Resistors and RCA Jack

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ChrisM91

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Joined 2014
#1
Can anyone suggest some female RCA jacks from Mouser such as
http://www.parts-express.com/Data/Default/Images/Catalog/Original/091-1120_HR_0.jpg ?

I need a few resistors for a 12B4 preamp. Two grid stoppers and one output "pull-down" resistor per channel.
Can anyone recommend some resistors (=< $1 each) from Parts Connexion?
www.partsconnexion.com/

I was looking at the Takman 1/2W carbon film resistors as I heard good things about them coming from the guitar amp world.

The original 12B4 preamp design recommends carbon composition resistors. Why is this? I thought those would be nosier and not as good as carbon/metal film. Carbon film seems like the best of both noise and tone.
 
#2
I wouldn't choose carbon compositions myself.

As someone whose career has been pro audio, I never felt being a resistor snob paid off in guitar amps. The hifi guys can worry about the graininess of the midrange or the 2.6 degree phase shift of the super tweeter, or whatever. If you are not making a guitar amp, then ignore this paragraph.

If Mouser has gold plated RCA jacks, then use gold as one of the search terms in their search app.
 
#8
mcandmar said:
Not entirely sure, but i believe its because they are non inductive.
Click to expand...
That was the theory, reality is that sensible values of metal film or oxide resistors have negligible inductance from their spiral cut. This is only an issue for sub ohm values. Lead length from the resistor to the grid is far more important.
Mosfet amplifiers with gate stoppers usually use conventional resistors for a higher frequency version of the same problem
 
#9
A little inductance in a grid stopper could be a good thing, not something to be avoided. No reason whatsoever to specify CC resistors for grid stoppers. It is just another common myth. Grid stoppers and ground leak resistors can be anything of the right value - and the value doesn't matter too much either. I use whatever I have in my spares box, although I avoid CC as it is noisy and unreliable.
 
#10
DF96 said:
A little inductance in a grid stopper could be a good thing, not something to be avoided. No reason whatsoever to specify CC resistors for grid stoppers. It is just another common myth. Grid stoppers and ground leak resistors can be anything of the right value - and the value doesn't matter too much either. I use whatever I have in my spares box, although I avoid CC as it is noisy and unreliable.
Click to expand...
Do pulldown resistors after the output cap matter at all? I was just going to use a nice but cheap metal film for that part.
 
#12
DF96 said:
That will be fine. "Nice but cheap metal film" resistors are fine for almost any audio purpose - as long as they are from reputable manufacturers.

Not "pulldown" - that has a specific meaning in digital circuitry. I assume you mean the ground leak resistors following an output coupling capacitor?
Click to expand...
Yeah, the resistor from signal path to ground after the output coupling cap. I always called it "pulldown", that's what people call it in the guitar audio world. Learned something new today!
 
#16
A normal spiral-cut resistor is not a good inductor. It is a very lossy inductor, so fine for killing parasitic oscillation. RF circuits often use lossy inductors to kill parasitic oscillation, while still allowing the wanted RF to get through. Not just ferrite beads, but sometimes a coil of thin wire wound around a resistor; the thin wire is lossy due to skin effect and the resistor provides a lossy core. Hence my puzzlement when audio people propagate the myth that you need non-inductive resistors for this purpose.
 
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