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In Reply to: hifi preamp with pro gear posted by Darryl on April 29, 2002 at 09:43:34:
There are prehaps three men in the world capable of designning pro gear that sounds musical. Rupert Neve is certainly one. Mostly, pro-gear is an assemblage of rush to market pieces of S%#@ that were designed by some empiricalist school trained EE whose idea of good music is Nazi goose stepping. I would listen to an Acoustic Research or Conrad Johnson any hour of the day to any of the modern fare choices any day. The best! James
Follow Ups:
James, you are certainly entitled to your opinion, but don't be so crass! Pro audio gear, the pro audio amplifiers in particular, are NOT rush-to-the-market products that are pieces of @#$@# or whatever you wrote. They are far superior to home audio/theater amps for the most part! Yes, I'm an EE, but being an EE gives me one advantage over the common "audiophile" who measures his equipment by the amount he spent on it like he's engaging in some replacement penis contest. That is, I KNOW what makes an amp tick. I know what makes most audio components "tick" as well. My home theatre rig includes one Crown Audio amplifier, one Crest Audio amplifier, and one BGW systems amplifier. I chose these amplifiers for three reasons: 1.) They beat the hell out of any Conrad Johnson, Mark Levinson, or Krell in terms of reserve energy, ability to handle musical transients dynamically, and put out raw power those aforementioned brands simply cannot match. 2.) The pro amps are equally as sonically transparent as the aforementioned overpriced, creampuff products(ie. Krell, M.L., and C.J.) In fact, My BGW Millennium 3 power amp will sound better than your C.J. in a blind listening test (that is provided we could compare it against a solid state C.J. if those exist.) 3.) Pro amps are still the business tools of professional musicians who use them to get the job done, so the cost stays reasonable. C.J., Krell, and M.L. for example, market themselves on the hype alone, and charge ass-raping prices that their quality does not merit. So, in brief, pro audio power amplifiers are cleaner sounding, more transparent or "airy" as so-called "audiophiles" like to call it, "color" the sound less, provide greater soundstage, handle bass frequencies MUCH better, generally have tighter sound control ('realistic' damping factor), put out way more raw power, and just look better (IMHO) with those big rack ears and pull handles on the front with blinking LEDs. FYI, no pro audio amp allows diagnostic circuitry or lighting circuits to interfere with the audio signal path. No pro audio amp allows fan noise (electrically from the fan motor) to interfere with the audio signal path. And last, no, no, no, that cooling fan on pro amps that kicks on only when it needs to (with most pro amps) does not detract from your musical listening enjoyment. Most of those amps' fans are in the 33 dB range. Across the room, it is nothing compared to the 105 dB to 115 dB reference level of most music -- even including the low volume passages of quality, dynamic, music content.Next, to the original poster, yes, your home product should work well with most pro amps and other pro audio gear. Make sure the input impedance of the amp you connect to your home unit is at least 10kOhms or greater. Almost all are, so that should not be a worry. I run 3 pro audio amps currently in my home theatre rig off of a home theater pre-amp/processor -- works beautifully. It also allows me to laugh heartily at those guys who think 5 channel home theater amplifiers are the best solution for a separates system. Wrong! Pro audio amplifiers are the only way to go, unless you're talking about an amplifier for use in an automobile (12 VDC.)
The so called pro-sound amplifiers that are used in discos, theaters, recording studios are to my ears crass, dischordant and offer pitiful holograms of what the original music was. Most of the companies are in this business only to make money and to my view are quick to embrace the newest technology which to me is a rush to market. They rush to market long before the jury is in on the sound quality. Most of them do not even bother to sort ICs or transistors for beta or collector to base capacitance. They are only concerned about selling and the bottom line. A few like FM Acoustics are doing a good job. And as long as their ministers of propoganda can keep the Johnny Wonders who took the three chord guitar course dupped into thinking that they are the best thing since sliced bread, then I see little hope for improving the signal chain. In most things, you get what you pay for. The best! James
Haha, ALL companies are in business just to make money! Where did that slip your mind? Home audio/theater companies are the most greedy, and are most likely to market their precious brand name rather than their customer support, their quality, and their reliability.-- Lewis
I appreciate hearing your view on the pro audio products. Yet, it is my experience that the home audio market, even the esoteric high-end home audio market, is where the almighty dollar speaks. Most home companies are in a "keeping up with the Jones'" approach to new model development. In contrast, most pro audio companies will not latch onto a new technology until after it is tried and true. In fact, most pro audio companies produce big, bulky metal boxes full of electronics that are if anything a step behind the current technology out there. My main experience is in comparing home audio amps with pro audio amps. Sure, the pro audio companies also beta match their transistors (in the higher end lines.) Pro audio companies also, for the most part, use many more output devices per channel, use larger, grossly oversized power transformers, provide more filter capacitance per channel, and have higher actual real-world damping factors. I agree that you only get what you pay for, but I also believe there should be a cap on what one would rationally spend for any given consumer electronic product. I am also only speaking on behalf of solid state amps, as I'm quite sure you are too. Try a BGW professional amplifier; try a Crown Audio Studio Reference amplifier. If you believe that your home gear is producing a sweet sound in contrast to "crass" stuff from the high end pro equipment, then I strongly believe either 1.) (in my opinion) you're delusionally happy with your home gear and the sonic effect of it is merely