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Amp shopping thoughts

rwortman

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So, as many may know, I recently purchased a Mcintosh C49 preamp because I wanted all the functions it has and no one really has all that for much cheaper. I have it connected to a Crown XLS1502 amp and PSB Imagine T2 speakers. Something in my semi-audiophile mind says that I should have a better quality amp even though I don't have any real sound quality objection to the Crown. I window shopped on line for over a week. I know the preference by most here is the Benchmark or a class D amp based on one of the newer modules.

I am an old fart retired engineer. I just don't like the idea of buying an amplifier from a company that doesn't make the actual amplification device because they probably don't have the expertise to engineer it. When it comes to state of the art class D, only a few companies actually design their own amps, the rest of them are merely packagers. Tech support and repair is just put a new module in it.

I have seen (and I know I don't have a statistically valid sample) well respected Hypex/Purifi amps being sold used by their second owner and they are less than a year old. In a few months, two owners have decided to sell them for something else. Is this just audiophilia nervosa or something else?

Even though I currently own a class D amp, I have always thought that class D in the home setting was a solution looking for a problem. An audio system is simply not a major contributor to household power consumption. I see it for the pro's as the efficiency and light weight make hauling and setting up much easier.

I know we are all about the measurements and I mentioned this in another thread and got dismissed, but a speaker amp is for driving speakers, not warming resistors. I read somewhere that I can't recall of a designer of respected amps that says they spend a lot of time investigating the behavior of their amps when actually driving a speaker. A speaker is not only a reactive load, it is an active load, generating its own voltages because of the inertia of its drivers. I suspect that how an amplifier deals with this is not completely described by a single number of output impedance or damping factor, neither of which are purely resistive or the same over frequency. I also suspect but can't prove that some of "amplifier sound" is attributable to this

I know that hi fi reviewers are held in little regard here. Heck, I have little regard for many of them myself. I do think that they are not deaf and, having listened to tons of gear, can probably make some value judgements. Bias is real but it doesn't overcome everything. If an audio device really sounds bad, bias can't completely obliterate that. Further, since these folks are heavily biased towards expensive gear, when they say something inexpensive sounds good, it probably does. I also recall that a couple of Stereophile luminaries got 100% correct on a blind amplifier challenge. Since it is a statistical probability that some test takers will score 100% by random chance it didn't weigh heavily on the test outcome that the amps were indistinguishable. If I had been running the test I would have retested those 2 guys enough to establish a statistically valid yes or no to their ability to distinguish. Some people just do have trained hearing and can hear things that are masked for most people. I have seen this in professional sound engineers. I have a disk for ear training for sound engineers. I haven't played with it yet but it is a for real course.

I ended up ordering a scratch and dent deal on a Rotel RB 1582 Mk II amplifier. It am sure it sounds fine. I am sure it would measure as mediocre by ASR standards. It may not sound better than my Crown. It is, however, a well made class AB amp that, should it fail, I know how to fix.

I have said here and other places that I was going to use my Crown amp until it failed, and then buy another one. I changed my mind. I have a suspicion that the switching frequency hash on the grounds has raised the noise floor of my phono preamps. I haven't measured it, but they seem noisier since I got this amp.

Anyhoo. This is entertainment not heart surgery so I am going to play with my new amp soon. I will soon be selling a DAC, phono pre, two preamps, and an amplifier.
 
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iMickey503

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Fran from Fran Labs said once, "Go with the Devil you know".
It's part of the reason why I stick with Chrysler. I know how to fix everything on it if it breaks.
And, I don't need anyone's help to do it.
.
My Volvo is by far the better car in many ways. But if something goes wrong? Its always going to be a $2,000 bill for parts.

Not to mention, I can't just plug in a OBDII reader to find out what's wrong.

Class D is always going to have its topology scrutinized and rightfully so. There have been so many BAD implementations of it for years. And to top it off? Many reviewers in the past were just biased from the get go. I doubt they heard much of any difference in the class D amp shootout I read and I think that was either in stereophile or the absolute sound.

if you can't trust your ears then trust your gut. Sometimes no matter how good the toyota is? I just can't bring myself around to buying one.

I wonder if there's a subconscious bias that when things sound exactly the same and can be repeated in exactly the same Perfection has the last performance, your mind is confused by it as it expects something different each time from listening to the same piece of music.

