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Old 3rd January 2010, 05:41 PM   #691
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In most of my designs a have a linear input stage then the 75usec done passive or active and then a second stage doing the rest. That reduces the amount of trebe to the second stage. Compared to RIIA topologies like the often used active bass and then passive treble (so the other way around) the hiss and the sound of blemishes from the record seem to come only from the speakers and exist not so much in the 3 dimensional phantom image. The sound of the hiss is also less anoying and old worn records sound better. The second aproach i like is ony the low bass timeconstant active in the first stage then the midrange and treble boosted in the second stage. I have shown here several version of the inductive RIAA that does that. That also unburdens the second stage much because it presents the second stage with a constant velocity signal that has lower treble content then before that active first stage. Those inductive solutions sound different to my ear. More open and clear. The "supress anoying artifacts" action is there but less pronounced then in the "75usec first" solution. This is my subjective listening notes backed up by professionals and amateurs that visited me. For example Martina Schöner of Garrard liked the 75usec first solution a lot because she likes opera from the first halve of last century and thoose records are often worn. She was surprised about the amount of information previously hidden in noise.
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Old 3rd January 2010, 05:54 PM   #692
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Quote:
Originally Posted by Joachim Gerhard View Post
For example Martina Schöner of Garrard liked the 75usec first solution a lot because she likes opera from the first halve of last century and thoose records are often worn. She was surprised about the amount of information previously hidden in noise.
That's my current solution but I am very interested in at least exploring other approaches. My favorite LP's (where it really matters) are older in most cases. Another lover of Muck's Wagner?
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Old 3rd January 2010, 06:38 PM   #693
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Originally Posted by Allen Wright View Post
Albert Lukachek (owner/designer of Benz and a near neighbour of mine) scoffed at any possible damage to any MC from 50uV offset.
So except for the temp induced noise (cascode tube is not close to the SSM), everything else is based either on "sound" or "good enough".

Funny enough, I was not concerned about the cartridge integrity, but by the "sound" when the bias exceeds the signal amplitude.

Anyway, sorting SSMs @ 50uV offset must be quite expensive...
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Old 3rd January 2010, 06:42 PM   #694
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WAGNER, R.: Parsifal (Muck) (1913, 1927-1928) - 8.110049-50

is it this one ?
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Old 3rd January 2010, 07:10 PM   #695
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Yes, just interested in your friends opinion and in general the work of Furwangler.
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Old 3rd January 2010, 07:18 PM   #696
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Depends on the topology, no? I use a high gain flat stage at the input with a >100mV input overload across the audio bandwidth. There's an all-in-one-lump RC network following, then another flat gain stage. The overall overload is compromised at low frequencies, but who cares? The cartridge is a velocity device. At high frequencies, where the problems are (mistracking, tip resonance), the overload is some ridiculous number above the max cartridge nominal output (like 40dB at 1kHz, and of course another 30 dB out where the tip starts ringing).

Given an excellent input stage with high overload, the passive-RC-between-gain-stages results in exceptional overload margins where it counts. The noise penalty can be made to be negligible.
Yep, same here, the HPS 3.1 and 4.1 gain flat head amp allows 200mV input overload. But I use active RIAA networks all over. This configuration allows the head amp defining the headroom @20KHz. When normalizing to RIAA, the headroom is 32dB flat across the audio band.
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Old 3rd January 2010, 07:21 PM   #697
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I have some trouble too with total passive RIAA and opamps. Tubes and high voltage circuits do fine though.
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Old 3rd January 2010, 11:36 PM   #698
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I worked a bit today on the noise from the RIAA coils. First i build some toroids myself to try that technology. After 5 hours of hard work the result was not better then with the feritte coils. I terms of impedance curve they where worse and the noise had more high frequency content. Then i started to play with the groundwire and by magic when i connected the groundwire to the headamp and from there to only one of the coil cases the hum was gone. It is now totally inaudible at high voume at the listening seat. When i crank the system to a point where the speakers whould dye after 5 seconds the hiss from my current 0.5nVQHz headamp was louder then the hum. I think i got that problem because of my double, double mono PSU setup and by connecting just one case and referencing it to the headamp the problem was gone. I am quite happy ! Still some coils in MU metal are comming when i am back from Vegas. I will tell you how they work then.
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Old 10th January 2010, 07:45 AM   #699
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I have thought more how a low cost transimpedance Head Amp could look and came up with a parallel symmetric circuit that has lower 2nd harmonic (the major source of distortion in the ECHO), lower noise (3 dB less because of the parallel symmetric nature) and lower DC and protection on the cartridge. Set the potmeters for minimum DC offset at the cartridge and around 3mA through the 750 ohm resistors ( a compromise between voltage and current noise). Without emitter resistors you should select for Hfe and Ube.
In the next post i show a version with emitter resistors that is not so sensitive for transistor tolerances.
Attached Files
File Type: pdf ECHO PSL.TSC - TINA.pdf (55.0 KB, 105 views)
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Old 10th January 2010, 08:38 AM   #700
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This version is more tolerant to differences in the transistors due to current feedback.
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File Type: pdf ECHO PSLCF.TSC - TINA.pdf (57.0 KB, 106 views)
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