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Old 25th January 2013, 01:48 PM   #8261
a.wayne is offline a.wayne  United States
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Well i guess we have to get ole D into music first , then we can discuss sound..

@Gootee ,

Tom whats this mystery amp putting out 1k into 1ohm ...?
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Old 25th January 2013, 03:39 PM   #8262
dvv is offline dvv  Serbia
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Wayne baby, ol' D. was in it over his ears as early as 1965, as an 11 year old, when Radio Luxembourg started broadcasting

So you young Turks have little to say on the subject that I ain't heard already.
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Old 25th January 2013, 10:14 PM   #8263
fas42 is offline fas42  Australia
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The problem I experienced with electronic tone control ICs was enough to convince me to forget them and leave them for TV and such like, where sound quality is not really very important.

True, that was over 20 years ago, it stands to reason they have been improved much over that time, so I'll have another look.
Put it this way: in recent years every time I experienced "good" sound that sustained its quality and I was in the position to, or was interested enough at the time to investigate further, I've found that the volume control didn't use mechanical wiper mechanisms ...

Like all parts, there's good and bad, AND there's a hell of a lot in getting the implementation right. If you use an electronic control and then add a micro processor to do the twiddling, then you're potentially opening up another can of worms - audio ain't easy! ...

Frank

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Old 26th January 2013, 12:52 AM   #8264
benb is offline benb  United States
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Put it this way: in recent years every time I experienced "good" sound that sustained its quality and I was in the position to, or was interested enough at the time to investigate further, I've found that the volume control didn't use mechanical wiper mechanisms ...
In the spirit of the "measurement" part of this thread, can you offer anything technically, even a hypothesis, why this might be so?

I can imagine the mechanical connection acting something like a diode, and/or I've read such a claim. I met a guy 20 years ago, back when Audio Amateur had the "POOGE" articles, who bypassed his receivers' A-B speaker switch and soldered his speaker cables directly to the amplifier's outputs.
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Like all parts, there's good and bad, AND there's a hell of a lot in getting the implementation right. If you use an electronic control and then add a micro processor to do the twiddling, then you're potentially opening up another can of worms - audio ain't easy! ...

Frank
There's nothing wrong with micrprocessors that can't be "fixed" with proper coding. The processor should normally be in sleep mode, without its clock or anything else running. Turning a front-panel quadrature switch should generate an interrupt that wakes it up to normal running state, changes the volume appropriately, waits a half second or so, writes the current setting to eeprom, then goes back to sleep. This way there's nothing "running" that could make a signal to be picked up by the audio circuitry.
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Old 26th January 2013, 01:05 AM   #8265
bcarso is offline bcarso  United States
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There's nothing wrong with micrprocessors that can't be "fixed" with proper coding. The processor should normally be in sleep mode, without its clock or anything else running. Turning a front-panel quadrature switch should generate an interrupt that wakes it up to normal running state, changes the volume appropriately, waits a half second or so, writes the current setting to eeprom, then goes back to sleep. This way there's nothing "running" that could make a signal to be picked up by the audio circuitry.
Always a good idea.

I once was part of a geographically-distributed design team, with the firmware people lacking a command of English (and forget about my Mandarin). I got a prototype in which they had defeated a bipolar supply for the integrated level control IC, and wondered why.

It turned out that they were continuously refreshing the IC from the uC and apparently using its readback capability to figure out what the level setting was. So they stripped away 6dB of range to be able to use the bus bidirectionally. Now of course there was more than ample memory elsewhere to keep track.

I was of course blamed for not knowing how the part worked.

You can't schedule stupidity, as Dilbert says.
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Old 26th January 2013, 07:18 AM   #8266
dvv is offline dvv  Serbia
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Originally Posted by fas42 View Post
Put it this way: in recent years every time I experienced "good" sound that sustained its quality and I was in the position to, or was interested enough at the time to investigate further, I've found that the volume control didn't use mechanical wiper mechanisms ...

Like all parts, there's good and bad, AND there's a hell of a lot in getting the implementation right. If you use an electronic control and then add a micro processor to do the twiddling, then you're potentially opening up another can of worms - audio ain't easy! ...

Frank
Frank, what you are saying makes sense to me, but is unfortunately totally beyond my real world capabilities. Remember, electronics are not my trade, it's a hobby, and the only part of electronics I can safely say I know well is the eeny weeny itsy bitsy part regarding my filters.

Digitally, I'm a complete dumbell.

If, for example, I needed a digitally controlle input switching system, I'd have to ask somebody to do it for me. The best I can do is use a mechanical switch to turn relays on and off.

My first redeeming value is that I do not try to pretend to know what I don't know well or at all. And I am reminded of what I don't know well enough each and every day, whenever I run into a problem.

My second and last redeeming value is that I am not afraid to ask those who know more than I. The only intellgence of mine involved in that process is that I have met and cultivated a lot of different people, in different fields, so it's rare that I have to search long and wide for an answer.

I have a degree in economics, majoring in foreign trade and keeping track of the systems theory for my own pleasure of knowing. Since the systems theory is in fact social sciences' version of electronics, with many common points, this was helpful to me in my hobby.

