Carver MXR 150

[gd420]

Hi fellow AK'ers,
I just picked up a free Carver MXR 150 receiver/amp I am very happy with the power and sound however I am hoping someone here might have an answer to a problem im having with it. First of I live off-grid and power consumption is an important aspect for any electronics I use. The Carver uses about 240 watts on idle (nothing playing) to me this seems like a lot of wasted power. For comparison my other receiver (yamaha rx7) uses about 30 watts at idle. Is this normal for this Carver or is something amiss? I really want to use it daily but I just cant justify the power use. Any thoughts or suggestions would really be appreciated.

 

[Jon_Logan]

I don't think it's really pulling 240 watts at idle.

It uses a TRIAC switched supply that will read higher than normal on most current measurement devices. I would consult the Owners Manual specs page to see what the spec'd power is.

Other than that, you could check the bias currents in the power stages to see what they're at. Check heatsink temperature at idle. If the heatsinks are anything more than warm at idle, you might need to adjust the bias(s).

 

[gd420]

It is definitely pulling 240 at idle I run my house of batteries and an inverter. The inverter has a digital power display on it so if I turn off all but one circuit I can monitor the usage. As for the design showing more power than it really is using I would think im pretty accurate as I also have a dc voltmeter on my batteries and the voltage drop is just about the same as when my fridge is running (also uses about 240 watts). Amp is only lukewarm I will try to find some internet info on this bias stuff (I am not an electriction) and see if that might be the issue. Thanks!

 

[Jon_Logan]

It is definitely pulling 240 at idle I run my house of batteries and an inverter.

Well see, that's what I was talking about. How can you be sure?

The inverter has a digital power display on it so if I turn off all but one circuit I can monitor the usage. As for the design showing more power than it really is using I would think im pretty accurate as I also have a dc voltmeter on my batteries and the voltage drop is just about the same as when my fridge is running (also uses about 240 watts).

Digital or Analog measurements can be fooled with the way the Carver consumes current. It uses a TRIAC to chop the inverters output waveform. To measure these currents accurately, the currents need to be integrated, or a true rms current measurement needs to be taken before a true caluculation can be performed. While the voltage drop measured seems to indicate that it is similar the the voltage drop of a 250W sine fed load, the voltage drop will be modulated by this TRIAC chopped Carver supply. You should expect 240 Watts of heat coming from the Carver (with speakers disconnected) if that is the true consumption. I don't think you have that. Another way of determining the actual draw is if you know what your Ahour battery capacity is, start fully charged and run them down while noting the time. I think you'll find that it runs longer than you think it will. It's all about the heating of calories burned. If the heat isn't there, the watts aren't being dissipated.


Do you know what kind of waveform your inverter puts out? The Carver's like to work off of a Sine wave. Some inverters put out something closer to a square wave. I'm not sure how the Carver will react to that.

 

[gd420]

However when I see the same voltage drop at the batteries as when using a load of about the same watts one would assume the reading is correct no?

 

[Jon_Logan]

However when I see the same voltage drop at the batteries as when using a load of about the same watts one would assume the reading is correct no?

Yeah, better get rid of it then.

Get something with lower power consumption.

 

[gd420]

Hmm thats what I was thinking although it sounds so much better than my rx7 thanks for the input