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Old 26th January 2012, 02:35 AM   #1421
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Quote:
Originally Posted by tvrgeek View Post
Vanderpol,
Did you ever hear the Stax that were big grey boxes and shot past your ears? Nearphones I think they called them. They did have less of the in-head effect. Circa late 70's.
No, "heard of them but never tried them; actually I never owned headphones, could stand more than two songs, drove me crazy. Getting more used to it since I got an Ipod for my birthday; ordered a pair of HD380 from Juno rcords for 118 including shipping see that goes..

Also Cross feed delay lines also seem to have been around since the late 50's, but I guess everyone's head size is different though & hard to tune. Also stuff a couple of microphones in a dummy and evidently you come close to realism.

I brought this up because headphones are super efficient ( easy to"amplify") but still "realism" seems even more remote. I am pretty good at DIY speakers
and definitely prefer that format for real enjoyment
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Old 26th January 2012, 05:18 AM   #1422
Previously: Kuei Yang Wang
 
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Hi,

Quote:
Originally Posted by a.wayne View Post
It appears avg at best on the test bench and sonically. I would suggest the weak sloppy bass was due to the small PSU and miniscule output stage, well vs the rest ...
In the case where I encountered it, (big round of amp swapping out of quite collection) it stuck out enough (and in a positive sense) for me to ask what it was. Turned out it was Goldmund... Didn't know what it was and it was by far the puniest amp in the collection.

As you suggest it is as best average sonically, I take it you have heard this Amplifier and compared it to other high end amplifiers?

Ciao T
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Old 26th January 2012, 06:20 AM   #1423
jcx is offline jcx  United States
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Quote:
Originally Posted by vanderpol4 View Post
No, "heard of them but never tried them; actually I never owned headphones, could stand more than two songs, drove me crazy. Getting more used to it since I got an Ipod for my birthday; ordered a pair of HD380 from Juno rcords for 118 including shipping see that goes..

Also Cross feed delay lines also seem to have been around since the late 50's, but I guess everyone's head size is different though & hard to tune. Also stuff a couple of microphones in a dummy and evidently you come close to realism.

I brought this up because headphones are super efficient ( easy to"amplify") but still "realism" seems even more remote. I am pretty good at DIY speakers
and definitely prefer that format for real enjoyment
Smyth SVS Realizer is an interesting work around for headphone listening

you "calibrate" the system setting in the sweet spot of a real room, loudspeaker setup with mics in your ears - the DSP measures your hrtf and the loudspeaker+room frequency response - has head angle tracking

then corrects your headphones

the result in a very convincing "out of the head" reproduction of the loudspeaker&room "sound" over the headphones
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Old 26th January 2012, 06:26 AM   #1424
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Tvr, the output inductor can be looked at another way. First, there is a series resistor between 1 and 10 ohms. It is this resistor that protects the amp. The inductor is added to the degree necessary that you get unconditional stability with EVERY cap load within the realm of reason OR 1000pf-10uF. Usually 2uH is enough. It was enough for the Crown DC300, for example. In recent years, designers have tried to reduce the amount of inductance necessary, sometimes down to 1/2 uH. OR some manufacturers have eliminated it completely, and still have relatively stable designs with virtually any practical cap load.
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Old 26th January 2012, 07:33 AM   #1425
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Quote:
Originally Posted by mr_push_pull View Post
see? that's exactly what I was talking about.

IMO, this a random assertion. and unless it's backed up by some research it stays that way.

what needs to be studied (and for some reason isn't) is what makes a specific topology sound better.
Or, maybe establish first which topologies do actually sound diferent from others. You can have a well-executed SE versus a sloppy NFB SS give one result, and a sloppy SE versus a well executed NFB SS another result.
First things first: do different, well-executed topologies reliably and repeatably sound different?

jan
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Old 26th January 2012, 07:53 AM   #1426
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Hi,

Quote:
Originally Posted by janneman View Post
Or, maybe establish first which topologies do actually sound diferent from others. You can have a well-executed SE versus a sloppy NFB SS give one result, and a sloppy SE versus a well executed NFB SS another result.
First things first: do different, well-executed topologies reliably and repeatably sound different?
In order to answer this question we need to define "well-executed".

This means we need to define objective criteria by which to measure the execution to determine if it is well executed or ill executed.

I think we all agree that the selection of such criteria should be evidence driven and not reflect various marketing campaigns over time.

The promotion of low measured distortion, of high damping factors and many other features in amplifier design have been marketing driven, since the day's when Harold J. Leak decided to outdo his competitors by rating his equipment at 0.1% Distortion and to heavily promote his gear as low distortion using the "point one" moniker.

In fact his equipment used what was at the time totally generic industry standard circuitry and parts and did not offer actually lower distortion then the competition using the same bog standard circuitry and parts, when the measurements where normalised.

At this point I find that there is little if anything evidence driven in the various measurements that are used to characterise Amplifiers (and other audio electronics).

In fact the situation mirrors to mind often the use of the ducking stool by Captain Tobias Slater in the "Scream satan scream" segment of "Dr. Terrible's House of Horrible" - namely when questioned on the utility of using the ducking stool to establish if a certain comely lass was in a fact a witch or not he replied:

"Charlotte: But I'm damned if I do and I'm damned if I don't. That doesn't make any sense.

Captain Tobias Slater: Yes... But we've got this ducking stool."

Ciao T
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Old 26th January 2012, 08:34 AM   #1427
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Quote:
Originally Posted by mr_push_pull View Post
see? that's exactly what I was talking about.

IMO, this a random assertion. and unless it's backed up by some research it stays that way.

what needs to be studied (and for some reason isn't) is what makes a specific topology sound better.
Or just get two amps (for example) that sound different in a reliable and repeatable way, this should not be a great problem.
THEN do listening tests to get an agreed position in what way they sound different, which might be more difficult.
Then try to find a technical reason for that, change it and repeat the listening tests.
It should all start and end with listening of course.

But it's a bit like asking Yves Saint Laurent to do a controlled catwalk with different dresses to find out what it is exactly what the customers like in his designs....

jan
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Last edited by jan.didden; 26th January 2012 at 08:36 AM.
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Old 26th January 2012, 09:16 AM   #1428
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well, my cochlea, basilar membrane and all neurons and nerves involved have no idea whatsoever what class A, AB or D is, nor do they care about transistors or tubes. they seem to only care about the way some oxygen and nitrogen molecules move.
certain people keep saying that the classical distortion/freq response/etc measurements tell us nothing or close to nothing but I haven't seen anyone coming up with a different set of measurements.
I can't help wondering how come it's 2012 and we have no idea.
I'm perfectly willing to accept for instance that SS could never compete with tubes (just a random example) as long as I see some serious research documenting specific features of the generated sound wave that are related to human perception. but mostly I see speculation.
also, some keep saying that formal analysis of what makes good sound has no point because tastes vary. that doesn't make too much sense, especially when the same people assert with great authority what is bad gear and what is good gear.
I believe that even subjectivity can be measured to a point. (it's one thing to say "I like this amp more" while "I like this amp more because..." is a whole different story)
what I find kind of sad is that there always has to be this dichotomy: subjectivists vs objectivists. it's always divided.
subjectivists says: these measurements are useless.
objectivist says: I'll just keep playing with these numbers, they must lead somewhere because it's all math.
both are wrong, obviously.
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Old 26th January 2012, 11:08 AM   #1429
DF96 is offline DF96  England
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Quote:
Originally Posted by tvrgeek
We add capacitance to cancel driver inductance, but is that a good thing? We add indictance to keep the amp happy with the capacitive load. But the speaker load is unknown to the amp designer, so how do we pick the best output filter?
Just think of it as a rough approximation to a diplexer, known as a crossover in the audio world. The idea is that at higher frequencies the amplifier does not see whatever impedance the speaker+cable presents, but instead sees the resistor in the Zobel network. We are not trying to "cancel driver inductance", just hide whatever reactance it has from the amp at high frequencies where the NFB loop has enough to do already to maintain stability.
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Old 26th January 2012, 04:28 PM   #1430
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Well said DF96. The 'key' is the resistor, rather than the inductor, which is really a parasite or necessary evil in order get max power and good damping factor at audio frequencies.
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