Mini LM1875 design

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I've used Advanced before and they are good. I would consider going with them if this were higher quantity but they're not as cheap for doing prototype stuff. Plus, they charge $50 for multiple part numbers on one board (almost all places do that anymore). Their barebones sevice, however, is almost the same price as expresspcb for the same size and quantity of boards. They would still probably tack on the $50 charge for multiple part numbers on one board.
 
Yea, no doubt regarding the no multiple parts per board being a deal breaker for this project.

If, however, you make the panels yourself and send them the Gerbers as one file, I don't think they care as long as you are willing to cut the boards yourself. I haven't ever tried, but it may be worth it if you have a couple of small projects that you could cut and paste into one file. . . .

Just thinking out loud. . .

David
 
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dfdye said:
If, however, you make the panels yourself and send them the Gerbers as one file, I don't think they care as long as you are willing to cut the boards yourself.

That is exactly what Advanced charges you the extra $50 fee for. Most places charge a similar fee or won't make your boards if you send them files like that. They do that because they don't make much on small orders as it is.
 
Well, if it helps a GB along, I would probably be in for something on the order of 40 boards (since I have about 40 LM1875s sitting around), depending on the price.

I can't imagine boards this small being much more than $2.50/pcb in any appreciable quantity. IIRC, the Guzzler USB DAC group buy from head-fi was around that price, even though it was shipped from Europe. I would guess these boards to be of similar size.
 
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motherone said:
(since I have about 40 LM1875s sitting around)

Perhaps you'd like to trade some of those chips for boards? ;)

I just finished the other "little layout" I mentioned earlier. It's a differential buffer that when used with the LM1875 configured as a differential amp makes a 3 op amp instrumentation amp. This is the same configuration I'm using with my LM3875 amps.

I managed to squeeze all that stuff on a 1"x1" pcb, make the power connections line up with those of the other two LM1875 boards, and make the outputs of the differential buffer line up with the inputs of the LM1875 boards so they could easily be stacked.
 

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That's an excellent question! I had originally planned to place a small mounting hole in the upper right corner of each board but it seems I forgot to do that while laying out everything :cannotbe:

I guess since the board will be so small and light that just running the 7 wires down from the upper board to the lower board will be enough to hold it in place. What do you think?
 
BatchPCB does a nice job for a very reasonable price, the only down side is it can take almost 3 weeks to receive your order. They are an excellent deal for small prototype orders. There are probably better places for large quantities.

Below is a pic of some boards they made. Six boards cost $59.60 and that included setup, silkscreen, soldermask, and shipping.

http://i30.tinypic.com/30b0i80.jpg
 
BWRX said:
That's an excellent question! I had originally planned to place a small mounting hole in the upper right corner of each board but it seems I forgot to do that while laying out everything :cannotbe:

I guess since the board will be so small and light that just running the 7 wires down from the upper board to the lower board will be enough to hold it in place. What do you think?
7 off 0.6mm wires will be quite rigid. If you are unsure, then increase the hole diam to 1mm and use 0.9mm wire.
 
BWRX said:


Perhaps you'd like to trade some of those chips for boards? ;)

I just finished the other "little layout" I mentioned earlier. It's a differential buffer that when used with the LM1875 configured as a differential amp makes a 3 op amp instrumentation amp. This is the same configuration I'm using with my LM3875 amps.

I managed to squeeze all that stuff on a 1"x1" pcb, make the power connections line up with those of the other two LM1875 boards, and make the outputs of the differential buffer line up with the inputs of the LM1875 boards so they could easily be stacked.

I'd be happy to send a few your way if they help get these boards moving forward. The LM3875/3886/4780 have had a ton of support, but there hasn't been nearly as much for the 1875.

If you're interested in the chips, you can e-mail me at m i k e a!t m o t h e r o n e d a w t co m.

Oh, and the awesome thing about these chips is evidently Radioshack in Canada sold them, so they're in the little radioshack cardboard/plastic parts packs.

Any chance you could put some holes on the board in the resistor areas so we could tombstone some if we wanted to go with something other than SMD? I certainly don't mind using SMD parts (having built quite a few projects with them), but it'd be fun and possibly more versatile if you had the ability to throw some boutique stuff on there. I can't imagine it would drastically increase the layout size.

Mike
 
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You can position through hole resistors vertically and solder the leads to the SMD pads on the board if you really want to (don't need through holes for that), but there is really no point if you use good quality metal film surface mount resistors. If you want to use some film caps for supply bypass instead of ceramic you can solder them to the pins on the underside of the board.
 
BWRX said:
I guess since the board will be so small and light that just running the 7 wires down from the upper board to the lower board will be enough to hold it in place. What do you think?
Well, I have used double sided foam tape under PCB's to mount stuff for lab gizmos in the past, so I probably shouldn't offer my opinion! :D

Seriously, the wire hanging trick sounds like a winner. I am not even approaching being concerned about the weight of both of the boards being supported by the chip.
 
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