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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 4 responses by eldartford

eldartford
4,262 posts
 
Of course the output of the CD player depends on how loud the recorded music is when you measure it. Two volts is the maximum rms voltage from a CD player when all 16 bits of the CD media are used, and this is called the 0 dB level. 20 dB down from this is an easier-to-use "-20dB reference" level.

A Denon test CD (CO-75046) is very useful for evaluating signal levels. I have been doing this just recently to set up my Behringer DEQ2496 digital equalizers. These have 24 bit A/D and D/A, but if the signal level going through the DEQ is too low you may only be using 8 bits or so...not good. I now have my gains adjusted so that when I play a typical disc the peak level (overall for the whole disc which is loged by the DEQ) is in the range of -6 to -3 dB. In other words, very high but no clipping. This is a lot like setting level for a tape recording.

One track on the Denon CD (#39)is a siren at 997 Hz and recorded at the maximum 0 dB level. My Denon 2900 player puts out 2 volts rms for this track. During most musical passages the player output is only a few hundred millivolts.
eldartford
4,262 posts
 
Germanboxers...2 vrms is what you get when the CD that you are playing is maxed out. Music has wide dynamic range so an average value would not make much sense. Now, if the player has been mod they may have made gain changes up or down. Increased gain might be intended to enable you to drive the power amp directly.
eldartford
4,262 posts
 
SPL vs Distance for Maggies vs point source is something I just recently looked at. From anpther thread...

Here are some SPL measurements.
Planar is a MG1.6. PS is a Dynaudio Gemini (small MTM).
Signal is pink noise generated by Prepro (intended for setting levels).
Distance is feet.

Distance..Planar...PS.....PS
........0........100.....100
........1.........98......90.....108
........2.........96......88.....102
........3.........96......85......99
........4.........95......83......97
........5.........94......81......96
........6.........93......80......94
........7.........92......79......93
........8.........91......77......93
........9.........91......77......92
.......10.........90......77......92
.......11.........90......77......92
.......12.........90......77......90
.......13.........88
.......14.........88
.......15.........87
.......16.........87
.......17.........86

The first PS column shows the SPL leveling out at 77 dB. I think this reflects room effect. For the second PS column I increased the volume so that the SPL at 12 feet was the same as the planar, 90dB. This required the near field SPL to be a lot higher, 108 dB at 1 foot.

I don't think anyone listens at a distance of 3 feet, although that is close to the 1 meter distance used for the spec. At a more reasonable listening distance, between 8 and 12 feet, the Planar SPL falls off by 1 dB over this distance range, while the PS falls off by 3 dB. To produce equal SPL at 12 feet the PS speaker would need to be about 3dB more efficient at 1 meter. I think that these results are generally in agreement with theory.
eldartford
4,262 posts
 
Ngjockey...Having a standard, like 2 vrms max, assures compatability. Good thing for the industry. When standards are not observed problems may arise. In this case a high signal level problem can be dealt with quite easily using a fixed attenuator, so that the preamp volume control range is better. I understand why a CDP with a volume control might have outputs with extra gain (so that you can drive a power amp directly) but I think that it ought to include a second set of outputs, fixed at the standard level.
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