Do amp designers use roasted components?

Discussion in 'AV Receivers & Amplifiers' started by fraggle, Feb 27, 2003.

  1. fraggle

    fraggle
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    After wiring up my new amp and leaving Radio 1 on it at a loud volume for a day to burn the amp in (still going) I started to wonder.

    The amp is made with new components. Now these components when initially used, for whatever chemical/physical reason, change their characteristics slightly producing the "burn in" effect, the sound of an amp changes from brand new as its used, the majority of change in the first 48 hours say.

    Now, the designers of amps when they're trying prototypes, do they use new components, bake the amp or burn it in, and then evaluate their design?

    If they're just changing a few components, it could make the design process very long winded... change a 2.2K resistor for a 1.9k one and put it back in the oven for 72 hours...?

    The alternative I thought of is they have a complete stock of components which are all "pre-baked" to bypass the "burn in" effect.

    So which is it, how do they design amps nowadays? (and in the age before CAD, Spice, etc?)
     
  2. Big_AL007

    Big_AL007
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    Have you thought about going out more dude :D :rotfl: :laugh:
     
  3. fraggle

    fraggle
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    I did whilst radio one was blasting out for hours :)
     
  4. alextgreen

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    A valid (and interesting) question, when engines are designed a computer simulation illiminates any major flaws before a proto is built, then they cain that on a 'death bed' to see how it goes. Speaking to one of the chief techs on the Rover KV6 product, funny story (too tired to type) about him being 2 seconds away from getting a conrod through the back of his head.

    Any of the techies around here able to enlighten us?
     
  5. Reiner

    Reiner
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    The alternative I thought of is they have a complete stock of components which are all "pre-baked" to bypass the "burn in" effect.

    Impossible judging by all the SMD (surface mounted device) components, as well the fact that some boards or cards may be supplied from 3rd parties - at least where lot's of digital processing is involved.

    I assume they need to burn the equipment in like you and me do but it would be nice to get some insight from e.g. John Dawson of Arcam on this.

    And how do the actually make prototypes? Produce a few and test or wire it up on a bench and hold it together with duct tape? :D
     
  6. CounterWhine

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    Surely Radio 3 would have been a better choice for running in.
     
  7. fraggle

    fraggle
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    Any particular reason why?

    Radio 1 is compressed, loud rubbish most of the time. So its ideal to make the amp do some work and get it warmed up. :)
     
  8. John Dawson

    John Dawson
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    It is true in our experience that it is good to let designs settle or burn in for a while before doing serious evaluation. This polarises parts like capacitors, especially electrolytic types, and allows other parts to reach their expected operating temperatures.

    As a rule we don't burn in components when developing products. IMO it doesn't really matter with parts like resistors and there is a wide range of voltages over which a capacitor might operate, so what voltage would you choose? But you can hear differences between different components - whether that is down to the part itself or its effect on other parts of the circuit is what has to be understood by the engineering team.

    Prototypes have to be made on proper circuit boards if you are to get meaningful results. Of course there probably will be a number of parts dangling in the air from time to time too!

    HTH.

    John Dawson (Arcam)
     
  9. fraggle

    fraggle
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    So I guess the designs are laid down on computer or paper first, built, evaluated and then tweeked to make minor changes?

    I'm just puzzled how manufacturers keep their signature sound (for want of a better word) when they design a new amp.

    Are the different "characteristics" that an amp may have (such as warm, harsh, laid back, transparent) effected by a type of circuit? I.e. if you wanted characteristic 'X' you could use pre amp design 'Y' and main amp 'Z', but if you wanted a different characteristic you'd use per amp 'A' with main amp 'Z'?
    (when I say "pre amp design" I mean for example "the pre amp is an existing design thats known to sound that way", and also I'm not talking about a seperate pre-amp in its own box, but a segment of the PCB in an integrated amp)

    The only other way I could imagine getting a "sound" is by desigining an amp purely from a technical point of view, and then once its good on the test bench you then tweek it to get it to sound right, bu say changing types of caps, or transistors, or bias levels, or maybe using FETs, etc. I can't see this way being practical, it'd take years of random tweeking!

    Basically do you have a known range of amp part designs that when put together give the companys "sound", that you choose from and then improve upon?
     
  10. EvilMudge

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    Can't speak about any other companies, but Bryston certainly give all their products a damn good thrashing (wahey:smashin: ) before they leave the factory, which is why they offer a 20 year warranty - they doubt their customers could better their self abuse!:D
     
  11. CounterWhine

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    That was my (ever so slightly tongue in cheek) point.

    Radio 3: Full range with lots of lovely transients.

    Radio 1: Compressed rubbish.

    D.

    PS. Radio 3 goes loud too ;) Not that I'd know. Radio 4 forever!
     
  12. fraggle

    fraggle
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    Aha! So I put Radio 3 on quite loud, go out for a few hours and come back to two smoking cones lying 5' away from the speakers :D
     
  13. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    I would hope that any electronics manufacturer is not trying to create a "sound". If they are trying to add warmth or brightness or whatever other adjective you can think of then I think they have lost the plot. I'd guess that most have a house "distortion" as they are varients on same design philosophy.

    Another interesting question would be how many prototypes get built with same design to see if there is a consistency in performance. From my time in retail I know that there can be qiute a varience in performance once units go in to production. Surely the same must be true for prototypes.

    Good thread....

    Gordon
     
  14. fraggle

    fraggle
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    Hmm, well you know the way the same comments seem to come from a lot of reviewers and users about a companies range of (say) amps? (I.e. Audiolab/TMC are transparent and clear, etc)

    I'd imagine each company builds up a loyal following of users who like this "sound" and look forward to upgrading to a more powerful amp, maybe with slightly more refined sound (bigger PSU & reservoir caps, higher damping factor - all the sorts of things you can do when you throw more money at an amps design).

    I don't know of any company (I'm talking mid to high end here)that makes a range of amps that have a completely different "sound" across the companys range, does anyone know of such a company?

    That fact leads me to believe companies indeed DO recognise they build components with a certain "sound" to them and tweek their new products (or design using the same stage design types if its that what introduces the "sound") to "keep them in line" with the companys "sound" (as it were).
     
  15. EvilMudge

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    I have heard a range of amps and also CD players and such where the sound has evolved over time, my guess being that such companies use a changing body of testers, whose tastes vary.

    I've heard of one company however which spends a fortune on R&D, tests in an enormous anechoic chamber, and then does ABX blind testing, where they quite often send prototype units back to the design stage because they fail the ABX improvement test.
    Does anyone else see anything wrong with this process (the blind testing isn't carried out anechoically)?
     

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