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Old 4th December 2012, 02:25 PM   #401
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So the remaining issue is the servo. We have to look into this ones more.
analog-sa, when you short the input of the Paradise : how is the noise then ?
As i reported many times : the Paradise has approximately the noise of a 10 Ohm resistor.
Connecting the DL103 that has a DC impedance of 40 Ohm worsens the noise 4 fold.
That is 12dB. That has nothing to do with the Paradise and is simply the Johnson ( thermal ) noise of the cartridge coil windings.
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Old 4th December 2012, 02:42 PM   #402
hesener is offline hesener  Germany
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Quote:
Originally Posted by RCruz View Post
Good news !!!

You mean you decoupled VCASCH and VCASCL ?
What cap value / type did you use ?
Can you post a picture so others can learn how you did it ?
By the sound of it, the decoupling analog_sa implemented is in parallel to the big elcaps (C6 and C7). Thats a good one, thanks for the tip!

As Joachim points out, Paradise is operating at very low noise levels so you may end up seeing some low-frequency output signals that are noise-related. Bipolar transistors don't have a lot of 1/f noise (unlike JFETs), so they have the edge here. Some of that low-frequency output signal can also be caused by thermal variations (try blowing on the input stage transistors.....)

From a "sound" point of view, this decoupling might better be done with foilcaps rather than ceramic caps, but that is pure guessing on my behalf.....
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Old 4th December 2012, 03:17 PM   #403
studeb is offline studeb  United States
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is analog_sa's build encased?
could it also be thermal wandering?
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Old 4th December 2012, 04:20 PM   #404
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Others may not have a problem. Just stripped a bit of the screen close to the 33ohm junction and soldered a 10n smd between the junction and ground. On both rails of course.

Btw, RC, how stable is your offset?
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Old 4th December 2012, 04:45 PM   #405
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Quote:
Originally Posted by studeb View Post
is analog_sa's build encased?
could it also be thermal wandering?

It is not fully encased. The dc drift has a frequency in the region of 1-2Hz; isn't that too fast for thermal wandering? Approximately 120mV of wandering with servo on and 2v without the servo.

Apparently my beta matching is not so great as there is a constant disbalance around +2v at output. At max it goes up to maybe +4v, so not using the servo effectively limits the max output swing on one polarity - not so great.

Haven't made a final judgement about the servo yet. Maybe speeding it up will cure the drift. Will do some more listening with and without the servo but if output offset cannot get below a few mV there will have to be an output cap anyway.

How was the dc stability in the beta run?
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Old 4th December 2012, 04:47 PM   #406
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Quote:
Originally Posted by Joachim Gerhard View Post
Connecting the DL103 that has a DC impedance of 40 Ohm worsens the noise 4 fold.
That is 12dB. That has nothing to do with the Paradise and is simply the Johnson ( thermal ) noise of the cartridge coil windings.

Good point. Will try a Kontrapunkt B as well. I think coil resistance is around 7ohm.
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Old 4th December 2012, 04:47 PM   #407
studeb is offline studeb  United States
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you could try to encase some of all of it
small metal or plastic box to test it out?
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Old 4th December 2012, 04:49 PM   #408
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You could also try to degenerate the positive input transistors some more so raise the emitter resistors somewhat in value until the +2V is cancelled.
You could also try this on the mirror emitter resistors but this part of the topology is extremely sensitive to even very small fluctuations of the resistor values. I think it is better to tune in the input stage.
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Old 4th December 2012, 04:51 PM   #409
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Instead of raising the positive side it could be easier to lower the emitter resistors on the negative side because then you do not have have to solder the resistors out but just parallel from the top.
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Old 4th December 2012, 04:53 PM   #410
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Thanks for the great suggestion. Will give this a try.
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