Schematic Question

[chris319]

Please have a look at the schematic for the Rane MS 1S mic preamp:

http://www.rane.com/pdf/ms1ssch.pdf

What kind of components are Z1 and Z2? What do they do and why are they measured in farads?

Many thanks.

 

[audiox]

They are 3-terminal feed through capacitors for EMI filtering. The idea is to get very low impedance to ground.

 

[chris319]

Thanks.

Why do you supposed they implemented those instead of the beads L2 and L4 that they had in a previous version of this product?

http://www.rane.com/pdf/old/ms1bsch2.pdf

 

[JohnRoberts]

Perhaps to keep the RF outside of their PCB.  Or save money. Or work better.

I see a few subtle things about latter design that I like better; proper mic termination, C to gnd after input series R, etc.

These may sound slightly different on mics sensitive to termination impedance, with the later design IMO the correct one.

JR

 

[chris319]

John, did you have anything to do with the design of the Peavey PV series mixers? I have a PV6 and it's a fantastic little mixer.

 

[JohnRoberts]

No that was after I left but I was in charge of all mixer engineering for several years so I probably know the engineer who did.

JR

 

[rlaury]

Perhaps to keep the RF outside of their PCB.  Or save money. Or work better.

I see a few subtle things about latter design that I like better; proper mic termination, C to gnd after input series R, etc.

These may sound slightly different on mics sensitive to termination impedance, with the later design IMO the correct one.

JR

Yo John:
I'm I correct in reading you prefer the "cost reduced" version, ms1bsch2.pdf, better than the first one?
The first one is almost directly from the application note. The evil accountants got hold of the second one.

Just wondering.
RonL

Sorry
The MS1S with the switching supply "is" the newer version. That's the one that is IMHO is the better design.

 

[JohnRoberts]

Of those two the first one,

http://www.rane.com/pdf/ms1ssch.pdf

has the correct nominal termination on the mic input (1.5-2k ohm), so should return the expected frequency response from any microphones that are sensitive to this loading.

I don't know or care which is the more expensive version, I'm just looking at component values wrt my understanding of proper design for the application.

JR