Bottlehead Forum

Bottlehead Kits => Legacy Kit Products => Foreplay III => Topic started by: audiblesoundwave on November 22, 2009, 06:10:10 PM

Title: Workable power amp sensitivity and gain ????
Post by: audiblesoundwave on November 22, 2009, 06:10:10 PM

Hi,

Can FP III work with a power amp that has input Sensitivity of 1.5V at 1KHz for the rated output and the gain of 19db?

Thanks,
Milton

Title: Re: Workable power amp sensitivity and gain ????
Post by: Paul Joppa on November 22, 2009, 06:20:17 PM

With a gain of 19dB, the output must be 13.4 volts, which is 22 watts into 8 ohms. You'll get 102dB peak sound if the speaker is 88.6dB sensitivity, and that would be a good combination. Foreplay has approximately unity gain with the volume set in the middle, and I'm assuming the Red Book standard of 2vrms pull scale from a CD player.  If your speaker is significantly more sensitive, you'll probably want to reduce the gain somewhere to maintain a reasonable setting on the Foreplay.

For more details, see my white paper on the Bottlehead Community page.

Title: Re: Workable power amp sensitivity and gain ????
Post by: Grainger49 on November 23, 2009, 01:56:22 AM

If you have a problem there are resistors to lower the output of the FP III.  That will give you more accurate volume control but the unity gain position probably changes also.

Come to think about it.  The resistor attenuates the input.  Unity gain is at the same spot but the input, redbook CDP output of 2V, is lowered.

Title: Re: Workable power amp sensitivity and gain ????
Post by: audiblesoundwave on November 23, 2009, 04:55:03 AM

Thanks Paul and Grainger,

My speaker is with 87db sensitivity and I think it is close enough to 88.6db!

Thanks again for the information and advise!

Milton