vibratoking wrote:
For a 200W amp into an 8 Ohm load:
P = V^2/R so V = sqrt(200x8) = 40 Vrms
Calculating the power consumed in the slave resistor divider with a 47k resistor and a 5k pot:
P = V^2/R so P = (40^2)/52k = 30.8mWrms
Calculating the voltage on the slave out out with a 47k resistor and a 5k pot:
Minimum voltage is 0V
Maximum voltage is (5k/52k)x40Vrms = 3.8Vrms = 2.7VAC
Looks to me like the max voltage could overdrive the line input, so if you have a pot, adjust it. BTW, too high of a resistance may make the slave out signal noisy, but the speaker output should be fine. Too low may affect the slave signal and the speaker output. Stay in the range of the values given and all should be fine.
I don't really know the spec so I'll take your word for it. I hope seeing the calculations, helps. This assumes that your amp can drive 200W into an 8 Ohm load. After seeing the math, you should be able to recalculate for a 16 or 4 Ohm load, for instance.
Thanks a lot for working that out - very helpful. You're right, I think I'm overthinking it a bit because there will be a pot to adjust the signal.
The only thing I don't get is how you got from the 3.8Vrms to 2.7VAC. I thought the conversion from rms to peak was to divided by .707?...At least that's what the Internet told me
The only thing I don't get is how you got from the 3.8Vrms to 2.7VAC. I thought the conversion from rms to peak was to divided by .707?...At least that's what the Internet told me
The numberss are correct, but the units were not in my original post. The issue is how VAC is defined. I just looked it up. VAC is the same as Vrms. I went back and edited my previous post to straighten out the nomenclature to show the proper designation for Vrms, VAC, Vpp, and the amplitude of a sine wave. Sorry, I hope it is straightened out now.
What's up with that?! The pot would have be on less than "1" to yield a typical line level.
Gaz, I don't know whether there's truth to this or not, but I've read in a number of places that Boogie intentionally published their schematics with errors; probably to discourage and confound would-be cloners. I haven't done the math in that Boogie example but you have and if it doesn't add up, well I might be inclined to believe you found a bad value on the schematic. Perhaps it's off by an order of magnitude to give someone a nice, smoky GFY courtesy of Randall Smith if they used those values...
What's up with that?! The pot would have be on less than "1" to yield a typical line level.
Gaz, I don't know whether there's truth to this or not, but I've read in a number of places that Boogie intentionally published their schematics with errors; probably to discourage and confound would-be cloners. I haven't done the math in that Boogie example but you have and if it doesn't add up, well I might be inclined to believe you found a bad value on the schematic. Perhaps it's off by an order of magnitude to give someone a nice, smoky GFY courtesy of Randall Smith if they used those values...
Just a few (non)cents.
Could very well be. 50 watts into 8 ohms is 20VAC. The max output of the slave out in the schematic is a whopping 11.9VAC, which seems way too high for any practical application. Even with the control set to "1" it's still 2.5VAC. And even if you assume it's a 10K Audio pot, setting it at "1" would still yield 0.845VAC.
Perhaps the real value is 68K, not 6.8K. ??? But then again, it's a Mesa, so who cares!
