I am posting a circuit I have been working for a while, which is based on the mature technology from the well known Paradise.
Name was chosen by Joachim and it is: MasterPiece.
I have simulation models and a working prototype on my desk.
I just need to change the servo from a common mode's to a differential one (schematic has the differential type) and then test it on the circuit.
There are some noise issue still with it that I would like to track down and maybe with the help of all of you guys we can make a beautiful no compromise full balance phonostage.
Intent is to have a 2 gainstage with two passive transimpedance RIAA circuit for max precision and also standard value for the capacitors can be used to allow very high quality standard caps such as V-Caps Cu-TFT and such.
Powered up with a low compensated shunt PSU (which I already have a functional design with layout) and battery operated and premium parts for the circuit.
My intent is to create the best of the best if possible.
Also this is not going to be for sale nor anybody here should consider it as such.
This is DIY ONLY.
Moreover,it is probably NOT going to be a DIY Group by like paradise kind of deal unless something on the way changes.
Last phase of this project will be to design HW and SW for the battery management system for it.
Like I said I have working prototypes and I can implement all the changes required measure and testing.
Also I will be designing the layout work on simuation for who is going to work with me on this so that everybody who is on board can test along if necessary.
Let's the journey begin!
Just for reference, this is where we have already been, over a year ago.
I am in and watching
This is interesting.
However for this one, with your approval and if you don't have any major concern with noise, I would like to go for JFETs instead of BJTs.
Also, the other thing I would want to avoid is the use of the "bootrasps" capacitors C5, C6, C12, C13 on your design.
The gain is going to drop down, but the main feature would be to have 2 gainstage with transZ RIAA filter if you don't have any concern here either.
The servo you see on my schematic conceptually works for differential DC, but I am concerned if it is going to take care of Absolute drifting or that will just wonder and that might be a problem if two stage are used and if one wants to use it SE.
If a viable soliution for differential servo wouldn't be found we can always use 2 separate servos for each side.
It appears that both of the circuits that you have developed are super symmetrical from end to end. Is there much difference in the thinking of the two designs besides that actual implementations?
I like J-Fets and have no objections at all. Two major advantages are : No input offset and no problem with RF demodulation. The sound is a bit a matter of taste. J-Fets sound a bit sweeter and have very nice tonal color in my experience. The only problem is to get enough low noise P-Channels. This should not be a major problem when only a few get build. For commercial use ore huge group buy this is another story.
I completely agree with you.
However the K170 and J74 are still avaialable even matched (of course at a higher price) on ebay.
I was also thinking of using the dual package if there would be any specific advantage since they are still available as well on ebay (not cheap at all).
Anyhow, Linearsystem shortly will come out with the replacement for the J74 so that should seal the deal for the near future hopefully.
Anyway, cutting to the chase, I am experiencing a pretty noisy output and I can't understand why.
The next post I will postI will include the schematic for the entire phono with the 2 RIAAs split.
I tried to connect it in this fashion without RIAA and I had a huge noise.
Compared to other topologies I have built in the past, this looks the noisiest one.
Noise simulation anyhow confirmed my fear.
I would like some inputs on this.
This looks like two paradise boards connected at the same time to one cart side output...
Am I too far away ?
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