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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
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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.
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.
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germanboxers OP
241 posts
 
Thanks for the responses so far!

Bob, I think the conversion is Bel=log(Vo/Vi), so dB=10log(Vo/Vi), right? So, 20db gain with Vi = 4V from APL should be: 20=10log(Vo/4) => Vo=400V. Isn't this right? I love the Rowland BTW, it is very smooth, clean, and articulate...even dimensional. I'm replacing it with a Cary SLP-05, a vacuum tube preamp.

NgJockey, my room is 19'x21'x8', so it's not huge. The maggies are ~85db, BUT, that's a 4ohm load @2.83V, not 1w. I also use balanced cables from the Pre to Amp.

I just got out my radio shack spl meter and measured an average loudness (c-weighted, slow) around 83-85dB at the listening position (11' from speakers) while listening to "Turn me on" by Norah Jones at "60" on my Rowland Pre. For this CD, that's about normal listening for me. This means that at 60/99 the Rowland must be putting out something over 100mV, right? I don't the relationship between distance and loudness for a dipole.

Eldartford, I thought when they say it outputs 2V rms that it means that is the average output, not the max, right? Maybe that's where I'm confused?

Thanks for the help, guys...is the general consenus that I should be fine with a 1.5-2V output player and only an 8dB gain preamp?

Regards,

Jordan
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drubin
3,275 posts
 
Jordan, I can't comment on your precise situation, but I have an APL Marantz which, after a recent mod to get the AKM DACs and the new upsampler, has a very low output (around 1.2V I believe, which is less than you will have). I am using it into a Rowland Concerto pre and then into either Rowland 201s or a Primaluna Prologue 5. I'm listening right now (as I type) at a VERY modest level and the Rowland is set at 60.0. If I had less preamp gain, I think I'd be hosed. My advice is to have the APL mod done before you sell the Rowland, just to be on the safe side.
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