I'm sure someone at the A.E.S. has done research on this kind of phenomenon.
maybe that's what it is?

because in the real world, you don't have something happen twice in the exact same way. And as reproduction of digital music is perfect every single time*, well that might be the reason why some of us prefer the older Technologies even though they don't measure well or have higher distortion. Its a theory.
 

Inner Space

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I'm sure the Rotel will be fine. It's easy to get lost in the weeds - if you're intending to use speakers in a room, then worrying about exact amp quality is like worrying about a hangnail when you're about to get hit by a freight train.
 

NiagaraPete

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rwortman

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I am not really interested in the newest Topping gizmo except for my engineering curiosity. Buying stuff from Chinese companies with almost no dealer or service presence in the US selling things that are nearly impossible for the user to repair has little appeal to me.

I have had the Rotel amp in my system for close to three weeks now. I can report that it unequivocally sounds different than the Crown. People in here believe that amps that measure with flat FR and low enough distortion will sound the same in level matched testing. Others have said that most of the differences we hear in audio components are due to FR. About a week after I got the Crown I noticed that there was an annoying shrillness in the upper range of some female vocal recordings. I hooked up my measurement mic and ran some REW scans. There was a 5 to 6db hump centered around 1Khz and a 4 to 5 db dip centered around 2.5K along with the usual peaks and valleys in the bass response caused by room modes. I corrected these with EQ and the recordings sounded much better. It still seemed like I was having a few less of those "wow" moments when everything comes together with a great recording on a decent system. I figured it was just me.

I put the Rotel amp in the system and ran an REW scan with the EQ bypassed to see if the FR variations I noticed before were the same. They were not. The FR from 200hz up was a nice flat downward slope like you expect a well behaved speaker to do in a room. I had to double check to see if I had really bypassed the EQ. With the Rotel amp the only corrections I needed to make were in the bass region. Obviously the output impedance of the Crown amp was interacting with the impedance of my speakers in a pretty big way. I probably did not have an exact inverse of that in my EQ so some of it was still audible. My "wow"s per listening session has gone up by a factor of about 5. It seems like I can hear the reverb space in the recordings better. My speakers sound better to me now than they ever have. From NAD C275BEE to Crown XLS1502 to Rotel RB1582 mkII on the amp side and Schiit Saga, Emotiva PT100, Mcintosh C49 on the preamp side.

I think two amps that measure similarly into an actual loudspeaker will sound the same driving that loudspeaker. Amps that have astonishing SINAD into a resistive load show us that the designer is really good at getting low distortion into a resistive load. I am not sure how that correlates to driving a complex driver/crossover load and reacting/not reacting to the back EMF from the speaker drivers. Most previous generation class D amps will vary their FR into a real speaker load. The new Hypex and Purifi amps are supposed to have solved that problem by taking phase corrected feedback after the output filter. I wonder if they have measured this into a variety of real world speaker loads or whether this just makes for great test bench measurements.

My current two channel signal path is now: Analog sources: VPI Scout/AT VM740M, Yamaha BDA 1060 universal disk player; Digital sources: Raspberry PI/HiFiBerry digi+ streamer, Grace Digital Grace Link, USB output of Roon server PC; Preamp: Mcintosh C49; Amp: Rotel RB1582MkII; Speakers: PSB Imagine T2; Sub: SVS SB2000 Pro. I think this will be it until something breaks or something truly revolutionary comes around. Another class D amp with a few more zeroes to the right of the decimal point in its distortion spec is not revolutionary. Class D itself is only revolutionary when it comes to portable audio. DAC design was a solved problem decades ago. Maybe some revolutionary transducers will come along or maybe some new method of creating an artificial sonic space in a room will come to market. We'll see.
 

NiagaraPete

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I am not really interested in the newest Topping gizmo except for my engineering curiosity. Buying stuff from Chinese companies with almost no dealer or service presence in the US selling things that are nearly impossible for the user to repair has little appeal to me.

