My LM3875 Amplifier

[berthej]

BTW, the eBay ad listing for my SP kit mentioned that AC 10V-36V will work.
Quote:
FEATURES
'Ultra High Speed Reacting
'Independent Two Channel Design.
'Trigger Voltage DC 0.5V
'Military / Audio Grade Parts / OMRON High Current Relay
'Suitable for 10W-250W Power Amplifiers
'Delay Speaker Turn-On (Thump Killing Function)
'DC Output Protection. Disconnects the loudspeaker when DC appears .
'Wide Power Supply Range AC10V to 36V
'Build-In Regulator System

Hi John,

Thank you for the feature list, the ebay seller was removed before I got a chance to save the specs. Of course, thinking about it, the limit is given by the LM317 where Vin-Vout must be <40V. Vout=12volt, so Vin max is around 50 volt DC, fitting well with 36VAC.

Like you I was surprised to find that the DC protection measures from speaker + to common ground. I was planning to use this with a classD amp where speaker - is different from GND, and while + to - has little offset, there can be quite an offset from + to common GND, in which case the circuit will block. 😡

sorry for OTing a bit

 

[VictoriaGuy]

Sorry to keep taking this OT, folks..

Berthej-
I would have sent you email/pm, but you have that disabled-it saves the OT stuff.
Try this speaker protection board which I've bought. They seem to work- and come with instructions. This may do the trick for your amp.

Cheers
John

 

[bill6300gp]

I find out the schematic speaker protection which I used.