Gain setting for both pre-amp and Audio Research power amp w/ high output cart

If this was my system, I would adjust the amplifier’s input sensitivity that gives me the most usable range on the pre-amp’s volume control.

brf, thanks very much again, for taking the time. So I think I’m on the right track. The way I have it now, 12:00 noon on the Spectral pre-amp dial is a good reference level. Too loud for the wife, just perfect for me. :-) I based that volume position on a memory that Spectral folks recommended the volume dial wind up in the 11:00-1:00 range. I have plenty of room to turn down the AR sensitivity if you suspect I might have better results with an even more wide open pre-amp volume. That’s a very easy experiment. I just assumed the AR needed to have those gain dials opened up, but I’m thinking like a guitar player where amps come alive with more gain.  But now that I think about it, even with guitar amps it's the pre-amp section you're opening up when you crank the volume.  

You want your phono + preamp to have enough voltage gain to be able to drive your amplifier to full power. Not enough front-end gain, you won’t be maximizing the power amplifier’s maximum output capability. This is often the case when someone purchases an ultra low output MC cartridge. Too much gain, you risk overloading the amp’s input causing potential clipping.

 

In your case, the Audio Research Model-115MKII needs 0.6 volts from your front end to reach full power. Your Rega cartridge produces 0.0068 volts, therefore, your phono section plus preamp must have sufficient gain to produce the required 0.6 volts that your amplifier needs to achieve maximum usable power output when your pre-amp’s volume knob is turned wide open. As previously calculated in the above post, your MM cartridge needs 39db of gain to produce the required 0.6volts required by your amplifier and your DMC-10 produces 40db, therefore, an excellent match.

 

The above exercise is not as important for digital source components as their rated output is typically 2-volt, therefore, most preamps are attenuating the gain downward (that is why many CD player can drive an amplifier directly).

 

Elizabeth’s comment about "Gain required to drive you amp to full power " is very different than the actual amount of power needed or used” is correct, but is a different subject matter that deals with amplifier and speaker matching to determine spl’s required for your room dimensions and listening preference.

 

If this was my system, I would adjust the amplifier’s input sensitivity that gives me the most usable range on the pre-amp’s volume control.

Sorry, I did not equate dials with trim pots in your post.

Your MM cartridge has an output 6.8mv and your amp’s input sensitivity is 0.6v. The DMC-10 provides 30db MM gain and 10db line level gain, for a total of 40db.

Gain required to drive you amp to full power can be defined as
20log(0.6 / 0.0068) = 39db

Based on the above calculations, the Rega MM cartridge is an ideal
match for your system. Are you sure you are not using the MC inputs?

No worries. And thanks very much for the research and replies. "MC inputs"? There are MC inputs? I’m confused. :-) The DMC-10 has a single phone input, and two options for output (not counting tape) DC Coupled and AC coupled. I’m using DC Coupled.

Sorry, I did not equate dials with trim pots in your post. 

Your MM cartridge has an output 6.8mv and your amp's input sensitivity is 0.6v.  The DMC-10 provides 30db MM gain and 10db line level gain, for a total of 40db. 

Gain required to drive you amp to full power can be defined as
20log(0.6 / 0.0068) = 39db

Based on the above calculations, the Rega MM cartridge is an ideal match for your system.  Are you sure you are not using the MC inputs?

Yes, as mentioned in my post they're at 10 on a 100 dial.  Last night I turned them even lower and turned up the gain on the power amp to compensate.  Keeping the 'reference level' on the preamp volume knob at about 11:00.  might be better but again, it's hard to adjust these gain ports on the fly and get immediate feedback which is why I posted here.  To see if anyone else has done this dance between amp & preamp gain w/ high output carts.

Have you tried adjusting the internal Left and Right gain trim pots on the main PC board?