Its not alchemy, but a designer does have to know what he is doing and it is the mark of a good engineer to know what is 'negligible' and what is not.
Beyond the alchemy part of your post, it is pretty much correct. Even a talented engineer will fall well short of possibility if he or she does not remain a student of the practice (or 'art'), especially that of the specific product and its goals. There is always something new to learn- I find that engineering/technical types that make the assumption that we know everything there is to know about audio are the same ones that have terrible stereos.
You have to have an open mind and in particular, be open to the fact that you don't know everything!! |
I am absolutely amazed to find this out Al. So it's more or less a matter of alchemy? Like an unguarded secret by someone successful in coming up with the right recipe but in the end not being able to put their finger on just what makes or breaks the design. So a great mind with knowledge and experience still must exercise some trial and error in designing a circuit. Like art. I've heard it said you're not an artist til someone else says you are. I think there's some merit in that saying. |
02-19-15: Csontos
If the relationship between technical parameters and subjective perception is indirect or vague, then how does someone set out to design a 'subjectively fast' amp? Is it just a crap shoot? Technically, what descriptors must an amp possess in order to facilitate subjective speed? Isn't this the goal? Thanks for the nice words in your post, Peter. I'm not sure how to answer your question, though. Consistent with Ralph's comment, there are simply too many variables that can be expected to be involved to be able to formulate a meaningful general purpose answer. It stands to reason that wide bandwidth and fast risetime and slew rate will tend to be helpful, but only indirectly if at all once they get above a certain point (for example, the 200 kHz bandwidth figure I cited earlier, corresponding to 10x the nominal upper limit of audibility). As with most sonic characteristics of audio components, I would expect accurate reproduction of those sonic attributes which contribute to a realistic perception of "speed" to be more than anything else a function of the knowledge, experience, and thoroughness of the particular designer, and of his or her priorities in addressing the innumerable tradeoffs that enter into any design. Best regards, -- Al |
"02-19-15: Csontos
But there's another question that hasn't come up and that's 'how much of an influence does a pre amp have in perceived speed'?"
Actually, I did bring that up. lol. All components in the system have an effect on a systems "speed". A good example is Naim because they are associated with the whole PRAT issue. I spoke to them and asked them about this and they suggested that I start off with a preamp if I really wanted to see what the Naim sound was all about. Ultimately, Naim wasn't for me, but its a good example of how other components effect a systems speed. When I said in my other post my MF integrated had a sound that was kind of like a "gimmick", for lack of a better term, there was just too much attack. It definitely had the speed that is a big part of the PRAT sound, but the sound fell short because there was no foundation to the music. For a more complete sound, and not necessarily just speed on the attack, but tempered with resonance and decay, some good examples would be my old ARC VT-100 and Quicksilver V-4's for tubes, and for SS, Ayre is the best I've heard in this respect. With these products, they components sense of speed is balanced with other qualities that give a more complete sound. |
But there's another question that hasn't come up and that's 'how much of an influence does a pre amp have in perceived speed'? |
I agree and the opposite is also true ime. Those Meridian 105s will fool you into perceiving a faster than normal pace. |
To me, "Speed" seems more of a real issue with various transducers than with amplifiers. |
If things are going well you will not hear 'speed' in an amplifier. If you do seem to recognize such based simply on highs and transient response, IMO/IME that is likely due to a coloration and not anything else (and often caused by trace amounts of higher ordered harmonic distortion).
