Archive

Posts Tagged ‘home theater’

In the zone (hacking the Denon AVR1905 to become multi-zone)

May 12, 2012 Leave a comment

Previously, on home improvement: I bought a Denon 1905 7.1 amplifier, to serve surround sound in the living room and stereo music to the kitchen.

To my horror, when I came home and turned it on, it didn’t have “Zone 2”.

WTF?! The product brochures I found on the internet said it has it. The product manual specified clearly how it should be operated. (well,

The remote didn’t have a “Zone 2” option on its mode selector, and the on-screen menu ended at option 24 (the manual I found on the internet says option 25 is “Power Amp Assignment” – that’s the one you use to switch between 7-channels and 5+2 channels). Argh!

The downside of buying an 8-year-old amp is, it lacks internet resources. It took an afternoon of internet searching before I found someone commenting,

“Sorry for flogging a dead horse, but doesn’t the 1905 Singapore version not have the Zone 2 capability? That’s what irritated me because I couldn’t really rely on reviews written by US reviewers. “

Which could either mean Denon models differ between territories, or that some local distributors are re-numbering the models. So I downloaded its service manual and opened it up to compare the board models, and they match: it really is a 1905. That’s frustrating, but also provides a glimmer of hope: Denon already issue 5-10 amplifier models each year, which is a lot. I bet they wouldn’t want to issue 3-4 times that number in models.

So I started reading the service manual thoroughly, and indeed, it has several (territorial) sub-models:

"Note: The symbols in the column "Remarks" indicate the following destinations. E3 : U.S.A. & Canada model; EU : U.S.A. model (AVR-785); E2 : Europe model; EK : U.K. model; E2A : Asia model; E1C : China model; EUT : Taiwan R.O.C. model"

Of course, the CPU and main boards are similar on all sub-models. One of the differences is the analog input board (INPUT-VOL), which seems – in the E3 model – to have additional relay switching the output going towards “surround back”, and twice the volume controlling components:

Comparison between the all-regions/E3 model of the INPUT-VOL board in Denon AVR-1905

So the use of the non-US sub-model of the amplifier would not allow me to control volume for Zone2, or the switching of the regular inputs (CD, DVD, AUX) to it. In my application, I want zone2 to be connected to computer audio, so I can have the surround-back bus permanently wired to the PC (by hooking the PC to the pre-amp output jacks which can also be used for input), and control the pre-amplified volume through the PC rather than through the amplifier. I just need to make the amplifier “think” that it is the US model.

As the CPU board is similar between all models, I was looking for a jumper or DIP switch that controls what sub-model it “thinks” it is. I took the amplifier apart and didn’t find such jumper, but did find a caption on the printed circuit board that specifies how the sub-model is determined:

Sub-model confiugration table printed on the Denon 1905 PCB AREA (57P) R216 R218
E3/BKEU 100K OPEN
E2/EK 100K 180K
GUT/G1C/G1K 100K 180K
N 150K 100K
Well, as they say in the treasure hunting biz, “X marks the spot”… All I need is to find and remove resistor R218. This requires some patience as it requires taking apart all of the boards in the amp (R218 hides on the lower side of the CPU board, which is hardest to reach). But once found, it can easily be taken off with a slight touch of a soldering iron.
AVR 1905 CPU board before modification AVR1905 CPU board after removing resistor R218
Before After
Putting it all back together and turning the amplifier on, and zone 2 works.
As mentioned before, input and volume selection from the amplifier controls does not have any effect on Zone 2 (while the amplifier lets you select input to be routed to Zone 2, it has no effect; volume control turns off the zone when turned all the way down to zero, and turns on to maximum volume when volume is raised above zero.
The AVR1905 now thinks it has zone 2 support

Cheap alternative to multi-zone audio amplifiers

In the home audio project I’m working on, I need to support 5 stereo audio zones (I guess earthlings would call it “rooms”). One of them is the living room, so I want to re-use the same speakers and amplifier I’m installing for the home theater system.

I wrote here a little bit about how I chose the home theater amp.

