You can find such speaker protection boards on Ebay, Amazon etc...
As an example I show you one AIYIMA 12 18V UPC1237 panneau de Protection de haut parleur kit de carte de Protection de haut parleur partie retard de demarrage moniteur DC-in Amplificateur from Electronique on AliExpress . I have NOT tried this one as I do not use one myself.
As an example I show you one AIYIMA 12 18V UPC1237 panneau de Protection de haut parleur kit de carte de Protection de haut parleur partie retard de demarrage moniteur DC-in Amplificateur from Electronique on AliExpress . I have NOT tried this one as I do not use one myself.
I've used this one in another application. It seems well made and will do the job although it needs a (small) separate supply I you want to avoid turn-off thump /noises too. It also provides DC offset protection.
UPC1237 Speaker Protection Board AC 12V-24V OMRON Relay for stereo 2 channels Amplifier
AliExpress
I modified mine so that it would (hopefully!) "crowbar" the amp should the relay contacts weld due to high current, protecting the speakers - however that scenario seems unlikely with an lm1875.
The supply transformer I used was this one
PE2820-I Power 3VA 230V/12V Expory resign encapsulated safety isolating transformer PCB Welding transformer power transformer
AliExpress
UPC1237 Speaker Protection Board AC 12V-24V OMRON Relay for stereo 2 channels Amplifier
AliExpress
I modified mine so that it would (hopefully!) "crowbar" the amp should the relay contacts weld due to high current, protecting the speakers - however that scenario seems unlikely with an lm1875.
The supply transformer I used was this one
PE2820-I Power 3VA 230V/12V Expory resign encapsulated safety isolating transformer PCB Welding transformer power transformer
AliExpress
LM1875 has no mute circuit and requires one for both turn-on and especially turn-off. Else you will hear that pop.
I use the one below
Hi, can you tell me more about this circuit? I mean supply voltage and about delay time. I want to use 30-36vAC CT transformer for lm1875.
Hi, can you tell me more about this circuit?
I run the one in #3 off the same rail as the amp. 34VCT for 23V rails under load. 24V relay, and delay time is calculated with time constant of R1xC1.
I used, from memory, 47k and 22uF but it could have been different.
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- Noise in the loudspeakers when my LM1875 are turned on