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Bruno Putzeys reaches out to the subjectivists

fas42

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The 'problem' may not necessarily be the Kiis specifically - a possible causal chain is the Kiis drawing power from the mains is adding extra noise to the mains, which the rig's DAC is plugged into. The interference rejection of the latter is not good enough, and the DAC's analogue output is degraded.
 

RayDunzl

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a possible causal chain

Maybe there is some corrosion in the wiring in the breaker box and it wouldn't happen if...

Whoa! You almost had me going there!


I WENT TO THE DR's THE OTHER DAY WITH AN IMAGINARY DISEASE.

HE DIAGNOSED ME AS BEING A HYPOCHONDRIAC.

I SAID, "HOW CAN AN IMAGINARY DISEASE HAVE A CLINICAL NAME FOR IT IF IT'S REALLY IMAGINARY?"

HE SAID, "JUST GO PAY YOUR BILL."

"CAN I USE IMAGINARY MONEY?" I REPLIED......
 

fas42

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I tawt I taw an Imaginary Post ...
 

cjf

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Over the years I've done a great deal of circuit simulation of amplifiers - which all work extremely nicely when all the conditions around them are "perfect". But throw in realistic mains behaviour, power supplies, load conditions, and it all goes bad, quite quickly - it's quite easy to get an amplifier which on paper works nicely to then exhibit distortion figures which are, say, 100 times worse, purely in a simulation, by giving it an environment which is realistic, rather than a dream state. And that includes feedback - again, purely in simulation it's quite straightforward to observe what the feedback is actually doing when "under stress" - and depending upon the circuit it may still be functioning textbook like, or, the circuit may be close to chaotic conditions, because the parts are working at the limits of their capability; all bets are off. This is where very wideband amplifiers win handsomely; the circuitry is alway working 'correctly'.

Based on my experience with all the Hypex amps I've used I would agree that only doing your testing in a "bubble" leaves allot to chance on the table. I've already posted about my experiences here and elsewhere while using these amps on certain speakers and found an incompatible issue that would most likely go unnoticed if the product was only tested in said bubble.

I've also found that using a known good top of the line preAmp regardless of what speakers are used to cause these Amps to misbehave. I hooked up an Ayre KX-R Twenty recently which arguably can be considered one of the best available today and it resulted in what can best be described as having too much gain in the Preamp. I heard immediate Pops/clicks/hum and other nasty sounds emitting from any speaker I choose to hookup with the Hypex amps in the signal chain. if I use my "cheap" Classe CP800 preAmp or even cheaper Benchmark DAC1 direct its a perfectly happy combination. Go Figure

Mr Putzey may be considered a genius in many aspects but if he wishes to play in the HiEnd pond selling expensive products it would be a wise decision to beg borrow or steal whatever testing methods are required to ensure his gear works with other known good, other highly respected gear that at some point may be hooked up to his stuff that clearly is only tested in said bubble.
 

fas42

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I've also found that using a known good top of the line preAmp regardless of what speakers are used to cause these Amps to misbehave. I hooked up an Ayre KX-R Twenty recently which arguably can be considered one of the best available today and it resulted in what can best be described as having too much gain in the Preamp. I heard immediate Pops/clicks/hum and other nasty sounds emitting from any speaker I choose to hookup with the Hypex amps in the signal chain. if I use my "cheap" Classe CP800 preAmp or even cheaper Benchmark DAC1 direct its a perfectly happy combination. Go Figure
It's one of the facets of this hobby that people want to experiment with combinations of gear. The trade off in my mind is that the behaviour of individual components then needs to be 'conservative', otherwise the sort of problems you mention arise - possibly preventing the "best possible" sound being achieved; witness brands of amplifiers requiring specific types of speaker cable, as part of the warranty. The manufacturer can't be expected to account for all the "strangeness" out there - best is protection circuitry that detects unusual running, and shuts the component down.

A better alternative is the "all in one box" solution, IMO - then full optimisation can occur, and the best sound for people who chase that goal - those who want to experiment still have plenty of items out there to play with, :D.
 

Sal1950

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I've also found that using a known good top of the line preAmp regardless of what speakers are used to cause these Amps to misbehave. I hooked up an Ayre KX-R Twenty recently which arguably can be considered one of the best available today and it resulted in what can best be described as having too much gain in the Preamp. I heard immediate Pops/clicks/hum and other nasty sounds emitting from any speaker I choose to hookup
That's very curious, that any modern amp should misbehave in a very obvious manner like this? Do you have any idea what aspect of the interface load is at work here?
 

