High Gain Amplifiers?

[mcstatz5829]

control artifacts of the interconnect cable between the preamp and amp

The last function is poorly understood in home audio (although it is significant as an entire cable industry around this issue demonstrates) although it is well-known in recording and broadcast.

Doesn't a well buffered source cover this problem? Just need the right output impedance? I thought it was pretty standard for a modern DAC to have adequate buffering and possible with the right phono amp.

 

[mcstatz5829]

digital-based volume controls that throw bit perfect out the window.

digital volume that compresses the bit depth is the worst. honestly should be considered a crime against humanity.

 

[atmasphere]

Doesn't a well buffered source cover this problem? Just need the right output impedance? I thought it was pretty standard for a modern DAC to have adequate buffering and possible with the right phono amp.

No, it doesn't all the time, although some are better than others. But when you put a passive device between it and the amps, that quality is lost.

 

[mcstatz5829]

No, it doesn't all the time, although some are better than others. But when you put a passive device between it and the amps, that quality is lost.

Do you mind walking me through this a little more? In my barely-passed-EE-101 brain:
Unity gain buffer on dac -> interconnect -> source switch -> volume control -> interconnect -> power amp
seems functionally equivalent to:
Unity gain buffer on dac -> interconnect -> +8db gain stage -> source switch -> volume control -> interconnect -> power amp
in terms of providing the proper impedance matching for the cabling. If the DAC output is already fine for driving the interconnect, why does simply adding a switch and volume control suddenly cause impedance issues?

Edit: is the difference practical vs theoretical? as in "theoretically you can go straight from DAC to passive preamp but practically speaking finding a standalone DAC that can handle it is not trivial"

 

[W9TR]

The 'variable gain amplifier'... is that a Voltage controlled amplifier chip?

We designed a pretty sophisticated reed relay based control that did the same thing. I think that was about 22 years ago. We could never get it to sound as good as the volume controls we were building from custom built switches. I'm guessing the relay contacts were not as good as the mechanical switch contacts but we really didn't pursue it.

They use the same relay based setup to adjust the gain of a discrete amplifier stage. Not a VCA. I can try and find a schematic of one. McIntosh uses vacuum sealed reed relays with Rubidium contacts.