Real speed is evident if the soundstage is deep and wide but not unnaturally so (this is because with speed comes correct phase response); the amp will be relaxed at high frequencies but obviously able to play them with a black background. I hesitate to say any more as so many other factors are involved/so many variables can exist... |
BTW, re "the two most technically knowledgeable," let's not overlook Bombaywalla, who is certainly no slouch when it comes to EE technical matters, and perhaps some of the others who have responded as well. thank you, Almarg, for the acknowledgement. :-) |
Thank you Al. I thought there is always going to be a direct causal effect of actual amp speed and subjective/sonic speed. That's very interesting. I understand the obvious descriptors of a really good amp but there's another effect/indicator of subjective speed which is observable. It may be that I have a too limited perspective on what transient performance is. The things I'm referring to are effects of ambiance being injected where you can hear it's instantaneous up front presence less subtly than the engineer may have intended probably expecting it not to be noticeable, and maybe with a sparkling almost grainy effect. As if you can hear that sound being constructed. Also for example a string being stretched or when they are sliding up or down the neck of the instrument, or soft consonants like the word 'you' for example where after the initial attack the remainder of the tone is so consistently immediate as to convey the same sense of speed as the transient. Or the precisely contained decay of a kick drum where you can hear reverberations clearly/sharply. Or even a trombone doing it's thing with a sense of strength and immediacy that denotes speed. I have a pair of Meridian 105s that are uncanny in their ability to convey this sense of speed. I also have a pair of the famed LOW TIM LSR&D Superamp monos designed by the late Dr. Marshall Leach of Georgia Tech. Although they both display equally competent transient performance, the Meridians have that sense of immediacy that raises them a notch above. I also have a GAS500 that has this sense of immediacy but not quite as fast in transient performance.
If the relationship between technical parameters and subjective perception is indirect or vague, then how does someone set out to design a 'subjectively fast' amp? Is it just a crap shoot? Technically, what descriptors must an amp possess in order to facilitate subjective speed? Isn't this the goal?
I do recognize those here with knowledge and pay attention to their conversations. But it's you and Ralph who seem to stand out among the others for me. |
Speed when it is incorrect can also be perceived as a slowing down, a lethargy as it were, of the music overall, as if something is a little wrong with the timing. Thus, a piece that would normally take 3:50 to play is perceived as taking say 3:57 to play. |
02-18-15: Csontos
Al, as you and Ralph are obviously the two most technically knowledgeable, I think it most appropriate for the two of you to also define/describe amplifier 'speed' from a subjective/sonic perspective. From a subjective perspective, I think of "fast" as referring to the ability to reproduce musical transients in a "clean" and accurate manner, as opposed to a "sloppy" and inaccurate manner. As ZD said on 2-9-15, "you need to listen to how the system is reproducing the attack, resonance and decay of whatever instruments are on the recording." I would emphasize, though, that speed from a subjective standpoint and speed as characterized by risetime, bandwidth, and slew rate are two different things, which do not have a necessary or direct relation. It seems entirely conceivable to me that an amp having a 100 kHz bandwidth could be subjectively "faster" than one having a 1 mHz bandwidth. Although in many cases there may be an indirect relation between faster bandwidth/risetime/slew rate and subjective speed. For example, use of a given amount of feedback in a really high speed circuit may not result in as much Transient Intermodulation Distortion compared to its use in a slower circuit (as Ralph, Psag, and I alluded to earlier). Less TIM distortion meaning more accurate reproduction of musical transients, by definition. BTW, re "the two most technically knowledgeable," let's not overlook Bombaywalla, who is certainly no slouch when it comes to EE technical matters, and perhaps some of the others who have responded as well. Best regards, -- Al |
"define/describe amplifier 'speed' from a subjective/sonic perspective. As yet, no one has given a description of what a 'fast' amp sounds like in comparison to something unremarkable."
If you recall, you did ask this question a few days ago. I did my best to give you an answer and you got mad at me because of it. Have another look.
"02-09-15: Csontos
I think it would be useful to get a subjective description of just what the attributes of a 'fast' amp are sonically. What does speed sound like in an amp in comparison to mediocrity? Anyone?"
"All components contribute to a systems illusion of speed, so its hard to isolate just the amp. But overall, from a subjective perspective, you need to listen to how the system is reproducing the attack, resonance and decay of whatever instruments are on the recording. When the attack, or leading edge of a note is being highlighted more so than the other 2, you'll probably interpret that as speed, or PRAT."
"02-09-15: Csontos
Can you give an example of an amp that is outstanding in this regard?"
"I bought a Musical Fidelity A3.5 integrated. It had way too much attack, or speed. So much so, that unless you have a really dull sounding system that needs a band aid fix like that, it just wears you down and starts to sound like a gimmick. Its kind of hard to find an example like that any more, because most designers have been trying to get their designs to have more of a balanced sound to them. And for the most part, they've been successful. Tube designers try to get they're gear to have more SS qualities, and SS designers trying to get some tube aspects in their designs. That type of thing.
