[Pablo32]

Here is the parts list. I will probably order from mouser since they have everything so I don't have to order from multiple sources.

Opamp - AD8620

C1 - 0.47 ìF 100V+ metalized polypropylene film capacitor

C2 - 1000 ìF 25V 30mm tall long-life electrolytic capacitor, radial

C3 - 1000 ìF 25V 30mm tall long-life electrolytic capacitor, radial

C4 - 10 ìF 16V

Texas Instruments TLE2426CLP

EL2001- Elantec EL2001CN buffer (3)

In/out - Stereo mini jack (3.5mm), Switchcraft(2)

VOL - 27mm ALPS "Blue Velvet", 50K

R1 - 1k ohm

R2 - 500k ohm(?)

R3 - 220 ohm(?)

R4 - 2k ohm(?)

R5 - 1.2k ohm(?)

R6 - 120k ohm

R7 - 47 ohm

R8,R9- NONE

R10 - ?

D2 - Reverse-power protection diode, 50V 1A, DO-41

SWITCH - Power switch (mini SPST toggle)

5.5/2.5mm DC power jack (type "N")

Q1, Q2 - JFET transistor

power supply -Linear regulated wall wart

Crossfeed circuit

QUESTIONS:

What voltage wall wart should I use? What value to use for R10?Do I need different resistor values to set the gain higher since i'm using crossfeed?

 

[puppyslugg]

Are you planning for portable use? Stationary? Or both?

 

[Pablo32]

Stationary use. Thats why i'm using a wall power source.

 

[jamont]

The canonical choice is the Elpac WM080, a good regulated single output PS. Elpac also makes dual output units, such as the WM072, that would also work well. Be careful not to exceed the maximum voltage for the AD8620, which is not the usual 36V but instead a weird value of 27.3V. The two units I have mentioned are 24V and would be fine.

 

[puppyslugg]

For AC use, you won't need the tle2426, the el2001(buffer), D1,or D2, if you are using a bipolar psu. I suggest making a your own ps for the Meta. And if your sources has low dc offset, you won't need C1.

 

[tangent]

Quote:

R2 - 500k ohm(?)

470K or 475K is a more "standard" value for this, with a 50K pot, since 470K resistors are commonly used in schematics, so the extras you get will be more likely to be useful later. If you don't care about that, the closest standard value to 500K is 499K.

Quote:

R3 - 220 ohm(?) R4 - 2k ohm(?)

Sure. R4=2.2K would also work. A gain of around 10 is a good place to start if you're uisng the crossfeed board.

Quote:

R5 - 1.2k ohm(?)

A bit higher, I'd think. 1.5K to 3.3K is a reasonable range, with a preference toward the higher values. You want the inner loop impedance to be relatively high.

Quote:

R6 - 120k ohm

If you're going to use the AD8620 only, or only that and faster chips, try an inner loop gain of 300 or so. 470K and 1M are good values for R6, which would make R5 1.5K to 3.3K. (You thought I was making stuff up above, didn't you?

)

Quote:

R7 - 47 ohm

Use 100 ohms, unless you have another reason to buy 47's and want to double up.

Quote:

R10 - ?

As the schematic says, 100 to 1K. You already have 1Ks for R1, and you may have 100's for R7. Double up on one of those values and be happy.

 

[Pablo32]

OK more questions...Would it be better to go with 470 uf caps for C2/C3? Or is bigger better. Do I need the power supply EL2001 buffer and rail splitter part?

 

[tangent]

Quote:

Would it be better to go with 470 uf caps for C2/C3? Or is bigger better.

Bigger is better within a particular line of caps. If you change to a different line of caps to get more capacitance, all bets are off. I really don't want to get into more details in a Head-Fi post. Books have probably been written on issues stemming from your line of questioning.

Quote:

Do I need the power supply EL2001 buffer and rail splitter part?

If you're going to use a single-voltage power supply, then yes. If not, then no. And if not, you need to do something different with D2.

 

[Pablo32]

I'm going to use the Elpac WM080, is that single or double?

 

[tangent]

Did you try to answer that question yourself before posting? Hint: try Elpac's web site.