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
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other tests
Volume = 0 dB +1dB_EN = 0 HV_EN = 1
Vout=4.9 Vp-p / 5.7 Vp-p
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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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Constantly questioning the experience of others seems to be your specialty.
If the Cary SLP 90 clone board wouldn't be markedly better sounding than any of the opamps be it IC or discrete I would never ask for help.
? I just don’t. The specialty is technical/logical view and not forced/dogmatic on only 1 item as you can read. Parameters should be rightly chosen and within margins a lot is possible. A chain is as strong as its weakest link. As said better play the ball not the person. Also there are other players in the Mannschaft waiting for the ball.
Tip: read the gain structure thread by Pano. For best overall results things can be done with structural approach.
Tip: read the gain structure thread by Pano. For best overall results things can be done with structural approach.
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I have quite a few DACs with rightly chosen components like OPA 1612/1656 developed by smart engineers. Non of these AKM/ ESS based textbook Streamers and DACs sound right compared to certain mostly cheap DAC output stage combinations I tried.
It's very simple, people don't miss what they haven't experienced before. I certainly can't go back to clean sterile nondimentional sounding setups only because they measure better.
This whole tube forum wouldn't exist if you could achieve the same sonics with IC based safe and cheap stages. To simply say it's sonic preference is not doing it justice.
It's very simple, people don't miss what they haven't experienced before. I certainly can't go back to clean sterile nondimentional sounding setups only because they measure better.
This whole tube forum wouldn't exist if you could achieve the same sonics with IC based safe and cheap stages. To simply say it's sonic preference is not doing it justice.
You seem to miss the point that features like gain and input/output impedances must be determined/chosen right regardless of topology. One can not throw in a random Chinese tube module without knowing its gain etc. and expect things are 100% right just like that. They for sure are not.
The process should be done in reverse order.
The process should be done in reverse order.
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Wow thank you for your work.
Just measured B+ myself it's 259v.
Measured also actual gain it's about 10db.
Was hoping to use the tube pre with my L20 amp as well as my Sennheisers HD540 Reference II (600ohms).
It's just not loud enough on the Headphones.
It's just not loud enough on the Headphones.
So both as output stage of a DAC and as headphone amplifier at the same outputs? It is not meant to drive headphones as it is originally a line stage. Also what did you calculate with regards to drive capability and 6.6 uF as output coupling caps?
The impression was that there was also a Hugh Dean tube preamp between the DAC with this tube preamp module turned to output stage and L20.
The impression was that there was also a Hugh Dean tube preamp between the DAC with this tube preamp module turned to output stage and L20.
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Does not matter if bypassed or not - that is -Ug negative grid bias value,
that means that half period of input signal Vp has to be lower than -Ug...
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For the sound quality, the issue is very low anode voltage of 71V cca.
Anode voltage Va is value between cathode and anode - not Vb of 290V as power supply voltage...
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And You taking out signal from wrong point, better to take output from the cathode (like in the next schematic...)
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Also 12AU7 FOR cathode follower is not good choice, because of low transconductace. The output impedance will be higher...
Use some other tube with higher trnasconductance, because approximately, output resistance will be 1/S ohms. PER section.
Even with sections doubled, still You can get lower output impedance with other more appropriate, same cost tube.
So 5687, ECC88 and others are more welcome for buffer end...
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Also 47K for R load, but for 2 sections, means that almost double value is per one section. about 100K R load for each section ECC82 / 12AU7 is huge, almost flat line. Unnecessary increase gain too.
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Try to set optimal working point in terms of given input max signal?
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Try to set optimal working point in terms of given input max signal?
I do not understand your statement. With the original circuit the grid is always negative against the cathode at up to 2.5V RMS input. 2.5V RMS input is a huge input signal for a pre-amp. Recorded classical music (googled it) has a typical dynamic range of less than 40db, therefore for a pre-amp being able to handle 2.5V RMS at the input is, in my opinion, more than enough.