Thomas savage

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That's very curious, that any modern amp should misbehave in a very obvious manner like this? Do you have any idea what aspect of the interface load is at work here?
Possible the output of the preamplifier was forcing the amp to clip.. My belles preamp puts out a maximum of 30vrms and made the TAD M2500 (class D) sound terrible even at fairly low volume.

A similar mismatch probably. I did start a thread on matching a preamplifier to suitable amplifiers understanding what's going on and what you need to know to avoid this kind of fate but got told all preamps work with all amplifiers. It was all in my head etc etc

Shame ( I was not talking mystical synergy here, as I was at pains to point out at the time )
 

Blumlein 88

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Possible the output of the preamplifier was forcing the amp to clip.. My belles preamp puts out a maximum of 30vrms and made the TAD M2500 (class D) sound terrible even at fairly low volume.

A similar mismatch probably. I did start a thread on matching a preamplifier to suitable amplifiers understanding what's going on and what you need to know to avoid this kind of fate but got told all preamps work with all amplifiers. It was all in my head etc etc

Shame ( I was not talking mystical synergy here, as I was at pains to point out at the time )

Shame on those people Thomas. Gain matching a system is no joke. I remember having a tube CJ pre-amp. It could at max put out something like 30 or 40 volt signals and was setup with way more gain than needed. So you always ended up operating it at very low volume settings. I eventually put some resistors ahead of the input to drop input by 20 db. Much nicer then and helped its noise floor a bit because it wasn't amplifying the noise to near audible levels on some sources.

One isn't blaming either pre-amp or amp when such things occur. Nor is it an indication Bruno needs to do differently than he does or this is a result of designing within a bubble. One needs to understand gain matching, and sometimes bandwidth matching. One had to be picky with Spectral amps with their megahertz flat power bandwidth. Plenty of pre-amps would allow some kind of stuff to leak thru that might burn up stuff that normally was no problem. Rational investigation into matching things or seeing what is causing issues is the path forward.
 

Thomas savage

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Shame on those people Thomas. Gain matching a system is no joke. I remember having a tube CJ pre-amp. It could at max put out something like 30 or 40 volt signals and was setup with way more gain than needed. So you always ended up operating it at very low volume settings. I eventually put some resistors ahead of the input to drop input by 20 db. Much nicer then and helped its noise floor a bit because it wasn't amplifying the noise to near audible levels on some sources.

One isn't blaming either pre-amp or amp when such things occur. Nor is it an indication Bruno needs to do differently than he does. One needs to understand gain matching, and sometimes bandwidth matching. One had to be picky with Spectral amps with their megahertz flat power bandwidth. Plenty of pre-amps would allow some kind of stuff to leak thru that might burn up stuff that normally was no problem. Rational investigation into matching things or seeing what is causing issues is the path forward.
Yea, I was hoping by helping audiophiles out with this kind of objective knowladge it would in their eyes add value to taking a more objective approach and we would gain some members along with helping guys out.

Iv lost count of how many times a audiophile has made such a complaint against a component, thinking it's all synergy of the mystical kind and being stuck with a expensive purchase they are now having to move on.. Even dealers etc seem rather clueless in this area too.

'Loud sigh'
 

Sal1950

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Shame on those people Thomas. Gain matching a system is no joke. I remember having a tube CJ pre-amp. It could at max put out something like 30 or 40 volt signals and was setup with way more gain than needed. So you always ended up operating it at very low volume settings. I eventually put some resistors ahead of the input to drop input by 20 db. Much nicer then and helped its noise floor a bit because it wasn't amplifying the noise to near audible levels on some sources.
Hear what your saying on system gain, as we discussed before I had same issues myself with my VTL amps and their 720 mv input sensitivity coupled to my 105 db sensitive La Scala's.
Even running a McCormack passive preamp I had to pay close attention to everything in the system. But that boils down to hum/RF issues from either grounding problems or interconnect shielding. Or a user might run into issues with input clipping from a very high gain preamp causing overload distortion.
But "Pops/clicks/" cjf mentions still has me scratching my head. ????
 