I have had the Rotel amp in my system for close to three weeks now. I can report that it unequivocally sounds different than the Crown. People in here believe that amps that measure with flat FR and low enough distortion will sound the same in level matched testing. Others have said that most of the differences we hear in audio components are due to FR. About a week after I got the Crown I noticed that there was an annoying shrillness in the upper range of some female vocal recordings. I hooked up my measurement mic and ran some REW scans. There was a 5 to 6db hump centered around 1Khz and a 4 to 5 db dip centered around 2.5K along with the usual peaks and valleys in the bass response caused by room modes. I corrected these with EQ and the recordings sounded much better. It still seemed like I was having a few less of those "wow" moments when everything comes together with a great recording on a decent system. I figured it was just me.

I put the Rotel amp in the system and ran an REW scan with the EQ bypassed to see if the FR variations I noticed before were the same. They were not. The FR from 200hz up was a nice flat downward slope like you expect a well behaved speaker to do in a room. I had to double check to see if I had really bypassed the EQ. With the Rotel amp the only corrections I needed to make were in the bass region. Obviously the output impedance of the Crown amp was interacting with the impedance of my speakers in a pretty big way. I probably did not have an exact inverse of that in my EQ so some of it was still audible. My "wow"s per listening session has gone up by a factor of about 5. It seems like I can hear the reverb space in the recordings better. My speakers sound better to me now than they ever have. From NAD C275BEE to Crown XLS1502 to Rotel RB1582 mkII on the amp side and Schiit Saga, Emotiva PT100, Mcintosh C49 on the preamp side.

I think two amps that measure similarly into an actual loudspeaker will sound the same driving that loudspeaker. Amps that have astonishing SINAD into a resistive load show us that the designer is really good at getting low distortion into a resistive load. I am not sure how that correlates to driving a complex driver/crossover load and reacting/not reacting to the back EMF from the speaker drivers. Most previous generation class D amps will vary their FR into a real speaker load. The new Hypex and Purifi amps are supposed to have solved that problem by taking phase corrected feedback after the output filter. I wonder if they have measured this into a variety of real world speaker loads or whether this just makes for great test bench measurements.

My current two channel signal path is now: Analog sources: VPI Scout/AT VM740M, Yamaha BDA 1060 universal disk player; Digital sources: Raspberry PI/HiFiBerry digi+ streamer, Grace Digital Grace Link, USB output of Roon server PC; Preamp: Mcintosh C49; Amp: Rotel RB1582MkII; Speakers: PSB Imagine T2; Sub: SVS SB2000 Pro. I think this will be it until something breaks or something truly revolutionary comes around. Another class D amp with a few more zeroes to the right of the decimal point in its distortion spec is not revolutionary. Class D itself is only revolutionary when it comes to portable audio. DAC design was a solved problem decades ago. Maybe some revolutionary transducers will come along or maybe some new method of creating an artificial sonic space in a room will come to market. We'll see.
Well Crown’s are PA amps and Rotel I’m surprised is still a brand.
 

xpop

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Hello @rwortman, you should describe the room in which you listen to your music because it seems that you have more of a speaker problem than an electronics problem. Your level of expertise in terms of audio sources seems very accomplished but I can't stop thinking that your speakers have diameters that are too small for your expectations. I take good note that whatever the intrinsic quality of the PSB Imagine T2 they cannot compare to speakers with larger diameter drivers, even if these are of lesser quality. And please, forget about using a subwoofer in music, it's so unattractive or even disturbing if you're really an audiophile.
 

iMickey503

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Your Volvo must be an ancient classic model if it has no ODBII - sounds nice, let's have a pic!
This summer. Soon.
1981 Volvo 240 Turbo 2 door with sunroof. IPD suspension, Braces, and other stuff.
Why has it not moved? If I put a Battery in it? Replaced the fuel pump? It would be gone tomorrow. And not by my choice.

And you know it's going to because it's a Chrysler, just get a Japanese car.
Some would say its a factory option. Lukas, the Prince of darkness has been hiding in my Multifunction switch for years.

I like cars that represent my personality.
BROKEN.
 
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rwortman

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Hello @rwortman, you should describe the room in which you listen to your music because it seems that you have more of a speaker problem than an electronics problem. Your level of expertise in terms of audio sources seems very accomplished but I can't stop thinking that your speakers have diameters that are too small for your expectations. I take good note that whatever the intrinsic quality of the PSB Imagine T2 they cannot compare to speakers with larger diameter drivers, even if these are of lesser quality. And please, forget about using a subwoofer in music, it's so unattractive or even disturbing if you're really an audiophile.
I don’t recall saying I still had a problem. The fact that one amplifier had a pretty flat frequency response in the room and the other didn’t is not a room problem or a speaker problem.

I am quite sure Paul Barton knows more about how to design a speaker than either of us. There are advantages to narrow baffles and multiple woofers. The 3 5.25” woofers in the T2 have the same cone area as a 9” single woofer. They will move the same amount of air. The -3db point is 34hz. Pretty low. Small cones are stiffer and therefore will have lower distortion. The narrow baffle moves the baffle step to about the same frequency as the crossover to the midrange driver so it can be easily dealt with. Three woofers at different heights means three small floor bounce cancellations instead of one big one meaning a smoother bass response.

I don’t have diameter expectations. I have good sound expectations and these speakers have it. The fault I was hearing was in the far upper midrange. This is not something cured by a bigger woofer.

“whatever the intrinsic quality of the PSB Imagine T2 they cannot compare to speakers with larger diameter drivers, even if these are of lesser quality.”

These is nonsense.

“forget about using a subwoofer in music, it's so unattractive or even disturbing if you're really an audiophile.”

More nonsense.
 

MattJ

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Hello @rwortman, you should describe the room in which you listen to your music because it seems that you have more of a speaker problem than an electronics problem. Your level of expertise in terms of audio sources seems very accomplished but I can't stop thinking that your speakers have diameters that are too small for your expectations. I take good note that whatever the intrinsic quality of the PSB Imagine T2 they cannot compare to speakers with larger diameter drivers, even if these are of lesser quality. And please, forget about using a subwoofer in music, it's so unattractive or even disturbing if you're really an audiophile.
Yowza. I guess I'm not an audiophile. I love my Hsu sub, especially for music.
 

Holmz

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…. And please, forget about using a subwoofer in music, it's so unattractive or even disturbing if you're really an audiophile.

All subs? Or which do you have experience with being bad?
I have one, and it seems o’roight.
 

HammerSandwich

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There was a 5 to 6db hump centered around 1Khz and a 4 to 5 db dip centered around 2.5K along with the usual peaks and valleys in the bass response caused by room modes.
<snip>
Obviously the output impedance of the Crown amp was interacting with the impedance of my speakers in a pretty big way.
Something odd's going on here. 5dB is an enormous difference between two SS amps, and the boost & dip should be reversed to match the T2's impedance per Stereophile.

Have you rechecked that the Crown's internal EQ is disabled?
 
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rwortman

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Something odd's going on here. 5dB is an enormous difference between two SS amps, and the boost & dip should be reversed to match the T2's impedance per Stereophile.

Have you rechecked that the Crown's internal EQ is disabled?
I agree that it seems odd. On the other hand, I haven’t read anything where people were measuring speakers using different types of amplifiers so I don’t know how odd it is. It doesn’t have internal EQ, it has internal crossover filters. I had the highpass filter engaged at 50hz. I don’t know how that impedance plotted by Stereophile would interact with the output impedance of the Crown amp because I don’t know what it is. What it surely isn’t is a resistor so thinking of it as a simple voltage divider isn’t correct. I didn’t try to repeat the measurements and the amp is gone now. I know we aren’t supposed to trust our ears but I do have some experience measuring and adjusting PA systems and that peak was pretty consistent with what I heard. The EQ is flat in that region now and I don’t hear that any more.
 
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freemansteve

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It seems to me to entirely reasonable that two amps with similar flat FR and distortion figures sound different when driving the same speakers in the same room.

The figure used for such comparisons are usually obtained with simple resistive loads. But speakers offer complex impedences and an amps output impedance is not itself 100% resistive (hence the term output impedance, not output resistance). Hence some amps will work better with some speakers than with others, including that thing of sounding 'shrill' or not.
 

HammerSandwich

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It doesn’t have internal EQ, it has internal crossover filters.
Got it, thanks for clarification. Crazy they implement DSP without including a few PEQs, but there you go. Guess that's why the iNukes remain popular for DIY subs.

I don’t know how that impedance plotted by Stereophile would interact with the output impedance of the Crown amp because I don’t know what it is. What it surely isn’t is a resistor so thinking of it as a simple voltage divider isn’t correct.
I'd expect more SPL where the speaker's impedance is higher & vice versa. Otherwise, the amp's output impedance is highly varied or even negative, right?
 
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