Help designing device to drain voltage? - diyAudio
Go Back   Home > Forums > Source & Line > Analog Line Level

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 13th March 2010, 02:43 PM   #1
diyAudio Member
 
Join Date: Apr 2009
Default Help designing device to drain voltage?

Forgive me for not knowing if this is the right forum, or if this is already covered somewhere.

I have an apparently unique problem in my system, that has been robust to changes in everything from the main breaker panel through the installation of a dedicated line, to the use of a d-i-y common mode choke and dc-blocker, and through replacement of power cords, components, interconnects, speaker cables, and speakers. After four years of on-and-off diagnostics, the problem seems to be that something is causing a DC voltage to build up between the components, and can only be dissipated by severing the interconnects, after which everything works fine for a while until it builds up again.

A next-door neighbor is finishing a graduate degree in electrical engineering, and he proposes skipping the messy business of trying to explain how this could be possible (clearly it shouldn't be), and going straight to the fix, by which he proposes to tie the chassis of each component to a capacitor, and thence to earth, with gates installed on either side of the capacitor to prevent the chassis of any piece from ever being tied directly to earth: When the capacitor is charging, the switch between the capacitor and earth would be open, and when the capacitor was "full," that switch would close at the same moment that the one between it and the chassis would open. Then, when the capacitor was discharged, the process would reverse itself.


Has anything like this been tried in these fora before? I'm presuming that there would need to be resistors in the line somewhere to slow the dissipation of the capacitor, but beyond that I'm not sure how much my EE-friend would have to know (in particular, whether he'd need access to the schematics on all my components), before we could proceed safely.

Thanks in advance for your help. Sorry if this is a newbie question.

Dave.
  Reply With Quote
Old 13th March 2010, 05:00 PM   #2
diyAudio Member
 
Speedskater's Avatar
 
Join Date: Sep 2002
Location: Lakewood, Ohio
I believe that the inter-web routed your question to the wrong planet, because electricity just doesn't work like that on our planet Earth!

For example, on our planet a small battery will have a DC voltage across it's terminals created by chemical means. To discharge this small battery you could use a jumper wire to short circuit the terminals. Placing a capacitor across the battery terminals will not discharge the battery.
__________________
Kevin
  Reply With Quote
Old 13th March 2010, 05:57 PM   #3
diyAudio Member
 
Join Date: Apr 2009
The problem is in my communication of the proposal, not the planet-of-origin for the electrical properties in question.

Specifically, the capacitor wouldn't be inserted between the components -- which is where it would have to be for the battery analogy to be germane. Instead it would be inserted between a component (?each component?) and earth, and its only purpose would be to store whatever pernicious energy is being shorted exactly as you describe, since it can't be shorted directly to earth without tying chassis directly to earth. Likewise, the energy building up between the components can't be shorted by a drain wire directly between the two chassis, a la the battery analogy, because that would create a ground loop.

The EE guy across the street proposed to get around this problem by creating a setup that works like a lock in a canal, wherein the chassis would never be tied directly to earth because one or the other of the two doors at either end of the lock would always be closed. In this analogy, the capacitor is only acting as the "tub" of the lock, filling with charge from the upstream side while the downstream switch is closed, and then discharging the rest of the way to earth while the upstream switch is closed.
  Reply With Quote
Old 13th March 2010, 06:14 PM   #4
diyAudio Member
 
event horizon's Avatar
 
Join Date: Feb 2008
Location: East Midlands, England
Quote:
Originally Posted by dogorman View Post
A next-door neighbor is finishing a graduate degree in electrical engineering, and he proposes skipping the messy business of trying to explain how this could be possible (clearly it shouldn't be), and going straight to the fix, by which he proposes to tie the chassis of each component to a capacitor, and thence to earth, with gates installed on either side of the capacitor to prevent the chassis of any piece from ever being tied directly to earth: When the capacitor is charging, the switch between the capacitor and earth would be open, and when the capacitor was "full," that switch would close at the same moment that the one between it and the chassis would open. Then, when the capacitor was discharged, the process would reverse itself.
I'm sorry, i just don't see how this would work. I'm pretty sure i understand what you are trying to get accross, but a capacitor won't charge unless both ends are tied accross something that is developing a voltage (IE the equipment & earth). With one leg tied to the equipment, even through a switch, the other end of the cap must be connected to something. If it isn't part of a circuit it'll do nothing at all

E2A:- if i was you i'd try attaching some high value resistors from the equipment chassis in question directly to earth. It appears whatever the problem is takes days to manifest itself, so try something like 10 megohm or greater resistors - i'd suggest 100 megohm & see what happens
__________________
"Never let your morals prevent you from doing what is right!" Salvor Hardin

Last edited by event horizon; 13th March 2010 at 06:23 PM. Reason: resistor thoughts
  Reply With Quote
Old 13th March 2010, 06:21 PM   #5
diyAudio Member
 
Join Date: Apr 2009
Okay, now we're getting somewhere. Perhaps what the EE-kid across the street is proposing is to complete the circuit back to (the other?) chassis while the cap is charging, and then the switch mechanism would interrupt both of those connections, and at the same time close a path to ground?
  Reply With Quote
Old 13th March 2010, 06:26 PM   #6
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
What stops working ? How long does it take to stop working ? What are the symptoms as you listen to it ?
All sounds very bizarre to me. The interconnects will tie all the equipment together anyway...
From what you describe it could be anything from aliens to dry joint/cracked print that disconnecting the interconnects "fixes"
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 13th March 2010, 11:01 PM   #7
diyAudio Member
 