OP
oivavoi

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I've struggled to understand this thing with gain matching. It doesnt't seem very intuitive to me. The chief engineer at B&O, Geoff Martin, recently had an excellent blog post about it though: http://www.tonmeister.ca/wordpress/2017/02/13/signal-levels-and-dynamic-range/

That post clarified a couple of things to me, even though I'm not sure if I really understand it yet. His main rule of thumb is to have as much gain as possible in the beginning of the chain.

My future chain of command will probably look like this:
Oppo 105 --> DBX driverack PA2 (crossover duties and eq) --> hypex amps --> speakers
The reason for the PA2 is that that's the crossover box that is used by the manufacturer of the loudspeaker I'll probably end up buying. The hypex amps have a set gain of 26 db. I will therefore probably have to turn down the digital volume control in the Oppo quite a bit, since my listening levels are moderate (usually 68-75 db as baseline), and the drivers of my future speakers have a sensitivity of 86 (woofers) and 90 db (tweeter).

Is this not an ideal gain match, for example? Would I be better off running the speakers with amps with adjustable gain or a lower set gain?
EDIT: Perhaps this amp for example - http://www.classdaudio.com/4-channel-amplifiers/4-channel-sds-450c-audio-power-amplifier/
 
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Cosmik

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Is this not an ideal gain match, for example? Would I be better off running the speakers with amps with adjustable gain or a lower set gain?
EDIT: Perhaps this amp for example - http://www.classdaudio.com/4-channel-amplifiers/4-channel-sds-450c-audio-power-amplifier/
I'd buy something like this for a couple of hundred quid off ebay:
http://www.arcam.co.uk/products,,,diva-avr300-receiver.htm
It has a multichannel direct mode where you have six (or is it eight? - not sure about whether you get control of all eight) channels of amplification via the unit's volume control, plus a separate +/-10dB trim range for each channel.

It also appears to have pre-amp outputs, so I think you could use it as a glorified volume control with external power amps if you felt you needed to. My guess is that it will sound magnificent on its own. I use a similar Sony amp (sometimes available for £40!) which is excellent, but this one looks even better.

User manual here: http://www.arcam.co.uk/ugc/tor/diva-avr300-receiver/User Manual/avr300e_manual.pdf
 
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OP
oivavoi

oivavoi

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I'd buy something like this for a couple of hundred quid off ebay:
http://www.arcam.co.uk/products,,,diva-avr300-receiver.htm
It has a multichannel direct mode where you have six (or is it eight? - not sure about whether you get control of all eight) channels of amplification via the unit's volume control, plus a separate +/-10dB trim range for each channel.

It also appears to have pre-amp outputs, so I think you could use it as a glorified volume control with external power amps if you felt you needed to. My guess is that it will sound magnificent on its own. I use a similar Sony amp (sometimes available for £40!) which is excellent, but this one looks even better.

User manual here: http://www.arcam.co.uk/ugc/tor/diva-avr300-receiver/User Manual/avr300e_manual.pdf

Thanks. Excellent suggestion. The multichannel direct input actually makes it possible to use it for running active speaker systems. The only problem is that I'll need to convert the balanced out from the pa2 to unbalanced input in the AVR. Which adds another box to the equation. But if I can find it on the cheap, it might nevertheless be worth it.
 

March Audio

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Based on my experience with all the Hypex amps I've used I would agree that only doing your testing in a "bubble" leaves allot to chance on the table. I've already posted about my experiences here and elsewhere while using these amps on certain speakers and found an incompatible issue that would most likely go unnoticed if the product was only tested in said bubble.

I've also found that using a known good top of the line preAmp regardless of what speakers are used to cause these Amps to misbehave. I hooked up an Ayre KX-R Twenty recently which arguably can be considered one of the best available today and it resulted in what can best be described as having too much gain in the Preamp. I heard immediate Pops/clicks/hum and other nasty sounds emitting from any speaker I choose to hookup with the Hypex amps in the signal chain. if I use my "cheap" Classe CP800 preAmp or even cheaper Benchmark DAC1 direct its a perfectly happy combination. Go Figure

Mr Putzey may be considered a genius in many aspects but if he wishes to play in the HiEnd pond selling expensive products it would be a wise decision to beg borrow or steal whatever testing methods are required to ensure his gear works with other known good, other highly respected gear that at some point may be hooked up to his stuff that clearly is only tested in said bubble.


