Mpp

[le´flu]

Hi there JG,

Originally Posted by Joachim Gerhard

That CCS i use in my tube RIAA on top of a self conducting tube cascode, Ulf, are you getting the idea ?

SY uses dn2540 as CCS in his phono stage posted here at diyaudio. What do
you mean with "self conducting" ? And yes i know what a cascode ist ;-)

By the way - what tubes are u using in your tube-RIAA ?

Greetings Ulf

[Joachim Gerhard]

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.

[RCruz]

I like the TS... Not so sure about the buffer... Can TS be terminated with the "stock" k170 + 1500Rs from the simplistic ?

[sampler]

Hi Joachim,
I'm back for holidays 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

[RCruz]

Hi Sampler

Can you post a file with the values you got in your sim ?

I need to find input stage output imp at 1kHz

Does your sim give the output imp with the riaa filter connected ?

Can you plot this impedance without the riaa filter connected ?

[brianco]

..........here we go - again!

[RCruz]

Originally Posted by brianco

..........here we go - again!

Fun time

[Joachim Gerhard]

Yes, Ricardo, you can use the simpler buffer from the Simplistic ( in Germany we call that word worm ).
Sampler, i use more or less the same input structure in my tube RIAA and it works.
For Ulf, i will show you the Transcendent RIAA. The input tubes in mine are aranged the same way.

[Joachim Gerhard]

Here we go :RIAA-2010

[sampler]

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.