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Post by Talley on Dec 27, 2017 22:19:08 GMT -5
Why does my Krell Showcase 7 amplifier at only 125w 8ohms sound better than my XPA-7 pushing 200w at 8 ohms?
There is a significant better sounding cymbals, mid bass, and vocals than the xpa... or is this just all in my head? You can't call it pyscho acoustics or anything because I lust/want the xpa-7 but I only need one amp so I was going to sell the xpa-7 and keep the krell.
Anybody got any insight?
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Post by monkumonku on Dec 27, 2017 22:56:36 GMT -5
Why does my Krell Showcase 7 amplifier at only 125w 8ohms sound better than my XPA-7 pushing 200w at 8 ohms? There is a significant better sounding cymbals, mid bass, and vocals than the xpa... or is this just all in my head? You can't call it pyscho acoustics or anything because I lust/want the xpa-7 but I only need one amp so I was going to sell the xpa-7 and keep the krell. Anybody got any insight? Wattage has nothing to do with sound quality. There are some on this board who would tell you their tube amp that puts out 35 watts per channel sounds better than the Krell or Emo amp.  |
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Post by kybourbon on Dec 27, 2017 23:05:18 GMT -5
Why does my Krell Showcase 7 amplifier at only 125w 8ohms sound better than my XPA-7 pushing 200w at 8 ohms? There is a significant better sounding cymbals, mid bass, and vocals than the xpa... or is this just all in my head? You can't call it pyscho acoustics or anything because I lust/want the xpa-7 but I only need one amp so I was going to sell the xpa-7 and keep the krell. Anybody got any insight? Why do you think more watts equals better sound? |
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Post by leonski on Dec 28, 2017 0:55:10 GMT -5
www.firstwatt.comIt's all about that vital 'first watt' It is just possible that Electrically, your speakers are a load which the Krell is simply better at driving. Impedance is fun, but only a small part of 'ease of load' when it comes to loudspeakers.
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Post by Casey Leedom on Dec 28, 2017 1:26:09 GMT -5
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Post by leonski on Dec 28, 2017 2:29:08 GMT -5
Class of amp has little or nothing to do with ability to drive difficult loads, I don't think.
Big and STABLE output section, and for class 'A' output bias, plenty of Heat Sink.
The Showcase 5 goes about 55lb, which I'm not certain is heavy enough for a full 5-channel 'A' amp.
High Bias? Sure.
It is 125 / 250 watts ONE channel. And the Krell spec calls for 90volts peak which indicates a fairly low regulation PS.
I'd expect 125 watts or maybe 105x5 watts of 'A' amp to go at least 100lb or MORE.
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Post by Boomzilla on Dec 28, 2017 7:07:36 GMT -5
Mr. Monkumonku & Casey Leedom hit the nail on the head. Different amps can sound differently, and sound is not directly related to power output. Your ears apparently prefer the "voicing" of the Krell over that of the Emotiva. So an easy decision - keep the Krell. FWIW, I'd probably do the same.
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Post by Talley on Dec 28, 2017 9:37:21 GMT -5
I don't think the more wattage translates to sounds better. Just offers more headroom is all before distortion kicks in. That article has a few things wrong. The Krell showcase series amps which I believe came in 5 and 7 channel offerings are not pure "a" amps. Their amplication stage is an a/b style amp. It's the input, pre-driver and driver circuitry that are operated in pure A mode. Also the toroidal power supply in mine is actually rated 1700w which was confirmed when I inspected it and also by the guy that recapped it in chicago. The only solid test data on the Krell I've found was here: www.soundandvision.com/content/krell-showcase-prepro-and-7-amplifier-ht-labs-measuresAgain I originally bought the Emotiva when the Krell started distorting I needed something until I could get the Krell repaired. Originally I thought the repair would be upwards of 800 but I got it overhauled by a guy in Chicago for $300. A trusted source my Uncle uses. Nothing wrong at all with the emotiva. I still need to do some comparisons though. I know the XPA-7 driving 2 channels on 8 ohms is rated some 500w/ch. The Krell can only push 160w. I think the bass is more defined with the Emotiva but the mids/highs definately go to the Krell. |
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Post by rbk123 on Dec 28, 2017 10:06:57 GMT -5
Originally I thought the repair would be upwards of 800 but I got it overhauled by a guy in Chicago for $300. A trusted source my Uncle uses. What did he do in his overhaul? Anything more than replacing the caps? |
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Post by mgbpuff on Dec 28, 2017 10:40:05 GMT -5
The Krell costs two or 3 times more; there must be something there for the money. The specs for distortion and frequency bandwidth vs the XPA do not tell the full story. I suspect the Krell has better transient performance than the XPA. This means not only perhaps a better bandwidth but also one with less phase shift vs frequency(the slew characteristic).
