Jims Audio - 30A Speaker Protection Kit

[FlyAndy]

Hi,

I am a little confused about one of the connections to this kit. On the ebay page:

eBay.ph: Speaker protection circuit stereo kit 30A protection ! (item 320496814744 end time Aug 02, 2010 00:32:49 PHT)

It shows a connector with "Power Amp Output Connection"
I also attach the schematic with the connector circled.

Initially, I thought that this required connection to the 'output' of the amplifier - but this cant be the case, why would they not do this routing on the board?

Can anyone shed some light on the purpose of this connector?

Many thanks for your help!

Cheers,

Andy

[gootee]

Where did you get the schematic? I couldn't read yours so I went to the ebay page through your link, but can't find it.

[FlyAndy]

Hi Gootee,

I received the schematic after I purchased the kit.
If you click on the thumbnail, the image should enlarge. If you still are having trouble reading it, PM me your email address and I will email you a copy.

Many thanks.

Regards,

Andrew

[smartx21]

Your schematic is barely readable, but it must be a protection for unwanted DC voltages in the output (OR gate = either channel).
It will cut both outputs if DC is detected, which would damage speakers, for K1 is a dual relay.
Regards,
Max.

[FlyAndy]

I have put a copy of the schematic on the web - hopefully it is more easy to read:

http://img682.imageshack.us/img682/8...tection30a.jpg

[smartx21]

Could you post detailed scanned images of PCB, both sides?
This would help finding any mistake in schematic.

[Ian Finch]

Hi Andy
I see the difficulty you are having when I compare this circuit (which is sketchy to say the least) with Silicon Chip Magazine's newest universal design. Don't discount the probability that this circuit may have to work in tandem with similar circuitry, a headphone switching arrangement, fuse or even crowbar circuit. With 30 amp rating, it's bound to attract pro. attention where such features are common. Consequently, there will be a need to sense faults upstream of these circuits and so the separate leads.

There are two other sensor circuits shown there, probably a thermal switch (lower) and a muting connection to a 12V control circuit. Are they real or just suggested to add this feature? If they are onboard, a connection to a sense point or 12V circuit might help them to work.

I suggest you check for continuity between the input points,the relay contacts and the 22k sense resistors anyway and let logic take its course. If no connection, you will have to add it, here or upstream as you prefer.

[Nrik]

Oh...that is not too hard.
If the PCB actually is what the schematic promise, then you can see all the light-grey textmarkers at the 'empty' pins, telling exactly where it is connected to. I marked the different stuff:

[Nrik]

The overload protection circuit will react when the voltage over the emitter resistor is above 0.5-0.6Volts. So if the emitter resistor is 0.22 ohms, it will be at 0.5/0.22 = 2.2 ampere, or 39Watt peak (19,5W rms) in 8 ohms.
To increase the allowed output current, add a resistor-divider between the emitter-resistor and the sensor input.

[ppcblaster]

Originally Posted by FlyAndy

Hi,

I am a little confused about one of the connections to this kit. On the ebay page:

eBay.ph: Speaker protection circuit stereo kit 30A protection ! (item 320496814744 end time Aug 02, 2010 00:32:49 PHT)

It shows a connector with "Power Amp Output Connection"
I also attach the schematic with the connector circled.

Initially, I thought that this required connection to the 'output' of the amplifier - but this cant be the case, why would they not do this routing on the board?

Can anyone shed some light on the purpose of this connector?

Many thanks for your help!

Cheers,

Andy

Anyone know what gets wired to the "L", "R"?