Systemic Development > Analog Devices

What are the design issues in making a Phono stage?

(1/1)

S Clark:
I was typing a PM to one of our guys, but realized we have lots of expertise here that might have something to add.
The question is what makes a good phono stage?  They seem to be all over the place in design, complexity, and cost-- and not sure what really relates to sound.  I know that every single one I put in my system sounds different, most with the typical trade offs of things they do well, and things done less well. 

Folsom:
Where to start... !

There's lots of things to know. Like how to control loops, because small innocuous ones for an amp are too big for a phono. Dualmono is the best thing you can do to help reduce that.

Then there's the matter of how much resonations occur electrically, and what to do to prevent that. The phono cables can easily resonate.

You have to pick the right capacitors, too. The smallest effects in them get big by the time you hear it. A huge mistake is using low ESR caps. But this kind of depends on the power supply voltage... You can't really get a well worked out RIAA curve from low voltage, not without unwanted and uncorrectable variation.

Shielding matters, it matters a lot.

Design choices come up like feedback? Active or passive RIAA? What kinds of transistors do you like? What about tube? Tube opens up many other cans of worms but in some ways are easier because high biases are more effective with capacitors, massive chokes can be used, and they're linear enough that you don't have to load them down anymore than necessary to stop oscillating.

If you can come up with any more specific questions, or even want to diagnose a phono, that might be easier than an open ended how to make one.

Navigation

[0] Message Index