Zd542 (Threads | Answers | This Thread)"
And for those answers, I got this.
"02-10-15: Csontos
Zd, I would think the opposite is the case in fact. Deliberately not designing true to life character seems to be the gimmick among tube amp designers especially. Just because of the well known quirky expectations of their market base. From what I gather, tubes sounding closer to ss is more trendy than vise versa. If the sound is 'balanced' as you say, it will display serious speed and attack...like reality does. If that's not what you want, it's okay to be honest and not obfuscate or try to reinvent the English language. "
"02-11-15: Csontos
Zd, I do own a few amps. You clearly favor tubes so I responded commensurate with your bent. Not everyone considers your subjective view as reality btw. I'm perfectly happy with your answer. I just think it's bullshit, that's all. I expected as much."
To sum up, you asked for a subjective opinion and I gave you one. Then you asked me for an example, so I gave you one. What exactly do you think the word subjective means? Maybe we don't think its the same thing. If someone else dares to give you an answer, are you going to attack them as well? |
Al, as you and Ralph are obviously the two most technically knowledgeable, I think it most appropriate for the two of you to also define/describe amplifier 'speed' from a subjective/sonic perspective. As yet, no one has given a description of what a 'fast' amp sounds like in comparison to something unremarkable. This goes to the op in reference to it's effect on the music. I'd like to hear references beyond HF transient performance/attack and bottom end definition. Grooming is necessary in this hobby just because of it's inherent limitations. The moon is too far away. |
Hi Al(marg). Your informed and considerate posts are "very"
much appreciated. Your background provides a great platform for your
insights. My Dad was a Civil Engineer so I appreciate how thorough and
appropriate an Engineer can be on a topic of interest. (Dad was a
woodworking craftsman and built the boat that so enhanced my youth).
Your comments invite me to further research. On a non technical side, I've
checked your system indicates stock power cords. Please don't be
offended at my totally subjective suggestion that you at least try an MIT
Oracle AC 3 (non-networked) power cord. In my Spectral based system
these have proven to be extremely effective in all components,including
digital,--batting much higher than their approx $600.00 cost via Joe
Abrams,their online dealer/discounter for Audiogon. I hope you will sense
increased speed and refinement :- ) |
Thanks, Ptss. I appreciate the nice words and the suggestion. And I've noted in the past your frequent advocacy of the importance of addressing power quality and power-related issues.
I'll keep your specific suggestion in mind, for a future time. Next on my list, though, as you've seen in the DEQX thread you initiated, is purchase of an HDP-5 in the next month or two :-)
Best regards,
-- Al
|
Hi Al(marg). Your informed and considerate posts are "very" much appreciated. Your background provides a great platform for your insights. My Dad was a Civil Engineer so I appreciate how thorough and appropriate an Engineer can be on a topic of interest. (Dad was a woodworking craftsman and built the boat that so enhanced my youth). Your comments invite me to further research. On a non technical side, I've checked your system indicates stock power cords. Please don't be offended at my totally subjective suggestion that you at least try an MIT Oracle AC 3 (non-networked) power cord. In my Spectral based system these have proven to be extremely effective in all components,including digital,--batting much higher than their approx $600.00 cost via Joe Abrams,their online dealer/discounter for Audiogon. I hope you will sense increased speed and refinement :- ) |
Yes the components I build. No caps in the signal path in my preamp. Caps cannot keep up.
Happy Listening. |
Bruce, I agree with everything in your post, and also with Bombaywalla's last post. The one about slew rate, that is; I have no experience with Quiznos :-) Upon careful reading I don't see the two posts as being inconsistent with each other.
Best regards,
-- Al
|
Bombaywalla, I generally get your points about slew rate specs and the impact on bandwidth, especially if there are large power demands placed on the amp at higher frequencies.
FWIW, I seem to recall many years ago that I spoke with Leonard, ARC's former customer service rep, about the slew rate issue. Len explained that the design of an amp takes into account many factors and compromises, slew rate being just one of many. The same hold true for negative feedback, DF and so forth.
So, in the end, Len wisely said that it comes down to how does the amp in question sound in real life operating conditions taking into account all of these design considerations and trade-offs. That's what engineers do all the time.
