Satyrnine Posted January 20 Report Share Posted January 20 (edited) Alright, the vast majority of my noise issue is resolved, but I still have noise on whichever "side" I connect the protector board power to. If I use low sensitivity cans, like my HE6SE, I can't hear anything, but high sensitivity cans, like my LCD-X, there is still a persistent and annoying very high frequency noise. I'm more and more sure the protector board is causing it. I'm currently running no shield at all from outputs to headphones, just 4 wires. I've tried connecting the protector board ground to the star ground as well as "chassis". No change. At this point I think I need a separate supply all together, or possibly a RC filter between the grlv and protector board, to both filter and drop the 30v down closer to 12v a bit. Bad idea? EDIT: I added 1k resistors on the +30v and -30v inputs. Noise is gone! Getting about 13v on the + input after the added 1k, before the regulator, and about 25v on the - input. Probably only needed the resistor on the + side that drives the relay, but can't hurt I guess. Everything seems to be functioning properly, looks like that did it, unless anyone can think of a reason this is a bad idea? If anyone else has this problem with 30v rails, give it a shot! Here's the wiring scheme and pics. Edited January 20 by Satyrnine Quote Link to comment Share on other sites More sharing options...
justin Posted January 23 Report Share Posted January 23 (edited) I made a SMD version of the Protector PCB for the CFA3, and after testing it this weekend I came up with some ideas for changes #1 - add blocking diodes in series with the power supply inputs. first thing I did was fry the V+ regulator by hooking up power backwards. other protection diodes for the regulators could be added, but I think they're less important #2 - add minimum load resistors for the regulators (R25, R26). I've previously noticed some 3-pin regulators can have an unstable output voltage if their load is too low. the resistors are so each regulator has at least a 5mA load #3 - option of getting DC voltage reference from the +/-12 regulators or the external supply. In this case, the +/-12 regulators could have as much as a 0.5V imbalance which requires hand selecting resistors to set the voltage reference (the voltage across R8 + RV1). if powering the protector with LT1021 referenced GRLVs, the voltage is going to be within millivolts for both + and - references. You would install either R1 or R9, and R2 or R10. the PCB could also be designed to allow switching between the two for two different range options. one feature of using the GRLV / higher voltage supplies for the reference is if those supplies were to become damaged and start outputting a different voltage, the reference will probably be thrown off more than enough to permanently disable the output jacks until the problem is found/fixed. #4 - added RV1 pot, the purpose is to adjust the range of the protection if it is too sensitive or not enough #5 - added dual indicator LEDs, for "Good" (D9/white) and "Protection On" (D10/orange). Not a bi-color LED, but 2 separate LEDs next to each other. The white "good" LED will be lit but very dim when the Protect LED is on, and the orange will overpower it. #6 - changed relay from 12 to 24V for 1/2 the current and to use more equal current from the +/-12V regulators #7 - added 4.4mm Pentaconn jack short protection. The 4.4mm jack has a switch in the back that only opens when the plug has been fully inserted. The relay keeps the L- and R- pins disconnected, which is every other pin on the jack, until the plug has been fully inserted + a .5 second delay, and then instant release of relay when the plug starts to be removed SMD version & in CFA3 Edited January 23 by justin 11 Quote Link to comment Share on other sites More sharing options...
justin Posted February 15 Report Share Posted February 15 Tested the 4.4mm short protection today. The relay disengages if the plug is even .5mm from fully inserted, so i think it will work IMG_3731.mov 6 Quote Link to comment Share on other sites More sharing options...
justin Posted February 17 Report Share Posted February 17 almost but not quite disconnecting the L- and R- with a relay didn't solve all the problems, I found 2 conditions that remain, depending on how far the plug is inserted: 1) R+ and GND becomes connected to L+, L- of the headphone I think this is OK, but I'm considering disconnecting the GND pin of the 4.4mm jack. As a balanced headphone jack, I don't think the GND has any real purpose 2) R+ and L+ connect to L+, L- of the headphone this is the condition just before the final push to get the plug fully inserted. I'm not thrilled with it, but it may be OK. adding a 2nd relay or using a 4 pole relay to switch all 4 pins would also fix both issues 1 Quote Link to comment Share on other sites More sharing options...
Pars Posted February 17 Report Share Posted February 17 The only purpose for 1) above would be if the user had an SE 4.4 adapter which would require GND. Quote Link to comment Share on other sites More sharing options...
justin Posted February 28 Report Share Posted February 28 (edited) I'm going to try an electrostatic HP version of Kevin's balanced HP protector. I may keep all 4 outputs separate, using 1kV rated relays, which are usually single pole anyway. Plus this way each output could have its own status LED, which would show which of the 4 outputs (L+, L-, R+, R-) was triggered. Here is a preliminary idea: Edited February 28 by justin 1 Quote Link to comment Share on other sites More sharing options...
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