Any Way to Determine Output Wattage at Home?

kevco

Member
Ok, I already know this is a tough order but I’m going to try anyway. I’m planning a purchase of a single ended DHT amp or monos. I’m undecided on whether the power output of 2a3 or similar triode will get me the kind of power for my desired listening level, or whether the increased power of a 300b will be required.
I’m already aware of my speakers sensitivity (about 98 dB/1 meter/watt, 8 ohm nom.) and I’ve read plenty on the power requirements of such sensitivity. What I’m more interested in here is this: My current amps are both about 15 watt/chan into 8 ohm and provide plenty of power for me. I’d like to be able to estimate approximately how much of those 15 watts are being used at a given listening level so that I can judge for myself if 2-3 watts of clean power is enough or if I need 7-8.
I don’t have any lab equipment, just a DMM and I could probably get a dB meter rigged up with my phone or something. Is there a method here in which I could estimate about how much of those 15 watts I’m actually using with a bit left for headroom? Perhaps a decibel reading and some math?
I’m all ears, so to speak....
 
You could rig a simple peak-hold circuit with a diode and capacitor, then read it out with a DC voltmeter. Anything near 15VDC would indicate that you're close to clipping on peaks. 1~10uF should yield about the right time constant, so the meter's 10M input resistance drains off the peak voltage very slowly. Add a few ohms in series with the rectifier, so the amp never sees a capacitive load directly.
 
Be very sure of what you get. For 4 watts out you are giving up about 7dB of output. At 8 watts, it is only a 3 watt drop in output.

Assuming that you listen at a level that requires you to shout in order to be heard by someone standing less then an arms length away, that is an average of about 85dB. Depending upon your music choice, peaks can be 10 dB higher then average or more. That means you need to get to 95 dB at least. That is pulling 0.5 watts from your amp. A 2 watt amp has only 6 more dB before it clips. Not taken into account here is the distance between you and the speakers and the possibility that you might turn it up louder on an especially clean recording, just because it is a clean recording and you don't realize it is that loud.

Hope this is helpful for you.

Shelly_D
 
I’d like to be able to estimate approximately how much of those 15 watts are being used at a given listening level so that I can judge for myself if 2-3 watts of clean power is enough or if I need 7-8.
Kev- You get a 3 dB increase in SPL for every doubling of the power. So at 1 watt / 1 meter, your speakers will produce 98 dB SPL. Which is loud ! 2w yields 101 dBSPL. 4w yields 104 dB. 8w yields 107 dBSPL. That's extremely loud.
 
I'd like to thank everyone that responded and I apologize for disappearing for so long. I'm in the process of opening a new restaurant and it's consuming the majority of my time. Interestingly enough I've determined that Im using in the neighborhood of 1 to at the most 2 watts for the majority of my listening. My speakers may be more efficient than I initially believed. My cabinets are a homebrew bass reflex with a front loaded port housing the Audio Nirvana 12" alnico "super" driver. Common Sense Audio claims them to be good for at least 97 db efficiency so 98 db seemed to be a fair estimate. My room is pretty small and they are corner loaded which doesn't hurt things any. I'm beginning to realize that I can probably even consider the 45 tube as a possible choice. There certainly seems to be no need to go to the 300b. Again thanks to all for the input .
 
Back
Top Bottom