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Post by Talley on Dec 28, 2017 11:56:59 GMT -5
Originally I thought the repair would be upwards of 800 but I got it overhauled by a guy in Chicago for $300. A trusted source my Uncle uses. What did he do in his overhaul? Anything more than replacing the caps? Here is the only thing I was told which is what was on the receipt. He did tell me that he unit is in fully on mode all the time and that the power button simply mutes the channels. This is why the unit sucks 90w at idle. Everything was checked to spec and the thing sounded so much better when I got it back. He explained it to me that the best way to turn the unit off was to literally unplug it from the wall or create an external switch of some kind on the power cord. If you read on the krell showcase amps you'll see alot of them have distortion problems and the problems is because of this. Simple fix. what Krell wants 800-1000 to do the guy did it for 300. The place is called StereoRehab in Chicago. www.stereorehab.com/If you read their amplifier section I think it explains some more details.  |
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KeithL
Administrator 
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Post by KeithL on Dec 28, 2017 12:02:31 GMT -5
I'm sure the Krell Showcase is a nice amplifier - and, quite possibly, well worth its price. However, I would challenge your blanket assumption about "there must be something there for the money". The reality is that, while there are plenty of expensive audio products that do deliver exceptional sound quality, or really nice fit and finish..... There are also lots of expensive audio products out there whose only excuse for their inflated price seems to be that "someone was willing to pay it"...... I'm also a little curious why you would assume that the Krell has wider bandwidth... or a higher slew rate... or that this would be desirable. (While insufficient slew rate or bandwidth can lead to various sorts of distortion, excessively wide bandwidth can also lead to problems, so a "happy medium" is usually the design goal.) The Krell costs two or 3 times more; there must be something there for the money. The specs for distortion and frequency bandwidth vs the XPA do not tell the full story. I suspect the Krell has better transient performance than the XPA. This means not only perhaps a better bandwidth but also one with less phase shift vs frequency(the slew characteristic). |
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Post by garbulky on Dec 28, 2017 12:27:50 GMT -5
Well it is krell so it just may be that good However have you repositioned/and toed in your speakers since the change? Because if you have not that may be your issue
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Post by Talley on Dec 28, 2017 12:30:12 GMT -5
Well all I know is that it's hard for me to do a quick a/b comparison because my speaker wires I land directly onto the back, I don't have connectors and another is the krell has a gain of 26db while the emotiva has a gain of 29. I have to adjust the volume to compensate that.
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Post by Talley on Dec 28, 2017 12:31:12 GMT -5
Well it is krell so it just may be that good However have you repositioned/and toed in your speakers since the change? Because if you have not that may be your issue No just moved the wires and xlr interconnects back/forth between one amp and another. and the power cable from one to the other. |
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Post by leonski on Dec 28, 2017 12:42:38 GMT -5
Well it is krell so it just may be that good However have you repositioned/and toed in your speakers since the change? Because if you have not that may be your issue even using the same equipment, with the addition ONLY of a power conditioner, I had to adjust the positioning of my speakers. The changes were fairly dramatic and the net was much improved. Don't forget that Dan D'Agonstino is No Longer associated with Krell. He has another company featuring his own name / designs. hometheaterreview.com/what-happened-at-krell-and-why-the-dagostino-family-is-out/So, unless Krell now has another 'lead designer' for name recognition, the newer products are 'house' designs. As for at least one measurable of an amp? Wide Bandwidth seems to buy you less or no phase shift in the 'audible' portion of the frequency response. Whether that makes a difference to YOU is up to you and your ears. I think that was one of the issues with my 'D' amp and why I eventually got rid of it and went to an A /A-B design with a conventional linear PS. |
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Post by Talley on Dec 28, 2017 13:18:12 GMT -5
My amp was made in 2002 and lasted 13 years before any issues came up. I fixed the amp because I simply cannot take sell for parts or anything as a good practice for a seller. I fixed it. It sounds great. I perceive it to be better sounding than the xpa-7. Maybe not because of wattage but for some reason.
I was simply asking if anyone had any insight.
