jtfoo

Hi Kenshinz, From your drawing, your switch only switches the LED, but doesn't affect the Vsupply to the opamps.

Jason, It seems you put bypass caps for the opamps? Those huge heat sinks makes your PPA look like a high end graphic card..

1) For cheap parts, try Koba..3rd storey people's park. The one opposite chinatown pt. 2) No particular shop SLT..I usually get my stuff from several shops on 3rd storey and basement. 3) The same board can be found at SLT. But you have to saw to minature size.. Alternatively just wire link them, not that hard. 4) Improvent.. Try increasing the value of C1 to 0.47uF or higher. Better bass response. IMHO, don't spend too much on the cmoy.

Then you'll need 12 AAA batteries for 14.4V. A fully charged can reach 16.8V.

The PPA needs all those AAA to give a decent voltage for the opamps to work optimally. With 15 cells, that's about 18V nominal, but can reach 21V for freshly charged batteries.

Jialat.. Hope the ELCO caps won't blow .... But I'll leave them there just yet. JAson, I don't have the means to measure temperature... I'll try and see if those thermometer from the SARs kit can do.

Yes, rated at 42V. Fromour friendly KOBA store.. You have them too?

The porn of the PPA with battery board.. Fast charging time suppose to be 2.3 hrs.. But initial fast charge took 3hrs 10 min to go into trickle mode. And here's the charging in process with all LED lighting up,

Finally completed the PPA project. i.e. giving meaning to the middle 'P' of the PPA. Actually doing up the battery board was much harder and health hazard than the amplifier board. Got myself cut in the process. But it's worth it. I also have to build a external power supply unit(PSU) to give the non-standard 27Vdc. The PSU is based on Wellborne PS1 layout. There's slight variation in parts and I added a 1uF reservoir cap. Another variation is I added 24Vdc so the PSU can power the Meta42 too. Some parts differences from the Wellborne are, Rectifier diodes - Schottky diodes (BYV10-60). They have very low forwarding voltage. I measured them to be about 0.18V to 0.2V. Snubber caps for diode, WIMA MKS3. 10nF ELCO- 3X Elna ToneREX(2200uF) and 1x Elna Silmic(100uF). Bypass - 0.1uF film cap from Rifa Evox, Reservoir cap - 1uF polyester cap from Rifa Evox. What made the PSU a audiophile PSU is the hot glue isolating the PSU board from the chassis. This reduce vibration and reacts with resonance in many good ways

Cut myself last nite while doing the battery baord for the PPA.. Damned!!!. Mod edit: This is a must-be-related thread. Looks like U have defaulted jtfoo.

You can check some old post from echoloft diy section. I remembered there's was a long discussions of diy DAC.. Yes, the TDA1541 crown version were mentioned too.

Used to hate the Grado SR125 for it's harshness. But I'm glad that I gave it a chance on the PPA and it really shine. Agree that it's fast pace and good rythm..

mychew, Interesting monk story.. The little monk should have filled the bowl with water to the brim..

Not easy to use a toroid on a tube setup, as they need multiple sets of secondary windings, which most toroids don't have.

Agree with Rameish. If you're not using the 4556, then it's too far from being a Grado Ra-1.

Just curious why call it Pass regulator supply?

Great that you finally got your boards...

Congrats to Oak on being a father.. Welcome to the club. Me also a newbie.

HY, I think most of us including myself are curious about what opamp are you using? Apparently from some of the post in this thread, the impression we got is you're not using the NJC4556, which is what the real Grado RA1 used. The NJC4556 has a higher current output than the other more audiohile opamps like OPA2132/4. That's why the NJC4556 can drives low impedance headphone better than most Cmoy(most people use the OPA2132/3).

I've already have an external cross feed base on cmoy's Linkwitz crossfeed. So I won't be adding a crossfeed. Anyway crossfeed isn't my cup of tea either.. Yes the green ones are the Nichicon Muse.. Got them from Koba..

Old fashion? well you could look it at another angle and call it a retro look instead. Sound better..

Hard to comment without knowing how you look... Maybe post a picture of yourself for those who haven't met you.

Bass boost is for the shiok factor on some of my music, especially the head banging type .. With a switch, it can be turned off easily.

Yes, I've tried the 637 and 627 for gnd last nite. The 8610 as expected sounded more aggressive, bright for some. 637 tame it a little. But the difference between the 8610 and 637 on the PPA is not that great as compare with meta42 on 8620 and 637. I didn't do any critical listening as I'm not a audiophile, and didn't have the time as I'm now trying to tame the bass boost so it'll work well with the DT880. Headache on this, if the bass boost is good on the DT880, it'll be bad on the eggo and Grado125.. Especially when I'm beginning to like the the GradoSR125 with the PPA.

Jason's parts are more than decent. I'm sure he didn't skimp on the PPA as we bought most of the parts together. safe for the 1uF reservior caps and accessory like sockets and switches. Bass boost is tricky, and is unneccessary for audiophile listening. But I put it there for I want the slam and rumble in my rock music. But at the moment it's too overwhelming with my DT880, but surprising good on the Grado SR125.. Will need to fine tune the R7 for the DT880..