As to your specific point that a 10K square wave pic might not look so pretty at high power outputs ... well that might be true. But as we all know, most of an amp's power demands are in the bass and midrange frequency spectrum.
I surmise that listening to an amp pumping even 50 watts of power into moderately sensitive speakers at 10K Hz would likely melt your ears ... assuming the tweeters could take the load.
Al ... what are your thoughts?? |
My vote for an amp as fast as Spectral goes to Hypex NC400 |
I think Quiznos makes a much better sub - too bad that they didn't have their biz model under control. In my area, they have all but disappeared.... |
I note, btw, that the ARC Ref 150 has a specified 3 db bandwidth of 120 kHz (at 1 watt, with an 80 kHz "power bandwidth" also being specified), and JA's measurements indicate a bandwidth of approximately 100 kHz (for an 8 ohm load connected to the 8 ohm tap), with excellent reproduction of a 10 kHz square wave (under small signal conditions, as noted under the graph). Hi Almarg, thanks for the feedback. I did also note the very same specs as you wrote above & also noted that these were mostly under small-signal conditions while slew-rate is a large-signal parameter (as you already noted in an earlier post). When the amp is outputting a lot more power then i believe that the distortion will be much higher & the various BWs cited in JA's measurements will constrict & that 10KHz sq wave won't look so pretty anymore . That's why a 66KHz BW at max rated power under the stated 13V/us slew rate did not seem unreasonable to me. The effect of the excess phase shift would thus be more discernible (vs. lower power outputs). |
JJ's doesn't have any locations in my area. But before playing a recording that might call for a sub (which doesn't happen too frequently with my speakers), I can always drive over to a Subway location if need be. :-)
Best regards,
-- Al
|
Give it a shot! By the way, it doesn't mean you will get your order within 5 minutes, it is just the way they map out their delivery to make sure you do get it within a very reasonable time. The only way I know this is 2 of my sons work for them in management and training. FWIW |
Fraz,
Inquiring minds want to know...
Next time a need a really fast sub... |
Map, I know this is way off the subject, but yes, JJ's is pretty darn fast for delivery, they only deliver if their typical drive time from store to your house is 5 minutes or less(barring non-standard events such as car accidents, weather etc.)Anyway, back to the good stuff.... |
Bombaywalla, thanks for the additional thoughts. However, while I agree with your math, I don't completely agree with the conclusions you reached. As I'm sure you recognize, my hypothetical example involving 200 watts at 200 kHz, as well as the figures you cited in connection with Bruce's Ref150 of 150 watts at 66 kHz, are not remotely within the realm of real world operating conditions for a home audio system. Or at least a home audio system that is not in the process of self-destructing due to some unimaginable defect-induced oscillation :-) A key point to keep in mind is that under realistic operating conditions bandwidth and risetime should not be and in general will not be limited by slew rate, as I indicated in my long post dated 2-6-15 (see more on that below). And as I indicated in my previous response to Bruce: ... a basic point in my analysis was to show that even relative to VERY conservatively drawn thresholds the speed-related parameters of the Spectral amps are **in themselves** extreme overkill. While at the same time citing the possibility that the overkill might provide indirect benefits in the design. Consider "VERY conservatively drawn thresholds" to mean parameters that are so extreme as to be well beyond the bounds of real world operating conditions. As you may realize but others may not, slew rate should be fast enough to avoid any possibility of the amplifier's output slewing under any realistic operating conditions. While bandwidth (and risetime) limitations mean that frequency components above a certain frequency are attenuated or filtered out, slewing results in essentially all frequencies that represent sonically meaningful information being filtered out and/or distorted. In a sense it can therefore be considered analogous to what happens in hard clipping, although of course that relates to amplitude limitations rather than speed limitations. I note, btw, that the ARC Ref 150 has a specified 3 db bandwidth of 120 kHz (at 1 watt, with an 80 kHz "power bandwidth" also being specified), and JA's measurements indicate a bandwidth of approximately 100 kHz (for an 8 ohm load connected to the 8 ohm tap), with excellent reproduction of a 10 kHz square wave (under small signal conditions, as noted under the graph). So while I don't think we can completely rule out the possibility of audible phase shifts occurring in the upper treble region under some circumstances, given the bandwidth of the Ref150, I would not expect that to be as much of an issue as your conclusion would seem to indicate. And to put that into context, I'll point out that more than a few other very highly regarded amps, including some tube amps costing vastly more than the ca. $13K Ref150, have bandwidths which are considerably more limited. Best regards, -- Al |
Is Jimmy Johns really that fast or are they just setting themselves up for failure by advertising to be?
