diyAudio

diyAudio (https://www.diyaudio.com/forums/index.php)
-   Parts (https://www.diyaudio.com/forums/parts/)
-   -   PGA2311 pre-amp static discharge problem (https://www.diyaudio.com/forums/parts/232501-pga2311-pre-amp-static-discharge.html)

activexp 21st March 2013 09:17 AM

PGA2311 pre-amp static discharge problem
 
I've built a PGA2311 based pre-amp like this one on eBay.

Works very well and sounds good but is extremely sensitive to static discharge which causes the pre-amp to "crash" and make the most appalling speaker destroying loud noise. It's like hum and buzz at full volume.

The "crash" can be triggered occasionally simply by touching the volume knob and more frequently by the static discharge from vinyl LP's :eek:

I've tried earthing the case but it hasn't made any difference.

Any suggestions to fix this problem are most welcome!!

marce 21st March 2013 01:07 PM

If the case is correctly grounded it should not be a problem as it is then I would suggest that the grounding scheme has a high impedance connection, probably a star point, run large seperate ground wires between points to improve and lower the ground impedance.

A schematic of the grounding would help give a more qualified answer.

activexp 21st March 2013 04:06 PM

Thanks for the reply Marce. Here's a schematic for the board:

https://i.ebayimg.com/t/PGA2311-Remo...Klw~~60_57.JPG

And here's my pre-amp:

An externally hosted image should be here but it is no longer accessible. Please upload images instead of linking to them to prevent this.




There's no obvious grounding point on the board. In fact the commercial assembled versions of the pre-amp on eBay do not appear to have any grounding. :confused:

jan.didden 21st March 2013 04:13 PM

I've had similar problems in similar circumstances. Check the grounding between the PGA digital ground connection, and the digital ground of your ucontroller and rotary encoder setup.

If there's an issue there, static discharge can look to the controller as a digital input stream. The fact that it happens when you touch the knob points that way. This can send all kinds of random commands to the PGA with the results that you see - random levels, quickly changing, sounding like hell breaking loose ;)

jan

wushuliu 21st March 2013 04:33 PM

Yep. Have the same problem wit that kit. Now I just avoid touching and use the remote...

gmphadte 22nd March 2013 05:06 AM

Check continuity between different chasis parts.

Gajanan Phadte

marce 22nd March 2013 07:09 AM

Yes anodising is a good insulator.
What concerns me is the damage that the discharges are doing to the actual devices, it can destroy chips.
I would affix a nice thick wire from the front panel to the safety earth at the mains input, also a thick GND wire to connect the two boards together, minimising the GND (0V) impedance, the aim is to create a low impedance path for the ESD energy to discharge down.
I would be interested to any links to the PCBs used as this problem is probably down to far from optimal PCB layout, and or things lacking in the circuit layout such as protection devices for ESD. It is srtrange to hear of these problems these days, they were more common in early to mid 80's!

activexp 22nd March 2013 09:25 AM

Quote:

Originally Posted by marce (https://www.diyaudio.com/forums/parts/232501-pga2311-pre-amp-static-discharge-post3421998.html#post3421998)
Yes anodising is a good insulator.
What concerns me is the damage that the discharges are doing to the actual devices, it can destroy chips.
I would affix a nice thick wire from the front panel to the safety earth at the mains input, also a thick GND wire to connect the two boards together, minimising the GND (0V) impedance, the aim is to create a low impedance path for the ESD energy to discharge down.
I would be interested to any links to the PCBs used as this problem is probably down to far from optimal PCB layout, and or things lacking in the circuit layout such as protection devices for ESD. It is srtrange to hear of these problems these days, they were more common in early to mid 80's!

Will give it a try, thanks for the suggestion :)

During my 50 odd years tinkering with audio gear, I recall RF breakthrough being an issue way back when, a lot less dangerous than chip-killing static discharge.

gmphadte 22nd March 2013 10:57 AM

It is preferred to not connect the safety earth wire, as it (earth connection) will give you ground loop problems.

Gajanan Phadte

marce 22nd March 2013 02:19 PM

No it may give a ground loop problem, but ground loops are solvable.
What do you mean do not connect the earth wire to the unit, dangerous and under no circumstances should it be ommited from ANY DIY gear.
And while I am on a roll, we have a major proble to solve ESD, no point worrying about possible ground loops.
Ground loops are caused by some high impedance point in the 0V (GND) scheme of a system, Henry Ott, Tony Waldron etc have plenty of info on interference grounding of audio systems.


All times are GMT. The time now is 08:05 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 17.65%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Copyright ©1999-2020 diyAudio

Wiki