TOPIC:

dirkwright wrote:

john.reekie wrote:

What on earth does FCC compliance have to do the AES/EBU buffer?

You apparently do not understand how RFI works then... and how cascaded interference can be a problem. Please see the documents I have provided for more information.

Apparently not. Can you provide a short version of RFI and cascaded interference for the dummies?

I'm sorry, but I don't have five or six units and/or cables that are 30 feet long.
But regardless, cables are a variable that would exist in any setup with any brand/type of unit and are not specific to this particular PWR-ICE unit. (At least regarding the latency aspect.)
You asked originally about the latency of the buffer feed-through of the PWR-ICE unit itself. Cables and cable length are irrelevant in that context, yes?

I'm not sure how you're determining if using five or six PWR-ICE units is a bad idea. Regardless, using your logic, five or six units from any manufacturer with 10 meters of AES interconnects would be a bad idea.

Dave.

There's no 10m limit, Dirk has misunderstood the following sentence in one of the papers he references: "Data signals start to suffer transmission line effects after only ten metres or so." This is by way of preamble to the guidelines on AES/EBU installation, they key points being 110 (more or less) ohm cable and 110 ohm terminations. With that, you're good up to about 150 meters... (according to that same paper).

dreite wrote:

I'm sorry, but I don't have five or six units and/or cables that are 30 feet long.
But regardless, cables are a variable that would exist in any setup with any brand/type of unit and are not specific to this particular PWR-ICE unit. (At least regarding the latency aspect.).

Maybe, maybe not. It depends on the quality of the installed equipment, including the cables. From what I can determine for these PWR-ICE plate amps, their AES interface is very basic.

dreite wrote:

You asked originally about the latency of the buffer feed-through of the PWR-ICE unit itself. Cables and cable length are irrelevant in that context, yes?.

Um, no. I asked what the latency was for a cascaded chain of PWR-ICE plate amps would be, not just the buffer inside the plate amps. I wanted to know what were the limits for an installation, among other things.

dreite wrote:

I'm not sure how you're determining if using five or six PWR-ICE units is a bad idea. Regardless, using your logic, five or six units from any manufacturer with 10 meters of AES interconnects would be a bad idea.

Dave.

Well, as I said, it depends on the equipment installed. If the parts are high quality, then there may not be a problem with cascading many of them.

john.reekie wrote:

There's no 10m limit, Dirk has misunderstood the following sentence in one of the papers he references: "Data signals start to suffer transmission line effects after only ten metres or so." This is by way of preamble to the guidelines on AES/EBU installation, they key points being 110 (more or less) ohm cable and 110 ohm terminations. With that, you're good up to about 150 meters... (according to that same paper).

I did not say there was a 10 meter limit. I intended to say that problems can start to show up at 10 meters of total or individual cable length. Obviously, whether or not there are problems depends on the quality of the installed equipment, including the cables and connectors.

In order to pass the 6.1 MHz clock used in some implementations of AES/EBU, the entire system has to have a bandwidth of at least 30MHz in order to avoid problems. Whether or not this equipment is capable of that is unknown to me, but I don't see good RF style engineering on the circuit boards in my units.

john.reekie wrote:

Apparently not. Can you provide a short version of RFI and cascaded interference for the dummies?

You're not a dummy, so no I don't have to explain it to you. I'm not playin games here, sorry.

FYI:
"Let's scale things back up to deal with real-world sounds, made up as they are of heaps of different sine waves at different frequencies, each one fading in and out as the pitch and timbre change. If we feed a drum loop to our two mixer channels, instead of a single sine wave, any delay in the second channel will have a dramatic effect on the tonality of the combined signal, rather than just altering its level. The reason for this is that, for a given delay, the phase relationships between sine waves on the first channel and those on the second channel depends on the frequency of each individual sine wave. So, for example, a 0.5ms delay in the second channel will put any 1kHz sine-wave components (the waveforms of which repeat every 1ms) 180 degrees out of phase with those on the first channel, resulting in total phase cancellation. On the other hand, any 2kHz sine wave components (the waveforms of which repeat every 0.5ms) will remain perfectly in phase. As the frequency of the sine wave components increases from 1kHz to 2kHz, the total phase cancellation becomes only partial, and the level increases towards the perfect phase alignment at 2kHz.

Of course, above 2kHz the sine wave components begin partially phase-cancelling again, and if you're quick with your mental arithmetic you'll have spotted that total phase cancellation will also occur at 3kHz, 5kHz, 7kHz, and so on up the frequency spectrum, while at 4kHz, 6kHz, 8Hz, and so, on the sine-wave components will be exactly in phase. This produces a characteristic series of regularly-spaced peaks and troughs in the combined frequency response of our drum loop — an effect called comb filtering (see the box below).

A delay of just 0.000025s (a 40th of a millisecond) between the two channels will cause total phase cancellation at 20kHz, but you'll also hear partial phase cancellation at frequencies below this. As the delay increases, the comb-filter response marches further down the frequency spectrum, trailing its pattern of peaks and troughs behind it, which themselves get closer and closer together. However, when the delay times reach beyond about 25ms or so (depending on the sound in question), our ears start to discern the higher frequencies of the delayed signal as distinct echoes, rather than as a timbral change, and as the delay time increases phase cancellation is restricted to progressively lower frequencies."

www.soundonsound.com/sos/apr08/articles/phasedemystified.htm

Here's a comparison plot for you to examine/ponder: Blue is monitored PWR-ICE125 digital input, red is PWR-ICE125 digital (feedthrough) output.
The major horizontal divisions are 0.5 microseconds. THe entire window is 5 microseconds wide.

Dave.