|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
150.148.14.6
In Reply to: RE: Can anyone here explain "Current Drive" phono stage design? posted by Paul Joppa on May 08, 2016 at 13:34:01
"Current drive" or "current driven" is a term coined by some makers of phono stages, lately. I've read about several such devices. I agree, the term is ambiguous. If it is unfamiliar to you, as it is to me, then I would tend to think it's jargon concocted to infer that one particular design has taken a novel approach, in this case with respect to receiving the output from a low output moving coil cartridge with a low internal resistance/output impedance. Some of these same phono stages are said to "automatically" adjust themselves to the "correct" input impedance to suit the LOMC used to drive them. Thus one need not be concerned about phono loading, or so it is said.
You asked, "Does the term in this case mean a current output or a current input?" Input from the cartridge. Obviously, for LOMC cartridges. Hence, such a phono stage could be said to be "current driven".
Follow Ups:
Thanks, that clears up the situation a lot.
You are probably correct that it's "jargon concocted to infer that one particular design has taken a novel approach" - I blush to confess I have done the same myself :^)
This can easily be done with feedback, or approximated by driving the cathode (tubes) or the emitter (transistors); it's often done in VHF radio receivers, with a cascode circuit. Usually it's necessary to have a large series capacitor between the cartridge and the circuit. I recall seeing circuits that do this 30 or 40 years ago - nothing new under the sun I guess.
There is a widespread theory that a low impedance load on a LOMC increases the electromechanical damping in a cartridge, helping reduce the high frequency resonance of tip mass and vinyl compliance. With a voltage input, the low resistance also reduces the output of the cartridge, so there's a tradeoff. This approach would get around that problem, and offer the most damping possible.
Your last paragraph is reminiscent of some of the claims I have seen for this type of phono input. Unfortunately, most companies won't show a schematic, so I don't know whether or not they use a series capacitance. That might be a case of the cure being worse than the disease.
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: