The most aggressive sounding amplifier?

[KentTeffeteller]

Yup, doubling down into 4 Ohm is a good sign. Doubling down again into 2 Ohm is a great sign.

Cables can change the sound to suit ones subjective preference. Cables are a tuning option. Lamp cord is just as good as 100 buck per meter cable as all subjective preference choices are valid. The validation is comparison listening to the cable choices to determine personal preference. I will never be a boutique audio salesman.

Sorry, not all amplifiers of quality double down in power with reduced impedance. McIntosh with autoformers being an exception. Advantage is full rated power into all loads, and protection from DC to your speakers if the amplifier misbehaves.

 

[SoCal Sam]

Sorry, not all amplifiers of quality double down in power with reduced impedance. McIntosh with autoformers being an exception. Advantage is full rated power into all loads, and protection from DC to your speakers if the amplifier misbehaves.

True, there are always exceptions. For example, the humble HK 690i receiver can pass a perfect square wave at less than rated power. At higher output when transients and monster bass draw are taxing the ability of the 690i to deliver power, compression and sagging ruin the show. In general though, the doubling down spec is a sign that reduced impedance will not degrade signal reproduction.

 

[damacman]

I don't see the correlation between producing perfect square waves and performance. Can someone be so kind as to enlighten me?

 

[Alan0354]

I don't see the correlation between producing perfect square waves and performance. Can someone be so kind as to enlighten me?

A square wave show if the amp is stable by looking at the ringing and overshoot. You can tell the slew rate of the amp. It is an important test. I use burst square wave to check for stability, slew rate, settling time. I don't even use sine wave for testing that often. I run burst square test and fix the stability of the amp, then I go to run FFT to look for THD at different frequency.

Another thing is when I do burst square wave, I vary the amplitude and even drive the amp to severe clipping. I look at the flat part and look for how the ringing change at different amplitude. One thing about these power amps, because of the capacitance of the transistors change with signal amplitude, amp that is stable at small signal might not be stable at large signal. You look at the flat part of the square wave to see how the ringing is at different amplitude particular close to clipping.

Square wave test is very important. Sine wave really doesn't tell you much.

 

[LordLunatic]

The question at that point is how much better than the pioneer they'd be, since the specs are very similar. The Pioneer is 300w 8ohm, 550w 4ohm, 800w 2ohm. THD 0.003-0.002%. FR 20-20k +0/-0.1 dB.
Or more importantly the Thule which has similar specs as well, but is balanced. And has its virtual class A system allowing it essentially full class A benefits without the power consumption or heat generation, meaning a longer lifespan. And for an integrated, dual 500VA trafos is pretty impressive.

 

[SoCal Sam]

A square wave show if the amp is stable by looking at the ringing and overshoot. You can tell the slew rate of the amp. It is an important test. I use burst square wave to check for stability, slew rate, settling time. I don't even use sine wave for testing that often. I run burst square test and fix the stability of the amp, then I go to run FFT to look for THD at different frequency.

Another thing is when I do burst square wave, I vary the amplitude and even drive the amp to severe clipping. I look at the flat part and look for how the ringing change at different amplitude. One thing about these power amps, because of the capacitance of the transistors change with signal amplitude, amp that is stable at small signal might not be stable at large signal. You look at the flat part of the square wave to see how the ringing is at different amplitude particular close to clipping.

Square wave test is very important. Sine wave really doesn't tell you much.

Yes, yes, yes, Alan0354 covers the use well. Any component in the audio chain can be tested with a square wave. Even preamps (with tone controls defeated) can degrade signal. 20Hz-20kHz sweep reveals what an amp can do and what it will sound like. Tilting in LF means the amp cannot maintain power when bass is reproduced which results in tonal imbalance. Cheaper amps round in HF indicating poor frequency response. Sloped rise indicates a slow ropey amp which can be heard as blurring or dullness. And so on. All of these departures from objective accuracy represent distortion using the strictest definition. These departures can also be thought of as coloration that may or may not be desirable based on the listener's subjective preference. For example, sloped rise can be interpreted as "warmth". In the context of finding an "aggressive" sounding amp, all defects are undesirable.

 

[Alan0354]

I have to also stress the use of burst square wave, not continuous square wave. Burst with low duty cycle enable you to really put large signal without the risk of over heating the amp. I don't think most amp.....yes, even the high end ones are meant to handle continuous max signal. I remember one time I tried to break in a new guitar speaker by using a signal generator driving the mighty Marshall guitar amp to give a continuous low frequency signal to loosen the cone. I only drive about 30W on a 50W amp. 15 minutes later, I blew the power tubes, blew the fuse..............I had to change to a variac, step down transformer to feed the 60Hz to the speaker to complete the break in.

Music has very high crest factor, you never do continuous dissipation. It is important to test the amp a high signal level and clipping to see how the amp recover from clipping. If the amp sticks upon clipping, you can see the duty cycle changes when going into clipping.

 

[LordLunatic]

I have to also stress the use of burst square wave, not continuous square wave. Burst with low duty cycle enable you to really put large signal without the risk of over heating the amp. I don't think most amp.....yes, even the high end ones are meant to handle continuous max signal. I remember one time I tried to break in a new guitar speaker by using a signal generator driving the mighty Marshall guitar amp to give a continuous low frequency signal to loosen the cone. I only drive about 30W on a 50W amp. 15 minutes later, I blew the power tubes, blew the fuse..............I had to change to a variac, step down transformer to feed the 60Hz to the speaker to complete the break in.

Music has very high crest factor, you never do continuous dissipation. It is important to test the amp a high signal level and clipping to see how the amp recover from clipping. If the amp sticks upon clipping, you can see the duty cycle changes when going into clipping.

To be fair, under normal use, with amps like these, you'd never get even close to clipping; my speakers are only actually using under 100watt in 8ohm, which is only a third of the available power - and thats peak usage, not rms. Most peaks are barely exceeding 20 from what I can tell on the VU meters. So at >300watts of power, none of these amps would ever be strained or come even close to clipping...

 

[Alan0354]

To be fair, under normal use, with amps like these, you'd never get even close to clipping; my speakers are only actually using under 100watt in 8ohm, which is only a third of the available power - and thats peak usage, not rms. Most peaks are barely exceeding 20 from what I can tell on the VU meters. So at >300watts of power, none of these amps would ever be strained or come even close to clipping...

Yes, I did stress that point that you never hit the max power, AND even occasionally clip, the crest factor is so high that it does not matter.

BUT what I worry about is potential instability when hitting the large signal and clipping. This was explained a little in post #67. To be more exact, for BJT, the collect base capacitance increase a few folds when the voltage across collect and bass goes below 5V ( that happens when the signal swing close to the rail). All of a sudden, you add a lot of capacitance when the signal hit that point, the amp can go into oscillation.

This is a very well know thing in power amp, that's the reason it is imperative to test that. That's why you use burst square wave to look for ringing. If a ringing goes beyond one or two rings, you have a potential problem. If you even try the square wave and vary the amplitude, you'll see the ringing change when you approach the rail particular the moment it goes into clipping.

Testing stability of amp is tricky, you use resistor for testing, for most part, it is resistive. But the impedance of real speaker is really funky, it can even have kick back ( back EMF) that drives back to the amp. You really have to make it perfect when testing with resistor. Not only that, I even put up to 0.5uF at the output and the amp has to be stable enough.

 

[LordLunatic]

By the way, a sidenote is, since some have mentioned the pre amp makes a big difference: not that I have many options, but would the pioneer C90 or questyle CMA800R be up to the task of being pre amps for the Vincents? From the little I've tried, I haven't experienced any noteworthy difference in pre-amps... Though to be fair, most of my testing has been with the Pioneer M90, which seems to be a bit of a gentle giant, in the sense that it has a lot of power, and can drive most things to mind melting levels quite easily, but something tells me it is a bit polite at the same time, so the pre-amp/source quality/coloring might not show through much...

 

[Alan0354]

I have limited experience, I designed my own preamp, just switching relays to route the signal to a motorized 100K volume pot, then drive a buffer to drive the coax to the power amp. But I actually have test fixture to compare quite a few of the top notch opamps like OPA2604, LM4562 etc. I even bought a $70 discrete opamp from recommendation. I can tell you they sounded different, just the buffer make a difference on transparency, brightness.......Don't ask me why, I am stumped.

So I would say preamp is important.

On the second note, I built fixture to compare power amps also, I bought big Monster 12 gauge to do all connections, I use 40A automotive relay that is a lot bigger and robust than those use for speaker relays for switching. I can switch from one amp to the other by a flick of a switch. I use the same speaker and preamp and source to just listen to the difference in the power amp. I have an Acurus 3X200 ( ok amp, low end of audiophile), a Nakamichi PA-7 stasis designed by Nelson Pass, then I have my own design, totally original, not from a kit or follow any particular existing circuit.

I was surprise the difference is so so small. The Acurus is slightly inferior, for the life of me, I could not tell the difference between the Nakamichi and my amp. It's not that I switch and it sounded the same. I don't know how many times I switch and forgot which amp I was on and guess WRONG. Just when I thought I hear the difference, then I found out I bet on the wrong amp. It went back and fore for over a day until I concluded that they are identical. I put through 3 different pairs of speakers, a pair of Kef, a pair of Monitor Audio book shelf, and then my main speaker the JM Lab 913.1. The difference between speakers are stunning, but result in switching amps remain the same, Acurus is a little worst, the other two were identical.

My point is if the amp is good enough, they don't sound as different as people want to think. Only the ones that is not good enough, then you can tell the difference. Maybe, if I get a $10K Krell, I might tell the difference. The Nakamichi is by no means a dog, it is very similar to the Threshold S300 but with even newer and faster transistors. My bet is the Nakamichi should be superior as it's designed in late 80s when the new generation of faster power transistor were available. Threshold used the slow 4MHz old transistors, the Nakamichi uses the 30MHz transistors. the rest of the circuit is the same Stasis design.

 

[LordLunatic]

Hmm... Interesting - I just figured out my Thule IA100 can be used as a power amp (a switch to bypass the internal pre amp so they can be daisy-chained for bi-wiring etc.), so I tried swapping (as well as I could by blindly fiddling with cables in the back of the cabinet) between its internal one, the Pioneer, and the Questyle. There was a difference - not a big one, but it was there. The Pioneer was warmer, and a bit bassier, the Questyle a bit more clinical, less bass, and the internal one seems somewhere in the middle.

Something to note on your point about the power amps, is that after getting irritated with the built in taps on the Pioneer M90, which are for bare wires only (which was driving me batty, when trying to compare with the Thule which uses banana plugs), I looked it up, and found a thread here on Audiokarma, where a guy had had an M90 basically since its release by the sound of it. He had gotten frustrated with the same thing and swapped them - in doing so he noted that the internal wiring and power chord is very thin/poor by modern standards, and that he had very rarely used it, because it compared quite poorly to pretty much everything else "hifi" he had been using - basically describing what I'm noticing, compared to the Thule, that it is too rounded, polite etc. Though he said it had no bass, which is definitely not an issue on mine, which has plenty. So though I do think the Thule is a very good amp for its price, it might just be that the Pioneer is a lot more outdated than I had been lead to believe... I mean the Thule is basically the only modern amp I've had a chance to compare it to.

I'm beginning to A) question if the Pioneer was just a poor choice for my tastes to begin with, and B) how much more there really is to get beyond the Thule... I mean its only 100Watt, but it plays loud, very detailed and controlled - I'm just worried that I waste all my savings on a big new amp, just to find out it was all for naught. On one hand I really wish there is more to be had from these speakers, but some part is worried I'm going to waste my money for next to no results at this point.

 

[Alan0354]

Your Pioneer is not the only that has skimpy wires inside, My PA-7 and Acurus are the same, I went in and double up the speaker output wires and the return wires. I won't worry too much about the power lines, but yes, beef up the speaker wires. I am not saying it will improve the sound, BUT I can tell you when I do FFT test to look at THD, that extra wire does help......at least on the graph.

Usually the single most import piece that define the sound of the system is the speaker. I don't have enough experience in audiophile to say whether the amp and preamp make that big a difference, I can only talk about I experience from my tests. I tried very hard to make it easy to switch back and fore, I spent days building those fixtures so I can switch back and fore by a switch, no disconnect and connect wires. I don't trust memory, from my experience of guessing wrong so many times which power amp it was, I would not go by memory how the sound is in the comparison if it is close..............BUT, I have no problem telling between my 3 pair of speakers. It is so distinct that no fancy switching is needed. Changing the speaker change the sound completely.

Only other time lately I can hear the obvious difference is when I change to the new speaker cable I made. But I assume you know a lot more about speaker cable than me.

Also, people have different ears, I never ever complain the system doesn't have enough highs, they always sound too bright, I always look for warmer sound, go figure. From my limited experience, you should stay away from tube amps and preamp. You should stay away from amp with JFET or MOSFET particular the input stage. All the opamp I tried that are warmer ( to my liking ) are JFET input stage( OPA2604, OPA2134). Again, don't ask me why as all of them are supposed to be so low distortion that they should not color the sound in any way.......but it does.

Sorry I cannot offer any more. The strongest point I have is the speaker cable which you know more than me. Only thing I can say is whatever cable you use, try parallel one or two more cables and see whether you can hear any difference. Call me crazy, I use 4 pairs for each speaker, I swear I can hear the difference. I use two for the mid/tweeter and two for the woofers. You make cables, so it won't cost you much to try. If it does not improve, you can laugh at me. I swear by this.

I hope you can share your opinion in my thread on speaker cable and THD. There is nothing opinion in that thread, it's all about measuring THD with instrument and look at different cables, experiment with the construction of cable to achieve lowest THD on the load. Only subjective comment from me was towards the end of the thread, I replace the two pairs of 12 gauge Monster cables to the Mid/tweeter connection with my self made cable and found that it has so much more attack, in your face and brighter. I was actually surprised. I was expecting that I won't hear a damn of a difference, that all the measurement, improvement are just like the power amp that is only an academic exercise.

 

[damacman]

I have limited experience, I designed my own preamp, just switching relays to route the signal to a motorized 100K volume pot, then drive a buffer to drive the coax to the power amp. But I actually have test fixture to compare quite a few of the top notch opamps like OPA2604, LM4562 etc. I even bought a $70 discrete opamp from recommendation. I can tell you they sounded different, just the buffer make a difference on transparency, brightness.......Don't ask me why, I am stumped.

So I would say preamp is important.

On the second note, I built fixture to compare power amps also, I bought big Monster 12 gauge to do all connections, I use 40A automotive relay that is a lot bigger and robust than those use for speaker relays for switching. I can switch from one amp to the other by a flick of a switch. I use the same speaker and preamp and source to just listen to the difference in the power amp. I have an Acurus 3X200 ( ok amp, low end of audiophile), a Nakamichi PA-7 stasis designed by Nelson Pass, then I have my own design, totally original, not from a kit or follow any particular existing circuit.

I was surprise the difference is so so small. The Acurus is slightly inferior, for the life of me, I could not tell the difference between the Nakamichi and my amp. It's not that I switch and it sounded the same. I don't know how many times I switch and forgot which amp I was on and guess WRONG. Just when I thought I hear the difference, then I found out I bet on the wrong amp. It went back and fore for over a day until I concluded that they are identical. I put through 3 different pairs of speakers, a pair of Kef, a pair of Monitor Audio book shelf, and then my main speaker the JM Lab 913.1. The difference between speakers are stunning, but result in switching amps remain the same, Acurus is a little worst, the other two were identical.

My point is if the amp is good enough, they don't sound as different as people want to think. Only the ones that is not good enough, then you can tell the difference. Maybe, if I get a $10K Krell, I might tell the difference. The Nakamichi is by no means a dog, it is very similar to the Threshold S300 but with even newer and faster transistors. My bet is the Nakamichi should be superior as it's designed in late 80s when the new generation of faster power transistor were available. Threshold used the slow 4MHz old transistors, the Nakamichi uses the 30MHz transistors. the rest of the circuit is the same Stasis design.

Been there. I built a switching unit like this about 20 years ago. They're just downright humbling.

 

[Alan0354]

Been there. I built a switching unit like this about 20 years ago. They're just downright humbling.

I just don't believe in memory, the time you switch the wires, you forgot how it sound already. You got to have the switching unit to switch back and fore. I spent like $140 or more building the fixture, just the Monster cable costed me like $70. Every connection is just as important. Relay are connected point to point if possible, anything over 2 inches were double up with 12 gauge wires. Still I think you loss something because of the fixture. But that's the best I can do. Look at post #52 for the pictures of my fixtures:http://audiokarma.org/forums/index.php?threads/does-a-good-and-expensive-amp-matters.757185/page-3

 

[LordLunatic]

Your Pioneer is not the only that has skimpy wires inside, My PA-7 and Acurus are the same, I went in and double up the speaker output wires and the return wires. I won't worry too much about the power lines, but yes, beef up the speaker wires. I am not saying it will improve the sound, BUT I can tell you when I do FFT test to look at THD, that extra wire does help......at least on the graph.

Usually the single most import piece that define the sound of the system is the speaker. I don't have enough experience in audiophile to say whether the amp and preamp make that big a difference, I can only talk about I experience from my tests. I tried very hard to make it easy to switch back and fore, I spent days building those fixtures so I can switch back and fore by a switch, no disconnect and connect wires. I don't trust memory, from my experience of guessing wrong so many times which power amp it was, I would not go by memory how the sound is in the comparison if it is close..............BUT, I have no problem telling between my 3 pair of speakers. It is so distinct that no fancy switching is needed. Changing the speaker change the sound completely.

Only other time lately I can hear the obvious difference is when I change to the new speaker cable I made. But I assume you know a lot more about speaker cable than me.

Also, people have different ears, I never ever complain the system doesn't have enough highs, they always sound too bright, I always look for warmer sound, go figure. From my limited experience, you should stay away from tube amps and preamp. You should stay away from amp with JFET or MOSFET particular the input stage. All the opamp I tried that are warmer ( to my liking ) are JFET input stage( OPA2604, OPA2134). Again, don't ask me why as all of them are supposed to be so low distortion that they should not color the sound in any way.......but it does.

Sorry I cannot offer any more. The strongest point I have is the speaker cable which you know more than me. Only thing I can say is whatever cable you use, try parallel one or two more cables and see whether you can hear any difference. Call me crazy, I use 4 pairs for each speaker, I swear I can hear the difference. I use two for the mid/tweeter and two for the woofers. You make cables, so it won't cost you much to try. If it does not improve, you can laugh at me. I swear by this.

I hope you can share your opinion in my thread on speaker cable and THD. There is nothing opinion in that thread, it's all about measuring THD with instrument and look at different cables, experiment with the construction of cable to achieve lowest THD on the load. Only subjective comment from me was towards the end of the thread, I replace the two pairs of 12 gauge Monster cables to the Mid/tweeter connection with my self made cable and found that it has so much more attack, in your face and brighter. I was actually surprised. I was expecting that I won't hear a damn of a difference, that all the measurement, improvement are just like the power amp that is only an academic exercise.

Considering how much measuring etc you've been doing, I doubt I know more than you, more likely just a different school of knowledge or different way of working - what's sad is that I can barely even afford my own cables (the good ones). I primarily make headphone cables, but on occasion speaker related things, and I generally only work with the absolute best wire I can get my hands on, which costs about 10$ per foot of 26awg strands; for speakers that would need to be doubled up ideally to 8 strands per channel for speakers as big as these (ideally even more), and I need 2x2.5 meters or so - some quick math and thats 4800$ just in materials for the wire... To be fair, on paper at least, that would be the best speaker cable it is currently possible to make with our technology (best conducting etc), but I'm never spending that much on a speaker cable - not even half! I have a cable of that type for my HD800 headphone, and thats enough for me
But the point is, I'm an idealist, and thats not cheap in the world of hifi, even the cheapest wire I use would be 700$ or so for a pair of speaker cables-worth of just the wire - I've long wanted to make some cables of that quality, but alas, I have to stick to the "dirty" oxygen free wires like everyone else for my speaker cables, and leave the better stuff for interconnects, headphone cables and rich people... But I still have some pride, so I stick to 11gauge silver plated cables, doubled up as biwire, just to have options, making it effectively 8gauge, taking the resistance in ohm/meter down to around 0.001ohm, and getting lower than that starts to quickly get either very expensive due to quality of the wire as mentioned above, or very difficult, because very few terminals will take wire thicker than 8 gauge - and it would be pointless anyway since the connectors and internal wiring would at that point become the bottle-neck at that point.

But coming back to amps, I've experimented far more with headphones than speakers, and as far as headphone amps, I for years dismissed their affect on the sound, beyond much more than the power needed on paper, and stuck to my portable amp, which was already overpowered. But then I head a Cavalli amplifier, with my HD800, and things changed! I noticed how soft and sluggish my small battery powered amp sounded in comparison! I was morified! So power was definitely important! So I started trying out more desktop amps again, and found that most sounded the same, and didn't have much to offer, but some had a bit of variance; the cavalli, which I dream of (but is impossible to get) has a warm, slightly bassy tone to it, which goes very well with my HD800, where as my Questyle CMA800R has a somewhat analytical signature, and then there is everything in between. Keep in mind though, that headphone amps for all intents and purposes are essentially integrated amps.. Or in somecases they can be used as pre-amps for speaker amps.

What set me on to looking for a new speaker amp, was the massive difference between the massive 20-something kg Pioneer C/M90 which I've been using for 5 years, and thought were fantastic, and the new little 12kg Thule. But it might turn out that even though many like it, for my tastes, the Pioneer is just rubbish, and the thule could risk representing what 99% of other good modern amps sound like, making an upgrade almost pointless... But its impossible to know really, without trying - but I'd need a home demo for that, which is pretty hard to get here.

 

[whoaru99]

Yup, doubling down into 4 Ohm is a good sign. Doubling down again into 2 Ohm is a great sign.

Halfing up works just as good and is usually a lot less cost.

 

[LordLunatic]

I might not be able to get the vincents, but I think from the descriptions I might have found a very promising option: the Krell KAV 500i. On one hand I'm a bit sad its integrated, because I like upgrade-ability, but you cant win them all. It has 250w/8ohm 500/4ohm, so plenty of power, and it is generally described as aggressive sounding, very punchy and powerful! Its at 2000$ - new price in 1999 was apparently 9500$ here.

Though a contender is a Parasound 21a Halo thats come up very cheap (1450$ compared to the new price of 4000$).

 

[FootFungus]

The Krell KAV 500i would definitely fit my description of aggressive.

 

[LordLunatic]

The Krell KAV 500i would definitely fit my description of aggressive.

I assume you've heard it? My only worry is wether or not the bass/lower mids are lacking? I cant find much about it, but what I can find is that it should be very well controlled and have slightly bright treble... The danger then becomes if the lower registers are left behind, because I'm a bit of a basshead... Not massively, but I just can not stand anemic bass - solid low end is some of the most important to my musical enjoyment...

And as always with older amps, though this isn't that old, whether it keeps up to modern standards... Because my Thule 2005 vs Pioneer 1986 really taught me how much can evolve...