Just wondering. have never experienced. |
But are Spectral amps freaky-fast like Jimmy Johns delivery? That is what I want to know.
Really though, all interesting information here. |
SPECTRAL gear just thinks it's fast and my 12 gauge Radio Shack copper speaker wire was fast but it pulled up lame during Wagner's Ride Of The Valkyries. |
02-06-15: Bifwynne
So Al, what does that mean in the context of ARC ref amps. As I mentioned above, the slew rate for my amp (150 wpc) is a paltry 13 volts/microsecond and the rise time is a sluggish 2 microseconds. The top of the line Ref 750 has a slew rate of 20 volts/microsecond and a rise time of 1.5 microseconds. Bifwynne, doing the math for your ARC Ref 150 tube amp - if the amp is outputting its full/rated 150W into 8 Ohms that would mean a RMS voltage of 34.6Vrms of a sinusoidal waveform & a peak of approx 49Vp of the same sine waveform. I.E. the peak-peak voltage of the sine wave would be 98Vpp. If amp traversed the 98Vpp such that the slew rate of the amp is 13V/us (as spec'd) then the maximum frequency that the amp could handle with this slew rate would be 66KHz. So, it appears that the freq BW of your amp is 20Hz (or 5Hz?) - 66KHz. Compared to the (fictitious?) example Almarg gave where the amp was a 200W unit & had a slew rate of atleast 45V/us such that it could handle a signal as high as 200KHz. So, the ARC Ref 150 has quite a bit lower slew rate compared the Almarg's example power amp & accordingly lower frequency bandwidth. This also means that since the ARC Ref 150 bandwidth is just 3X (rather than 8X or 10X) the music bandwidth (of 20KHz) one can expect to hear the amp impart its own phase shift onto the higher frequencies of the music. This can manifest itself in a few ways - the highs could sound rolled-off or they could sound warmer or there could be less sparkle/shimmer compared to an amp of higher bandwidth. Nothing wrong with this sort of attribute of a power amp - many like it & many others don't. Something keep in mind. Just some additional info, FWIW. |
"Have you forgotten that I'm never wrong?"
Well, no. In order to do that, I would have to believe it before I forget it. Regardless, the statement if factually incorrect. I proved that in my last post. |
Okay, well thank you for showing me the error of my ways. From now on I'll try and do my best to not actually respond to your rants. Have you forgotten that I'm never wrong? Perhaps if you go back and read a past post or two you'll come finally to the realization that I've made it abundantly clear. |
"02-11-15: Csontos
Zd, I do own a few amps. You clearly favor tubes so I responded commensurate with your bent. Not everyone considers your subjective view as reality btw. I'm perfectly happy with your answer. I just think it's bullshit, that's all. I expected as much. "
Well, it took you long enough. Trying to figure out how to "win" and make yourself look good. Take as long as you want, but you'll never get it. The secret to winning an argument is don't argue. Just use facts. Why? Because you can't argue facts. Facts are facts regardless of what you, me or anyone else says. Can't do a thing about it.
I referenced a Musical Fidelity A3.5. You can't agree or disagree with me, subjective or otherwise. Why? Again, because you never heard one. Its a factual statement. Neither one of can change it. But we know you'll try and fail anyway.
Also, wrong on my preference for tubes. I knew you wouldn't get the example. I don't have a preference for anything, I just pick what I think sounds best (from actually listening, not guesswork). Right now, my entire main system is all SS. |
Soulution advertises 'fast' amps. My understanding is that this enables them to use large amounts of negative feedback in order to achieve low distortion. Because they are 'ultrafast' negative feedback loops, they do not degrade the sound. So says Jonathan Valin as he currently sings their praises in The Absolute Sound. |
Zd, I do own a few amps. You clearly favor tubes so I responded commensurate with your bent. Not everyone considers your subjective view as reality btw. I'm perfectly happy with your answer. I just think it's bullshit, that's all. I expected as much.
