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Group order of non-inverted LM4780 pc boards? Anyone interested?

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#342
The bridging board is definitely in the plans, but I didn't have much time recently to play with it. I received today a transformer that could be used for splitting single ended signal into balanced and will see how this works: http://www.edcorusa.com/transformers/audio/wsm/wsm10k-10k.htm

I will be not pursuing DVR134 option, as this has been already taken care of by digi01. His little boards are cute and present good value.

I will try to come up with some other solution, which is more of a challenge 😉
 
#343
I am afraid that the Edcor transformers are, well, not very exciting. Note however that only the Talema and Edcor results are from my testing; the Cinemag and Jensen are from the datasheets. But I will probably buy some Cinemags in the near future.

As you can see I had significantly better LF performance from the Talema at roughly the same cost.
 

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#345
Me too

Maybe I'm also a bit slow, but I dont see a schematic for the boards? I see the layout, but is there a schematic showing the full circuit with labels corresponding to the layout and silk screen?

It would be really helpful if there were.

Also, I see the parts list on chipamp.com and some values don't match up to the National data sheet. Trying to figure out which parts to use where is a little tricky w/o a schematic. Maybe I missed the schematic after browsing page after page of this thread?
 
#347
LM4780 Mini guide

In order to save some time for others a road map follows.

PCB National schematic Value
R1 RF1 22k
R2 RF2 22k
R3 Ri1 680
R4 Rin 22K
R5 Ri2 680
R6 Rb1 1k supplied parts list indicates 2k.
R7 Rb2 1k see above
R8 Rout1 0.1
R9 Rout2 0.1

My kits only came with one 10k muting resistor which is through hole, I'm sure I have a few in the parts bin so should be OK. There seems to be only a provision on the board for an SMD muting resistor. I'm assuming that I'll attach the 10k directly to the pins of the LM 4780 or would one be able to tack it to the SMD pads?😕

For those of us who will use the Zobel, it appears as though we need to connect the capacitor to ground via a piece of hook up wire running on the bottom of the PCB. I'm assuming og.

I hope someone will confirm the correct road map above is correct, I'd hate to steer people wrong, and hope someone can confirm my assumptions as well.
Thanks
T:clown:
 
#348
re zobel and mute resistor

the zobel circuit does not matter which is resistor or cap to ground
I found circiuit is fine no jumper needed, tho momentary confusion about extra hole for cap but extra hole must be for longer lead span on different size cap.

I applied 2 pads with solder, then bent the leads tight on muting resistor and then bent lead to make 2 "knees". One touch on the solder pad and it sucked lead on, almost like smd. They are barely off the board.

I also found it convenient to use the solder side for zobel resistor
the leads can be much shorter.
 
#352
On the topic of Heatsinks

Speaking of heatsinks for the L4780... I like this little guy.
http://www.coolermaster.com/index.p...5-6J31C-01&other_title=CP5-6J31C-01CPU Cooler

Most local computer shops will stock this CPU heatsink and it is less then $10 US with the fan. If you run the fan at a slow enough speed you don't hear it. I power the fan from an old wall adapter from an external modem. Resister in series to slow it down.

Notice the copper at the bottom of the heat sink. It is actually pretty beefy. It is 50mm x 45mm and 4mm thick. It is screwed on with 4 screws. The spacing of the screws is 1mm short of the spacing between the two screws for a L4780 chip. To solve that you take a metal hacksaw blade and cut into the chip by 1mm. Put a little paint on the now exposed metal where you hacksawed. Two L4780 chips fit on the heatsink. There you have it, a nice little, inexpensive heatsink. No drilling or hole tapping required. To bad about the sawing, but that is minor.

If you want to insulate the chip from the heatsink then I suggest you put your insulating materal between the copper and the heatsink. If you use an old computer power supply case like I do in the picture below then all you have to do is drill 4 holes in the case and screw it on. The case is thin enough to transfer the heat through the case. The chunk of copper directly attached/touching the L4780 chips provides a nice heat buffer/transfer to the rest of the heatsink/case.

Most of my amps are not in cases, because I am still messing with them. Using this small heatsink makes it easy to handle them and use them without a case.

If you try it, let me know how you like it.

An externally hosted image should be here but it was not working when we last tested it.
 
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