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Old 20th September 2011, 02:18 PM   #2731
MiiB is online now MiiB  Denmark
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nice you had a great trip....will you have time to go back to the testing again.. would sure like to have some listening impressions on the N-jFet riaa....but I guess ample food and wine has the same effect as jet-lag...
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Old 20th September 2011, 02:40 PM   #2732
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No, i am fine. I do not overdo it any more. I spend even the second evening alone in the hotel. MiiB, i swear i will build the second N-channel phono as soon as i can. I am very curious too. That P-Channel tragedy is really bugging me. I already know that it can be done with N-Channels alone. Some time ago i build an N-Channel phono ( with feedback ) that sounded rather excellent so the perspective is not that bad. By the way a nice guy, lets call him KW made a simulation of the P-N channel variety with mirror plus cascode.
That particular mirror proved to be superbly low in distortion but the output impedance was a little bit too low for textbook RIAA components. See the simulation results and also variations of the bass feedback resistor and the cap before the buffer to compensate that. Noise was low too. In the meantime i send him my anti RIAA so i await graphs that are more easy to interpret. I also designed a "cascode the cascode" variation so even Italian wine and food can not totally stop my german brain.
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Old 20th September 2011, 02:47 PM   #2733
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Here is the noise plot. You can see the GR noise in the Fets but also that the transimpedance RIAA lower noise in the treble.
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File Type: png Naked_Truth_MC_Mirror_with_Cascode_2-1.1.TSC_-_noise.png (146.7 KB, 333 views)
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Old 20th September 2011, 02:59 PM   #2734
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Salas, i see you are watching. Yes, this little B1 buffer does not seem to introduce much distortion. It´s really good actually.
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Old 20th September 2011, 04:08 PM   #2735
MiiB is online now MiiB  Denmark
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Have been working with that (n-P channel)in the simms as well but have some trouble in getting it working right..can't raise the gain sufficiently. but to be honest I hope the N-channel will perform brilliantly...Your brain i not too typically German...as it seems to work in less structured and more creative manner...
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Old 20th September 2011, 04:59 PM   #2736
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Picasso said, the common man needs order, the genius is allowed to do anything.
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Old 21st September 2011, 02:25 PM   #2737
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More and more circuits of mine make it to a PCB. After Holger Baske has laid out the Nobrainer and Ward Maas has done the FPS i designed for the 0 issue of Linear Audio i got now the PCB boards for the L`Art du Son La Finta Giardinera. It has switchable MC-MM, one MC input is tansimpedance and one transconductance, MC inputs are switchable in loading resistance, MM input is switchable in loading capacitance. Both inputs have a second set of RCA jacks for loading customization. The EQ has the option of 50usec and 75usec.
That is because Neumann cutters had a switch for that and many records cut in Germany, for example an Esther and Abi Ofarim album i know where cut with 50usec.
We solved that many options with a modular design and timer IC´s plus micro amp relays. The switching of transimpedance to transconductance plus 50usec to 75usec is done from the front with push buttons. This stage has a dual mono PSU of my own design. Many circuit elements have being published on this thread so excuse me for not publishing the circuit diagram. I think Klaus has done a wonderful job with the PCB.
Good for him and bad for me, he is in retirement so he can do only so much. The board is etched traditionally with tin plating on copper, so no nickel plating. The tracks are delicate and round and he uses his spider web ground plane for low amount of metal.
It is star earthed and the vias are from solid copper inserts. The input jacks are directly fixed to the board and the input circuit is also on the backside, direct behind the input board. The 2 RIAA modules sit on the dual mono PSU mother board.
Attached Images
File Type: jpg La Finta PCB1.jpg (94.3 KB, 294 views)
File Type: jpg La Finta PCB2.jpg (92.4 KB, 164 views)
File Type: jpg La Finta PCB3.jpg (90.3 KB, 155 views)
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Old 21st September 2011, 02:43 PM   #2738
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The tin plated PCBs look great (like in old HP measurement gear).
How can one do this at home ?
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Old 21st September 2011, 03:22 PM   #2739
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I can not tell you. My layout man also takes care handling the suppliers. He is a graphics designer and that shows. This is mostly for prototyping. In series we will use a more conventional double layer board.
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Old 21st September 2011, 03:27 PM   #2740
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Quote:
Originally Posted by gk7 View Post
The tin plated PCBs at home ?
Euh, what's wrong with a tin solution bath.

(before www1, grandpa's just bought a bottle of powder, e.g. by SENO)
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