speaker level sub hookup on class D?

Magfan, you're right - I forgot about it.

Kij,
Yes, and I'd expect the 250ASP to also have 2 voltages. Since I own the ASP500 I haven't bothered to look at the other 2 modules.

Don't forget...and I don't know how this plays into it, that these modules are designed to power other B&O modules....from another series which are not self powered. So, for the ASP500 powering a lower power module, it may make sense to tap the 50v rail and if powering a 500 watt module, use the 80v rail.

If I were doing 'professional' sound reinforcement gear, this would be an option to look at.

Magfan, both 500ASP and 1000ASP have two voltages 50V/80V and 80V/120V respectively, where first (lower) voltage they call "preload". I'm not sure what it means but from my calculations they use higher of two voltages for output stage.

Thanks for half/full notes:
I think the IR module I have out in the garage is ALSO half bridge. The IR white paper lists some considerations for the designer when choosing to go with full or half bridge.

Isn't the 500ASP also 80v? My spec sheet lists 'Nominal DC voltage 1=50v' and 'Nominal DC voltage 2=80v'

Thanks to all who posted. Here is an update. I spoke with E.J. at Wyred 4 Sound and he told me to use a multimeter to measure Ohms at the subs speaker level input.

1. Measure from Pos to Neg on eacdh channel
2. Measure from the left and right neg. to plate amp ground, which I was able to use the outer ring of an RCA input jack.
3. Measure from left to right neg speaker inout leads.

He said they should not be zero. Well he was right, the left and right negative posts measured 200 Ohms across each other and 100 Ohms to ground for each one. The hot leads measured OL to ground, and OL to each other.

That gave me the confidence to try the hi-level inputs from the amp to the sub..... well it worked fine. I had to lower the sub volume a bit from the line level I was using, but not a whole lot.

Now, to answer everyone as to why I wanted to hook it up this way. You see my passive preamp was splitting the signal to the sub and my amp, but the highs sounded soft and muted. I think the reason was because of the input impedance of the sub is much lower than the amp, and placing them in parallel would change the input imp. of my amp from 64KOhm to just a bit under whatever the Velodyne sub was. So I was using an input tube buffer to help keep the impedance up, but a tube circuit in the subs line seemed like a waste of time and money.

So now I'm comming off the amp and it sounds great. Thanks to all who posted.

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.

Good to know.....ICE is 'half bridge' topology and makes sense for the whole thing to 'float'.

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.

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