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Old 3rd December 2012, 12:30 AM   #7851
Salas is online now Salas  Greece
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No worries, I forget test gear buttons all the time too.
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Old 3rd December 2012, 01:07 AM   #7852
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Well, the depletion Mosfets are not the solution anyway. I may try my original BJT design.
When the thermal drift and the noise from the CCS is in check this may work.
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Old 3rd December 2012, 01:29 AM   #7853
MiiB is offline MiiB  Denmark
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I would make a balanced +/- PSU for the buffer.. Then You don't need the top biasing resistor for the buffer. and you can adjust offset, so you don't need the output cap.
That bias resistor is A/C vise in parallel to the CCS, and reduces the PSSR drastically.
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Old 3rd December 2012, 02:50 AM   #7854
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Quote:
Originally Posted by Joachim Gerhard View Post
Well, the depletion Mosfets are not the solution anyway. I may try my original BJT design.
When the thermal drift and the noise from the CCS is in check this may work.
Is it something you posted here on this thread?

I just checked out the thread: have you built the circuit simulated by sampler?
Have you measured the gain it it actually boosts out about 60dB?
Is just the DC drift a concern? Keeping in mind this is OL design, my practice is to eliminate the output capacitor, power the buffer, like MiiB also suggested, with dual supply and trim the offset down and close the servo around the buffer to correct DC drifting.

Would this work? I would be interested to get this model up on my simulator to check noise out.
For instance speaking of paradise, re-designing the circuit with BJTs and eliminating the bias el cap, simulator forecasts a whooppy 1.3uV/rtHz @1KHz.
Building it confirms exactly simulation and puts too much noise out which if in one hand sound is much better, the noise is something definitely unwanted.

Therefore after this test I became really concern about having a low noise phono as it is something I really like about the paradise topology.
Just a thought.
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Old 3rd December 2012, 03:50 AM   #7855
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Post 7760 is the original design.
Concerns are low noise from the CCS and little thermal DC drift of the input stage.
I already know that a one stage RIAA is theoretical possible.
My tube RIAA comes close but has some gain in the output stage and that with only 8mA in the input. Here we have 50mA on tab so enormous gain in one stage is the attractive idea. So far i have only build a prototype of the input stage but my tube RIAA supports the theory.
I think it is not wise to take out the elcaps in the Paradise. Be careful with noise, that can at first listen sound very attractive because some unpleasant artifacts can be " analog dithered " away. We had a discussion with Salas here on this thread. If you want low noise without the elcaps redesign the Paradise for Fet input. That is simple.
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Old 3rd December 2012, 10:55 AM   #7856
MiiB is offline MiiB  Denmark
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This design can't be switchd to bjt's as you need the selfbiasing of the jfets..
I see the single-ended One shot design being possible too, but as I'am away, I can't get it into my simulator.
I don think the buffer need,s a servo. It's quite steady, low in drift, so weny you dail it in it stays there. Off course if you play with an unregulated supply's then a servo would be good.

Last edited by MiiB; 3rd December 2012 at 11:02 AM.
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Old 3rd December 2012, 02:30 PM   #7857
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Quote:
Originally Posted by Joachim Gerhard View Post
Stefanoo is back, hello.
No, this is a Spiral Groove SG1. I am very happy with that deck.
Just saw your post! Thanks! Hello to you too!
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Old 3rd December 2012, 02:43 PM   #7858
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Quote:
Originally Posted by MiiB View Post
This design can't be switchd to bjt's as you need the selfbiasing of the jfets..
I see the single-ended One shot design being possible too, but as I'am away, I can't get it into my simulator.
I don think the buffer need,s a servo. It's quite steady, low in drift, so weny you dail it in it stays there. Off course if you play with an unregulated supply's then a servo would be good.
it's about time to throw on the burner the one-shot design too (I will probably take that back to the masterpiece thread).

The goal for me would be to design an alternative using same custom V-Cap Cap 11nF and 32nF that work on Paradise as well.
Let's see!
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Old 3rd December 2012, 02:43 PM   #7859
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Quote:
Originally Posted by Joachim Gerhard View Post
Post 7760 is the original design.
Concerns are low noise from the CCS and little thermal DC drift of the input stage.
I already know that a one stage RIAA is theoretical possible.
My tube RIAA comes close but has some gain in the output stage and that with only 8mA in the input. Here we have 50mA on tab so enormous gain in one stage is the attractive idea. So far i have only build a prototype of the input stage but my tube RIAA supports the theory.
I think it is not wise to take out the elcaps in the Paradise. Be careful with noise, that can at first listen sound very attractive because some unpleasant artifacts can be " analog dithered " away. We had a discussion with Salas here on this thread. If you want low noise without the elcaps redesign the Paradise for Fet input. That is simple.
I will try to simulate your original desing from post #7760
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Old 3rd December 2012, 03:23 PM   #7860
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I entered the circuit on the simulator and this too behaves uncorrectly accordingly to the model I have.
Please review the schematic and let me know if there is any change I need to make.
Attached Images
File Type: jpg Sim-1.JPG (88.3 KB, 132 views)
File Type: jpg FR-1.JPG (57.9 KB, 125 views)
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