Oh, I've never read or bothered with one of those mags. |
I would be hard pressed to believe Hegel is not as fast. It is very fast. |
Unsound you are right I was thinking spectron not spectral. |
"02-10-15: Csontos
Zd, I would think the opposite is the case in fact. Deliberately not designing true to life character seems to be the gimmick among tube amp designers especially. Just because of the well known quirky expectations of their market base. From what I gather, tubes sounding closer to ss is more trendy than vise versa. If the sound is 'balanced' as you say, it will display serious speed and attack...like reality does. If that's not what you want, it's okay to be honest and not obfuscate or try to reinvent the English language. "
You asked the question and for some reason, it looks like you're not happy because I was able to answer it. You make up all this crap and back it up with guesses. It doesn't work that way, regardless of what you think. The only way you can legitimately challenge my findings is if you have some of your own to back yourself up with. You can't do that. I've owned the amp and based my findings on reality. If you want someone to listen to you and take you seriously, then put your money where your mouth is and get one yourself. But we all know that's not going to happen, so keep reading the magazines, come up with more useless crap and keep us entertained.
"Btw, a soa amp will always display serious speed and attack."
Btw, more useless crap. Audio Note, Shindo, Jadis... The list goes on, and no, I'm not explaining it to you when you pretend like you don't understand. Everyone else will. (although you probably wouldn't be pretending) |
Mapman, to the best of my knowledge the Spectral amps are not Class D. |
Zd, I would think the opposite is the case in fact. Deliberately not designing true to life character seems to be the gimmick among tube amp designers especially. Just because of the well known quirky expectations of their market base. From what I gather, tubes sounding closer to ss is more trendy than vise versa. If the sound is 'balanced' as you say, it will display serious speed and attack...like reality does. If that's not what you want, it's okay to be honest and not obfuscate or try to reinvent the English language.
Btw, a soa amp will always display serious speed and attack. |
Is "fast" a desirable attribute? Yes. The human ear/brain system has a tipping point wherein if the reproduction of music is not 'fast' enough, the processing moves from the limbic system (emotional center) to the cerebral cortex (intellectual center). But by and of itself speed is not the final arbiter- it must occur within an otherwise musical framework. |
"02-09-15: Csontos
Can you give an example of an amp that is outstanding in this regard?"
I bought a Musical Fidelity A3.5 integrated. It had way too much attack, or speed. So much so, that unless you have a really dull sounding system that needs a band aid fix like that, it just wears you down and starts to sound like a gimmick. Its kind of hard to find an example like that any more, because most designers have been trying to get their designs to have more of a balanced sound to them. And for the most part, they've been successful. Tube designers try to get they're gear to have more SS qualities, and SS designers trying to get some tube aspects in their designs. That type of thing. |
Can you give an example of an amp that is outstanding in this regard? |
"02-09-15: Csontos
I think it would be useful to get a subjective description of just what the attributes of a 'fast' amp are sonically. What does speed sound like in an amp in comparison to mediocrity? Anyone?"
All components contribute to a systems illusion of speed, so its hard to isolate just the amp. But overall, from a subjective perspective, you need to listen to how the system is reproducing the attack, resonance and decay of whatever instruments are on the recording. When the attack, or leading edge of a note is being highlighted more so than the other 2, you'll probably interpret that as speed, or PRAT. |
*
Is "fast" a desirable attribute?
* |
I think it would be useful to get a subjective description of just what the attributes of a 'fast' amp are sonically. What does speed sound like in an amp in comparison to mediocrity? Anyone? |
I once knew this girl who was really fast, very high slew rate, but I don't think as fast as Spectral gear :) |
Interesting.
It might be hard to quantify or even identify but it makes sense to me that higher performance in general enables design options that might not be viable otherwise. To what extent any of those are beneficial or not of course may still be up in the air, but it is always a good thing to have options in design, at least that has been my experience over the years in other areas of engineering.
Isn't that what "high end audio" is really about from a technical perspective? Doing things bigger, better faster....sometimes just because you can. |