Am I remembering correctly that these were the speakers with the absolutely pathological impedance curve?
 

cjf

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That's very curious, that any modern amp should misbehave in a very obvious manner like this? Do you have any idea what aspect of the interface load is at work here?

Strange indeed. I really haven't a clue about what can bring about such behavior but taking a SWAG anyway leaves me wondering if it had to do with a rather high Output Voltage from the Preamp which according to Stereophile's last test of the Ayre KX-R Twenty said that it can put out more than 27v with volume level buried. But in my case, it didn't matter what volume level I set on the Preamp, the problem occurred immediately as soon as the amps were turned on and the volume level of the Pre still turned all the way down. o_O

An interesting thing to add here is that my Classe CP800 Preamp which has the same 300ohm output Impedance as the Ayre but with a "meager" 18v worth of Output Voltage works perfectly fine with these Amps
 
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cjf

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Am I remembering correctly that these were the speakers with the absolutely pathological impedance curve?

Yes, you are remembering correctly but there is a twist in this case. It didnt matter what speakers I had connected, even an el-cheapo set of Infinity Outdoor speakers had the same issue with the Ayre connected to any of the Hypex Amps I have on hand (Mola Mola Kaluga & DIY NC400). I've sold off my Merrill Audio Veritas already but I would bet the issue would happen on them also.
 

Blumlein 88

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Based on my experience with all the Hypex amps I've used I would agree that only doing your testing in a "bubble" leaves allot to chance on the table. I've already posted about my experiences here and elsewhere while using these amps on certain speakers and found an incompatible issue that would most likely go unnoticed if the product was only tested in said bubble.

I've also found that using a known good top of the line preAmp regardless of what speakers are used to cause these Amps to misbehave. I hooked up an Ayre KX-R Twenty recently which arguably can be considered one of the best available today and it resulted in what can best be described as having too much gain in the Preamp. I heard immediate Pops/clicks/hum and other nasty sounds emitting from any speaker I choose to hookup with the Hypex amps in the signal chain. if I use my "cheap" Classe CP800 preAmp or even cheaper Benchmark DAC1 direct its a perfectly happy combination. Go Figure

Mr Putzey may be considered a genius in many aspects but if he wishes to play in the HiEnd pond selling expensive products it would be a wise decision to beg borrow or steal whatever testing methods are required to ensure his gear works with other known good, other highly respected gear that at some point may be hooked up to his stuff that clearly is only tested in said bubble.

Actually that Ayre preamp only has .55 db of gain. Very close to nothing. It does have the ability to pass on very high voltage signals. Feed it 27 volts and it would put out28.76 volts. Feed it a typical 2 volts from a DAC and it would output 2.13 volts. So it has very little gain, but tremendous headroom.

It has a 2 mega-ohm input impedance, and is relatively wide bandwidth. Flat to near 250 khz and probably has substantial response to more than 1/2 a megahertz.

Now just conjecture on my part, the Mola Mola rolls off around 50 khz and will have an output filter. It is possible some low level grunge at high frequencies that normally gets drained away with 20 kohm input impedances was being buffered and passed onto the Mola Mola using the Ayre with its high impedance and wide bandwidth. This might have interacted at high frequencies to mix poorly with the Mola Mola in some unforeseen manner. Without some testing of the output hard to say.
 

Blumlein 88

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I've struggled to understand this thing with gain matching. It doesnt't seem very intuitive to me. The chief engineer at B&O, Geoff Martin, recently had an excellent blog post about it though: http://www.tonmeister.ca/wordpress/2017/02/13/signal-levels-and-dynamic-range/

That post clarified a couple of things to me, even though I'm not sure if I really understand it yet. His main rule of thumb is to have as much gain as possible in the beginning of the chain.

My future chain of command will probably look like this:
Oppo 105 --> DBX driverack PA2 (crossover duties and eq) --> hypex amps --> speakers
The reason for the PA2 is that that's the crossover box that is used by the manufacturer of the loudspeaker I'll probably end up buying. The hypex amps have a set gain of 26 db. I will therefore probably have to turn down the digital volume control in the Oppo quite a bit, since my listening levels are moderate (usually 68-75 db as baseline), and the drivers of my future speakers have a sensitivity of 86 (woofers) and 90 db (tweeter).

