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OK, so I heard a pro amp last weekend driving some Quad speakers. One amp on top and another driving subs. The model was QSC RMX 1450. I couldn't believe how good and powerful this amp sounded on the very revealing Quads. It sounded as good (not better) than many mega expensive amps that I have heard over the years.Are these really as good as audiophile amps?
Thanks!
Follow Ups:
I just purchased the QSC SRA 3622.
I.M.O. this is an audiophile quality amp. Simply amazing sounding.
I all I want to do is listen to all my records over again because I am hearing stuff I never heard before I added this amp last week.
Powerful and clean sounding music.
Heard QSC Power Wave last summer in a PA, the best PA bass I've ever heard.
....you have to find first gear in your giant robot car....
FWIW - got "unfounded notion" that using a pro-amp for hi-fi - - that 1st opamp (for balanced input) if bypassed (as possible with some cheap designs having RCA input jacks) will have a better "stage" less harsh presentation than using an adaptor to feed that 1st opamp.anyone else here have similar observation?
not "into" hi-end - have owned Threshold Stasis/800, Belles class A, Acoustat,many others solid state plus tube stuff.
any new QSC with RCA jacks and shortcut path?
The QSC Studio Reference Amplifier (SRA) all have RCA inputs.
My 2 cents:Having chatted with Bob Lee on a couple of occations and owning about 24 QSC amps over the years when I had my sound company I feel somewhat qualified to give an answer.
My current home hi-fi amp is a Forte' 1a pure class A amp. I have listened to a QSC, Yorkville (AudioPro), BGW, and Crown in addition to the Forte', a Belles, and a Threshold on my system. My impressions - for pure slam a professional amp such as a QSC is great. For the subtile nuances such as 3D imaging, attack, presence, and so on the audiophile amps that I have heard win. So it depends on what you're looking for. If you need big power and don't have a lot of dollars lokk at the QSCs, as they were the best sounding pro units in the un-offical tests we did, with the AudioPro's a close 2nd, and the Crown 3rd.
YMMV..
Al
Hi Al,QSC's philosophy is that the "3D imaging," "attack," "presence," and other such qualities have to be in the audio signal first; the amp has no business adding to (or taking away from) them otherwise. How the amp handles the signal is paramount; there is no side-channel to tell the loudspeaker that the audio from this amp is supposed to sound sweeter and smoother than the audio from another.
-Bob
Hi Bob! Hope things are going well for you this Holiday season!I agree totally, the amp should add nothing. Unfortunatly, no amp is truly a straight wire with gain, but some are closer than others. I certainly would not want to use an amp that was designed otherwise. That said, using my Conrad-Johnson preamp with the Forte', Belles, or Threshold created a wonderful soundstage. Replacing the amp with a 200 wpc Pioneer power amp totally collasped(sp) the soundstage. With the QSC amp (it was a MX1500a if I recall) the soundstage got smaller, but was still there. One thing to remember, the Forte' and the Threshold are class A designs, with the Belles being class A up to about 20 wpc. The "pro amps" are not.
Al
Hi Al,I agree that some amps are closer to the ideal metaphor of a straight wire with gain than others. It's also no secret that many "audiophile" pieces of equipment reject that ideal in favor of a certain coloration that, while often sonically pleasing, is still an arbitrary alteration of the audio signal. Highly accurate amps, however, will tend to sound alike, which may not be a marketing advantage in the hi-fi market.
The Belles sound from your description like class AB (as are QSC and most other pro amps). Is that correct?
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
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
QSC amps are designed to be highly accurate, with no deliberate coloration; that is, we intend that you get out of them what you put into them. That said, the RMX amps are our entry-level series, and the bias network in the output section is fairly simple, with an also simple temperature tracking scheme. In the PLX amps, for example, the bias network is much more complex and tracks temperature much more accurately, which makes the section much more linear, especially in the transition region where positive signal voltages cross zero and become negative and vice-versa, over all operating temperatures.Still, we're talking about improvements in very small non-linearities; in real-world situations you might never detect an audible difference except in a very well-controlled listening test.
The PLX amps and their derivative models also have extremely low noise floors, with hum components that are barely even measurable with test equipment, let alone audible. In fact, they would make good reference amps because of their accuracy and low noise.
-Bob
Hear, hear. I use two PLX series for home audio and they are great.
Bob, I appreciate your post. I use a professional amplifier for the critical mastering stage. I have used audiophile standards of many types and some of the audiophile equipment is designed with the intention of "selected coloration" or "voicing". This trait gets in the way of precision mastering and I am happy to know that signal accuracy is the goal with QSC amplifiers.
.
I've owned maybe 5 qsc amps - I like them a lot. I've owned only two amps that you might call "audiophile". (One is a Conrad Johnson). I've AB'd them. The audiophile amps win hands down.... unless you are using very ineffecient speakers in which case the big headroom offered by the pro amps really helps a lot. The fans in the pro amps are also a significant issue.The best compromize between pro and hi fi are the "studio reference" type amps which have big headroom, pro features, and sound great. Try a Bryston or Hafler.
you need to look at different specifications, if you are looking for Real Audiop. Quality ... Slew rate for onePro amps are meant to produce a lotta power, and survive ... most deal with different reproduction conditions, i/e. heavy compression, that you would not expect to produce high fidelity sound
that said .. i use a cheezy pro amp, a mexican mfg' Ross as my power amp, 'cause my phase 400 went burnt !
It is possible for an amp to have too much slew rate; such an amp may exhibit high sensitivity to RFI or EMI. Low-pass filtering at around, say, 70 to 100 kHz will help, but it will decrease the slew rate spec. Some amps are sold more on specs than performance, though.The minimum slew rate an amp needs is directly proportional to both its maximum output voltage and its maximum signal frequency. For example, if one amp used for full-range or high-frequency audio has a maximum output voltage of 40 volts and another has a maximum output of 80 volts, the slew rate on the less powerful amp can safely be half of what the minimum safe slew rate of the larger one is.
I remember back 25-30 years ago when slew rate became the big buzzword among audiophiles. I read 'The Audio Amateur' at the time, and Walt Jung was a contributing author, writing many articles for the magazine. I believe it was Walt who finally got to the bottom of the slew rate debate, and did an article called something like 'Slew Rate- How much is Enough'. The bottom line was that any device, whether it be a preamp or power amp, needed to slew 0.5v/us for every peak volt output, in order to avoid SID (Slew Induced Distortion).
You are certainly right about too many products being sold based on specifications. The prey on the uninformed. Everything is a balance, and good engineering carefully weighs all sides.
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