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PPAS Build Thread. - Page 6

post #76 of 254
Quote:
Originally Posted by pddjsteve
So I was going through some old electronics crap I've got sitting around, and found that I've got a wall wart (probably unregulated?) that puts out 24V @ 100mA, and my PPAS is drawing about 40mA. Will this be ok to use with a pint-style trickle charge circuit (lm317, resistor, diodes) or should I be looking for something with a bit more current avaialble?
steve - that is definitely enough current to charge even the longest lasting NiMH rechargeables that I have seen at the standard .1C trickle charge rate. Seeing as how it is unregulated, it may even put out enough voltage for the 8 cell (9.6v) series of batteries. It does put out enough current to charge the batteries and run the PPAS though you may have audible noise introduced into your circuit. The other thing to worry about if you plan to listen with the power supply plugged in is isolation. Many cheap power supplies tie V- to earth ground, this creates a problem as it will fight your TLE set virtual ground which is a few volts above earth ground. The TLE will not win this fight. This will not be a problem if you only use the wall wart to charge the batteries.
post #77 of 254
Thread Starter 
Quicksilver nailed it.. also be sure to use a larger rail capacitance if you're going to power it off the wall.. 660 uF of capacitance wont smooth out 60Hz ripple from mains.
post #78 of 254
Thanks, everyone. I actually found some specs on it here, it apparently is not regulated. I really don't know whether or not I'd run it off this or not, I've always just used batteries before - maybe I should just use it to charge.
post #79 of 254
Pop a Tread between them. You really only need about half a tread coming off most wallwarts.
post #80 of 254
When will some general build notes be posted ? I am about a week or two away from building two of these, and I'd really prefer not to make a mistake like putting something in backwards or in the wrong spot.

Thanks !
post #81 of 254
Quote:
Originally Posted by ozshadow
When will some general build notes be posted ? I am about a week or two away from building two of these, and I'd really prefer not to make a mistake like putting something in backwards or in the wrong spot.

Thanks !
Go carefully, have a copy of the board layout printed out or otherwise handy. (just flip the "back" image around in an image manipulation program)

Don't do something stupid, like invert one of the buffers. Like I did.
post #82 of 254
Thread Starter 
Id say the notes on the front are pretty much final ..

note that 90% of failures for this comes from the JFET isolation parts. The advantage of them is that they blow before any other component, the disadvantage is that they die.

So when you get very strange behavior, first thing to check is your TLE voltage. if its not 18 volts, your JFETS are dead.
post #83 of 254
As for the jumper for wideband or not with the Buf634's - would a simple mini-switch be ok ? As in, would it be safe to work between positions of wideband not wideband while the amp is on. If so, I'll just imbed a tiny toggle on the back panel.
post #84 of 254
Just Finished the "Normal" Configuration of the PPAS. It sounds nice.

post #85 of 254
Looks great! Did you purchase or make that case?
post #86 of 254
I built the case from an old iPod and a block of wood (Exacto knife & grinding wheel).
post #87 of 254
What opamps and buffers, etc. did you use ? How does the setup sound to your ears and with what cans ?
post #88 of 254
What opamps and buffers:
AD8620,8610, BUF634U, BSR57 (in place of the SST310 JFET)

How does the setup sound to your ears:

I am now listening to Gorillaz (Demon Days) and the details are very clear and accurate. I typically prefer the “mellow” Burr Brown sound, but the AD8620/10 combination seems to quite acceptable. I tried the AD8620/10 combination on a Pimeta and didn’t like the results (too harsh). To contrast this, I have been listening to a Millet Hybrid. It is definitely a keeper.


And with what cans ?;

HD580, ATH-A900,PX-200, Kraptastic earbuds


Comment:
Drives the HD-580’s and the ATH-A900’s sound great.
post #89 of 254
Has anyone run theirs off a single 9v battery? Most everyone seems to be using 2.
post #90 of 254
4.7k R4 resistor gives this a gain of about 5.7 correct ?
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