Speedskater's Avatar
 
Join Date: Sep 2002
Location: Lakewood, Ohio
a) Most soon to be EE's have access to multi-meters and should know how to use them. Maybe he could measure these mysterious voltages.
b) Many audio equipment chassis's are already connected to ground. Only units with rated insulation are not.
c) What happens to the sound when this voltage builds up?
d) Are you sure that it's an EE he's studying for?
__________________
Kevin
  Reply With Quote
Old 13th March 2010, 11:55 PM   #8
Banned
 
Join Date: Jan 2008
Blog Entries: 2
Perhaps you could tell us what the functional symptom are as opposed to relaying a diagnosis and solution.

Forget the voltage. What actually happens in practise? You turn on the system, play something, then some kind of fault occurs which is alleviated by disconnecting the elements of the system. What happens?

w
  Reply With Quote
Old 14th March 2010, 04:00 AM   #9
diyAudio Member
 
Join Date: Apr 2009
Thanks for asking, Speedskater & Wakibaki -- I definitely need to start at the beginning but I'm not very articulate in these fora and I didn't want to inundate you with needless details.

What happens is that over hours or, in some cases, days, there accumulates a dry, reedy overmodulation -- not unlike the high-midrange and low-tweeter distortion that one would associate with damaged crossovers -- that gets progressively worse in spite of powering everything down, and can be "reset" to perfect sound by disconnecting the rear aprons.

The problem is robust to a one-item-at-a-time change of everything in the entire system, and has changed in its sonic characteristics so little that, after four years of fighting this, I can barely tell the difference between amps -- and even speakers! -- compared with the difference between listening with this problem and without it.

I'm convinced it's not listener fatigue (or tinitus, or something else personal) for two reasons: First, because non-audiophile friends have commented unbidden on the difference, with the problem vs. without, and second because multiple performance problems only tangentially related to sound quality have failed to reproduce themselves on anyone's test bench.

Here are but four examples:

1) A Parasound A23/P3 combo that would develop a staticky whooshing sound in one channel and eventually drop that channel to zero -- never happened for the local tech, or at Parasound HQ, either one.

2) A Naim Nait 5i whose input selector would periodically freeze and not accept input either through the front panel or the remote until the AC power was disconnected and reestablished. Sent to NAIM USA, they had it for two weeks -- including taking it home to play with, at one point, and never could make it happen.

3) An Arcam FMJ CD-23 that, when playing with IC's connected, gets so hot to the touch, both at the top chassis cover just above the transformer *and* at the interconnect sockets, that you jerk-back your hand. Doesn't happen when powered-up but not connected, and doesn't happen nearly as bad when powered-up and connected and not sending a signal down the IC's. Sent to two out-of-town service specialists, neither of whom could ever make it happen.

4) A series of three separate Sony DVD-players, all of which would periodically issue a loud, scratchy "bang" down the signal path, and none of which have ever done so in any of the houses of the three friends to which I gave them.

...The reason for the OP's emphasis on dcv between components is that this is the only measurable aspect of this thing I've ever been able to replicate with any predictability: When I was using conventional interconnects (coaxial design where the signal return was also the shield), I could set my multimeter to dcv and hold one lead to the shell of the rca connectors at the amp end, and the other lead to the amp chassis, and I would get a voltage that would get progressively bigger as the problem got audibly worse, and would not reset to zero as a result of powering down.

Whether this is the cause or a symptom is not clear to me. Neither is the science behind how this could ever happen, since the rca interconnects themselves are connected directly to chassis at the point of contact, are they not?

Anyway, that's where I'm at. Sorry this one got long.
  Reply With Quote
Old 14th March 2010, 07:18 AM   #10
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
Certainly weird...
I'm no expert on the mains distribution system in other parts of the world, so perhaps you could clarify some points.
The mains supply is the only common link in all this... all the symptoms, many pieces of kit etc.
I take it you are on 120 volts or so ?
Is all the equipment connected to the same socket in the house ?
What I am getting at is, is it possible there is an external distribution issue.

Is your 120vac mains from a "centre tapped" transformer (that gives the option of 240vac for large items of powerconsumption somewhere in the street ?)
Could there be an issue there.
A floating/poor/damaged "ground" or center tap.

What your friend is suggesting seems more like trying to "fiddle" the issue rather than find the real cause.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Why collector/drain output stages are so rare??? Leolabs Solid State 67 3rd September 2011 09:37 AM
Best voltage reference device for a cascode BJT CCS? ray_moth Tubes / Valves 2 1st July 2009 09:38 PM
snake cable - drain wire connects to..?? redrabbit Parts 5 9th August 2006 04:42 AM
single stage common-drain amplifier Music_Sg Solid State 4 4th July 2006 05:45 PM
PSpice modeling, MOSFET, Turn-on Charge, Reverse drain current naula Parts 0 21st January 2003 02:00 PM


New To Site? Need Help?

All times are GMT. The time now is 03:43 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2