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Thread: Ker pow!!!

  1. #171
    Join Date: Jan 2008

    Location: Wrexham, North Wales, UK

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    I'm AudioAl'sArbiterForPISHANTO.

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    Yup, and because you essentially had the basis of something good to work with, the finished product turned out really well

    Marco.
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    Paul Hynes MC head amp/SR5 PSU. Also modded Lentek head amp/Denon AU-310 SUT.

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  2. #172
    Join Date: Feb 2008

    Location: South Wales

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    I'm NotTakingLifeTooSeriouslyTheseDays.

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    Quote Originally Posted by Marco View Post
    Yup, and because you essentially had the basis of something good to work with, the finished product turned out really well

    Marco.

  3. #173
    Join Date: Apr 2015

    Location: Central Virginia

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    I'm Russell.

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    Here I am late to the party yet again!

    I want to drop back to the talk about Rise Time and Slew Rate. I didn’t read where anyone gave an accurate description of them. So here’s my two cents.

    Both of these measurements are not so much about the output stage, as how you feed the output stage. And why two amps, both claiming the same watts, and even having the same output transistor compliment, sound different. (I won’t comment on tubed gear, not my area)

    Rise Time is how long it takes to bring the output up to spec, so when a sudden transient happens, how quickly can it be ready for the next one.

    While Slew Rate measures the decay, how able is the amp to maintain a transient. A sharp pop of a snare drum, the amp delivers the specified power to the speaker, but it can’t keep it up forever, the voltage drops off over time. An amp that claims 25V/us, is a very good amp. Meaning, after the transient, the amp is unable to keep up, it loses 25 volts per microsecond. And another 25 volts every microsecond after that, until it runs out of power. Compared to an amp that claims 150V/us, this can make a very audible difference! The snare pop dives off much faster in the second amp, smearing the decay, then Rise Time brings the output back to full potential before the next one. A slow rise time can cause subsequent drum whacks to be Lower than the one before, if it isn’t rising fast enough to keep up. Both are more about the power supply, the capacitive storage for the output stage, and why two amps that both claim 100wpc can perform extremely different.

    If you want a good tube amp, buy it by the weight! The heaviest one has the biggest transformers. I’m not sure the exact correlation between amps and weight, but the amp I own now is the heaviest one I’ve ever owned, and the best sounding. Just lucky maybe?

    Russell

  4. #174
    Join Date: Apr 2015

    Location: Central Virginia

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    I'm Russell.

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    Quote Originally Posted by RothwellAudio View Post
    Sorry Russell, that's just wrong. Slew rate is the speed at which the output can move. However, you're right that it's measured in volts per microsecond, but the stuff like "...after the transient, the amp is unable to keep up, it loses 25 volts per microsecond. And another 25 volts every microsecond after that, until it runs out of power" is just wrong.
    Perhaps my wording is not great but the meaning is still true. With Slew Rate the lower the number the better, it is a measure of the rate of decay.

    Russell

  5. #175
    Join Date: Feb 2008

    Location: South Wales

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    I think on the whole, Russell gave quite a good insight into what is going on, although by his own admision, his wording may be a bit misleading to the tech savvy here,[ I am sure I, and others here have been guilty on that score at times too] Its a matter of getting the balance right when trying to get your point accross to those who may not be paticularly technicaly minded, but know what they hear, Sometimes people can get turned off a subject they may otherwise find interesting, if things get too technical.
    Quote Originally Posted by RothwellAudio View Post
    Sorry Russell, that's just wrong. Slew rate is the speed at which the output can move. However, you're right that it's measured in volts per microsecond, but the stuff like "...after the transient, the amp is unable to keep up, it loses 25 volts per microsecond. And another 25 volts every microsecond after that, until it runs out of power" is just wrong.
    "Today scientists have substituted mathematics for experiments, and they wander off through equation after equation, and eventually build a structure which has no relation to reality"
    Nikola Tesla



    Its now a conspiracy theory to believe that the Immune system is capable of doing the job it was designed to do.
    A fish is only as healthy as the water its swimming in ! [Dr Robert Young]


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  6. #176
    Join Date: Mar 2017

    Location: Seaford UK

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    I'm Dennis.

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    Both are defined mathematically.

    Andrew defines slew rate accurately, and rise time is defined as being the time taken for the response time to go from 10% to 90% of the total step change.

  7. #177
    Join Date: Feb 2008

    Location: South Wales

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    Quote Originally Posted by RothwellAudio View Post
    No, sorry Russell, that's not correct. Slew rate is a measure of rate of change - usually how fast the output can change voltage. 50V per microsecond is a higher slew rate than 25V per microsecond, and is better.
    https://en.wikipedia.org/wiki/Slew_rate
    "Today scientists have substituted mathematics for experiments, and they wander off through equation after equation, and eventually build a structure which has no relation to reality"
    Nikola Tesla



    Its now a conspiracy theory to believe that the Immune system is capable of doing the job it was designed to do.
    A fish is only as healthy as the water its swimming in ! [Dr Robert Young]


    www.tubedistinctions.co.uk

    Matthew 5:10

  8. #178
    Join Date: Feb 2008

    Location: South Wales

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    I dont think anyone was questioning Andrew's account Dennis.
    Quote Originally Posted by Pharos View Post
    Both are defined mathematically.

    Andrew defines slew rate accurately, and rise time is defined as being the time taken for the response time to go from 10% to 90% of the total step change.
    "Today scientists have substituted mathematics for experiments, and they wander off through equation after equation, and eventually build a structure which has no relation to reality"
    Nikola Tesla



    Its now a conspiracy theory to believe that the Immune system is capable of doing the job it was designed to do.
    A fish is only as healthy as the water its swimming in ! [Dr Robert Young]


    www.tubedistinctions.co.uk

    Matthew 5:10

  9. #179
    Join Date: Apr 2015

    Location: Central Virginia

    Posts: 1,736
    I'm Russell.

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    Quote Originally Posted by RothwellAudio View Post
    No, sorry Russell, that's not correct. Slew rate is a measure of rate of change - usually how fast the output can change voltage. 50V per microsecond is a higher slew rate than 25V per microsecond, and is better.
    https://en.wikipedia.org/wiki/Slew_rate
    What it says on that Wikipedia page, if you scroll down under the word Definition, (I tried to copy and paste but it wouldn’t act right) is exactly what I am trying to say, a measurement of change over time, and when that is referring to the output of an amp, the output does not resemble the input, just as the illustration of the square wave being skewed, this is all I am trying to get across, just as described on this Wikipedia page. The larger the number, the greater the deformation of the waveform, so bigger is not better, at least when talking about the output of an amp.

    Apparently it can mean many things when talking about the Slew between stages, or involving digital circuits, I am not referring to those situations.

    Russell

  10. #180
    Join Date: Apr 2009

    Location: Near Saffron Walden, Essex

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    I'm Dave.

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    Makes perfect sense.

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