If you don't use the inputs, short them instead of leaving them open.
No, the amp would still be oscillating and switching, just at a 50/50 pulse width ratio.
What you can do is put diodes on the unused outputs that clamp the output voltage to the supply rails.
Better to use a couple of 8 ohm resistors.
Check if all chips are indeed sta508, you have several ampboards and 4 per ampboard I assume, chinese robots make mistakes 
then open sta508 datasheet and check the chippins of all chips, I looked at one foto and quickly looked at others and it looked the same, but not my ampboards. Chippins like that, I don't know how to make them disappear, what it would take, or maybe only foto suggests some are totally gone but in reality they still are on chip?
then open sta508 datasheet and check the chippins of all chips, I looked at one foto and quickly looked at others and it looked the same, but not my ampboards. Chippins like that, I don't know how to make them disappear, what it would take, or maybe only foto suggests some are totally gone but in reality they still are on chip?
If you short the inputs and then put a small-ish (say, 5w ceramic to be safe) on the unused outputs, I'd expect that to negate any oscillation conditions on the unused channels. It needn't be a high-power resistor, since all you're doing is completing the low-pass filter, rather than leaving it as a resonant notch filter.
The battery switching problem looks interesting, too. Definitely use a switch in future.
Oh, and make sure your batteries have fuses as close as possible to their terminals. If you develop a short somewhere, a popped fuse is fine. A popped battery could put you in hospital.
Chris
The battery switching problem looks interesting, too. Definitely use a switch in future.
Oh, and make sure your batteries have fuses as close as possible to their terminals. If you develop a short somewhere, a popped fuse is fine. A popped battery could put you in hospital.
Chris
You should short out the inputs to the unused amplifier channels and terminate the outputs with 8 ohm resistors. Leaving inputs open will allow them to pick-up all sorts of signals they may also oscillate causing them to overheat and overload. These are Class D amplifiers and must have the outputs terminated in a load or they will oscillate. If the inputs are shorted then there will be no significant output so the load resistors only need to be about 1 watt.
By shorting the inputs I mean connecting the signal input terminal on each unused channel to the earth point.
By shorting the inputs I mean connecting the signal input terminal on each unused channel to the earth point.
Could someone please advise me exactly how/where to solder this onto the board if possible? and if i am running at 30v 400w max do i get the sac26 or sac30 or sac36?
400W is a lot of noise. You've already had 2 of these blow up. When I want more power, you say. How much power do you want?
If you really need these power levels, you should think about trying to obtain them from an amp that is not being run at 100% continuously.
There could be a generic fault, but the chances are they blew up because you treated them a bit cavalierly. Settle down to a permanent or semipermanent arrangement and try not to cause any undue stress such as at switch-on or when plugging or unplugging speakers. Do not hot-swap.
1:
run 12v from 1 of my 12v bats (2x 12v in series 24v supply) to power my effects pedal at the same time (would this be likely to cause such a fatality?)
Yes.. I'll bet your issue is a ground loop issue. "Shield" is not always "Common" to the power source. A simple isolation transformer between any audio connection to another device will cure your problem..
You should never half tap a battery to get a voltage you need, in your case, half tapping to get 12 volts to run another device in your system.
When you half tap, you may find the voltage you need but you must remember the 24 volt device is always at a different ground potential.. (Re: Amp/24 volts.. Effects Pedal/12 volts) The commons between the two could be different as much as 12 volts!
Hope this helps..
run 12v from 1 of my 12v bats (2x 12v in series 24v supply) to power my effects pedal at the same time (would this be likely to cause such a fatality?)
Yes.. I'll bet your issue is a ground loop issue. "Shield" is not always "Common" to the power source. A simple isolation transformer between any audio connection to another device will cure your problem..
You should never half tap a battery to get a voltage you need, in your case, half tapping to get 12 volts to run another device in your system.
When you half tap, you may find the voltage you need but you must remember the 24 volt device is always at a different ground potential.. (Re: Amp/24 volts.. Effects Pedal/12 volts) The commons between the two could be different as much as 12 volts!
Hope this helps..
It's easy as is, just solder in parallel with the amp, cathode to plus. If used as a crowbar, put a fuse in series with the amp right before the diode, so when clamped, fuse gets blown. At normal, the diode is not carting any current.
@ Julf..
I've made the same mistake myself. Fried a brand new TV while connecting an amp via the earphone jack for some external speakers. Both were connected to a common battery but obviously the shield potentials were at different values. (Both were 12 v.d.c. items)
It worked for a while but I noticed the audio was a little low and slightly distorted. I didn't heed the warnings. I just cranked the volume up, figuring that's just about the way it is..
A few days later, I turned on the TV and left the room to get a beer and noticed no sound. Went back to the room where the TV is and all I seen was smoke! Although everything was fused properly, not one popped! Didn't hurt the external amp but destroyed the audio section of the TV..
From that day forward, I made it common practice to use isolation between everything dealing with audio powered from my common battery. (Whole house operates @ 12 V.D.C.)
I've made the same mistake myself. Fried a brand new TV while connecting an amp via the earphone jack for some external speakers. Both were connected to a common battery but obviously the shield potentials were at different values. (Both were 12 v.d.c. items)
It worked for a while but I noticed the audio was a little low and slightly distorted. I didn't heed the warnings. I just cranked the volume up, figuring that's just about the way it is..
A few days later, I turned on the TV and left the room to get a beer and noticed no sound. Went back to the room where the TV is and all I seen was smoke! Although everything was fused properly, not one popped! Didn't hurt the external amp but destroyed the audio section of the TV..
From that day forward, I made it common practice to use isolation between everything dealing with audio powered from my common battery. (Whole house operates @ 12 V.D.C.)
We won't talk about the 20 installs I did in 24 volt school busses, half tapping the battery to get 12 v.d.c. for the 2-way radios. Ran the common/red lead directly to the battery. (Radio common before the Cole-Hersee switch that disconnects the battery from the vehicle) Whoops..
Heh, yes. I am so glad I never make mistakes like that.
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