MPP

Here is a more detailed schematic of the TS ( Transimpedance Simplistic ).
I have substituted the BJT Cacode CCS with a depletion mosfet CCS.
The RIAA values are valid under the asumplition that the output impedance of the input stage is infinite. That is not the case so it apears in parallel to the RIAA. That may likely truncate the bass response with the chosen values. The solution is to raise the bass resistor or make the RIAA lower impedance. That will reduce the gain though. Anyone willing to simulate this circuit ?
The drawing has to be turned left-
 

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Ulf, you drive me cazy :)
If you are really interested in the tube RIAA all the information you require is in this thread. I simply can not repeat everthing for everybody all the time. I have to drink, to eat and sometimes to sleep.
Self conducting Fets also known as depletion Fets conduct when you connect the gate to the source. They do not require external bias like BJts or enhancement Fets.
The value that you then measure is the IDss. Tubes are the same. A self conducting depletion mosfet cascode is a series connection of two Fets. You can do that with tubes too. The CCS post 7810 is that way with a twist of a bias multiplier.
The Rosenblitz Trancendent Phono has a self conducting tube cascode as i have in my Tube Phono.
You can of cause build a cascode with fixed bias, that is the usual way.
 
Hi Joachim,
I'm back for holidays :hohoho: and always ready to sim something simple.
Here is a plot of TS input stage's output impedance. With such a sky high impedance and lots of gain, my biggest concern would be dc stability. Setting real circuit for operating point would be close to impossible I'm afraid. How a tempco of DN2540 looks like ? Will check riaa values, but I guess they will be spot on ;)
 

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Ok, here is what my simulator spitted out. Gain is 57dB and good riaa compliance with increased shunting resistor from 130k to 142k. Typical nice SE harmonic distribution for 1Vrms out with H2 dominant. There was missing bias resistor for buffer, added that.
 

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