Anyone have this turntable issue?

In addition to the experiment Jim suggested, did you try this experiment I suggested earlier:

... if you are still using the Plinius Odeon amplifier you mentioned in a post a few months ago you might try changing the setting of its ground-lift switch to the opposite of what it is currently set to. It would be prudent, though, to turn the amp off and wait about 30 to 60 seconds before changing that setting.

While Bryston provides schematics at their website for many of their models, unfortunately they don’t for the SP3. And neither does hifiengine.com. But I took a look at the schematic for the SP1.7:

http://bryston.com/PDF/Schematics/SP1pt7_SCHEMATICS.pdf

As is the case in many designs it appears that the muting function is accomplished with relays that short the various outputs to ground when the mute function is activated. It also appears that the outputs are AC coupled via 100 uF capacitors, which are "ahead" of the relays in the signal path. I would expect that the SP3 is similar in those respects. If perchance you have the ground-lift switch on the amp set to the lift position, while I can’t formulate a complete explanation I’m thinking that the issue might be related to the fact that with the switch in that position and no signal existing within the SP3 the AC coupling would allow the input of the amp to "float" to an uncontrolled and arbitrary level relative to its chassis and to AC safety ground and to the chassis and the circuit ground of the SP3, **if the muting relays are not activated.**

That may or may not have anything to do with the problem, of course, but intuitively it seems to me that it's a possibility. And in any event if you are using the Odeon the experiment I suggested is easy enough to do. Also, as Jim suggested contacting Bryston and describing your findings to them may be worthwhile.

Regards,
-- Al

@jea48 

Hi Jim,

Not a dumb question at all about seeing if the pop occurs when a different input is selected.  That would definitely be of interest, as would the answers to my questions one of which was about whether the pop disappears if the SP3 is muted.  And yes, a grounding issue does seem conceivable.

The fact that the volume control utilizes a rotary optical encoder isn't particularly helpful, though, at least without detailed information on the circuitry that follows its photo-detector, both within the control and externally to it.  That kind of control works by shining a LED near the circumference of a rotatable disk having a large number of radially-oriented slots through which the light can shine.  As the control is rotated a photo-detector produces an output in the form of a pulse each time a slot moves in front of the LED, and subsequent circuitry utilizes the string of pulses to control how much attenuation is introduced, perhaps after first converting the number of pulses into a corresponding change in a DC voltage. 

Best regards,
-- Al
 

Jim (Jea48), thanks for providing the links.  Not sure if you noticed that the OP is using a step-up transformer between the turntable and the dual chassis Sutherland phono stage, with the phono stage presumably being used in moving magnet mode.  Here is the manual for the step-up:

https://www.ortofon.com/media/148266/ortofon-st-7-userguide01_web01.pdf

It shows that a single ground wire should connect the turntable to the ground terminal on the SUT, and another ground wire should be connected from that terminal to the phono stage.  Which in this case would mean that a single wire should be used to connect that terminal of the SUT to the ground terminals of both phono stage chassis.

Before commenting further I'll await the OP's response to the questions that have been raised since his last post, as well as confirmation of how the ground connections are implemented between the turntable, SUT, and phono stage.

Best regards,

-- Al
 

Does the pop still occur if the mute function of the SP3 is engaged prior to and at the time the stylus hits the record?

Also, by any chance do any of the components in the system, such as a powered subwoofer, have a signal-sensitive auto-standby feature?

Finally, and this is just a hunch, if you are still using the Plinius Odeon amplifier you mentioned in a post a few months ago you might try changing the setting of its ground-lift switch to the opposite of what it is currently set to. It would be prudent, though, to turn the amp off and wait about 30 to 60 seconds before changing that setting.

Regards,
-- Al