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Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

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Old 26th September 2012, 04:02 PM   #1281
bcarso is offline bcarso  United States
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Originally Posted by Wavebourn View Post
I found one more interesting discrete opamp. Looks like an instrumental amp loaded on output transformer. V/I converters drive controlled by current common cathode stages with deep feedback by voltage. However it is power amp, but can be used as line level output stage with smaller tubes. Thanks to transformer output can be balanced, for professional studio usage.
Actually getting back to the thread topic! Give that man a coupon.
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Old 26th September 2012, 04:02 PM   #1282
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The multitone tests most closely simulates a music signal source and produces both Im and harmonics. In checking the available published test data when using such, the 'noise' or grass between the tones grows by 20db when 15 tones are used. Rises another 20db when 30 tones are used (40db rise). I assume this increase in noise/unwanted freqs continues with ever more applied tones. So, we can assume that the level will contribute to the coloration of sound heard if the amplifier (opamp) does not have an extreamly low distortion to begin with. Thx - RNm
Reference? On the surface these numbers don't make physical sense. 2X the tones at the same total energy yields 10X the "noise" power. There are a lot of details missing here, crest factors, levels, 15 tones is 20db over what?
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Old 26th September 2012, 04:03 PM   #1283
RNMarsh is offline RNMarsh  United States
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Originally Posted by bcarso View Post
Yes. And iirc you can drive a ribbon microphone to low but audible levels, though you wouldn't want to. Reminds me of the time I drove a tuning fork crystal a little too hard and heard it break.

Speaking of bad news for cartridges, one could put d.c. current through one you weren't too fond of and listen to the changes to the frequency response.
Or put the same make and model cartridge in the feedback loop.
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Old 26th September 2012, 04:27 PM   #1284
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Originally Posted by Joachim Gerhard View Post
Scott, i have not found the patent yet but here it is mentioned at least.Phono Pre-Amplifier P-75 mkII
Its difficult to get a copy as it was filed in australia, patent AU1986058306, anyway it has expired many years ago.
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Old 26th September 2012, 04:28 PM   #1285
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Originally Posted by RNMarsh View Post
Tie R3, R4 together and change to cascoded jFEts? Change pentodes to low power triodes = line stage.
If you tie r3 and r4 together you damage it's functionality. But you can replace pentodes by MOSFEs and BJTs by JFETs, right.
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Old 26th September 2012, 04:34 PM   #1286
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Or put the same make and model cartridge in the feedback loop.
...on the same disk, in the same point.


You can't compensate resonances by filters. The only way to minimize resonances is to suck an energy from them. For example, loading the cartridge on zero dynamic resistance (or on negative one) is the best that you can do, but such a way you can damp only resonances that are immediately and linearly translated into electrical output.
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Old 26th September 2012, 04:56 PM   #1287
RNMarsh is offline RNMarsh  United States
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Originally Posted by Wavebourn View Post
...on the same disk, in the same point.


You can't compensate resonances by filters. The only way to minimize resonances is to suck an energy from them. For example, loading the cartridge on zero dynamic resistance (or on negative one) is the best that you can do, but such a way you can damp only resonances that are immediately and linearly translated into electrical output.
You might also take out nonlinearitties caused by the cart (magnetics). That is what I was thinking. I agree re. resonances. I published a circuit that had very low Zin specifically for MC cart (TAA 1/82). Been there, done that. :-)

Last edited by RNMarsh; 26th September 2012 at 05:01 PM.
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Old 26th September 2012, 06:18 PM   #1288
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Its difficult to get a copy as it was filed in australia, patent AU1986058306, anyway it has expired many years ago.
It looks like US4644517 is it and it has nothing to do with mechanical damping or resonances. He proposes a transformer coupled virtual ground load to extend low frequency distortion of the magnetics to a lower frequency. Is this a problem in reality?

John would appriciate that he has far more patents on advanced fuel injection for cars.
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Last edited by scott wurcer; 26th September 2012 at 06:24 PM.
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Old 26th September 2012, 06:46 PM   #1289
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Originally Posted by SY View Post
No, that's not minimum phase and it's also not single-valued.

We are making progress.
The two necessary conditions for a mechanical or acoustical resonance to be electrically equalizable is that the physical system that resonates should be minimum phase and expressed mathematically by a single-valued function . Is this correct?

For minimum phase, you will ask for linearity and time invariance. Say you have it.
Then causality. You have it too.
Next comes stability. Thank you, thatís a valuable input. But oops! Problem. Is there a maximum Q allowed?

Single-valued function.
My understanding is that a function is a single-valued one when and only when itís graph contains no closed loops. Please correct me if I am wrong.


George
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Old 26th September 2012, 06:59 PM   #1290
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It seems we have gone way off topic here but let me throw it off a little bit more here. When speaking of a loudspeaker and resonance what do you do about sympathetic resonances that are not caused by any electrical impulse stimulation? Harmonic stimulation's caused by acoustical excitations? How so do you counteract that, and wouldn't this same phenomena happen with the cantilever, headshell, tonearm and gymbal mechanism?
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