Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Solid State Talk all about solid state amplification.

Another simple DC protection
Another simple DC protection
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 5th September 2011, 02:02 PM   #61
Esperado is offline Esperado  France
Banned
 
Join Date: Jul 2011
Location: Portugal
Quote:
Originally Posted by Mooly View Post
this working prototype aims to eliminate that delay by comparing input and output of amp. If there is a difference... the relay trips.
Oh, gosh, i had exactly the same idea 20 years ago, and that's how work my own protection since those years.
A working amplifier must have the same signal (scale apart) out and in.

And this gives a lot of advantages. it protect from everything: Clipping, HF, oscillations as well as DC and short circuits on the loudspeaker line. And it is instant.
The only problem is, because the complex charge witch is the loudspeaker and its motional signals , and because the phase switch that the amplifier can introduce, we need to adjust a gate for the relay does not switch-on at each drum kicks.
On my side, i do not introduce any temporal delay before protection switch on. Just my circuit authorizes the good amount of errors from the loudspeaker line. But i have a delay witch keep the protection on for 3s after the cause of the trouble had disappear .

By default, on my circuit, the Loudspeakers are not switched, and i have an additional circuit witch wait 5sec after power on operations before the relay can switch them on. And cut the relay instant when power off.
In fact, when you power off, first the relay cut the loudspeakers, then the power relay switch off the power.
When you power on, there is a resistance in serial with the PSU condensers to avoid huge transients. After 2sec, a relay short circuit this resistance. After 5 more seconds, the power is send to the loudspeakers protection relays. All that use only a quad OP AMP, 3 transistors, few resistances and condensers, and 3 LEDs shows the sequence and states (power on > condensers on > loudspeakers on).
Works like a charm, with not a single "clic" during all those years.
  Reply With Quote
Old 5th September 2011, 03:02 PM   #62
Bigun is offline Bigun  Canada
diyAudio Member
 
Bigun's Avatar
 
Join Date: Jan 2009
Location: Waterloo, ON or Herefordshire UK
Another simple DC protection
Esperado, that sounds like a great circuit - can you post the schematic. I'm looking for a speaker protection circuit and this sounds like a good candidate.
__________________
"The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.
  Reply With Quote
Old 5th September 2011, 04:07 PM   #63
Esperado is offline Esperado  France
Banned
 
Join Date: Jul 2011
Location: Portugal
Quote:
Originally Posted by Bigun View Post
Esperado, that sounds like a great circuit - can you post the schematic. I'm looking for a speaker protection circuit and this sounds like a good candidate.
I'm building a new system, so i will post the shematic and circuit board design within the next month.
It will be here:
http://www.diyaudio.com/forums/digit...m-project.html
If you are in a hurry, i can open my actual amp to recover my original schematic with precise values, but i feel lazy ;-)
  Reply With Quote
Old 30th September 2011, 10:20 PM   #64
RCruz is offline RCruz  Switzerland
nhinstruments
diyAudio Member
 
RCruz's Avatar
 
Join Date: Sep 2006
Location: Wallis
Another simple DC protection
After building the DCB1 buffer (and not being able to go back due to the big improvements relative to my previous line buffer that uses a cap in the output) I am worried that a PSU failure might cause excess offset and kill my speakers (or worst).

I read a lot and only found designs and ideas of protections that use relays on the speakers.

Is it possible to implement one of these designs to control relays between the buffer output and the power amp ?

I am using a complex simetrical PSU and am afraid of possible failure (due to housekeeping damages, and not to the implementation or design).
__________________
RC
  Reply With Quote
Old 1st October 2011, 09:11 AM   #65
AndrewT is offline AndrewT  Scotland
R.I.P.
 
Join Date: Jul 2004
Location: Scottish Borders
you can fit a mute to the output of the DCB1,
or fit a mute to the input of your power amps.
or fit a cutoff in the power supply rails of the power amps,
or fit a crowbar to the output of the power amps.
All of these avoif placing any sound interfering relay in the speaker lead.
Finally a cutoff of amplifier output.

