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Old 28th June 2010, 05:31 AM   #101
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Quote:
Originally Posted by abraxalito View Post
I'm not suggesting the design isn't legitimate, just that the specs are overly optimistic. But that's fairly common in the audio world.



It certainly suggests it should be a reliable piece of equipment. But what does he know about achieving high quality sound from the design of medical power supplies I wonder?

He's been designing audio a long time, is an avid audio gear type, probably just like you. Give him a call if you really want to offer some comment.



This is interesting. If my amps had low performance in THD+N I'd not be trumpeting the fact. Or is there something of the hair shirt mentality coming in here - low performance in THD means its optimised for something other than linearity?

I'm sure its a typo


Where full power is 100W into 8R? I can't help but see the irony here - the reason it never gets hot at full power is because it thermally limits and effectively shuts down.

You're guessing here


More hype here - the min specified slew rate is 7V/uS for the chip, 10 is the typical figure. Are we to believe that he hand picks the chips for better than typical slew rate?

I don't know, do you?
A rather dismissive set of replies


I don't have a copy of IEC 60268-3 so maybe it allows short term output power to be put on the spec sheet. Anyone else know about this?
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Old 28th June 2010, 08:56 AM   #102
AndrewT is offline AndrewT  Scotland
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Hi Phil,
Abrax has read the specification and rightly draws his conclusions, much of which he says are exaggerated.
You have read the specification but literally accept everything printed but with no thought about how the numbers have been massaged to look better than achievable.

I would be more inclined to put more faith in Abrax's interpretation.

Go back and read the spec again and the datasheet and compare Abrax's comments to what is printed in those sheets.
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Old 28th June 2010, 10:53 AM   #103
madass is offline madass  Netherlands
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How good is a chip amp compared to the cheapest stereo amps like the Pioneer A-209R (140 euro)? If both of them are not clipping.
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Old 28th June 2010, 10:54 AM   #104
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Quote:
Originally Posted by philmagnotta View Post
He's been designing audio a long time, is an avid audio gear type, probably just like you. Give him a call if you really want to offer some comment.
Can't think why I'd need to call him to repeat what I've already put in the public domain here.

Quote:
You're guessing here
Yep, but its an educated guess based not only on the manufacturer's datasheet but my own experience with the part in question. Your basis for supporting the claims is what?

Quote:
I don't know, do you?
Nope, but another educated guess suggests not - its consistent with some of his other claims (and potential typo) that this >10V/uS is an erroneous claim.

Quote:
A rather dismissive set of replies
On the contrary, your replies are dismissive as they don't engage with the content of my arguments. Have you looked at the datasheet yourself? Have you seen ST Micro's own claims for the TDA7294 and compared them with the claims for this amp?
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Old 28th June 2010, 01:02 PM   #105
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Only in reference to amplifier heating--- the lower the value of damping the less heat any amp seems to make. My amp has lots of feedback and very high damping. My first use of it on a sub with 100 square inches of heat sink was not even close to enough heat sink. It over heated right away. Further testing for the sub got me to the 300 square inches of heat sink value. This is for two of the chips (3886) running on 35 volts.

Yes in my circuit the slew rate of the composite amp was 1 volt per microsecond higher with the very same chip than the chip by itself. Nice surprise. Not the same number, the very same part.
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Old 28th June 2010, 03:16 PM   #106
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I apologize for being dismissive.
I do think that it is better to keep the analysis less judgmental tonally.
However, it appears that those here who are more qualified than I, may in fact be correct in their assumptions.
I still accept that the designer may be correct unless I can prove otherwise.
As always, I very much appreciate this forum.
We all make mistakes and I hope to get better at not making them.
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Old 28th June 2010, 03:21 PM   #107
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Originally Posted by abraxalito View Post
Quote:
[*]Low THD+N performance
This is interesting. If my amps had low performance in THD+N I'd not be trumpeting the fact.
I think you're misinterpreting that line. They are saying "Low THD+N" and added the marketing word performance.
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Old 28th June 2010, 04:36 PM   #108
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Quote:
Originally Posted by philmagnotta View Post
I apologize for being dismissive.
I do think that it is better to keep the analysis less judgmental tonally.
I agree with you, no judgement is better. But that's exactly the way I write - without judgement. Maybe because I write without judgement I'm more inclined to speak directly - that directness is what you interpret as being judgmental.

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As always, I very much appreciate this forum.
We all make mistakes and I hope to get better at not making them.
I hope to continue making mistakes myself as with no mistakes, there's no learning. So even though my style is to write directly, please do point out my errors - sure, we all make them.
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Old 28th June 2010, 04:40 PM   #109
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Quote:
Originally Posted by Redshift187 View Post
I think you're misinterpreting that line. They are saying "Low THD+N" and added the marketing word performance.
Yep, I had thought of that way of looking at it and probably its what was in the writer's mind. But I decided to take the words at face value and have some fun with them It is quite common when an amp is marketed as 'audiophile' as this one is that distortion is either not specified or is quite high as a way of suggesting 'we concentrated on the sound in this design, if the distortion suffered in the process then tough, that's the price of great sound!'
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Old 28th June 2010, 05:09 PM   #110
jez is offline jez  United Kingdom
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Well I use a pair of LM3886 built to the standard NS circuit but good quality parts and very good earthing (it's DC coupled also) and I use this in preference to a Musical Fidelity A370 and Leak Stereo 20 valve amp. My 25WPC split rail supply JLH class A probably just beats it but some times I'm not so sure....
So yes they are pretty damn good by any standard.
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