Chinese speaker protection circuit kits

[audiogymp]

Hi

There are a range of low-cost speaker protection circuit boards and kits available from China. I recently bought/assembled the one in the photo attached. My initial impressions are reasonably positive, so I've started this thread to see if anyone has any comments about them and how they can be used.

The one in the photo was less than AU$10 inclusive of postage and is now selling at a little over $5. It seems to work fine. I hooked it up to an amp and the relays engage after a fews seconds - seems to work like a built-in protection circuit, although it needs its own power supply. I haven't tried it with amp-based DC but it responds to a AAA battery with the relays opening (and closing again a few seconds after removing battery DC).

Here is a link to an eBay listing, which will give you some basic info:
http://www.ebay.com.au/itm/1-Set-Au...045364?hash=item3f707af2b4:g:vvUAAOSwYIxX~zst

I'm not sure if it will protect the amp from a short circuit on the speaker line. Any thoughts?

It requires a power supply of 12-15V AC. I doubt it draws much current. There are a few different examples of this type of circuit for sale but they all seem to have about this power requirement. That said, it would be a simple matter to bypass the bridge to supply it with DC.

Some amps might have AC for a lamp or such at this voltage but I expect that this will be the exception.

Any thoughts about these circuits and what could be done to run them off the higher AC supplies in an amp if you wanted to incorporate one as a mod?

If nothing else, this one will find a use protecting test speakers.

 

[mbz]

I went for the slightly more expensive model, though basically the same.
http://www.ebay.com.au/itm/121317580107

I've yet to evaluate it, expecting it to provide power ON/OFF muting for "dc thump suppression" and also
detection of abnoramally high Vdc, say 1-1.5Vdc and above. These units won't provide over current/short
protection. All amps should have basic dc protection circuits. While these circuits are not state of the art
using questionable quality components they are basically all that's required for basic protection.

 

[gadget73]

Most of those things are only intended to protect the speaker from DC coming from the amp. It doesn't have any ability to monitor current on the speaker circuit in order to deal with shorts on that side. You'd have to set it per-amplifier anyway since each power level has a different max current.

you'd need to drop the internal voltage, depending on the input a simple LM7812 could do it, but that wants no more than 35v input. There are probably others that will take higher input voltages.