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Old 30th June 2011, 02:34 PM   #2311
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Quote:
Originally Posted by Joachim Gerhard View Post
Weird and wonderful world.
If one is weird, the wonderfull comes free.
(without detail differences, it would be half the fun, sorta like the "artisanale" craft of painting)

http://www.takman-e.co.jp/pdf/rtm.pdf
There's no word for capless in (traditional) Japanese, キャップレス is phonetic writing for capless (capres actually) in kata-kana (aka chop-chop writing )
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Last edited by jacco vermeulen; 30th June 2011 at 02:36 PM.
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Old 30th June 2011, 04:10 PM   #2312
MiiB is online now MiiB  Denmark
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Those Talkman's could be just IT.....
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Old 2nd July 2011, 12:53 AM   #2313
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On the weekend i was at the Frickelfest 2011 in East Germany. Some of the people there have tried to follow my thread, some have given up because of the broad and varied material presented and discussed. The main question is " Can you recommend me a phonostage i can build that can compete with the best there is". You can imagine that i am a bit hesitating to answer that. As i already told you i found that a lot of topologies can be made to sound good when they do the job properly. A kind of minimum would be ( for an MC stage ) RIAA precision of plus - minus 0.5dB from 20Hz to 20kHz, noise lower then say 72dB unweighted against 0.5mV, good channel matching, distortion lower then 0.05%, preferably low order ( some may start to cry now that are used to 0.0001% or better but i did not find a good correlation between extremely low distortion and good sound, that does not mean that ultra low distortion circuits with high amount of feedback sound bad ), decent overload margin, enough gain etc. you can ad your favorite spec here. The PSU plays a major part, so does the choice of components and Layout.
What i can do on the other hand is present you a circuit that combines much of what i learned the last two years. A kind of amalgam of proven and tested methods. First i will publish a general circuit diagram. It is an AIOG ( All in one go ) solution, so it differs a bit from the two stage solution i discussed before by being as straight as possible. I build various versions of this circuit successfully. Circuits can be build that have higher overload margin and lower distortion but that comes at the price of more amplification stages, mostly Opamps i assume. Most of the DIY`ers i met would like to build something discrete without overall feedback. Opamp stages can be made to work well too but let´s face it, it is a bit boring. Buy a Cambridge Phonostage for less then 200,- €, modify it a bit and then you are done. The circuit i present is very basic and most of the parts have not being dimensioned. When there is enough interest we could make something out of it so a good layout man and a good simulator is welcome. I call it MPP Summer 2011.
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File Type: pdf MPP Summer 2011 FET AIOG.TSC - TINA.pdf (14.9 KB, 168 views)
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Old 2nd July 2011, 07:51 AM   #2314
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Joachim, as of now you are only looking for a good simulator man

jan didden
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Old 2nd July 2011, 07:59 AM   #2315
MiiB is online now MiiB  Denmark
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Like the circuit.....
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Old 2nd July 2011, 11:01 AM   #2316
RCruz is offline RCruz  Switzerland
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I really like it too.... Can you provide a list of values for the components ?
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Old 2nd July 2011, 12:49 PM   #2317
Salas is online now Salas  Greece
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How much PSRR can be lent in practice from those mirrors loading the cascodes?
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Old 2nd July 2011, 01:04 PM   #2318
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So Jan you could do the layout and Michael do the simulation ? Then we would have something like the official MPP DIY version. A PSU has to be developed too. I could make a suggestion . Another option would be to use the Jung - Didden regulator that Pilgham Audio makes. Ricardo i will fill in some values but they have to be checked. Especially the servo is not that easy because it will influence the deeper frequency range of the RIAA. The input stage has some thermal drift. After adjusting the 10 Ohm pot i get around plus - minus 1V over the RIAA. If we make the Servo too quick it will influence the RIAA more then necessary, if we make it too slow we end up with a drifting offset. Earlier i solved that with a cap in front of the buffer but then Vds of the input Fets floats around. With the servo we can adjust the 10 Ohm pot for minimal distortion and still get less then 1mV offset.
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Old 2nd July 2011, 01:13 PM   #2319
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Salas, you could look at the mirrors as cacoded current sources so PSSR rejection should be good. I am no expert on simulation but output impedance of my special mirror should be several MegOhm at least. Lets say we use BC550C and make the emitter resistors 150 Ohm. Then we have (150 x Hfe x Hfe ) / 2 = 37500000 / 2 Ohm. In praxis there is some Miller and Early effect plus some stray capacitance from the Layout. In praxis it can be checked how far the RIAA is from the mathematical model. The output impedance of the mirror appears parallel to the RIAA. Especially the resistor that defines the lower frequencies.
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Old 2nd July 2011, 01:20 PM   #2320
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You wouldn't fold them to ground, would you? Or you prefer more bias current that the telescopic usually allows?
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