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post #151 of 627



in which one can find active circuits to pass a balanced signal into an unbalanced one, and vice-versa.


Why add yet another active stage when it's not necessary?




Now I would like to keep balanced line through the pimeta, so I should pick up the signal, and have it re-balanced to an output.


Look into 4-channel amps.  You could probably use the PIMETA v2 scratchpad to build a fourth channel and hack the ground channel to be its mate.

post #152 of 627

Maybe so, the more I think about it, the more I think it will be easier to use an unbalanced input into a balanced amp rather than the contrary.





post #153 of 627

I've been working the last couple of days on a Pimeta v2. I've gotten it mostly put together, successfully tested the power supply, and gone on to the buffers. I soldered pin 1 of the first buffer to its pad, and then gently nudged one of the other pins with my iron. The chip simply fell off the board, pad and all.


I think the work that I have put into the amp has instantly been trashed. These are the only components that absolutely have to be surface mounted, and with no pad, there is no way to attach it. Correct?


I am going to get a drink.

post #154 of 627

check the schematic... that pin is probably not used if it fell off that easily...  (Something similar happened to me on a Mini^3.)

post #155 of 627

Yes, thanks, I figured out what to do after I stopped freaking out about it and looked at the schematic. Pin 1 goes to V-, I will jerry rig that pin and hopefully it will work fine.

post #156 of 627

If I want 3 milliamps from biasing by using the stock values and don't want adjustability, do I solder RBLIM so that it "spans the switchable bias jumper pads" as shown in the step by step assembly guide, or do I solder it so that it spans all the way into the RBIAS slot too?

post #157 of 627

Your question is answered at the bottom of the parts selection guide section on RBLIM: http://tangentsoft.net/audio/pimeta2/pguide.html#RBLIM  There's even a picture.

post #158 of 627

Well I mean, that's what confuses me. So the assembly guide assumes that you'll be wanting to use an adjustable trim pot and the selection guide doesn't. I was just making sure is all.


Oh also, the schematic values for C3 says that it should be 470 uF but the part selection guide/list says and gives parts for .1uF. This also confuses me and I'm kind of wary of soldering any on since the values are so different.


I didn't want to bump the thread so edit: Thanks for fixing things! I appreciate the clarifications.

Edited by yaaayoldthings - 6/14/10 at 9:26pm
post #159 of 627

All fixed now.

post #160 of 627


Aw nuts!!  Just checked my DC offset. OG about 1mV; OR about 25mV; OL about..... 233mV!?*#%

Solder joints look good, nothing gets hot, everything else checks out. Using AD8066/8065. Battery

power (1 - 8.4V NiMH). Any ideas?


Oops! Just realized I don't have anything in C6G 'cuz I only ordered two cap's instead of three.

Maybe that' the problem with the ground channel.

Edited by funch - 8/8/10 at 12:51pm
post #161 of 627

Yes, C6 is most definitely not optional.

post #162 of 627


     Well, um, er, it appears that all I did wrong was install the L channel buffer BACKWARDS!!!!


     Jeez! Now I know why my name and the word 'smart' never appear in the same paragraph.



post #163 of 627


All is well. I replaced the L channel buffer, installed a 33pF C6G that I had and it's up and it's sounding great. Now I need to

order some 25V C2's as I'm measuring a little over 17V to the (16V) C2's I've got in there now when I connect

the 18V PS to charge the battery. The 25V cap's are 16mm tall, so I hope they'll fit.

post #164 of 627

Good to hear it.


A cheaper way to fix the C2 problem would be to put another diode or two inline with the power supply's V+ line.


Also, be sure you're measuring at the caps, not at the power inlet pads on the board.  The existing on-board diode OR bridge will buy you a half a volt or so already.

Edited by tangent - 8/9/10 at 8:47pm
post #165 of 627


Yep, measured at the cap's; 17.1V. I'll try new C2's since I have to put in an order anyway. I'll report back if the 16mm tall cap's fit in the Serpac. Or should

I say, how I got them to fit. :)

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