Gain Structure help, Mcintosh D100 to Primalune tube amp

Hi John, just found this out for you, looks as though the front right panel knob is digital in the way it send the coding onto the analog side of things. "maybe"

Quote from "The Ear" review

"Mostly the output mode is chosen with the use of DIP-switches or through software. Volume control takes place in the analogue domain within a special chip driven by impulses from the front panel rotary knob."

Maybe you can set this front panel vc low for your max you want (preset), then use the remotes vc as the master vc, if indeed it is analog??

Like I said before Mac can do some crazy things.

Cheers George

You maybe right, because the manual I looked at said

"0 to -60db digital volume control"

Maybe I looked at another model by accident. If this is correct then you have no trouble going direct no mater how low the volume is.

Here are some pics

This one shows the VC on the right, connected to the digital side of things

http://www.avmagazine.com.hk/common/createthumb.asp?w=640&h=480&p=/image/content/personal/D100_640.jpg

This one shows the analog output board and analog outputs on the left with the selector switch attached to it.

http://www.audio-activity.com/uploads/1/3/0/9/13098779/_9628528_orig.jpg

The only pot that goes to this board is a selector switch, if the VC is analog it should go to this board, not the digital board. Makes me wonder now. I guess they know??

Cheers George

What Mark Levinson and Wadia did in their great R2R Multibit dacs/cdp of yesteryear, was to use a digital domain VC, which is the best if you don’t "bit strip"

But they allowed and instructed the user to get the best sound was to set with bridges across small two pin connectors the amount of gain the analog output stage had 10 different levels from 1 to 5v each channel. So then you could use the digital VC at or down to 1/4 below full output.

Very smart they knew about "Bit Stripping" before it was even named

Cheers George

Mac do do some crazy things in my view, like putting output transformers on solid state amps. But I loved some of their old stuff from the 60,s 70,s.

Cheers George 

Yes you can still use the remote variable out of the D100, but preset the Schitt so the maximum out of the D100 is the loudest you ever want to go. In other-words the Schitt becomes a fixed attenuator, and you still have the remote volume of the D100 to use.

The whole idea is to be able use the D100 variable output in it’s top 1/4 of the range so you don’t run the risk of "bit stripping"

I’ll try to explain:

The reason to use the Schitt, is that we know it’s a 10kohm passive which is still a perfect impedance match with your D100 (150ohm) and Primaluna amp (100kohm). Where inline attentuators like Rothwells and the one you mention can have impedance mismatches as we don’t know what series shunt resistors have been used inside them.

Cheers George

You have way too much gain. And the volume control in the D100 is digital domain, so anything below 3/4 and you run the risk of "bit stripping" the music

Your Primaluna input sens is about normal, and high impedance. If you use the fixed outputs of the D100, they are 1/4 the level of the variable.

You could then use a $49 Shitt sys and run the fixed output of the D100 and use the Schitt's level control. 

Or using the variable out you could turn it up full, then for the loudest you want to hear and adjust the Shitt to that level, then you can still lower the remote level up and down but you’ll be using it the top 1/4 of full. So no "bit stripping"

http://schiit.com/products/sys

Don’t bother with those inline attenuators, I’ve haven’t heard any that sound good.

Cheers George