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Old 27th December 2009, 12:12 AM   #521
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I have the solution ! I was thinking wrong. The iductor makes the response falling AD INFINITUM until it flattens out to 1x at ultrasonic frequencies. So the cap in the MPP let the resonse fall even more instead of providing the 318usec and 75usec shelve. I can only explain that by too much Bodeaux Superieur this time. I thought i am imune to it.
So here comes a circuit that works. See the simulation. Quite interesting phase response.
I do the 318usec - 75 usec shelve passive now between the Opamps. The advantages are:
Constant feedback in the output amp, no capacitor in the feedback, smaler value of the EQ cap (10nF instead of 0.1uF) so it could be of better quality.
The only thing i loose is the scratch filter action of the 2.2usec amp and i can not fake the Neumann constant any more. I do not have all the parts to build it but i will buy some next week. i am looking forward to how it will sound.
Anyway it was not a totall loss of time. I found i could reduce the DC offset even more by wrapping the Servo around both Opams and the dark sound was quite fasinating but i could not stand it longer then one minute.
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Old 27th December 2009, 12:17 AM   #522
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a resistor in series with the 10nF cap can provide the Neumann curve if desired
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Old 27th December 2009, 12:53 AM   #523
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Default Neumann Pole

If you whant to ad the Neumann pole according to Allen Wright. no problem !
Add a 68 Ohm resistor in series with the 10nF cap. I have slightly other ideas and i am working on my own solution. In the meantime you can read this:Stereophile: Cut and Thrust: RIAA LP Equalization
Holger, itīs for you. My xmass present.
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Old 27th December 2009, 02:10 AM   #524
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And now DRUMROLL come my atempt for compensatimg the Neumann cutter.
For you speedfreaks this and the High Z MPP will be my Masterpiece.
I am working on 2 versions. One is a cascade of 2 treble boosters and the other is a one stage inductive Q Booster. I will publish the design of the treble booster but will keep the circuit of the Q booster for myself now. Sorry, but it is too importand for me. I am planning to sell stuffed boards, so you can try it but it will cost a little.
First i will show the response of the Neumann head as far as i know it. You have to multiply all frequency grafs by 10.
Attached Files
File Type: pdf Neumann Lathe.pdf (38.8 KB, 110 views)
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Old 27th December 2009, 02:15 AM   #525
Salas is offline Salas  Greece
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Many employ that pole. Never worked better for me. Neither in JFET nor in Valve. Got a bit bright. So I took it out. There was some Tag McLaren phono that had an in/out button for it, had it around once, easy A/B, same effect to my ears. I think that JC said something about it too? Anyway, maybe its my speakers. Works better 4U Joachim?
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Old 27th December 2009, 02:19 AM   #526
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Now comes the treble booster then the Q booster and then the step response of the Q booster including the response of the cutter head.
The treble booster raises the -3dB point from 50kHz to 61kHz and the Q booster has the -3dB point at 65kHz. But look at 200kHz ! the response is down only -9dB and the step response is ideal. This give even SACD a break in the case of an ideal cartridge that of cause does not exist but i see no fundamental problem to compensate the cartridge too !
Attached Files
File Type: pdf Neumann Lathe + 2nd order treble boost.pdf (38.7 KB, 76 views)
File Type: pdf Lathe + Q Booster FRD.pdf (38.5 KB, 61 views)
File Type: pdf Lathe + Q Booster Step.pdf (25.8 KB, 51 views)
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Old 27th December 2009, 02:23 AM   #527
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Salas, the 3.2usec Neumann pole is ********. It just is not right. It always sounded bright to me too but what i make here has a passband ripple of under 0.1dB so should not do harm provided your system can take a lot of ultrasonic energy. SACD promissses that, so in a sytem where unfiltered SACD works it should give no problem.
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Old 27th December 2009, 02:30 AM   #528
Salas is offline Salas  Greece
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So you decided to take it a step further, also emphasizing caution to ringing. Interesting.
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Old 27th December 2009, 02:35 AM   #529
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20 years ago i worked a lot with Mr.Manger the inventor of the bending wave driver and i still have a friendship with his doughter Daniala. He really alerted me to time domain behaviour and itīs importance for 3 dimensional imaging. Itīs a long story. I think Mr. Manger had at one time also contact to John Curl. Mr. Manger is in retirement now but he is still workig on a microphone and a book about nature.
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Old 27th December 2009, 02:39 AM   #530
Salas is offline Salas  Greece
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Is the world small, or its you just knowing everybody? Seriously.
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