DC protection Velleman K4701 - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 10th May 2008, 01:05 PM   #1
diyAudio Member
 
Join Date: Jan 2007
Default DC protection Velleman K4701

I am rebuilding a DIY amp I built many years ago using Elliot P3a power amps.

I realise I need DC protection for the speakers and obviously Rod's P33 project would be a good choice. Problem is no room in the case.

All I need is the DC protection not the soft start or muting. Came across the Velleman K4701 kit that fits in the speaker cabinet and disconnects the amp when DC is present.

It needs no auxillary supply so must get its power from the speaker line - and here is the question. Will it affect sound quality because of this? Anyone any experience of it?
  Reply With Quote
Old 10th May 2008, 01:38 PM   #2
diyAudio Member
 
Join Date: Nov 2002
It gets its power supply from the amplifiers power supply. I'm sure there would have to be load dropping resistors from the main supply in order to power this unit. Not the best Velleman kit to choose in my opinion. Velleman has another one with its own 6 volt supply on board and it is a much better piece.

There are those here that will argue that they hear a difference between a signal going thru a relay as opposed to going straight to the speaker. I do not hear any such difference.

While your system is much more primitave than other more expensive sounding systems there is still a need to try to guard against any damage that might rear its ugly head.
  Reply With Quote
Old 10th May 2008, 05:13 PM   #3
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
I think it probably uses any DC offset present to power the relay.
Don't you just connect it in series with the speaker. It should have no audible effect in practice, and although it's not the ideal way it has to be better than nothing.
Regards Karl
  Reply With Quote
Old 10th May 2008, 05:33 PM   #4
diyAudio Member
 
theAnonymous1's Avatar
 
Join Date: Feb 2004
Location: Anonymityville
The other Velleman kit is the K4700. Below is a guide to improve the circuit.

http://www.anidian.com/audio/deconstruct/k4700.shtml
  Reply With Quote
Old 10th May 2008, 07:48 PM   #5
diyAudio Member
 
Join Date: Nov 2002
Quote:
I think it probably uses any DC offset present to power the relay.
I don't think so... It would take a heap of DC offset to power the relay.

Go with the 4700 and make the modifications.
  Reply With Quote
Old 10th May 2008, 08:56 PM   #6
diyAudio Member
 
nigelwright7557's Avatar
 
Join Date: Apr 2008
Location: Carlisle, England
The same job can be done with a very basic PIC micro and a relay and a few other components.

I use a PIC12C508, its only 8 pins but it does the job very well.

Mine holds off the realy on power up for 3 seconds.
If the DC level stays above 20 volts or below -20 volts for 500ms it imediately drops the relay.

I use the PIC inputs as comparators using voltage dividers.
I know fro mexperience the threshold for a PIC (5V VCC) input
is 2 volts.

If you want the circuit and software let me know.

Nigel
__________________
PCBCAD50 software. http://www.murtonpikesystems.co.uk
  Reply With Quote
Old 11th May 2008, 02:13 AM   #7
diyAudio Member
 
theAnonymous1's Avatar
 
Join Date: Feb 2004
Location: Anonymityville
Quote:
Originally posted by burnedfingers
I don't think so... It would take a heap of DC offset to power the relay.
I believe it takes at least 10vdc to trigger the relay with the K4701.
  Reply With Quote
Old 11th May 2008, 02:55 AM   #8
diyAudio Member
 
Join Date: Nov 2002
Quote:
I believe it takes at least 10vdc to trigger the relay with the K4701.
That is why I recommend using the 4700. The 4700 trips with 1VDC. While 1VDC is a little much it is still far better than 10 or 20 volts.
  Reply With Quote
Old 11th May 2008, 08:14 AM   #9
diyAudio Member
 
Join Date: Jan 2007
Thanks for the input guys

I will certainly give this more thought. The 4700 kit with mods may be a better alternative but I will need another box to put it in.

I suppose if the amp has a serious fault it will give full supply rail voltage to the speakers (35V) and even the 4701 kit would prevent this.
  Reply With Quote
Old 11th May 2008, 09:42 AM   #10
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
Quote:
Originally posted by burnedfingers


I don't think so... It would take a heap of DC offset to power the relay.

Go with the 4700 and make the modifications.
Hi, had a look on the Velleman web site, No extra PSU needed, uses the DC offset to operate the relay, that's why I said it was less than ideal, but there you go. I don't know what minimum voltage is needed to trip it
Regards Karl
  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
modify Velleman kit protection cld1354 Solid State 6 3rd January 2007 10:32 AM
Are these Velleman speaker protection modules any good? Spasticteapot Parts 3 7th November 2006 06:43 PM
velleman k4700 speaker protection circuit cyteen Solid State 6 27th May 2005 03:16 PM
speaker protection velleman k4700 wuffer Multi-Way 2 1st March 2005 05:09 PM
FS/trade: Velleman K4701 x2 Cobra2 Swap Meet 0 12th January 2004 11:10 AM


New To Site? Need Help?

All times are GMT. The time now is 08:40 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