Peter- not sure if you can answer this one. I go right from NOS1 to K&H active speakers so I can't test for a DC on the speaker out terminal as you post. Is there any way I can tell what will happen if I engage PA? Is there a safe way to tiptoe in, with lots of attenuation? Or nothing but cross my fingers?
Attenuation will not help. Better would be to use a battery with a > 47kohm potentiometer in series with the input of your amp/speaker to create your own DC Voltage.
The battery will then be your "NOS1" for a while.
This way you can just give it just a little DC and see how the woofer reacts (or if the amps safety circuit - if present - helps you out).
Another advantage is that this test can be very short making things burn less obvious if DC is to become a problem. Just disconnect the battery and the DC is gone again...and that works a lot faster than trying to stop XX playing!
Do measure the manually created DC first before you connect to check though and keep it low at first. 50mV should not give a problem to any amplifier and then check what is the Voltage at the output of the amplifier.
If you're not sure how to do this or when you have no idea what I am talking about then DO NOT APPLY or simply use PA and cross your fingers...or ask the manufacturer of your speakers if the amps are DC protected or have somebody come over with knowledge and check it for you.
If DC is a problem then you will NOT have time to cross your fingers...
BTW, People with tube amplifiers should not be worried to try the above, those amps always (99% sure) have a capacitor on their inputs. Not to protect the amp from external DC but to protect eveything else connected to the amp itself for its own DC (300V-1200V!).
Bert
