battery powered 3875

[garbage]

hi all

i p2p a 3875 gc running on 4 SLA 12v batteries.
the only psu caps i have are 2 47uF silmic ars at each chip itself.

ran them without cap initially, but got some crackles when i turned up the volume.

just wondering if anyone experienced turn on/off thump with a 3875 on batteries? there is no mute pin on 3875, any one has ways to solve this thumping?

would a relay on outputs help with turn off thump as well?

thanks.

 

[garbage]

no one's replying...

maybe some pics would help?

in the test rig

An externally hosted image should be here but it was not working when we last tested it.

closer shot of the chips

An externally hosted image should be here but it was not working when we last tested it.

is it normal for 3875 to have turn on/off thumps?
there is a thread in here that suggested using a switch on speaker outputs to switch in/out the speaker after and before turn on and turn off.

 

[scottw]

Yes, they can thump with a battery power supply. I can't tell from the pics how you are switching on the power but it helps if both rails(+&-) switch at exactly the same time. If you are already using a double pole switch for power try a different switch. I had a breadboard battery powered GC that had a separate switch for each rail and even trying to switch them at the same time would cause wild cone movements on my cheap test speakers.

Increasing the cap size(~1000uf) may also reduce the thump but may change the voicing of the amp.

good luck,

Scott

 

[garbage]

hi scott

thanks for your reply.

i'm only switching at 0 now. will be getting a 4P2T/3T switch so that i can switch +, 0 and - and also to toggle between batteries and charging.

4P is required as i would be using 2 x L200CV. one L200CV to charge 2 x 12v cells.

the 47uF value was suggested by peter daniels in response to one of my questions on this forum. when i was using w/o psu caps, the turn on/off is not that audible.

cheers
vincent

 

[DT]

try to switch battery PS with relays.