As you can see, your suggestions are all well and fine, but way beyond me. And I intensly dislike dabbling in something I am unclear about, I have a need to really know what I am doing. I try to keep my ego in check, so, for eample, when I set about building my own tailor made car from the ground up, it was natural for me to assemble a team of friends, each of which excelled in one field or another. As a result, that car works way better than its factory counterparts and has never once broken down. And when it eventually does, it's likely to be classic wear and tear rather than a malfunction.

However, if you should get down to it, and if you're willing to share, I am certainly willing to give it a go.
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Old 26th January 2013, 09:45 AM   #8267
fas42 is offline fas42  Australia
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Quote:
Originally Posted by benb View Post
In the spirit of the "measurement" part of this thread, can you offer anything technically, even a hypothesis, why this might be so?

I can imagine the mechanical connection acting something like a diode, and/or I've read such a claim. I met a guy 20 years ago, back when Audio Amateur had the "POOGE" articles, who bypassed his receivers' A-B speaker switch and soldered his speaker cables directly to the amplifier's outputs.
Your thoughts mirror my own; I know micro-diodes and such are considered bad form by many in these parts, but everything over the years has sent a clear message to me that subtle levels of non-linearity in areas such as non-"perfect" metal to metal and similar contact are enough to introduce audible distortion, very conceivably by low-level rectification. I have not the access to equipment that can measure such behaviour, but I do know that every time I effectively bypass simple mechanical connections I improve the sound.

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There's nothing wrong with micrprocessors that can't be "fixed" with proper coding. The processor should normally be in sleep mode, without its clock or anything else running. Turning a front-panel quadrature switch should generate an interrupt that wakes it up to normal running state, changes the volume appropriately, waits a half second or so, writes the current setting to eeprom, then goes back to sleep. This way there's nothing "running" that could make a signal to be picked up by the audio circuitry.
Agreed, this is all solvable. I did it using completely discrete logic, as an exercise, and was happy with the results.

Frank
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Old 26th January 2013, 10:18 AM   #8268
fas42 is offline fas42  Australia
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Remember, electronics are not my trade, it's a hobby, and the only part of electronics I can safely say I know well is the eeny weeny itsy bitsy part regarding my filters.
Me too. Computing was my real game, and where I got a buzz from being highly analytical. Cooked my brain doing this, I'm afraid, so I have to do things these days in a very measured, and non-stressful way ...

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If, for example, I needed a digitally controlle input switching system, I'd have to ask somebody to do it for me. The best I can do is use a mechanical switch to turn relays on and off.
I find it hard to believe that someone hasn't posted a DIY version of such. The way I've done things is very much in the prototype mode, never as a finished, polished unit; my interest is in understanding what the factors are that influence sound quality, and these days how "low class" you can go in the kit and still deliver impressive sound.

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My first redeeming value is that I do not try to pretend to know what I don't know well or at all. And I am reminded of what I don't know well enough each and every day, whenever I run into a problem.

My second and last redeeming value is that I am not afraid to ask those who know more than I. The only intellgence of mine involved in that process is that I have met and cultivated a lot of different people, in different fields, so it's rare that I have to search long and wide for an answer.
What I find intriguing is that the "big" answers aren't known by anyone, it seems. And what I mean by that is that if you hand any individual a selection of nominally well behaved gear that they will achieve satisfying sound from it, there's no magic lookup cheat sheet that guarantees success every time.

The best that I've achieved is an understanding that exceptional performance is possible, if persistence is applied. And that excellence is achievable at relatively low cost, if one is prepared to do things "one's own way".

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I try to keep my ego in check, so, for eample, when I set about building my own tailor made car from the ground up, it was natural for me to assemble a team of friends, each of which excelled in one field or another. As a result, that car works way better than its factory counterparts and has never once broken down. And when it eventually does, it's likely to be classic wear and tear rather than a malfunction.
I'm impressed!! Sounds just like how I'd do my own audio, if I had the means ...

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However, if you should get down to it, and if you're willing to share, I am certainly willing to give it a go.
Happy to give it a go - but fair warning, I run out of energy easily, a result of over-stressing the grey matter ...

Cheers,
Frank
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Old 26th January 2013, 11:00 AM   #8269
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Carbon, cermet and conductive plastic pots all measure very low harmonic distortion on the bench. They may well have low frequency distortion problems due to high temperature coefficients, but swamped by LF speaker distortion.

Far more likely they have problems with (sound) vibration affecting contact pressure and modulating the wiper position. The contact is not a point, so various parts of the contact zone must be at different tap positions.
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Old 26th January 2013, 01:09 PM   #8270
dvv is offline dvv  Serbia
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...

Happy to give it a go - but fair warning, I run out of energy easily, a result of over-stressing the grey matter ...

Cheers,
Frank
Since you have no obligations, you can't really fail, Frank. You can get there or not, in which case I'll just go on using what I already have.

Obviously, I'd prefer you to get there eventually.

If you'd like a few shots of what I did with the car, just drop me a line at dvv@beograd.com .
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