sounds like (I'm a guitarist - I believe you play bass, right?) and when I can listen to a piece of music and identify the instrument then I know I'm getting close. The bad news is we can only get close - I've yet to hear a system that sounds "real". (and I've listened to some really high dollar systems, in excess of $100k. They sounded fantastic, but not real) The recording process itself alters the waveform, so "real" is actually gone from the get-go. So in the end, it really is a subjective process, much to the dismay of all of us engineers who really want to be able to measure accuracy.
Anyway, that's my story and I'm sticking to it...:+)
Al
Get the Stereophile recommended components list and check which amplifiers are listed as Class A or B and go from there. You will not find QSC, Crown, Yamaha, Peavey, listed as soundstaging and 3D are not the criteria for most Road Amps...power, stability, and reliablity are. Brystons are listed and are used in many "live" venues where sound quality truly matters and they carry a 20 year warranty that I believe is transferable. Julian H. of Stereo Review fame used to rave about the old Crown DC 300A and the Phase Linear 400's as they were generally the beginning of true affordable high power amps. Headroom is not the only criteria for sound quality. Many still prefer the sound quality of mosfet based Hafler amps to this day, especially if you have bright and harsh horn loaded speaker cabinets. They do sound more tube like than most AB amps. Amp sound quality will be debated until the new millenium. The other question to be asked is are there any road or installed speaker cabinets that anyone would consider using as a true home audiophile speaker system? Not many if any I would doubt. Bag End? JBL?
Yer all wet. I defy you to be able to tell the difference in listening to soundstaging and 3d, or any other factor, between a QSC PLX series pro amp and any quality high end home amp (that is not introducing its own coloration), and
B) there are more than a few road/install speakers that have WAY lower distortion than 99% of all home audio speakers. I can give you several older examples, but to fast forward, the new SRX series from JBL shows potential, and would have better measurable and sonic performance (freq. response, polar response, power response, distortion, etc.)than most other speakers of any stripe.
I would recommend to anyone to quit reading things like Stereophile and TAS. I fell into that trap myself. I was happily listening to my horn/bass reflex loudspeakers, using mostly home made electronincs, and then got a 'gift' subscription to TAS. I went through a decade of becoming dissatisfied, thinking I must 'upgrade'. After going through many thousands of dollars, I had high rated loudspeakers and components, but...I was enjoying it less. The recommended components never had the realism of my old horn system and homemade electronics. I have since gone back to horns and given up TAS and Stereophile, and now my system again sounds more like real music. Go listen to live unamplified music, and trust your own ears!
Right on!
Quality/transparency is a criterion for "road" amps, too. "Soundstaging" and "3D" are primarily dependent on the source material.I would take a list of Stereophile recommendations by with some grains of salt. ;^)
-Bob
There are two theories on what makes a great amp. One is that it has to be tube driven, preferably SET, and not necessarily free of coloration. Adhering to that criteria leaves out not only QSC but also 99% of the rest of the amps out there. The other approach is that of acheiving 'straight wire with gain', and when that's the goal QSC reaches it as well as most and better than many.Bob is being quite conservative with regards to his 'grains of salt' advice. A truckload is more like it with regard to any reviewing source that gains its income solely from advertising dollars provided to it from the self-same subjects being reviewed. That doesn't mean that the reviews are necessarily over-inflated in their praise, but on the other hand when have you seen a recommendation made by one of these publications not to purchase something?
Amen, Bill.
Actually, until J. Gordon Holt sold Stereophile it happened quite a bit. My amp, A Forte' model 1a came about because Gordon reviewed the model 1 and claimed it too dark to be acceptable. Threshold then revised the amp to the model 1a.'Twas the good ol' days...:+)
Al
I have heard many many high end amps and the same for pro audio amps
Belles ranks as one of the best sounding high end amps I have
heard... period.
The amp has superb sound and performance
Well designed gear
The Belles pre amp matched up with the Belles amp and fine
cables and loudspeakers gives you a very wonderful experienceAs far as a pro amp for home audio...who can stand the sound
of power fans on your home audio gear?
:)
Yes, Belles equipment is very good. I will say I like my Forte' better, but I certainly could like with a Belles 150 without complaint. David Belles is a pretty nice guy too.And yes, the fans on pro amps are certainly annoying in a hi-fi room.
Al
Hi Al,True, measurements don't fully explain how a piece of gear performs, but the right ones sure help! ;^)
The accuracy of an amp (or any other piece of gear that has electrical signals as inputs and outputs) is actually fairly simple to determine objectively by just comparing the output voltage to the input voltage. Any aberrations WILL show up in the output signal waveform; they may be pleasing to the ear or not. That is one shortcoming I find with using the human auditory/psychoacoustic system to judge accuracy instead of aesthetics. But as I mentioned before, quality (or the lack thereof) is all there in the audio signal; if two different devices inserted alternately into the same system produce identical signals, they will sound identical.
Bass is my main instrument, but I also play guitar, mandolin, keys, bodhrán, Cajun accordion, and a few others. So many [instruments, jam sessions, et al], so little time!
-Bob
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