Swanny:
No, I was using the single ended outputs. I am not sure about the 6 dB more gain beacuse it depends on how the line pre-amp handles balanced inputs. Uncertain about the JC2, but some pre-amps I know of divide back the 6 dB gain when they convert back to single ended internally, so they match the same levels of other singel ended inputs.
Since my original posting I had a chance to make some measurements on a spectrum analyzer. I thought I might have a defective unit. Although PS Audio does not publish noise specifications, I thought I might compare it's performance with some other products (such as the Cambridge Audio 651, which has some pretty good noise specs).
What I found was the noise performance is pretty good. At the x48 dB gain position, I got a noise level of -105 (200 Hz) to -110 (20 KHz) dBV (ref to 1 V RMS output) at the 1:30 volume positition, or 40 dB actual gain. Moving the front volume control to MAX CW position, gain is x48 dB, and noise increases to -90@200 to -100@20K dBV, which tends to indicate you are picking up a bit more noise than you are gaining in gain. These measurements were made with the internal 1 K source resistance (not shorted), which is more realistic source impedance of a MM cart. These are raw measurements, with no weighting (A or C). The range of about -10 dBV indicates the drop in noise with frequency from about 200 Hz to 20 KHz.
At the 66 dB gain position, I measured noise levels at the 1:30 volume position (actual gain of 60 dB) to be essentially the same as the x48 dB gain setting; -90 to -100 dBV. But increasing the volume to MAX, noise increased to -75 dB (200 Hz) to -90 dB @ 20KHz. Source resistance was 100 ohms. Here you lose a wopping 15 dB SN for an increase in gain of only 6 dB.
So at x66 dB, MAX volume, you get a worse case noise level of -75 dB, un weighted, which is pretty good. Weighting and shorted inputs always improve the numbers somewhat. But -75 db is pretty audible based on my earlier criteria of listening to the drivers directly. The SN in my system is worse than -75 dB because my gain is set for a listening level ref to 300 mV, not 1 VRMS (which is now actually -65 dB ref 300 mV RMS).
So with the GCPH, if you need gain use the main gain switches at the back, and try to keep the volume control at 1:30 or below.
No, I was using the single ended outputs. I am not sure about the 6 dB more gain beacuse it depends on how the line pre-amp handles balanced inputs. Uncertain about the JC2, but some pre-amps I know of divide back the 6 dB gain when they convert back to single ended internally, so they match the same levels of other singel ended inputs.
Since my original posting I had a chance to make some measurements on a spectrum analyzer. I thought I might have a defective unit. Although PS Audio does not publish noise specifications, I thought I might compare it's performance with some other products (such as the Cambridge Audio 651, which has some pretty good noise specs).
What I found was the noise performance is pretty good. At the x48 dB gain position, I got a noise level of -105 (200 Hz) to -110 (20 KHz) dBV (ref to 1 V RMS output) at the 1:30 volume positition, or 40 dB actual gain. Moving the front volume control to MAX CW position, gain is x48 dB, and noise increases to -90@200 to -100@20K dBV, which tends to indicate you are picking up a bit more noise than you are gaining in gain. These measurements were made with the internal 1 K source resistance (not shorted), which is more realistic source impedance of a MM cart. These are raw measurements, with no weighting (A or C). The range of about -10 dBV indicates the drop in noise with frequency from about 200 Hz to 20 KHz.
At the 66 dB gain position, I measured noise levels at the 1:30 volume position (actual gain of 60 dB) to be essentially the same as the x48 dB gain setting; -90 to -100 dBV. But increasing the volume to MAX, noise increased to -75 dB (200 Hz) to -90 dB @ 20KHz. Source resistance was 100 ohms. Here you lose a wopping 15 dB SN for an increase in gain of only 6 dB.
So at x66 dB, MAX volume, you get a worse case noise level of -75 dB, un weighted, which is pretty good. Weighting and shorted inputs always improve the numbers somewhat. But -75 db is pretty audible based on my earlier criteria of listening to the drivers directly. The SN in my system is worse than -75 dB because my gain is set for a listening level ref to 300 mV, not 1 VRMS (which is now actually -65 dB ref 300 mV RMS).
So with the GCPH, if you need gain use the main gain switches at the back, and try to keep the volume control at 1:30 or below.