Am I likely to blow up my amplifier?

Here's a typical example:

Have you looked into whether HDMI ARC (audio return channel) would help you?

Thanks for the thought.

The Denon does actually offer a second Zone 2 audio feed which is pre-out, bypassing te power amp, and that would be ideal - if I could persuade it to work, which I can't. Searching around the various AV forums and help sites, it seems I'm not alone: you need an advanced Masters degree from Hogwarts to coax it into life, and even then you also need a healthy helping of sheer luck.

Which is why I was so pleased when I discovered the HDMI separator thing. Am I right in thinking that it wouldn't be a good idea to plug its audio output into a second amp?

Would be safe to connect any HMDI-OUT port to any HDMI-IN, no guarantee it will work if e.g. HDCP gets upset by what it thinks you're doing.

I don't think you'll do any damage because the high impedance input of the amp will limit the current which results from the (relatively) high voltage speaker output.

If you're worried you could always use something to provide impedance matching and attenuation, such as:

Thanks for that. I took an experimental plunge and acquired the unit. Whatever the reason, you were quite right: the separated audio feed generated a signal completely akin to the other sources feeding the external amp.

The unit I have supplies a complete HDMI feed which I connected to a TV: both audio and video passed through with no level problems.

But...

I did run into other snags. Not all source material makes it through the unit unscathed. In particular, the audio from Sky HD channels either doesn't make it all or loses the centre front channel. The same is true of some files from my media player. This happens whatever combination of settings I try on my Denon amp and on the unit itself.

So more experimentation is required...

I use something similar to intercept the HDMI output of a Chromecast to a monitor, and fee stereo audio into a line level input on a Cambridge Audio amp. Works fine.

I had only limited success: the unit I bought gave three outputs: HDMI, digital audio (via a 3.5mm socket) and optical audio. The full HDMI-out (connected to a TV in another room) worked flawlessly, but the separated audio (fed to a second amp) proved fussy: with (for example) my Sky+ box as a source, the only audio ouput was from SD programmes with two channel sound. Anything else produced only silence.

I tried every combination of settings I could manage, both on the Denon amp and the separator box itself, to no avail.

For clarification, the "Works fine" claim was specifically about the compatibility of a headphone out being used to drive a line in input of an amp.

The ability to work with different audio streams encoded down the HDMI is a somewhat different topic. That will depend on the capabilities of the audio extractor, and its software and how that plays with your various source devices. It might even come down to licensing and things like HDCP compatibility (although if it were a HDCP issue, I would expect you to lose video as well - or at least have the resolution downgraded to SD).

On my one, I have not had any content where the audio extraction did not work, however I have only used it with one source, a chromecast.

In my case it seems that it depends on the amplifier: I emailed Denon tech support about the problem and they got back to me splendidly quickly. They sent a long and detailed reply but the core fact is this: on the Denon AVC X300H (and possibly on the entire range) the Zone 2 pre-outs can only handle 2-channel PCM audio: any multi-channel input is rendered as silence.

So my clever plan is a non-starter. Oh well.

Could you move the audio extractor to the *input* on the amp? Obviously that then only catches audio from one source device.. although I suppose you could have more than one extractor and then mix the analogue audio from multiple ones into the amp.

Ingenious! But unfortunately, as you say, the entire point was to take the output of the amp whichever source was selected. And multiple extractors would really be complicating things more than the eventual result would justify, I think.

But thanks for the thoughts.

Another option to check is if the TV has a facility to drive an external amp or speakers... it might be able to present its audio on a set of phono sockets (or even a headphone out - although that might mute its internal audio)

In the early hours of this morning another possible approach suddenly occurred to me, so blindingly obvious that I hadn't come anywhere near to it before.

I'll try it after breakfast and report back...

Well, that was a short-lived experiment: it didn't work.