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Old 30th September 2012, 08:11 PM   #7431
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Sorry I can not quikly cek whitout servo as my R2 it is in constant use.

Well lab suply normaly means switched mode...?

Easy to shield Paradise from it with small resistor and litle bank of caps
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Old 30th September 2012, 10:33 PM   #7432
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The Paradise R3 seems to be very interesting and I'm planning in building one. I found enough information to build my own PCB. In the mean time after reading all these posts I compiled a detailed Parts List for North America using the usual suppliers Mouser, Digikey and Newark. It doesn't include the pre-regulator circuitry thought. I'll make it later on...This list may be useful to others. Feel free to point any error I may had done. I still to go through all the schematics to make sure no part is missing.
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Old 1st October 2012, 01:45 AM   #7433
AVWERK is offline AVWERK  United States
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Doesn,t want to open?
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Old 1st October 2012, 03:00 AM   #7434
Salas is offline Salas  Greece
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It opens on mine and its Oxygen Office even.
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Old 1st October 2012, 03:44 AM   #7435
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I managed to have a decent offset...at least good enough to give it a listen to.
Comment on the sound:

It is very crispy and fluid and very nice overall. Pretty quite back ground, fast preamp.
The only thing I think I need to check out is that it is at times a little glossy, I am talking about a tad glossy on the highs.
Wonderful midrange, very controlled bass, nice depth.

It is running directly out of 12V premiul SLA battery and bypass caps on the board.
Tomorrow I will put my shunt PSU design on it which I am pretty sure it will make solve what I am hearing

Now a technical question:

Beside tomorrow I am odering the OPA used here, right now I am using a discrete op amp module, but that is not the problem.
I wanted to ask how the offset is once the servo is connected and what is the offset without servo (how much is wondering).
The thing is that if offset is pretty bad, it means that servo is controlling a lot.
The offset on my board with the servo on seems to be pretty bad to me and I would like to know based on the expierence accumulated here with this pre-amp, what it could be caused by.
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Old 1st October 2012, 10:48 AM   #7436
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Quote:
Originally Posted by Joachim Gerhard View Post
I found this phono stage where they are used.
look like Erno phono...
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Old 1st October 2012, 11:39 AM   #7437
MiiB is offline MiiB  Denmark
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there are a few sources for offset... temp-co, variance in mirror gain and resistor tolerances.
The Jfet buffer also causes a permanent offset. To my knowledge the offset is pretty stable, and when the stage is running and temp. stable the servo is pretty much just injecting DC into the household.
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Old 1st October 2012, 11:44 AM   #7438
RCruz is offline RCruz  Switzerland
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Quote:
Originally Posted by MiiB View Post
there are a few sources for offset... temp-co, variance in mirror gain and resistor tolerances.
The Jfet buffer also causes a permanent offset. To my knowledge the offset is pretty stable, and when the stage is running and temp. stable the servo is pretty much just injecting DC into the household.
Hi MiiB

Can you quantify jfet buffer permanent offset ?
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Old 1st October 2012, 03:34 PM   #7439
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It's about 150mV if I am not mistaken
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Old 1st October 2012, 04:14 PM   #7440
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Quote:
Originally Posted by MiiB View Post
there are a few sources for offset... temp-co, variance in mirror gain and resistor tolerances.
The Jfet buffer also causes a permanent offset. To my knowledge the offset is pretty stable, and when the stage is running and temp. stable the servo is pretty much just injecting DC into the household.

I am not concerned with the permanent offset caused by the buffer.
My concern is with the DC drifting, that seems to be pretty drammatic in my case.
It starts up at 8V or so then goes down then up again (without servo).
Also with servo in, for some reason, output is not 0 but it stayies at 50mV-60mV and drifts too much for my personal opinion.

Just want to make clear that I am not using the layout for R2 nor R3 but it was the board designed for my gainstage and re-adapted with few cuts and jumpers.
I am not using matched transistors nor using the 337/327 for the mirrors but only for the input devices.
For mirrors I am using BCP53/56 with about 40HFE gain I think.

I am wondering if on the Paradise's layout there was applied some "special trick" to deal with the thermal drifting that I can re-use here.

Also, what is the effect of building it with not matched device?
Resistors are 1% tol so don't think the culprit could be that one.


I remember one post somewhere along this long thread, where something was done for the DC drifting, but I can't remember if it was the heatsink on the Power supply or what else.
Any input here will be very helpful to complete the built with the Paradise.


Accordinlgy to what you say, if I understand corretly, if you have a preamplifier AC coupled at the input like I do, you could run it without servo as well, am I right?
If that is the case, the built I have done so far, for some unknown reason, is not even close to the actual desired result.



Thanks for the attention.
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