John Curl's Blowtorch preamplifier part II - Page 3716 - diyAudio
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Old 24th March 2013, 07:46 PM   #37151
PMA is offline PMA  Europe
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I would have another question. Any electronic circuit adds something and changes the sound in its own way. Why not to replace Blowtorch with high quality stepped attenuator and resistor network? Stepped attenuator of 10k input impedance would have output impedance of 2.5k and less, when driven from low impedance signal source. This is not much more than Blowtorch's 1k output impedance and for practical listening volume setting like -20dB and less the output impedance of the 10k stepped attenuator would be lower than that of Blowtorch. So why not to avoid the electronic circuit that undoubtedly changes the sound in its own way (probably pleasant way?) to get something more neutral. Simpler is better, right?
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Old 24th March 2013, 08:14 PM   #37152
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Most test systems I know of have the DUT in a pretty static state when measuring. Even FFT won't easiily show a 1/2 second time constant on a resistor temp change.

Maybe we just need a test that shows what happens on longer time scales. Human hearing takes a finite time to process the stimulus. Is there any research on human response times to level changes etc?
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Old 24th March 2013, 08:59 PM   #37153
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Swept THD/IM ought to, no? Same with swept power/voltage vs. frequency.
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Old 24th March 2013, 09:35 PM   #37154
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I am more and more convinced that perfect signal transmission is the last thing audiophiles are seeking for.
Instead of that, loss of details is preferred. This loss of details is achieved by:
- higher background noise (tubes, vinyl records, tape hiss)
- non-linear distortion that rises noise floor for complex signals

Though higher background noise, and thus less real resolution, is generally preferred by audiophiles (tubes, groove noise, tape hiss), non-linear distortion must be thoroughly controlled to stay at pleasing side.
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Old 24th March 2013, 09:41 PM   #37155
gerhard is offline gerhard  Germany
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Quote:
Originally Posted by john curl View Post
Demian, let's get Scott to tell us what IC's from ADI are specifically made for audio reproduction. '-)
You say that as if audio reproduction wasn't in the easiest 5% of jobs in electronics.

Gerhard
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Old 24th March 2013, 10:11 PM   #37156
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I am more and more convinced that perfect signal transmission is the last thing audiophiles are seeking for.
Instead of that, loss of details is preferred.
It let more space for imagination :-)
I agree with your analysis.
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Old 24th March 2013, 10:16 PM   #37157
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Quote:
Originally Posted by PMA View Post
Any electronic circuit adds something and changes the sound in its own way.
Why should it? That's called distortion, and these days it's "ridiculously easy" to have circuits that by normal standards, at least at the design stage, have inaudible distortion.

So where's that "change in sound" coming from ...?

Frank
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Old 24th March 2013, 10:25 PM   #37158
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So where's that "change in sound" coming from ...?
Depends on the high end designer and the particular "sound" they're trying to get; each has their own set of tricks to turn a box of gain into an effects box. It's trivially easy to make a clean amp- it takes some skill and imagination to make an effects box that hits the designer's target.

Mid-grade equipment is generally reliably transparent (assuming ears-only, of course), as is some high end gear when the designer truly does want a simple box of gain. IME, John's designs don't have an audible signature, for example.
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Old 24th March 2013, 10:29 PM   #37159
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Quote:
Originally Posted by PMA View Post
Why not to replace Blowtorch with high quality stepped attenuator and resistor network?
This is an interesting question because it raises an issue for me about blowtorch o/p impedance.

I have found that amps very often sound better when driven by a low impedance.

I wonder how blowtorch manages to sound so good in systems with such high o/p impedance.

Is there something I'm missing here ?

mike
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Old 24th March 2013, 10:42 PM   #37160
fas42 is offline fas42  Australia
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Mid-grade equipment is generally reliably transparent (assuming ears-only, of course), as is some high end gear when the designer truly does want a simple box of gain.
Okay, string a set of 10 of such devices in series, with suitable, "transparent", attenuation separating them as necessary. Would it still be "reliably transparent"? If not, why not, and would it be straightforward to pick up this reason by measurement?

Frank
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