Top Mall-Fi poster. The T in META42. Formerly with Tangentsoft Parts Store
Sep 27, 2001
Buffers: Intersil HA5002
You're not going to be building on the META42 printed circuit board, then, unless you build some kind of adapter. The PCB only works with the Elantec buffers. If you're going to build on protoboard, then of course you can use any buffer you want.
V. Gnd: no
I have no idea what you mean by this. Since you're using a single-voltage power supply, I should think "virtual ground = yes".
Are you using a 20K pot? If not, make R2 10x the pot's resistance, as the META42 article says to do. The only reason to use a low resistance on R2 is if you're using a bipolar-input op-amp and high resistances would cause problems. The AD8620 is FET-input, so you can use up to 1M here without even a slight worry.
47.5 ohms, surely, not 47.5Kohms.
And as I say in the article, R8 and R9 are there to solve problems. If you populate them before you know you have a problem, you can get an amp that doesn't work as good as it possibly can. I say, jumper both of these positions to begin with. If in testing you have hiss problems with low-impedance headphones, only then should you consider putting some resistance in either position.
You either got that from someone who hasn't actually built a META42 or you've pieced together these resistor values from those used in two different amps. You can't take the R5 value from one working amp and R6 from a different working amp and assume that they will work together. R6 should be at least 80x higher than R5.
If you're piecing together these resistor values without knowing what you're doing, you need to either stop and just pick one complete set of resistor values chosen by someone who does know what they're doing, or read and re-read the META42 article until you do understand what all of the values do and how they interact.
Wiring using cat5 wire.
Surely you mean you're going to strip off the jacket from a length of CAT-5 and use the individual wires within. When you say that you're going to use CAT-5 like that, it implies that you're using the entire assembly, like you would for making DIY interconnects. When you break it up into individual wires, it isn't CAT-5 any more.