After spending some time on ebay, here’s what I found:

  • Multi-zone amplifiers (10, 12 channels etc) are very expensive. Not an option.
  • 5 stereo amplifiers is also not an option. Too wasteful in energy and space.
  • Surround amplifiers come in 3 flavors: 5 channels, 6 channels and 7 channels (“what about the dot-one” you ask? well, a “5.1” amplifier is almost always a 5-channel, and the 6th channel – LFE – is amplified by a dedicated subwoofer amp). There’s also 8 channel amps, but these are relatively new, so I couldn’t find any second-hand.
  • Two of the living room speakers double as speakers for the audio system, the other three are used only for home theater.

It’s easy to see, as my combinatorics TA would say, that the optimal solution is to use a 6-channel surround amp for 3 audio zones, and a 7-channel surround amp for another audio channel + the living room (switching between surround and stereo audio). Should be easy, and since I’m perfectly good with 10-year-old used amps (as I wrote here), should not be expensive.

So I bought a wonderful 2002 Marantz SR5200 6-channel amp for the first 3 zones. I hope the  cabinet will be strong enough to hold it, as it weighs a tonne, but it’s an excellent amp for my needs, which I bought for a mere 500ILS (about $130).

As for the 7-channel amp, after some reading I figured out a Denon 7.1 receiver will be a good choice: they all seem to have equal power to all channels (mostly 7x80w), they have analog fail-over when they don’t receive digital signal (which I intend to repurpose for automatic switching between TV and audio), and they support “Zone 2” – the ability to have it act as if it were a 5-channel amp and a separate 2-channel amp. And, used Denon amps are abundant, so it should be easy to find a good one in Tel Aviv.

And I did find a guy, here in Tel Aviv, who sells a Denon AVR1709. 500ILS ($130). Or, he thought he was. He was actually selling an AVR1905. No biggie, all I cared was it’ll have 7x80W and “Zone 2”. I didn’t care about the HDMI support of the 1709, and I hope I can manage without its automatic calibration.

Total expense: 1000ILS ($260).

HT amps are just wrong

I hate home theater amps.

Nothing personal, I just think they’re the paramount of bad UX. It feels they were designed for early adopters – audioholics, audiophiles and other types of geeks. People who want the super-huge 50-button remote control. People who wouldn’t be frustrated when their popcorn gets cold while they figure which preset they wanted to use for their movie (if they ever find the remote, anyway, because it’s hiding so deep inside the sofa cushions).

Huge amplifier remote from Yamaha Huge amplifier remote from Pioneer Huge amplifier remote from Onkyo Huge amplifier remote from Marantz Huge amplifier remote from Harman/Kardon

Anyway, my in-laws, who’s home is the victim of my multi-zone audio/home theater project, are not early adopters. They definitely don’t want a 50-button amplifier remote in their living room. I definitely don’t want them to have a 50-button remote, because 49 of those are the wrong key, and if any of them is pressed – they’d call me to fix it.

You don’t need to be a usability expert to figure out, that 90% of these buttons are redundant – the features people actually want to use on their HT systems are on/off, volume control and input switching. And maybe they can even do without the power control.

Now, you have your TV remote anyway, and it’s supposed to do input switching and volume control. Why can’t you use it?

I think this is an archaic leftover from the early days of home theater, when amps supported surround sound and TVs didn’t. So amps were in charge of input switching, and were wired between the sources and the TV. Of course, this meant the amps also needed to support video switching (and then HD video switching, and then HDMI… so people also needed to upgrade their amps every few years).

But today many TVs have “Variable digital surround output”, that goes through the TV’s input selection and volume control. So you can connect your TV directly to its sources, and connect its output to the amplifier. Now, the TV remote control does the input selection and the volume control, and 0% of the amplifier remote is actually used (just put it away!). How’s that for usability?

This opens up an interesting opportunity. Because, if you’re not using your amp’s video switching capabilities, you don’t care about HDMI 1.3 and 1080p video support. Hack, you can buy a top-quality 2002 amplifier instead of a mid-range 2012 model, and it will cost you much less.

The main disadvantage of this setup is if you want to use your amp for music, when the TV is off. If you’re dependent on the TV for input selection, you’d need to turn it on for selecting the audio source.

However, if you have only one audio source that you’d want to listen to when the TV is off, there is a solution. Most (maybe all) amps have automatic detection of digital inputs, and switch to analog inputs if they detect no digital signal. So if the TV is hooked to the digital input, and the audio system (CD? multi-zone audio server?) connected to the analog input, you can set up your amp to automatically switch between them when the TV is turned off and on.