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Old 8th January 2013, 07:57 PM   #32351
gpapag is offline gpapag  Greece
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Originally Posted by simon7000 View Post
So if you like to brighten up your recordings with more distortion, chip amps are more than adequate to give you that result.
ES
Why such a dismissal for real engineering on anything in an IC package?

Ed, data please!

The fact that chip manufacturers publish distortion figures for circuits with published schematics/materials and published pcb, calls for duplicating the exact same construction, conducting measurements and comparing figures. Then, call them liars, cheaters, demand liabilities compensation and whatever you like.

Next step: These distortion figures don’t correlate with good sound. Old news/no news or -in other words- prove it.

Is it a disadvantage of such power op amp that a few external –cheap and available to anyone-components can do an amplifier, true to it’s published specs? (PSU is important of cource but is equally important with discretes)

Yes, here more is needed than conformance to specs (Published? Reproducible? What are all these?)

Some years ago I was recording (using data acquisition module) temperature variations on the drivers, output transistors, heat sinks multiple positions ect and correlating these with input signal on an amp with discrete components, in a quest to optimise the Vbe multiplier’s remote sensing temp tracking abilities.
More than 10ths of seconds response delay, whatever I did. ( chapter 14 in Bob Cordell’s book if one is interested on the subject).
Does anyone bother to take just this important parameter into account when bushing these ridiculous power op amp ICs?
Component matching, inter-routing optimisation? Bah!


George
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Last edited by gpapag; 8th January 2013 at 07:59 PM.
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Old 8th January 2013, 08:40 PM   #32352
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Originally Posted by simon7000 View Post
Pavel.

To me the interesting issue was the use of a low wattage, low quality resistor in the feedback loop. I suspect that is actually the dominant distortion source. So if you like to brighten up your recordings with more distortion, chip amps are more than adequate to give you that result.


ES
Which one are you talking about, the DS app note for the LM3886 has 50mW peak power in the feedback resistor?
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Old 8th January 2013, 08:55 PM   #32353
qusp is offline qusp  Australia
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try lme49830 pushing 400-600mA bias (pretty much Class A for 45W of the output) + Semelab laterals

heaven...

sorry dismiss the latest round of chip and hybrid chip+discrete amps at your peril, the sound AND the measurements are pretty much faultless IMO

simple frequency response error like seems to be being claimed, would seem a very easy thing to measure, so I agree, lets have it!

Last edited by qusp; 8th January 2013 at 08:58 PM.
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Old 8th January 2013, 09:16 PM   #32354
fas42 is online now fas42  Australia
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Originally Posted by TheShaman View Post
This is the 2-part interview of Andrew Jones (Director and Chief Engineer of TAD Laboratories) I got the quote from:
Andrew Jones of Technical Audio Devices - Part one
Andrew Jones of Technical Audio Devices - Part two

Very interesting read IMHO.
Hallelujah ...

Quote:
... undertaking a research study, experimental procedure is important: single-variable change. So many people donít account for all of the things that could be changing as a result of the intended change they thought they were making (in which case, one canít be sure that the intended change was actually the cause of the identified result)
The audio world is riddled with absurdities of thinking because due diligence of this nature is not applied ...

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Old 8th January 2013, 09:56 PM   #32355
fas42 is online now fas42  Australia
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Yes, a good read, all comes across very impressively. Yet, when I listened to the latest TAD effort, with all their electronics, at the Sydney hifi show it was just a YAH, Yet Another Hifi. Probably highly competent, in those technical areas that mean so much to many people; but it didn't sound like music. Was bored within minutes, and moved on ...

Frank
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Old 8th January 2013, 10:15 PM   #32356
morinix is offline morinix  United States
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"You have a hierarchy: a mathematician, a physicist (which is a failed mathematician), and an engineer (which is a failed physicist)." - Andrew Jones
The funniest and most true thing I have heard all week

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Originally Posted by fas42 View Post
Yes, a good read, all comes across very impressively. Yet, when I listened to the latest TAD effort, with all their electronics, at the Sydney hifi show it was just a YAH, Yet Another Hifi. Probably highly competent, in those technical areas that mean so much to many people; but it didn't sound like music. Was bored within minutes, and moved on ...

Frank
To draw a parallel between cooking and audio design. Good audio is like good food. Any technical type can offer up nutrition and likewise audio that measures very good. It takes an artistic flare to cook a really tasty dish and likewise design a really good sounding piece of audio gear. At the Sydney show you heard the audio equivalent of a vitamin pill. Some times that vitamin pill is what is needed but usually the application is a professional one like mixing. The vitamin pill usually does not satisfy in a home stereo.
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Last edited by morinix; 8th January 2013 at 10:26 PM.
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Old 8th January 2013, 10:18 PM   #32357
fas42 is online now fas42  Australia
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This actually came from the hypex ncore thread - from someone associated with building a commercial unit using hypex modules:

Quote:
The faster your transients get, the more interactions chassis, placement, wires, footers, powercords, fuses, interconnects have. The silker your mids/highs are the more you will notice any minor change in wires, components, even a fuse.
Followed by a sequence of posts mainly rubbishing the ideas in that post: it's rather disheartening to see how many just don't get it -- the better a system sounds the fussier you must be to ensure that the last bits and pieces are just right. Otherwise, most of the quality possible is thrown in the rubbish bin ...

This is a truism of audio, and it needs to be beaten into the skulls of many in the game, over and over again, it seems ...

Frank
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Old 8th January 2013, 10:25 PM   #32358
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Originally Posted by gpapag View Post
Why such a dismissal for real engineering on anything in an IC package?

Ed, data please!


George
George,

The point was that the IC had less distortion than the feedback resistor. So the amplifier was was good enough or in other words not the limiting factor.

Scott,

Given 50 mW as the data sheet value (I don't know the production number) it would be a much higher number than the level at which I tested resistors.

As shown in the attached measurement of a higher wattage resistor at 50 mW, one could expect 12 db more distortion from the smaller resistor body, and another 9 to 12 from the low frequency content. (Most musical energy is found at the LF end say 150 Hz.) Then this is a sample of an Ohmite resistor, others of the same type of construction mostly measured worse and none better. So your distortion just from the feedback resistor could be -60 db. re full power. As there are thermal relaxation issues, the tail should be enough to be heard.

I suspect that is the actual limiting factor, not the rest of the circuitry. So to me this would be how to make a "Bright" or "Brings out ..." amplifier.

ES
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Last edited by simon7000; 8th January 2013 at 10:30 PM.
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Old 8th January 2013, 10:40 PM   #32359
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Originally Posted by fas42 View Post
Followed by a sequence of posts mainly rubbishing the ideas in that post:
Take-me for one of them.
I don't mean nothing is important, but i don't agree with this true tote.
Fuse, power cord ? What does-it means when followed by the trasfo and huge caps, if correctly sized and RF/EMI filtered ? Chassis ? What the hell ? It has to provide shielding to electronic components and good air circulation. . Placement : Did you mean some magical effect of the north pole ? Yes, it is not good for a power amp to be several miles away from the enclosures. Footers ??? With Solid state ?
We have survived to the end of the world, time to stop with middle aged magic. We have enough to do with REAL things.
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Old 8th January 2013, 10:56 PM   #32360
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Originally Posted by Esperado View Post
Take-me for one of them.
I don't mean nothing is important, but i don't agree with this true tote.
Fuse, power cord ? What does-it means when followed by the trasfo and huge caps, if correctly sized and RF/EMI filtered ? Chassis ? What the hell ? It has to provide shielding to electronic components and good air circulation. . Placement : Did you mean some magical effect of the north pole ? Yes, it is not good for a power amp to be several miles away from the enclosures. Footers ??? With Solid state ?
We have survived to the end of the world, time to stop with middle aged magic. We have enough to do with REAL things.
Christophe, we are essentially coming from the same direction, we see eye to eye on most things, . But, the need to be meticulous in those things which are not one's own particular bent, fetish, obsession, take your pick ... , is also part of the picture. There is no MAGIC in this, I repeat, stamping my foot solidly on the ground, no magic!! These are all electrical influences, easily measured if one has the right test gear, and more importantly, the right attitude! Just wishing they would go away ain't gonna make it happen, and if one keeps one's mind open, and ears, it is plain that that these things DO matter, when the SQ is high enough ...

Unfortunately, it is a fact of life in sound reproduction and things will only really improve, in the wider sense, when these things are taken seriously ...

Frank

Last edited by fas42; 8th January 2013 at 11:00 PM.
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