Guys thanks for all the suggestions.
The pre was advertised as a buffer.
I have not traced the board yet.
I have the suspicion that the supplied schematic is not from the actual board.
If you red carefully you can see that I want to substitute the opamp in my DAC.
I am driving the marigno modified L20 amp.
If the thing wouldn't sound so phantastic with the TungSol tubes I would use a Lampizator stage instead of trying to manipulate this board. I am just sold on the sound of this thing.
Heck the power supply of my Hugh Dean tube pre was more expensive than this whole Cary SLP 90 clone board so if I mess up it's not a big deal.
The pre was advertised as a buffer.
I have not traced the board yet.
I have the suspicion that the supplied schematic is not from the actual board.
If you red carefully you can see that I want to substitute the opamp in my DAC.
I am driving the marigno modified L20 amp.
If the thing wouldn't sound so phantastic with the TungSol tubes I would use a Lampizator stage instead of trying to manipulate this board. I am just sold on the sound of this thing.
Heck the power supply of my Hugh Dean tube pre was more expensive than this whole Cary SLP 90 clone board so if I mess up it's not a big deal.
So You using this device for amplification stage after the DAC chip?
Is Your power supply fixed value of 290V or can You get more?
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You already have very sufficient output voltage p-p, maybe You need a tube buffer only?
From the datasheet of CS43198
With DSD
RL =600 or 10k
CL = 200 pF
DSD_DIRECT_GAIN = 1 Vout=3.8 Vp-p
DSD_DIRECT_GAIN = 0 Vout=2.85 Vp-p
.
other tests
Volume = 0 dB +1dB_EN = 0 HV_EN = 1
Vout=4.9 Vp-p / 5.7 Vp-p
.
The circuit You propose is not good.
First, Anode voltage is too low just a bit from 70V 🙁
-Ug is about 3V which is lower minimum for input signal of say 5.7Vp.p/2=2.85 Vp for not to overload input stage.
You said there is no DC at the output of DAC so inpt C has to be removed...
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The first stage's cathode is not bypassed. It will go up together with the input signal, up to a point, of course.
Blue is grid, green is the cathode, here with a 2Vrms input
To be clear, I'm not advocating for the original circuit. I just simulated it. As @Zoran mentioned, Va is a bit low for the first stage, I'd use around 100~120V. Also it is not clear why parallel sections of a 12AU7 at the input. Just one triode is way enough for that, especially taking into account that the next stage is a cathode follower. It could be also converted to a differential input by using the 12AU7 as an LTP.
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It supposedly brings things like stage depths and precise imaging.
Too lazy to look it up and it is not my task either but it would not surprise the marigno modified L20 amplifier is very content with 0.5 … 1V input signals.
Too lazy to look it up and it is not my task either but it would not surprise the marigno modified L20 amplifier is very content with 0.5 … 1V input signals.
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