[Iniamyen]

It seems as though I didn't research part availability enough before starting my PIMETA, and now I'm looking at really long lead times and/or minimum orders in the $100's to just get a few of them.

I was wondering if anyone has any on hand that they'd be willing to sell, OR if anyone perhaps knows of smaller suppliers that stock them, that maybe I haven't found yet.

I've found plenty of threads dealing with this issue but I still haven't been able to source any.

 

[dbfreak]

I've been searching/tracking their availability for the past six months and have run into the same dilemma you have. The lead times keep getting shoved into the future. How many do you need? Are you going to stack them?

 

[MrMajestic2]

Quote:

Originally Posted by Iniamyen /img/forum/go_quote.gif It seems as though I didn't research part availability enough before starting my PIMETA, and now I'm looking at really long lead times and/or minimum orders in the $100's to just get a few of them. I was wondering if anyone has any on hand that they'd be willing to sell, OR if anyone perhaps knows of smaller suppliers that stock them, that maybe I haven't found yet. I've found plenty of threads dealing with this issue but I still haven't been able to source any.

Local dealer Elfa.se here in Sweden has them in stock, but they are expensive. I think also that schuro.de has them listed, but not sure if they are in stock.

 

[FallenAngel]

Well, you have a few options:

1) Use LMH6321 - they're better buffers anyway, but they have higher current draw and remember to cut off pin 5.
2) Build some discrete buffers, it's easier than it sounds, very cheap and the best choice.
3) I have 2 BUF634U I can toss you for $5 each if you want, but you'll still be out 1 buffer and should consider the other options first.

 

[n_maher]

I would look into whether using the OPA551 as a substitute buffer.

Have a look at this thread - http://www.head-fi.org/forums/f6/sub...pimeta-143341/.

 

[Iniamyen]

Thanks for the suggestions.

I was originally going to just get 4 (3 for the amp plus one extra), but now I'm thinking if I do find them available anywhere, I may stock up on a few more.

Elfa may be my only option at this point if those are the ones I go with (damn USD being weak against the Euro and all =).

It looks like the LMH6321 is only in stock as a SOP package from the main distributors, which means I'd have to mount it on an adapter. I guess I'm not opposed to this but I'd want to make sure it would work. Are there any other tweaks necessary in a nominally-working PIMETA circuit?

I guess I would be interested in building discrete buffers, but this would require some more research that I haven't done yet. Is it required that I tightly match resistors for these?

I'm not quite sure whether using the OPA551 would be easier or harder than using the LMH6321 - I might not need to mount it on an adapter but I'd still have to do some tweaking that I don't understand from reading that thread.

Historically speaking, do parts like the BUF634P remain in short supply, or do the manufacturers eventually catch up? I may wait a month or two if there's reason to believe it will get stocked up.

 

[FallenAngel]

LMH6321 is ONLY available in SOIC, just mount it on the other side of the PCB, there are SOIC pads, just remember to cut off pin 5 first.

Discrete buffers are very simple and no, you don't need to tightly match anything, but it would be nice to get the HFE of the NPN/PNP transistors matched, not absolutely necessary though. I prefer the Sijosae ones, they're small, easy to build and cost under $1 not including perfboard, just a couple resistors and a pair of BC327/BC337.

It'll be a while for BUF634 to be back in stock, it's been years since they were readily available.

 

[Iniamyen]

Is there readily-available perfboard for different discrete buffers? I assume the pinout would remain the same as a BUF634 if this is what they're designed to replace.

 

[FallenAngel]

Perfboard is not a PCB, there are not traces, it's a pad per hole board you can pick up anywhere like radioshack for a couple of bucks, the size of the buffers is very small. Check out Sijosae's page for this buffer.

 

[Pars]

There's also a modified Sijosae buffer that was in a link in a post of mine in the thread that Nate linked. I linked it below.

http://www.head-fi.org/forums/f6/sta...uffers-131422/

I used these in a Pimeta for my son and really like them, much better than BUF634s... they require a few more parts though, and a home-etched board is best, though I would guess you could just build them on perfboard.

 

[IcantHearU]

Pretty sure Newark/MCM has the TO-220 versions for $7 or so - maybe you can rig up some type of socket to adapt it to a DIP 8 configuration? -

 

[rickcr42]

The National LME49600 is the BUF634 "rebranded" with the only difference being the buffer package

8-Pin DIP & TO-220 for the BUF634

http://focus.ti.com/lit/ds/symlink/buf634.pdf



TO-263 SMD for the LME49600

http://www.national.com/ds.cgi/LM/LME49600.pdf

Maybe Brown dog will come out with the adapter

 

[Nisbeth]

Quote:

Originally Posted by Iniamyen /img/forum/go_quote.gif I'm not quite sure whether using the OPA551 would be easier or harder than using the LMH6321 - I might not need to mount it on an adapter but I'd still have to do some tweaking that I don't understand from reading that thread.

IIRC, the only tweaking you have to do is to connect pin 2 to pin 6 (inverting input to output) on the underside of the board. If you're in the US, buying a pair of OPA551P's from AMB or whoever else stocks them would probably be the least expensive option.


/U.

 

[n_maher]

I think on the PIMETA you also have to clip one of the legs (leg 8) because of a V+ trace that gets routed through that position. Details are in the link that I provided earlier in the thread. The only other consideration (mentioned by MisterX) was the potential for power supply mods, but I'd try it without those and just check offsets from time to time to see if anything is going wrong.

 

[gtp]

.