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Old 25th September 2012, 12:18 AM   #1181
gpapag is offline gpapag  Greece
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Quote:
Originally Posted by bear View Post
George,

Your diagram shows explicit filter elements or intrinsic resistances and inductances?
It showed intrinsic resistances and inductances.

Quote:
Originally Posted by bear View Post
A bit of this depends on exactly which, since serial filtering *might* yield vanishingly low noise and hum at the end of the chain.
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This is correct bear. It comprises a cascaded RC or LC low pass filter.
In terms of noise and hum reduction is very good and is an economic solution. In theory and more so in practice though has one drawback: Each succeeding stage's DC, rides on the modulations of the previous. If you probe there with an oscilloscope, you will see low frequency modulation. This, together with the voltage drops at the common return line which are different at each stage, cause the signal input from stage to stage to low frequency wander up and down. Visualize a coupling capacitor, the two ends of which are on different, -unequally moving- DC potentials. This, in severe cases may give rise to low freq. oscillation (motorboating).
All these do not occur with parallel connecting the amplifying stages to the PSU

For clarity, I have attached a new sketch, this time with explicit filter elements.
Circuit B is no good at all. It is not a parallel connection (common return) and it lacks the cascaded low pass filtering of the serial circuit.

Quote:
Originally Posted by janneman View Post
a good way is to determine the stage with lowest PSRR and put the psu closest to that.
jan
With series connection, the circuit closest to the PSU has to be the one with the higher current demands. The furthest away has to be the least hungry for current.
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And, if you're serious, use remote sensing for the regulator at that stage.
jan
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Originally Posted by Joachim Gerhard View Post
I know that phono cartridges with -20dB crosstalk can just sound fine. Some bleeding in the other channel may even enhance the perception of spaciousness…I rather prefer that not be a characteristic of the electronics.
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Originally Posted by john curl View Post
Good stereo separation in the electronics is VERY IMPORTANT. Don't be fooled by phono cartridges Joachim.
Joachim
This time Mr. Curl is correct
The crosstalk within the cartridge is relative “clean”.
The crosstalk between L/R channels in electronic circuits happens mostly through the common PSU lines and less so through spacial multiple capacitive/inductive couplings. All these produce “dirty” crosstalk signals (undefined amplitude phase/delay relationship).

George
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File Type: jpg PSU 2.jpg (57.1 KB, 276 views)
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Old 25th September 2012, 01:25 AM   #1182
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It's about time that I was 'correct'. '-)
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Old 25th September 2012, 01:30 AM   #1183
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George,

There is a 4th possibility. That would be the first example, but with the grounds of the third.

Also, if the L used is sufficiently high, and the L/C combination "tuned/scaled" well it seems unlikely that there would be much VLF passing. I suppose that if a prior stage was a big current hog that had wild current draw swings, perhaps. But this is not likely for class A stages certainly, class AB stages that are output stages might be another story. There, if we're talking a situation like this thread's design goals, I'd guess that the way to handle it would be along the lines of what Jan suggested, separate regulator/psu.

Where the "ground" is physically/electrically is another issue. Jneutron might be the one to have something on that.

Hey, kids! Get your all NEW and IMPROVED do-it-yourself Op-Amp design kit today! It's easy, It's fun, It's ON SALE NOW!!


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Last edited by bear; 25th September 2012 at 01:32 AM.
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Old 25th September 2012, 03:18 AM   #1184
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Didn't quite catch that last bit, bear, ya gotta learn to speak up clearly, you hear ...?

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Old 25th September 2012, 03:24 AM   #1185
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Old 25th September 2012, 05:01 AM   #1186
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by john curl View Post
Blend, is flat over frequency, Xtalk is NOT!
Does it matter? As any frequencies tend towards mono the effect at those freqs is to cancel and loose information. That it may happen more at certain freqs (highs usually) isnt the point.

If you want to focus on phono cartridges for a source.... they tend towards mono at the high freqs. But the same thing happens due to crosstalk for a number of reasons and mechanisms. Thx - -RNM

Last edited by RNMarsh; 25th September 2012 at 05:04 AM.
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Old 25th September 2012, 07:41 AM   #1187
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In addition to a losing details, when the channel seperation become less, the imaging shifts towards the middle/center.

So to have max accuracy in detail info reproduction and to keep accurate imaging, you need to have much better isolation between channels than was recorded.
-RNM

Last edited by RNMarsh; 25th September 2012 at 07:44 AM.
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Old 25th September 2012, 09:23 AM   #1188
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http://www.ibink.com/tnufire/docs/XTalkCancelation.pdf (misspelling in link is not mine)

Also, more recent work that received a lot of publicity: http://www.princeton.edu/3D3A/Public...CHPaperV4d.pdf

Last edited by bcarso; 25th September 2012 at 09:26 AM. Reason: additional ref
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Old 25th September 2012, 09:37 AM   #1189
bcarso is offline bcarso  United States
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Another item of interest: based on level differences only, apparently the threshold for perceiving "all" of the signal coming from one loudspeaker of a conventional stereo pair, in the absence of time delay differences: 13dB, in the most sensitive spectral region (!). The notion that crosstalk reduction into the highest quoted extremes (like the dual mono pursuit) is audible is not supported by data.

However, if the "crosstalk" is really some bleedthrough of severe distortion associated but not identical to signals on the other channel, which can be observed in poorly designed amplifiers, especially low-cost chip amps, this can be quite audible at lower levels. Whether it's appropriate to call it crosstalk or not is another issue.

Also, it's often stated that standard same-signal crosstalk that gets worse (i.e. larger) at higher frequencies is due to capacitative coupling. Although this can be a mechanism, it doesn't have to be the only one.
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Old 25th September 2012, 10:20 AM   #1190
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I hope I´m not too late to ask a question regarding the schematic
John showed in post #971:

http://www.diyaudio.com/forums/attac...scott-type.jpg

What would the approx. open loop gain be ? Would it be usable as a phono preamp
(withsome sort of buffer added to drive the RIAA network) ?
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