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Old 31st October 2017, 10:05 PM   #51
MarcelvdG is offline MarcelvdG  Netherlands
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Now I'm confused; where does that 4.1 dB in post 45 come from?
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Old 1st November 2017, 09:28 AM   #52
Hans Polak is offline Hans Polak  Netherlands
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Quote:
Originally Posted by MarcelvdG View Post
Now I'm confused; where does that 4.1 dB in post 45 come from?
Posting 45 mentioned that going from 68 Ohm to 510 Ohm resulted in a SNR Loss of 4.1 dB.
In posting 50 the accompanying SNR figures were given, being resp. 64.9 and 60.8 dBA.

Hans
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Old 1st November 2017, 02:15 PM   #53
Hans Polak is offline Hans Polak  Netherlands
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In posting 50, SNR for a certain point with specified nV/rtHz and pA/rtHz is made the same for the MM and MC setting.
However dBA is just one cumulated figure of all A-Weighted noise and tells nothing about the nature of the noise.

That's why I have included the image below, to show the spectra of the noise for MM and MC, in both cases for 66dBA, ref 5mV and 0.5mV resp.
So the area under the curves is the same (the MC amplitude has been multiplied by a factor 10) but the curves are rather different.
Peak in frequency for MC lies at 2 KHz and for MM at 6.5 KHz.

The noise from an MM will therefore sound more like a hiss.
So far the differences in noise production between both.

Hans
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Old 2nd November 2017, 05:42 AM   #54
xx3stksm is offline xx3stksm  Japan
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Default the measured data

I measured real noise power of ADA4004. My post #42 used estimated data for RIAA compensation(0.57=5dB). My SIM was 7dB because of 2dB for A-filter and 5dB for RIAA. That was almost correct like fig.1. The true value is 6.4dB(76.8-70.4=6.4). The more precise input Referred Noise of ADA4004 is below.

3.6nV/sqrtHz with 510ohm(Rg) under 20kHz bandwidth
This may be from 3.2nV of Johnson and 1.6nV of ADA4004 because 3.6*3.6=3.2*3.2+1.6*1.6.

1.8nV/sqrtHz with 68ohm(Rg) under 20kHz bandwidth
This may be from 1.2nV of Johnson and 1.0nV of ADA4004 because 1.8*1.8=1.2*1.2+1.0*1.0.
The difference between 510ohm and 68ohm is 6.5dB like fig.2.

ADA4004 has 1.8nV(typical value) residual noise. It may be a little bit high performance to have 1.0nV with 68ohm. But I'm sure this is correct. Because this is calculated by three parameters, FS of the ADC, noise power and the gain of the amplifier. I measured them and calculated the value. If you can use the measured value of 0.5nV opamp with 68ohm, you can get 1.3nV residual noise(1.3*1.3=1.2*1.2+0.5*0.5). This can be probably available but over performance for vinyl recording, IMHO.
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Old 10th November 2017, 06:58 PM   #55
tiefbassuebertr is offline tiefbassuebertr  Germany
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Quote:
Originally Posted by xx3stksm View Post
I measured real noise power of ADA4004. My post #42 used estimated data for RIAA compensation(0.57=5dB). My SIM was 7dB because of 2dB for A-filter and 5dB for RIAA. That was almost correct like fig.1. The true value is 6.4dB(76.8-70.4=6.4). The more precise input Referred Noise of ADA4004 is below.

3.6nV/sqrtHz with 510ohm(Rg) under 20kHz bandwidth
This may be from 3.2nV of Johnson and 1.6nV of ADA4004 because 3.6*3.6=3.2*3.2+1.6*1.6.

1.8nV/sqrtHz with 68ohm(Rg) under 20kHz bandwidth
This may be from 1.2nV of Johnson and 1.0nV of ADA4004 because 1.8*1.8=1.2*1.2+1.0*1.0.
The difference between 510ohm and 68ohm is 6.5dB like fig.2.

ADA4004 has 1.8nV(typical value) residual noise. It may be a little bit high performance to have 1.0nV with 68ohm. But I'm sure this is correct. Because this is calculated by three parameters, FS of the ADC, noise power and the gain of the amplifier. I measured them and calculated the value. If you can use the measured value of 0.5nV opamp with 68ohm, you can get 1.3nV residual noise(1.3*1.3=1.2*1.2+0.5*0.5). This can be probably available but over performance for vinyl recording, IMHO.
Datasheet under
http://www.analog.com/media/en/techn...4-2_4004-4.pdf
don't show the internal schematic.
Where I can find it (at least a simplified version to understand the theory of operation) ?
concerning residual noise check post #7 under
Reducing Record Surface Noise - I want to know all Approaches

Last edited by tiefbassuebertr; 10th November 2017 at 07:04 PM.
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Old 10th November 2017, 07:04 PM   #56
Mark Johnson is offline Mark Johnson  United States
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an mm/mc phono stage
Call your Analog Devices sales rep and ask her/him.
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Old 10th November 2017, 09:01 PM   #57
MarcelvdG is offline MarcelvdG  Netherlands
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Quote:
Originally Posted by tiefbassuebertr View Post
concerning residual noise check post #7 under
Reducing Record Surface Noise - I want to know all Approaches
...which refers to a website of someone who basically re-invented the DNL system Philips used to build into cassette players: a low-pass filter that automatically reduces its cut-off frequency when the signal is weak.
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Old 11th November 2017, 06:26 AM   #58
xx3stksm is offline xx3stksm  Japan
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If you want an effective method to reduce the surface noise of vinyl, The best way, as far as I have experienced, is digital processing, for example, iZotope RX4 like attached. The first generation of noise reducing(de-noise) had not sufficient performance like the first generation of a CD player. Bad reputation still exists and is making digital processing phobia.
So is me before I know the second generation(de-construct).

De-noise is effective only in small amplitude while de-construct can process both large signal and a small one. It probably deconstructs the input into signal and noise. Then It reduces only noise spectrum before It reconstructs the original. That's why signal spectrum is almost same while noise spectrum is less than 6dB before processing.

Surface noise to human perception deeply depends on frequency. As far as I have experienced, from 1kHz to 8kHz is the most important. If you decrease this by 3dB, you can feel enough improvement. If you get a 6dB decrease, you can feel surface noise has almost gone. De-construct can decrease noise spectrum only without unexpected sonic side effect. I'm very satisfied with this. The disadvantage is cost. RX4 with de-construct is a little bit expensive.
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Old 22nd December 2017, 01:12 AM   #59
rjm is offline rjm  Japan
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an mm/mc phono stage
This thread got derailed.

Please go here to follow the phono stage project.
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