[Soymilk]

so i was planning on building a pimeta and the upgrade bug hit me before i'd even ordered parts for it :O

i'll be posting a parts list for a ppa v2 later, if you have the time please glance over it and see if there's any glaring mistakes or missing stuff or suggestions in general.

for now though, i have a question: is the elpac wall wart listed in the optional parts section of the parts list on tangent's site enough to power the ppa on its own, or would i still need a tread with it?

 

[Soymilk]

are the molex 3 pin male connectors in the optional parts just headers? also, what are the crimp terminals used for?

here's my parts list, any feedback is appreciated

(left out jacks, psu, case, knob)


C1 - 330uF 50V (4)

C2 - odd(3) .01uF, even(2) .1uF (is there an optimal material or would any film cap work?)

c4 - 100-220uF (6)

C5 - 1.0uF/50V metalized polyester box cap (6)

C6 - 10-100pf silver mica or npo/cog





Q1 - 2N5484 (3)

Q2 - 2N5486 (3)

Q3 - 2N5486 (6)

Q4 - PN4392 (3)

Q21-23 - 2N5087 (9)

Q31-33 - 2N5088 (9)

Q24, 34 - MJE243/253 or BD139/140 (characteristics?) (3 each)

TLE - TLE2426CLP (3)

OPAMP - OPA627 L/R, OPA637 G




R1 - 4.32K (3)
R2 - 1M (2)
R3 - 1K (2)
R4 - 10K (2)
R4G - 4.32K (1)
R5 - 3.32K (2)
R6 - 470K (2)
R7 - 10K (2)
R8 - 10 (6)
R10 - dont see one?
R11 - 1K (3)

R21/31 - 220 (6)
R22/32 - 220 (6)
R23/33 - 10 (6)





R24/34 - 2.2ohm 2W (6)

R12 - trim pot, bom calls for 2k; would a 5k work? not sure if we have 2k's at work (3)

R9 - trim pot (3) as before, would 5k work instead of 2k?

D1 - 50V 1A DO-41 (1)

POT - ALPS RK27 (1)

RLED - i'll play with values to see how bright i want it

 

[tangent]

Quote:

Originally Posted by Soymilk /img/forum/go_quote.gif is the elpac wall wart listed in the optional parts section of the parts list on tangent's site enough to power the ppa on its own, or would i still need a tread with it?

Yes, the Elpac is there for those that don't want to DIY the power supply. It's not as good as a TREAD or a STEPS, but it's not bad and it's certainly easy.

Quote:

are the molex 3 pin male connectors in the optional parts just headers?

Yes, they're just suggestions for use in hooking up panel components, and hooking a battery board to the PPA amp board.

Quote:

what are the crimp terminals used for?

You need them for the female side of the Molex KK system. They attach to the ends of hookup wires, which you then snap into the female KK housing, which until that point is just a block of molded plastic.

 

[Soymilk]

ah, thanks. i'll just get the elpac for now and do a tread or steps in the future.

for the trim pots, would 5k work in place of 2k? it would just give a wider (partially useless) range, right?

 

[tangent]

Only use 5Ks if you have them on hand already. Don't buy bigger ones just because they're bigger. Not only will they have no value, they'll even raise the noise floor. (Audibly, maybe not. But they will.)

 

[Soymilk]

yeah i have them on hand already, im not asking if they're ok just because they're bigger.

 

[applegd]

Quote:

Originally Posted by tangent /img/forum/go_quote.gif Only use 5Ks if you have them on hand already. Don't buy bigger ones just because they're bigger. Not only will they have no value, they'll even raise the noise floor. (Audibly, maybe not. But they will.)

From your Part Selection Guide, it said "For most purposes, 2 KΩ will be fine. You might choose to go with a 5 KΩ unit instead if you need extreme adjustments, such as when you are experimenting with the buffer.", This is why I bought 5 KΩ ones.

 

[Soymilk]

oh yeah, i'd forgotten about that part. comforting to know that it'll still work fine.

edit - i'm also debating whether or not i want to match my transistors (well, as much as possible, i only bought a few extra of each). is the hFE easily measurable with a fluke 189? i tried googling how to measure it, but i got some weird circuit with diodes and resistors and maybe even an inductor (i didnt look that closely at it) and using an amp meter and then multiplying the current by 100 to get the hFE or some crap like that; hopefully there's a much easier way than this.

 

[tangent]

No, that's exactly the right answer. And it's really not that complex a circuit. It's just a constant current source and an assorted resistor or two. You can get suitable parts at any Radio Shack and assemble them on protoboard in less than half an hour.

 

[Soymilk]

ah, nuts, i was hoping there'd be a setting that i could just clip onto the leads and it'd read it out. i guess it depends on when my parts arrive and how much time i have to build, then

 

[mono]

There are a bunch of cheap multimeters that'll do hFE, maybe not as accurate in an absolute sense but for relative picking of the best pairs in a bag full of transistors, they'll do. For example, $10 or $14 , though the tradeoff from this vendor is to get the low price it takes an extra week to receive it.

 

[Soymilk]

i'm in the process of putting together the amp, and was wondering what should i set the bias to for class a biasing? i'm gonna just go with 1mA for now, but have people gotten better results with giving more current? this ppa is going to be wall powered 100% of the time, so i dont need to try to limit my current draw to preserve battery life or anything.