Flat Phono Preamp Based on John's P10 and 2SK389

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mediatechnology
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Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by mediatechnology » Sun Aug 30, 2015 4:46 pm

I think the biggest overall improvement comes from true, fully-balanced shielded twisted pair wiring and an instrumentation amp input.
You gave us the balanced instrumentation input in '82.
Logitek took it away for awhile.

Though there is a significant benefit to having a balanced input with RCA coaxial connections the improvement using shielded twisted pair is significant.
I've never heard a phono input with that low of a hum.
Almost none.
It's so low that the second sound card in the PC was ground looping enough to degrade the monitoring of the preamp's hum.
The small buried in the noise floor hum I do hear seems to be induced into the cart body.

The one thing I am disappointed with is the "sound" of the FFT-based DSP RIAA.
I need to tweak the curve.
It seems to have a +/-20dB asymptote on both ends due to a Cool Edit setting.
I need to check the various points on the curve to an actual RIAA because I think the table values are wrong.
They don't look quite right visually and the LF/HF balance is off.

The P10 analog RIAA just sounds better.
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JR.
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Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by JR. » Sun Aug 30, 2015 5:22 pm

Somewhere in my files I have the old school RIAA data tables... They literally published a table of amplitude vs. spot frequencies.

Not sure I understand "FFT based DSP RIAA". Is this using FFT to measure the response of an RIAA network?

JR
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ricardo
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Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by ricardo » Sun Aug 30, 2015 6:43 pm

mediatechnology wrote:
but in reality the edge rates from cutting lathes and vinyl are just not very fast...
True.
Clicks do.
Though I really wouldn't have thought it the ultrasonic harmonics created by mechanical distortion (mistracking) may not have high edge rates but they sure create a lot of ultrasonic energy.
I'm certain the analogue de-clickers used ultrasonic detection of clicks.

Certainly the Garrard (?) unit I had did this. It might still be in my sister's shed at the other end of the continent.
______________________
The one thing I am disappointed with is the "sound" of the FFT-based DSP RIAA.
An FFT filter is a FIR and is truly EVIL for LF stuff like RIAA. The Cool Edit one is also Linear Phase so even more EVIL :o

The finite length of FIRs (including all the FFT based ones) make them almost useless at LF

You are better off using the Parametrics in most DAWs. These will be Bi-quad based and hopefully Minimum Phase (Phase as God intended). ;)

I pontificate on this in http://www.aes.org/e-lib/browse.cfm?elib=14786

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mediatechnology
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Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by mediatechnology » Sun Aug 30, 2015 6:58 pm

I think part of my problem is that the filter definition is for 44.1 and the file I noticed the errors on is 96 kHz.

I'll have to download your e-paper.
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Plandemic Series: "Pland3mic - Indoctornation" https://proaudiodesignforum.com/content ... nation.mp4
Plandemic Series: "Plandemic - Doctors In Black" https://proaudiodesignforum.com/content/Plandemic.mp4

CDC: "For 6% of the deaths, COVID-19 was the only cause mentioned. For deaths with conditions or causes in addition to COVID-19, on average, there were 2.6 additional conditions or causes per death." https://www.cdc.gov/nchs/nvss/vsrr/covi ... /index.htm

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mediatechnology
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Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by mediatechnology » Sun Aug 30, 2015 8:24 pm

ricardo -

You got a DiamondCut 8 or Audacity plug-in recommendation for RIAA?

EDIT : Interesting paper at TDL-Tech: www.tdl-tech.com/arscj.pdf
Looks like DC8 is recognized as having a fairly accurate RIAA phase response...
https://ka-electronics.com

Plandemic Series: "Pland3mic - Indoctornation" https://proaudiodesignforum.com/content ... nation.mp4
Plandemic Series: "Plandemic - Doctors In Black" https://proaudiodesignforum.com/content/Plandemic.mp4

CDC: "For 6% of the deaths, COVID-19 was the only cause mentioned. For deaths with conditions or causes in addition to COVID-19, on average, there were 2.6 additional conditions or causes per death." https://www.cdc.gov/nchs/nvss/vsrr/covi ... /index.htm

ricardo
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Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by ricardo » Sun Aug 30, 2015 9:29 pm

mediatechnology wrote:rYou got a DiamondCut 8 or Audacity plug-in recommendation for RIAA?
I'm afraid not. Gotta remember I'm a REAL beach bum.
EDIT : Interesting paper at TDL-Tech: http://www.tdl-tech.com/arscj.pdf
Looks like DC8 is recognized as having a fairly accurate RIAA phase response...
I'm not sure these guys understand DSP 101.

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mediatechnology
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Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by mediatechnology » Mon Aug 31, 2015 6:03 am

I'm not sure these guys understand DSP 101.
TDL or Diamond Cut?
https://ka-electronics.com

Plandemic Series: "Pland3mic - Indoctornation" https://proaudiodesignforum.com/content ... nation.mp4
Plandemic Series: "Plandemic - Doctors In Black" https://proaudiodesignforum.com/content/Plandemic.mp4

CDC: "For 6% of the deaths, COVID-19 was the only cause mentioned. For deaths with conditions or causes in addition to COVID-19, on average, there were 2.6 additional conditions or causes per death." https://www.cdc.gov/nchs/nvss/vsrr/covi ... /index.htm

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JR.
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Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by JR. » Mon Aug 31, 2015 8:56 am

It seems you use the inverse RIAA network to test phase and amplitude accuracy of the DSP playback transfer function.

JR
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Gold
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Re: Flat Balanced Input/Balanced Output Moving Magnet Phono

Post by Gold » Mon Aug 31, 2015 2:22 pm

mediatechnology wrote:This is the latest schematic of the Flat Balanced Input/Balanced Output Moving Magnet Phono Preamp.
I know there is a trasnsformerless MC preamp in the works. I think I would like to try my Denon 103 with a step up transformer into the MM preamp. I believe you said somewhere that this was a valid approach.

It would be helpful to me and possibly others if we go over how to calculate the proper resistive cartridge load into this balanced arrangement. The Denon 103 says it wants to see a load impedance 100Ω. The source impedance is 40Ω. The Lundahl transformer is wired 1:16. I have another set wired 1:32 if that works better.

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JR.
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Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by JR. » Mon Aug 31, 2015 3:51 pm

a 1:16 voltage transform is a 1:256 impedance transform. So to look like 100 ohms at the primary would require 25.6k at secondary termination. (or 56k in parallel with 47k)

a 1:32 voltage ratio is 1024x impedance so 102k ohm secondary termination.

You can probably change existing MM 47k termination to 100k.

JR
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