Effect of incorrect load

relic245

Why would this happen?

Signal chain is Drive pedals into blackstar amped1 driving the speaker of a Peavey bandit.

All was well until recently I started noticing some background noise. I would describe it as what some people call digital artifacts. Hard to describe but something in the sound that shouldn't be there.

Turns out that id reconnect the bandit amp and forgotten. Although the bandit wasn't powered up its output stage was connected to the speaker as was the amped1.

Just curious why that would alter the sounds. 

If it's too technical then probably don't answer as it will probably go over my head

Modulus_Amps

You have changed the load the amped 1 sees. 

if you are very unlucky you could blow both the peavey and the amped one by doing this.
If you are lucky nothing has been damaged but don't ever do it again.

If you plan to use the bandit speaker I would get a junction box fitted that forces you to only ever have one amp connected to the speaker at a time.

relic245

Wow thanks for the warning.

The stupid thing is I did fit a junction box with a jack for the amped1 to plug  into. I never got round to fitting a jack on the bandit out and just disconnect the spade connector. 

Then it was so easy to reconnect it again but clearly forgot that I had done.

Again thanks for explaining and for the warning.

Modulus_Amps

hardwire the speaker to the junction box on the rear, then put only one input into the junction box so you can only plug one thing in at a time.

I had a friend many years ago blow up two Ashdown bass rig combo's by doing what you did, cost him a fortune to get both amps fixed fixed and one wasn't even his.

ecc83

I have read several reviews of the "Amped" amps and wondered why they state the minimum load as 8 Ohms? Most modern transistor OP stages are rated at full power into 4 Ohms.

I was told that the design does deliver its full power into 8R but it will not be damaged by 4R, it will not however work at its best.

I conclude therefore that the weird load you imposed caused the protection circuits to kick in and they caused the nasty noises. Kudos!

Temping fate I know but I am yet to read of anyone destroying any Blackstar solid state amplifier?

Dave.

Danny1969

Normally with class D you have a PID controller feeding back into the PWM as error control. It's a sophisticated system used to protect the output from all kinds of things including the MOSFETS shorting through each other. 
If I understand what you did then the output stage of the Bandit was in parallel with the speaker and connected to the Amped 1 ... this could have presented almost a direct short to the  Amped 1 ... could easily have damaged it and you may have shortened the life of the output switching MOSFETS .

If you get a 4 connector Cliff socket or similar and wire the speaker to the conductors that lift up in contact with the jack plug and connect the output of the Peavey to the other 2 static conductors then plugging into the socket will automatically disconnect the Peavey making this accident impossible 

ICBM

I’ve come across this quite a few times when people have seen the ‘extension speaker’ jack on the back of a combo and thought that means you can use it *as* an extension speaker, for another combo or just to plug a head into. It often doesn’t end well for one or both amps, even if they’re types that are normally robust.

As already said the output stage of the amp you’re plugging into acts as a very low-impedance load on the one that’s connected to it, even if the ‘receiving’ amp is turned off. You’ve probably got more chance of one or both of them surviving if they’re valve amps, but I still wouldn’t try it.