Ampeg SVT5 Pro

[Jazz P Bass]

Does anybody know why Ampeg SVT 5 pro output relay grounds the outputs when it is off?
I have a repair here that requires a relay.
The one that I have is SPST.
The one that is in the amp is SPDT. NC contact grounds the speaker jack.
If I use the SPST relay, the speaker out jack will not reach ground when off.
Will this be a problem?

[Jazz P Bass]

Ampeg SVT 5 speaker relay

In searching the internet I stumbled upon the answer, as given by good old Rod Elliott.
Loudspeaker Protection and Muting
Quote:"The DC arc can (and does) destroy even 10A relays under some circumstances. To provide greater speaker protection, the relay wiring in Figure 2 is designed to short the speaker to earth in case of a fault. This way, even if the contacts do arc it will be directly to earth. This is much safer (for the speakers), and the arc to earth will blow the fuse a lot faster than if an 8 ohm load is a part of the circuit. It is strongly recommended that this scheme is used as a matter of course. It is worth noting that any DC protection system that does not use this method will almost certainly fail to protect the speakers with a medium to high powered amplifier. (My thanks to Phil Allison for the information.)"

I am buying the correct relay!SPDT
Thanks Rod.