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System Gain, Volume, and component matching?

I'm facing a bit of an unknown regarding proper gain matching of components and could really use some help in understanding this. First, with my current setup I typically listen at ~60 out of 99 on my Rowland Pre (maybe 90db or so). Here is what I believe my component gain structure is right now:
APL3910 4V output
Rowland 20db overall gain
JC1 amps 1V=28.3V out (56.6V max power)
Magnepan MG3.6 85db at 2.83V (4ohm load)

Am I correct in saying that to reach 85db at 1m on a continuous test tone, my pre would need to feed the JC1's 100mV?

If this is true, it seems that my pre would have to attenuate that 4V output from the APL a huge amount? But given the Rowland Pre's 20db overall gain, doesn't that suggest that: 1.) at max vol setting, Vout/Vin = 100? 2.) With APL outputting 4V, at max vol setting, the pre would be outputting 400V (no chance). 3.) If the volume knob is linearly calibrated, that would suggest that 4V per vol point (0-99) (no chance).

Could someone help me understand this? As I said earlier, I usually listen at ~60 out of 99 on the Rowland. I'm replacing the Rowland with another Pre that has 8db of gain (Rowland has 20db), and I'm sending my APL back to have a linear power supply upgrade which will drop output from 4V to around 1.5 to 2V. If I used the mathematical approach above, I wouldn't be worried about a thing. However, from a practical point, I currently listen at 60 out 99 on the Rowland, will be decreasing Pre gain from 20db to 8db, and will be reducing APL CD Player output from 4V to possibly 1.5V.

So, with those changes, am I going to be craving a pre that will "go to 11"? Will I run out of gain? And finally, I've heard people mentioning problems with too high of gain in a system causing certain distortions and very little (e.g. 7 to 9o'clock) control of volume, but is it possible to have too little gain when source is only a line level source with outputs in the 1+V range (No phono in system)?

Lots of questions in there I'm sure. I really appreciate any help in understanding this matter.

Thanks!!!

Jordan
128x128germanboxers

Showing 3 responses by ngjockey

ngjockey
1,042 posts
 
By comparison, the JC1's are moderately sensitive with the range from 0.75 to 1.5. Lower being louder. The Maggies are on the low end of the scale and the CDP is twice the standard. You already know all that. What you might not be taking into account is the logarithmic scale. Still, 60% of the max seems unusual for that setup for normal listening levels. Must be a big room... I said, IT MUST BE A BIG ROOM :)

I went from a pre with 20 db gain to a passive and the volume setting went up marginally. Not nearly double. That 20 db of gain has probably never been used.

I also changed a jumper in a DAC that doubled it's ouput from 3V to 6V and that did halve the knob rotation. Even with the passive, that was way too much. I'm dealing with a more senstive amp and speakers though, 0.8V and 91db. I'm also using balanced cables, which may be an option as those outputs can be double.
ngjockey
1,042 posts
 
Can't comment on the Rowland. Never been fortunate enough to own one. It could be nonlinear for obvious reasons. I can think of a few, that I know of, like that. However, standard practice for actives is to amplify and then attenuate. There would be some loss going from 20 db to 8 but mostly at the end of the scale.

Volume is directly related to voltage. For example; on resistor based passives, the selected resistor will reduce voltage but current remains the same. Reducing the output of the CDP will reduce volume significantly, all other things being equal.

Eldartford - There are many CDPs/DACs that have higher than standard output stages. Consider the AA Capitole or many of those with volume controls that max out at 6V. Wadia has settings to tailor the output. Many preamps such the SFL-2 specifically state not to use more than 2V supplied to RCA inputs (4V XLR) to avoid damage.
ngjockey
1,042 posts
 
I agree. Absolutely. No argument here.
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