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Post by mgbpuff on Dec 28, 2017 13:22:41 GMT -5
Slew rate refers to the amount of delay the signal experiences on its way through the amplifier. The slew rate which is necessary to avoid creating distortion depends on the frequency involved, the signal voltage, and the gain of the amplifier (the amount of feedback it uses). So, for example, an amplifier that has a higher output power would require a higher slew rate in order to avoid distortion at high frequencies. However, as long as you exceed that minimum by a reasonable margin, exceeding the minimum by 10x is no better than exceeding it by 5x. In theory, there would be no reason to not want infinite bandwidth. However, in practice, there are two reasons why you would want bandwidth to be limited. First, as you suggest, noise is a problem. You wouldn't want your tweeters to catch fire when you walk near your amplifier with your cell phone. (This really could happen if the length of your interconnect just happened to be an even multiple of the length of the antenna in your phone.) And you certainly wouldn't want your head to explode when your microwave oven turns on. Now, obviously, this is only going to be a problem if the amplifier is sensitive to high frequency noise. However... guess what... one of the ways designers reduce sensitivity to high frequency noise is to limit the bandwidth to what is useful. (It might be cool if your amplifier could accurately reproduce 10 mHz square waves; but it won't sound any better; and it's a lot more likely to blow up.) Second, each individual design has inherent relationships between frequency and phase. In most cases, this means that, as the frequency increases, the phase shift also increases. With a normal amplifier design, if you allow the gain to exceed unity, while the phase shift exceeds about 270 degrees, the amplifier will oscillate. (Which will destroy the amplifier and/or your speakers.) The way we avoid this is to design the amplifier so that the gain decreases at high frequencies - where phase shift is increasing dangerously. We make sure that the gain drops to below unity before the phase shift is high enough to cause oscillation. In other words... we limit the bandwidth. A well designed amplifier has plenty of bandwidth to accurately reproduce any legitimate audio signal... But is designed so that it won't try to reproduce high-frequency noise or signals with enough phase shift to cause instability or oscillations. (Many older designs were "just naturally limited" to a safe bandwidth; and some were "just barely good enough"; but many modern components have such improved performance that they must be explicitly limited.) The "take away" from this is that modern amplifiers are not designed to have "the widest possible bandwidth". (Modern components would allow us to build amplifiers with bandwidths far wider than would be useful or prudent...) Modern amplifiers are virtually always designed to have a specific bandwidth - chosen to result in the best overall audio performance. As a result of this, the idea that "an amplifier with a wider bandwidth is a better design" is simply no longer specifically true. I'm sure the Krell Showcase is a nice amplifier - and, quite possibly, well worth its price. However, I would challenge your blanket assumption about "there must be something there for the money". The reality is that, while there are plenty of expensive audio products that do deliver exceptional sound quality, or really nice fit and finish..... There are also lots of expensive audio products out there whose only excuse for their inflated price seems to be that "someone was willing to pay it"...... I'm also a little curious why you would assume that the Krell has wider bandwidth... or a higher slew rate... or that this would be desirable. (While insufficient slew rate or bandwidth can lead to various sorts of distortion, excessively wide bandwidth can also lead to problems, so a "happy medium" is usually the design goal.) The Krell costs two or 3 times more; there must be something there for the money. The specs for distortion and frequency bandwidth vs the XPA do not tell the full story. I suspect the Krell has better transient performance than the XPA. This means not only perhaps a better bandwidth but also one with less phase shift vs frequency(the slew characteristic). Well, I certainly don't want to get into a battle of the brains with you for I am not fully equipped.  But reproduction of a transient signal accurately depends on a summation of frequencies, many beyond the audible, and those frequencies must not only be magnitude amplified accurately but they must occur in phase precisely as per the input transient signal in order to reproduce an accurate but amplified transient copy. I mentioned slew, but I think that refers to an internal amplifier integration speed limitation (or is there really any difference between slew limitation and overall transient performance?). I fail to see how a wide bandwidth could be detrimental unless you're thinking noise amplification, but the high frequencies would not be audible and many speaker systems would not even respond to such higher frequencies. However, some tweeters, such as wire type or extremely light metal cones in this age can respond; So, the reproduction of a transient depends on the sound transducer also. |
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Post by garbulky on Dec 28, 2017 13:49:12 GMT -5
Yeah definitely reposition your speakers. Almost every electronic change I had provided some benefit with speaker repositioning/toe in. Also if possible, use the amp without the power conditioner. Though it's not the end of the world if you do use it with.
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Post by pknaz on Dec 28, 2017 15:36:46 GMT -5
I'll add a dissenting opinion on speaker positioning, I think it has 99% to do with the room characteristics and 1% to do with psychoacoustics |
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