psychological or 2.) You like the home gear that you're used to because it actually is adding something to the original signal that the pro gear isn't. A true amp will be as revealing as possible, and perhaps your home gear isn't picking out all the details. I will play devil's advocate however and agree that there is home gear that sounds just as clean and sweet as pro gear. My caveat is that home gear lags behind pro gear in these respects: poor performance with varying load impedance, poor thermal management capabilities, poor reliability over the long haul (10+ years), poor realistic damping of large subwoofers, low relative power output, and absolutely terrible price:performance ratio. Since the home gear is sub par to the pro gear on at least those critical areas, then the claim of highest performance at any cost is shot down instantly. Maybe you might be unfamiliar with the law of diminishing returns. If a $2,000 amplifier gets you so close to the sonic bliss you desire, and provide other things much better in the process, then why pay up $75,000 for the ultimate "I am better than you" posh home brand just to get that tiniest extra bit of bliss? No thank you, I'll take a top of the line amplifier, and 2 new BMWs -- one for daily driver and one for the track. One last thing, you mentioned discos and theatres. Add to that list even worse sounding venues like pro sports arenas (especially basketball) and airport P.A. systems. Do you realize that you are hearing more sonic defects from the speaker systems attached to those amps, than from the amps driving them? I hope you do. FYI the ONLY fair way to judge a pro amp is to bench it alongside your other amp(s) in your home, hooked to your favorite home reference speakers.
Kevin, I appreciate and respect your thoughts. I am self taught. I did not have the opportunity if going to a high prophile engineering school. I built all of my amplifiers from scratch, not a kit. I've learned much. The most interesting thing I've gleaned from building almost thirty amps to date is the abysimal state of entertainment and consumer electronics in this country. I also know how amps work and if anything I've proved to myself is that school trained engineers are taught not to think outside the box. They are for the most part conformists and pragmatists that have been beaten with the EFFICIENCY STICK. They only copy what has been preciously done. Why I ask is the pretora of amps all using the op amp topology with a diff amp at the head, Class AB, feedback returned to the - input, plenty of lead and lag compensation and a brute force filter on the front door and another on the back door. The reason is that most solid state amps are totally unstable without such appliances. They simply will not work. Most all the amps are variations of the same theme. Few are original and of quality. Why do most transistors that are avaliable to the conumer electronics industry vary by more than 60% in beta and collector to base capacitance? Because american business want to unload their S%$# on the american public. Why are other ideas not tried? A company in America has yet to provide us with a solid state amp that operates PURE Class A without gross stability problems. They are always quasi ClassA. I don't care about the efficiency. I want it operating ClassA. I'm sure that if the space or defense industry wanted or needed such an "instrument" that National and Motorola would do triple back flips trying to get them the transistors they need. But to a lowly amp maker trying to break into the market, then he has to buy barrels full and spend an inordinate amount of time sorting the transistors he needs. I believe that the Swiss, Austrians, and Germans can beat our a%% in spades at anything in engineering and electronics and it's sad. Once Americans built things of quality but that time is past. We are now in the age of quantity, no product backup, and GET RICH AT ANY COST mentalities. When the bean counters and the marketing people and yes the engineers get finished then the product is MEDIOCRE BEYOND BELIEF.
I once too owned a Crown and several other brands of reputable solid state amps and I have tested many and the consensus is that most of them run out of steam quick. Most all of them have a erie solid state glare, euphonuc signature that is fatigueing and music is simply not about being fatigued by the experience. I proved to myself that I can build things much much better than american business ever could. I forgot about buying products on the market and I'm glad I did. The music that is eminating from my system satisfies me. We are in this hobby because we love music and we don't want our music to be reproduced with ANYTHING EXTRA that is electroniclly induced. It is amazing to me how school trained engineers look at audiophiles as part of the "idiot fringe" especially if they are inclined to listen to ""those awful antique vacumn tubes. I wish we could arrive at a common ground. Otherwise one group can't see the forest for the trees and the other can't see the trees for the forest. Respectfully, James
James,
Wow, I have to say I'm pretty much in agreement this time. One thing about university-taught engineers in the U.S. is that, no, if an engineer has the passion for what he/she is designing, then there are no limits. I believe that we have some of the finest engineers and finest minds on the planet in the U.S. Unfortunately, unless those bright engineers can dump a limitless amount of money into their own hobby or their own business, they are controlled by the business world. It impresses me to see how much you know about audio electronics being self-taught -- my hat's off to you. But, from an engineer's perspective, please understand that it is EXTREMELY frustrating to work for a company doing design work. It is not that engineers don't think outside the box; they do. If engineers were turned loose to compete against each other, then companies would start making products that simply can't be beat, because product development would be driven by engineers instead of business majors. Either the companies would unfortunately go under because nobody can afford the high quality products, or the companies' marketers would suddenly have to step into overdrive to keep their company competitive. It's that employers, like you said, are trying to churn out mass-produced, mediocre-at-best quality products. I know how the American buying public is. They don't want the best in one or two categories, they want to have everything, and get as much for as little as possible. I think this sort of makes America the great place that it is. If I had to buy all Ping to get into golf, buy all Theta and Classe to get into power amps, and buy all Ferarri to get into cars, then I'd never have it all. But, give me some Wilson clubs, a Sony receiver, and a Chevy Cavalier and suddenly I'm the American that has it all, even though I might not have the best. Does that sound right? Audio is an area where I personally put more emphasis into quality however, yet perhaps not as much emphasis as others, including yourself. If I could have the opportunity to listen to some of your designs, I would probably save up and stand in line to purchase an amplifier from you. You heart is certainly in the right place with your audio likes.Now, about operating in pure class A... ouch, pure class A limits the amount of output power you can have naturally. I know that Krell uses some gigantic tubes to make a respectable amount of power from pure or quasi-class A designs. But, is it reasonable to expect 300W per channel from a class A design? About the topic of negative feedback, please share, what are your dislikes with using negative feedback? My BGW amp sounds more open and musical than my Crown amp most likely for the reason that it uses very little negative feedback. I'm interested in hearing your thoughts on neg. feedback. Regarding the input drive stages you mentioned, most pro audio products feature a discrete class A drive stage. Many even use opto-couplers to control the gain knobs so that the pots don't get into the signal path. I would bet that most home products (beyond the run-of-the-mill receivers) use a discrete drive stage. Some pro amps have power factor correction features, but those are typically on the multi-kilo watt models. All I have considered in my personal designs for power supplies is: use a huge, well-wound, clean power transformer, beyond the rectifier use a generous amount of capacitance. Please share thoughts you have along these lines.
Kevin: Push pull topologies are just wrong! Some weak musical signals that are not strong enough to push or to pull get cancelled, erased, eviscerated by push pull topologies. This is because if the signal expresses itself as common mode disturbances then it falls by the wayside. Diff amps belong in calculators and power supplys not music amplifiers. The tail current in a diff amp is loaded and there is no way around it except not to use it. There are useful alternatives but I may want to consider it proprietary. Summing the output signal and feeding it back to the - input multiplies odd distortion products exponentially. Odd distortion products are mostly responsible I believe for most of the solid state grunge or glare we hear that is fatigueing. Feedback will multiply these out to the 99th. Feedback is a pandora's box if not laboriously and infinitely controlled. It must be something akin to giving an elephant an enema. One doesn't have enough means to control it and invaribly in most every case is gets out of hand. It changes every single parameter in the amp. I would go for lead compensation of each stage as opposed to overall feedback. And when we slow the transistor down with lead compensation, then we invaribly also multiply odd distortion products. They are generally applied to make an otherwise unstable transistor work or behave. If we had better transistors that would work without the lead compensation this would be un-necessary. The semiconductor industry has turned away from the design of disreet transistors for the audio industry in preference for digital processors. One of the best transistors I use was a fairly early device 2N2219A and 2N2905A but I have to go through barrels of them to find two that have the same characteristics that will behave properly. And then they are getting increasingly hard to find. And output devices in TO-3 or TO26 cases are abysimally slow in turn on and turn off times. The higher the power the slower the device. The output stage in the amplifer is the weakest link in the chain. No one yet has perfected controlling a output stage where the collector is turned toward the output (the best current transfer) as opposed to the emitter follower topology. Crossover notch distortion and dead zone cannot be cleaned up and is extremely audible in a class AB amp. The only away around it is to bias the output stage Class A. You better get out your water-cooled or refregerated heat sinks and get the transformer out of mothballs and re-invent the transformer coupled Class A output stage because it's coming. We could conceivable get 50% efficiency. The well designed low turns ratio transformer is still the best way to interface a reactive load like a loudspeaker to an amplifier. In every solid state amp virtually on the market, the speaker is looking into an unprotected output stage that the only thing seperating the speaker and enough stored energy in capacitance to lift a twenty pound dog six feet into the air is two tiny emitter to collector junctions. It's just not safe for my $3000 speakers to be abused so unfairly. Cordially, James
I will always agree that class A is the most pure design. I really like the way you look at everything that determines what happens in the signal path. Thanks for the info. on neg. feedback... I've heard a lot of mixed reactions on that topic. I know tube lovers have to their advantage the way tubes tend not to amplify odd order harmonic distortion... making higher THD levels in those amps acceptable. But like you said, until new class A designs take hold, we'll have to bias large class A designs and cool them with ventilation systems designed to chill a walk-in freezer. Plus, don't forget and leave the amp turned on when you're not listening to it or you're electricity bill just doubled :) Hmm, class A topologies, including power supply loss approaching 50% efficiency? That's great! It's been a long time since I've studied some simple transformer coupled output designs. I remember reading some bad effects of doing that, and of course, some good effects. I cannot remember what those bad effects are. But, I wouldn't trust my expensive speakers to my own designs. That's why I like buying what I can afford from reputable vendors, so if their amp fries my speakers, then they have to pony up the cash to replace them.
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