Is this not an ideal gain match, for example? Would I be better off running the speakers with amps with adjustable gain or a lower set gain?
EDIT: Perhaps this amp for example - http://www.classdaudio.com/4-channel-amplifiers/4-channel-sds-450c-audio-power-amplifier/

Actually this looks like it would prove no problem in gain structure. The PA2 has several adjustments for setting system gain structure anyway. One is setting input sensitivity of the PA2 at either +4dbu or -10 dbv. Which is about a 12 db difference between those two. The 26 db gain of the amps is about right for you. If fed the max Oppo output into the amps directly it would be outputting between 200 and 250 wpc into 8 ohms. That would drive your speakers somewhere around 109 db give or take a few if they are 86 db sensitivity. If your normal listening is the level you describe you might well be just about perfect with +4 dbu settings on the input of the PA2.
 
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cjf

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Actually that Ayre preamp only has .55 db of gain. Very close to nothing. It does have the ability to pass on very high voltage signals. Feed it 27 volts and it would put out28.76 volts. Feed it a typical 2 volts from a DAC and it would output 2.13 volts. So it has very little gain, but tremendous headroom.

It has a 2 mega-ohm input impedance, and is relatively wide bandwidth. Flat to near 250 khz and probably has substantial response to more than 1/2 a megahertz.

Now just conjecture on my part, the Mola Mola rolls off around 50 khz and will have an output filter. It is possible some low level grunge at high frequencies that normally gets drained away with 20 kohm input impedances was being buffered and passed onto the Mola Mola using the Ayre with its high impedance and wide bandwidth. This might have interacted at high frequencies to mix poorly with the Mola Mola in some unforeseen manner. Without some testing of the output hard to say.

Thanks for your reply and for the info.

My initial use of the term Gain was an attempt to describe the sound that I was hearing while connecting this combo of gear together. Another way to explain it would be like this:

Imagine having all your gear powered up and you are using XLR connections between your Preamp and Amps. Then for what ever reason you decided to unplug the XLR connections (With everything still powered on) and repeatedly "tapped" the 3 prongs of the XLR cable against the Female XLR Inputs of the Amp. I've done this by accident in the past and the sound I heard was just like that. You get a pop, buzz and crackle from the speaker upon initial contact of the prongs together. Then, imagine for some other reason you thought it would be cool to hear what would happen if you decided to press the prongs of the XLR cable against the XLR Input of the Amp and just hold it there without fully seating the cable. From past experience you normally get what could best be described as a loud and constant feedback sound from the speaker.

These are exactly the sounds I heard with these two components connected together. Needless to say, but I only let this take place a few times before giving up and putting the Preamp back in its box admitting defeat. The cables involved are in perfectly good working order also.
 

March Audio

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Thanks for your reply and for the info.

My initial use of the term Gain was an attempt to describe the sound that I was hearing while connecting this combo of gear together. Another way to explain it would be like this:

Imagine having all your gear powered up and you are using XLR connections between your Preamp and Amps. Then for what ever reason you decided to unplug the XLR connections (With everything still powered on) and repeatedly "tapped" the 3 prongs of the XLR cable against the Female XLR Inputs of the Amp. I've done this by accident in the past and the sound I heard was just like that. You get a pop, buzz and crackle from the speaker upon initial contact of the prongs together. Then, imagine for some other reason you thought it would be cool to hear what would happen if you decided to press the prongs of the XLR cable against the XLR Input of the Amp and just hold it there without fully seating the cable. From past experience you normally get what could best be described as a loud and constant feedback sound from the speaker.

These are exactly the sounds I heard with these two components connected together. Needless to say, but I only let this take place a few times before giving up and putting the Preamp back in its box admitting defeat. The cables involved are in perfectly good working order also.

Im not sure I fully understand what you are saying here but it sounds like you are describing mains buzz 50 or 60hz on top of connection issue.

This catagorically is not the fault if the hypex amps.

As blum mentioned the Ayre very high input impedance and practically no input filtering.....mmmmm......dont live near any transmitters do you? Probably best to keep your mobile phone away from it also. Its not a good idea to have the input open that wide IMO, open to all sorts of RF getting in there including that from some DACs / CD players.


Think the penny has dropped. The Hypex class D amps oscillate at about 400khz....

Change the pre amp and I will bet your problems all go away. Its a radio receiver not an audio pre amp :)
 
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