[grenert]

Quote:

Originally Posted by error401 /img/forum/go_quote.gif [*]The gain of 10 in the default BOM seems much too high to me, but it may be largely due to the reversed pot wiring. For low impedance phones, change R4 for a lower gain.

In the original version of the PPAS, I made mine with the following resistor values, to give 5X gain:
R1=4.42K
R2=1M
R3=1K
R4L/R4R=1K
R4G=4.42K
R5=3.32K
R6=1M

I didn't add an LED on mine.

Quote:

Originally Posted by pinkfloyd4ever /img/forum/go_quote.gif Anyone heard anything from grenert or tcpoint lately?

I got my boards a few days ago, but I needed to finish another project first. I plan on doing the same setup as I did with version 1, which was OPA2365 for R/L, and the equivalent single OPA365 for ground. That way I can directly compare the two. I should've fried those opamps, since they're spec'ed to only 5.5V

but no problems after over a year of use. My NiMH 9V battery is the Accupower 270mAH 8.4V one, so it may blow up if one of the true 9V batteries is used.

 

[pinkfloyd4ever]

got my parts from digikey! I knew I shoulda used priority mail for my mouser ones too, but I figured since fedex was the same price, why not? The tracking site says the expected delivery date was today, but the last update was it arriving at the fedex location in Ft. Worth....damn snow & ice I guess.

Oh one more thing. My LMH6321 buffers came in a vacuum sealed anti-static bag with a sticker that says "Moisture sensitive parts. Bake prior to vapor or IR soldering to reduce the chances of damage" I know I'm not vapor or IR soldering (not sure what vapor soldering even is), but do I need to worry about this at all?

 

[error401]

I'm not totally sure what that warning is about, but I'm sure you don't need to worry about it.

 

[pinkfloyd4ever]

errroorrrrr, u get that placement guide done yet? I got my Mouser parts. I guess I could always suck it up and read the schematic though

 

[error401]

Yes! It's done!

http://audio.gotroot.ca/ppas/PPAS_placement.pdf

Most labels are directly over the part in question. If anything is unclear, suck it up and read the schematic

Oh, do note that the layout is already updated for the pot bug, so that area looks little different, but the part locations are the same.

 

[FallenAngel]

Nice work error401, I'm sorry I haven't been participating more in this, just way too busy with other pressing projects. I did get the boards and will try to build this in the coming weeks but no promises.

 

[cetoole]

Quote:

Originally Posted by error401 /img/forum/go_quote.gif I'm not totally sure what that warning is about, but I'm sure you don't need to worry about it.

Its about moisture expansion during wave and reflow soldering, I believe, so if you bake the parts before, you eliminate any moisture there may be, and eliminate that chance for damage. Absolutely not a concern with the way we do things, since we arnt heating the whole package significantly.

Good to see this project coming together so nicely. I had some involvement in the initial PPAS, though never built a board, and this one looks much nicer.

 

[pinkfloyd4ever]

YAY! should have mine done (or at least able to be listened to) by the end of this weekend

 

[pinkfloyd4ever]

will it work to just put the pot on the bottom of the board? Obviously it won't fit in the hammond case, but if it does work, it'll be alot easier than cutting traces and jumpering.

For anyone who reads this later, this is just for the prototypers. Those using production boards just put it on the top where the silkscreen for it is

 

[tcpoint]

It should work. Clever idea. You could also put the electrolytic caps on the bottom over the transistors and surface mount capacitors. Don't know if it'll fit in an hammond enclosure with the extra height from being over the surface mount components. I, already, cut the traces and just have to wire it up and test it.

 

[tcpoint]

After second thought, I'm not so sure that putting the electrolytics over the transistors are a good idea. Not sure how heat the transistors generate.

 

[pinkfloyd4ever]

well I didn't think of that till you suggested it...my 'lytics are already soldered and the leads are trimmed. I doubt the heat from the jfets would be a problem as long as you left a little bit of a gap between the transistor bodies and the rubber on the bottom of the cap.

I just wanted to make sure I was seeing it correctly that the holes for the pot pins are exactly reversed, allowing me to just solder the pot as-is to the other side of the board

 

[tcpoint]

I just fired my amp up and tested the rail splitter voltage and dc offset (1.5 mV) on each channel. I'm going to do a listening test tomorrow. I haven't added the ccs, either. My jfets didn't even get warm during my initial tests. I don't think they will hurt your caps.

 

[FallenAngel]

Quote:

Originally Posted by tcpoint /img/forum/go_quote.gif After second thought, I'm not so sure that putting the electrolytics over the transistors are a good idea. Not sure how heat the transistors generate.

In a portable amp, I can't imagine this ever becoming a problem. I've been itching to start assembling my boards, just 2 project that must be done first (and one is going to be done tomorrow).

Soon, very soon.

Clever idea, I was totally thinking of just turning the pot 90 degrees and air-wiring it.

 

[SpudHarris]

I just stumbled over this thread....I have a PPAV2 which I love to bits.

How will the SQ of the PPAS compare?