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speaker level sub hookup on class D?

I have a W4S ICE amp and was wondering if it would be OK to use the hi level speaker inputs on my Velodyne DD-15 sub? Reason being that the amp is fully balanced differential something and my sub seems to sum both channels to a mono signal. Since my amp does not use a common ground is it OK to do this? I have already asked W4S and they were not sure. Velodyne tech help is away until after the New Year. I would like to run wires from my amp output to the subs hi level input. Thanks for all replies.
koestner
kr4's avatar
kr4
3,707 posts
 
I suspect that you can but I really wonder why. The sub will only convert that input to line level for its own internal amp and processing. The additional amp is adding nothing except its own noise and distortion; low though that may be, there's no reason to add it.

Do you have a line-level mono signal for the sub?

Kal
kijanki's avatar
kijanki
4,451 posts
 
Outputs on Icepower amp behave the same way as outputs of the bridged amplifier - both terminals of each output are active. If your Velodyne has both speaker level inputs referenced to same level (internal GND) it will short Icepower amp. This connection is only possible if Velodyne speaker level inputs are balanced or floating/isolated.

I second what Kal said - why bother? You have line level mono input and line level stereo inputs on your Velodyne. As long as you have mono signal out or two stereo outs you can make safer and better connection.
magfan
1,583 posts
 
Good to know.....ICE is 'half bridge' topology and makes sense for the whole thing to 'float'.
kijanki's avatar
kijanki
4,451 posts
 
Magfan, ICE is 'full bridge' meaning that load (common mode choke, zobel network, speaker) is placed across the bridge of four Mosfets while two other arms of the bridge are GND and +VCC. At one state two Mosfets on opposite (diagonal) arms of the bridge are conducting while at the other state two other arms are conducting. Speaker is always connected between +Vcc and GND but polarity changes (at about 0.5 MHz). Zero output is when Mosfets switch at 50% duty cycle (perfect square wave). Each of the speaker wires is switched between +Vcc and GND making voltage (since it is filtered by common mode choke and zobel) equal +Vcc/2 hence difference between them is zero. Placing DC voltmeter between any terminal of the speaker connected to ICE amp (with no signal) and earth ground will show half of the module supply voltage. In case of largest 1000ASP module it should be +40V since module has +80V supply. 40V vs. GND is still safe voltage but I would not touch such terminals with wet fingers or tongue.

Half bridge, used in Hypex (Channel Island), has only two Mosfet switches but two opposite voltages +Vcc and -Vcc. One speaker terminal is always connected to GND while the other is switched between +Vcc and -Vcc according to duty cycle.

Each configuration has advantages but one obvious disadvantage of 'full bridge' is inability to further bridge amplifier (for more power) or use for some subs.
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