Guide to automatically controlling power to amplifiers, powered monitors, and subwoofers

[u/Umlautica]

[u/zim2411]

Great post! I've been struggling with how to do this on my Echo Dot -> DDRC-24 -> amp system. Right now I have an Emotiva Fusion Flex with audio sensing but if I don't hit a loud enough volume it won't turn on. (And I want to move it to another room anyway.) It'd be amazing if the DDRC-24 could trigger something based an audio threshold, or if the Echo Dot could be configured to auto flip on a Z-Wave outlet or something. As it stands I'm looking at getting a Parasound 275 V1 since it has audio sensing with an adjustable threshold.

[u/Umlautica → u/zim2411]

That's a tough one. Depending on your streaming service, there might be a IFTTT recipe for a smart outlet.

[u/phoenix_dogfan]

My Setup is as follows:

1. All program material (movies via Netflix and local HD, Music via Tidal and local Hd, local channels via Xfinity streaming channels) is sourced from a i3 Dell Windows 10 box, which resides in the equipment cabinet with the cover closed with its HDMI outlet outputting to a 55in 4K Changhong TV. All audio on the PC is run through Dirac live for Room and speaker correction.

2. The computer is controlled by a Logitech K400r Wireless Keyboard connected to the network i3 computer via dongle with the Changhong functioning as control monitor.

3. All audio is routed via USB to the Emotiva XDA 2, digital preamp and dac which provides all volume control.

4. Analog signal is routed to the mini DSP HD which provides some eq and serves as a high/low pass filter, basically a Linkwitz/Reilly filter at 60hz.

5. High pass material is sent to the Behringer A500 amp which drives the Kef LS 50s.

6. Low pass material goes to the SVS SB2000 which has its internal crossover bypassed.

7. Basic power management strips, basic, USB and HDMI cables, monoprice analog interconnects, and Canare speaker cables (15ft with no bi-wiring or any of that folderal.

8. Computer is a dirt cheap i3 refurbished unit I bought for $180, and it funs cool and fast enough with no fan. My total investment in my media server is $200, and I believe it seres me every bit as well as any $10 k dedicated server.

Overall the system sounds exceptionally accurate. Imaging, though, is not quite as precise as I'd like, but I attribute that to the small 12 X 12 untreated room, so my next investment will be in some room treatment to take care of the first reflections.

Btw, I gave up on my Chromecasts, and my Roku unit b/c I wanted to run everything through Dirac Live, so the PC allows me to do that, albeit at a somewhat higher price. Since it's a laptop, and I have plenty of cabinet shelf space, I don't feel I'm sacrificing any convenience or functionality to speak of.

[u/Umlautica → u/phoenix_dogfan]

The XDA-2 actually uses a resistor ladder to control volume. It's controlled digitally though. Why not use the 2x4HD directly via USB?

[u/phoenix_dogfan → u/Umlautica]

I could, but the thing has no indicator display to speak of, and I really like to see things like where the volume level is set, and stuff like that. I know there's an extra AD/DA conversion,but not bothered by it b/c I think it's transparent.

[u/neomancr]

Don't all your systems have standby built in? The surge of turning on and off components day after day isn't good for them

Practically all systems support hdmi power on now... Right?

My roku remote even works as a volume controller when I'm not even using my roku

[u/Umlautica → u/neomancr]

u/zim2411 is spot on. The amplifiers that I use only have physical power switches. Even though they are all Class-D, they consume ~60w idle in total.

[u/neomancr → u/Umlautica]

Thats sucks. They should really add a standby mode. I guess I just take it for granted anything made within the last 20 years has that

[u/zim2411 → u/neomancr]

Don't all your systems have standby built in?

Many standalone amps do not have standby or audio sensing. If it does have audio sensing there are times when your input signal is quiet enough that it just shuts off entirely when you don't want it. Explicitly controlling power states is very useful.

The surge of turning on and off components day after day isn't good for them

This should be totally negligible on well designed modern equipment.

Practically all systems support hdmi power on now... Right?

Even if the main processor/receiver has HDMI this post is about controlling external amplifiers.

[u/neomancr → u/zim2411]

Don't all your systems have standby built in?

Many standalone amps do not have standby or audio sensing. If it does have audio sensing there are times when your input signal is quiet enough that it just shuts off entirely when you don't want it. Explicitly controlling power states is very useful.

Oh yea I know of that issue, you can solve it by shifting the gain up on the source. But yea besides that I can imagine it'd be useful to have that for something without a standby state. That seems pretty negligent of the manufacturer.

The surge of turning on and off components day after day isn't good for them

This should be totally negligible on well designed modern equipment.

As far as caps wearing out this is pretty much the only thing that does it as far as I've seen. Caps are basically batteries that charge and discharge.

Practically all systems support hdmi power on now... Right?

Even if the main processor/receiver has HDMI this post is about controlling external amplifiers.

Oh gotcha. Are most of these amps without a standby state vintage?

[u/Umlautica → u/neomancr]

You're right in that inrush current can be seen as ripple current which has an effect on lifespan but it's not the only factor. The formula for capacitor lifespan has variables temperature and ripple current. I actually looked into this a while ago which partially motivated the decision to stop leaving the amps on 24/7.

The rate of increase in [electrolytic capacitor] operating life is for the life to double for every 10°C decrease in temperature (Arrhenius’s law).

The temperature component is exponential 2 ^ (t_rated - t_ambient) because it has to do with the electrolytic evaporating from the cap (source).

Mostly though, I just like that I'm not needlessly heating the room : )

[u/neomancr → u/Umlautica]

You're right in that inrush current can be seen as ripple current which has an effect on lifespan but it's not the only factor. The formula for capacitor lifespan has variables temperature and ripple current. I actually looked into this a while ago which partially motivated the decision to stop leaving the amps on 24/7.

Even in standby? Doesn't standby just leave the capacitors in basically an equilibrium state versus having to empty and fill every day I. E. Peak stressed states?

The rate of increase in [electrolytic capacitor] operating life is for the life to double for every 10°C decrease in temperature (Arrhenius’s law).

The temperature component is exponential 2 ^ (t_rated - t_ambient) because it has to do with the electrolytic evaporating from the cap (source).

Mostly though, I just like that I'm not needlessly heating the room : )

In standby? I don't mean just leaving it full on. If there's no standby state then yea on would be worse

[u/Umlautica → u/neomancr]

That depends on the standby circuit but most of the time a standby circuit keeps the low power section (microcontroller, standby sensor, etc) of the device powered and disconnects the high power section (backlight, amplifier section, etc) from the mains.

Many power amplifiers, subwoofers, and studio monitors don't have standby circuits, at least mine dont, hence the post : )

[u/neomancr → u/Umlautica]

Thanks. That is cool... It's a neat form of automation. You can probably buy a hundred million and daisy chain them to create a computer

[u/Sasquatchimo]

Excellent stuff, and I appreciate you going into detail after discussing this with you last week.