There is a recent discussion on replacing relays with FETs to improve the reliability of the cutoff and avoid some of the sound degrading properties of relays.
__________________
regards Andrew T.
  Reply With Quote
Old 1st October 2011, 01:07 PM   #66
Esperado is offline Esperado  France
Banned
 
Join Date: Jul 2011
Location: Portugal
Quote:
Originally Posted by RCruz View Post
Is it possible to implement one of these designs to control relays between the buffer output and the power amp ?
The purpose of a protection is to... protect. An amplifier can broke itself for a lot of reasons, then burn your valuable speakers. So there is two places you can only put relays, it is between power supply and amp, or between amp and loudspeaker. The first one can be ok in case of faillure, but not protect against power-on/off noises and DC . Devinitively, the best place is between amp and Loudspeakers. Of course, you can add an other relay in the Amp input, but why ? A well designed amp is able to manage any kind of signal at the input up to peak +-15v if no charge. And it is the max that can feed your preamp. More, you need to continue to compare the signal when the protection is "on", that suppose your amp continue to amplify the input signal: the protection will stay "on" until the input signal returns to a normal level/frequency range.
  Reply With Quote
Old 1st October 2011, 03:13 PM   #67
CopperTop is offline CopperTop  United Kingdom
diyAudio Member
 
Join Date: Feb 2009
Location: UK
Quad fitted a triac-based crowbar circuit to the Quad 405. It uses a Silicon Bilateral Switch to trip the triac at about 10V or so, with an RC delay. I don't know where to buy an SBS in the UK, but the data sheet for the device gives a transistor equivalent. I built it, and it seems to work fine. However, from what I can tell, I notice that Quad now doesn't bother with such a circuit, using a floating ground PSU topology that inherently protects against DC faults (although I think the energy in one of the caps has to discharge through the speaker).

Am I correct in thinking that series relays are not so good for this application because the contacts have a tendency to weld closed when attempting to open them during a high surge of DC?
  Reply With Quote
Old 1st October 2011, 03:41 PM   #68
Esperado is offline Esperado  France
Banned
 
Join Date: Jul 2011
Location: Portugal
Quote:
Originally Posted by CopperTop View Post
Am I correct in thinking that series relays are not so good for this application because the contacts have a tendency to weld closed when attempting to open them during a high surge of DC?
I don't think so, if the relay is correctly dimensioned and their contact well protected. But you can think about a more complex circuitry: Mos fet for switching followed by the relay, relay first followed by the Mosfet when protection switch on. Here the relay will be there only for reducing the serial impedance of the MosFet and will not deal with noticeable current or tension. I had tried-it. Not a difference in sound for an increased complexity, and never a problem of relay during 2 years on my personal 2x140W amp with a lot of output short circuit tests: forgotten on my side.
  Reply With Quote
Old 1st October 2011, 03:50 PM   #69
RCruz is offline RCruz  Switzerland
nhinstruments
diyAudio Member
 
RCruz's Avatar
 
Join Date: Sep 2006
Location: Wallis
Another simple DC protection
I need a protection on the output of the DCB1 because I want to use it in different amps.

I am using a simetric PSU (+-10V)... Is it easy to design a sensor that detects failure in one of the PSU´s (+ or -) and cuts out the output ?
__________________
RC
  Reply With Quote
Old 1st October 2011, 05:18 PM   #70
Esperado is offline Esperado  France
Banned
 
Join Date: Jul 2011
Location: Portugal
Quote:
Originally Posted by RCruz View Post
I need a protection on the output of the DCB1 because I want to use it in different amps.

I am using a simetric PSU (+-10V)... Is it easy to design a sensor that detects failure in one of the PSU´s (+ or -) and cuts out the output ?
A simple comparator between input and output signal of the amp does-it instant, as well as HF, clipping, switch-on " clocs" and DC errors. It is global !
  Reply With Quote

Reply


Another simple DC protectionHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
simple loudspeaker protection needed Flavio88 Multi-Way 0 11th January 2007 11:34 PM
A simple speaker protection circuit Russ White Parts 38 11th December 2006 01:39 PM
speaker protection (OR) overload protection myanmar Solid State 7 13th July 2006 08:21 AM
My first simple mains conditioner/surge protection: maxlorenz Parts 29 7th January 2006 05:53 PM
simple super-tweeter protection circuit Macdude443 Multi-Way 3 22nd December 2004 05:16 PM


New To Site? Need Help?

All times are GMT. The time now is 05:53 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki