G'day Guys,
A question of design.
If one were using a DPST relay for the protection of a single channel of an amplifier.
Is one better to run the 2 poles in series or in parallel.
I have seen it suggested somewhere that running the poles in series provides more chance of breaking a fault current.
A question of design.
If one were using a DPST relay for the protection of a single channel of an amplifier.
Is one better to run the 2 poles in series or in parallel.
I have seen it suggested somewhere that running the poles in series provides more chance of breaking a fault current.
But parallel reduces the effect of the contact resistance building up due to oxidation over time, and reduces the current per contact which might reduce the chance of contacts welding.
However you do it, one contact will open slightly earlier than the other the whole current gets diverted to one contact anyway.
Perhaps better to find a higher current rated SPST relay?
However you do it, one contact will open slightly earlier than the other the whole current gets diverted to one contact anyway.
Perhaps better to find a higher current rated SPST relay?
Parallel would be best for high current and low voltage rails. BUT... in reality, high current also tends to be associated with reasonably high voltage DC rails. And a relay's DC rating is typically 'much' less than its AC rating. Which is a problem when the DC is enough to sustain an arc across the relay contacts; the drivers will still be hammered via the arc - should the amp's output devices fail.
In the absence of a huge costly industrial relay with a massive gap, then yes series contacts may help to break the arc. So you would end up with multiple relays in parallel and series to cover both bases. However, Rod/Rode on his ESP site has suggested using double throw relays instead, with the 'off/open' pin grounded. The arc will sustain, but will then be directed more to ground rather than via the speaker-driver. After some short time later a fuse should blow, if there is one.
The relays for that still need to be pretty chunky, but are considered sacrificial, in preserving the drivers. Which I feel is sensible, because a relay that could properly handle the current and DC voltages of a reasonably sized amp failing would be extremely costly, and it shouldn't happen often.
Obviously, this post is about an amp actually failing; protection just against turn-on thumps (via a delay) is much less demanding.
In the absence of a huge costly industrial relay with a massive gap, then yes series contacts may help to break the arc. So you would end up with multiple relays in parallel and series to cover both bases. However, Rod/Rode on his ESP site has suggested using double throw relays instead, with the 'off/open' pin grounded. The arc will sustain, but will then be directed more to ground rather than via the speaker-driver. After some short time later a fuse should blow, if there is one.
The relays for that still need to be pretty chunky, but are considered sacrificial, in preserving the drivers. Which I feel is sensible, because a relay that could properly handle the current and DC voltages of a reasonably sized amp failing would be extremely costly, and it shouldn't happen often.
Obviously, this post is about an amp actually failing; protection just against turn-on thumps (via a delay) is much less demanding.