I was thinking along those lines, but in this case, wouldn't I just omit the cap and put a 50ohm resistor at R1(E$38)? Jumpering would bypass the resistor alltogther, though maybe you had that in mind?
If that diode is there for biasing I will leave it out, but it might be nice to know what to use should I decide to try try it. I will read back through the thread.
Pavel's schematic shows 50 ohm resistors at the circuits input, output, and one from output to ground.
I am thinking of using smaller value resistor at input, and output. 50ohms seems high.
I was going to use 6.8ohms at the circuit's input and output.
One question, on the final output there are pads for a resistor to ground, what does this do?
Pavel's schematic shows 50ohms here.
Can I omit this resistor?Or, if I use it should I change the value to corrospond with my output resistor(6.8R).
Thanks.
Russ
I am thinking of using smaller value resistor at input, and output. 50ohms seems high.
I was going to use 6.8ohms at the circuit's input and output.
One question, on the final output there are pads for a resistor to ground, what does this do?
Pavel's schematic shows 50ohms here.
Can I omit this resistor?Or, if I use it should I change the value to corrospond with my output resistor(6.8R).
Thanks.
Russ
I think Russ is talking about my board, which is based on pavels schematic, yes.
I was planing on using the same value as in pavels schematic (apart from the gain obviously) so I wouldn't know where to start with value changing.
carlosfm would be the best person to ask about values, i think he has mentioned his final opamp and component choices in his own thread.
So check out his thread first, as a few have posted their values, and search this forum and many threads will be found on this preamp subject.
The output to ground resistor is for noise canceling/reducing purposes, it can be omitted and is not neccesary.
hope this helps.
I appologise im just back from the pub
I was planing on using the same value as in pavels schematic (apart from the gain obviously) so I wouldn't know where to start with value changing.
carlosfm would be the best person to ask about values, i think he has mentioned his final opamp and component choices in his own thread.
So check out his thread first, as a few have posted their values, and search this forum and many threads will be found on this preamp subject.
The output to ground resistor is for noise canceling/reducing purposes, it can be omitted and is not neccesary.
hope this helps.
I appologise im just back from the pub
tobias_svensk said:
Looks good!
tobias_svensk said:
Thanks
tobias_svensk said:
Hehe, I get asked this all the time.......I dont know. I have used LM3886 and LM3875 and didn't use them enough to be able to tell the difference or my speakers are not that accuurate. But they both sound good! I just prefer the LM3886 because my speakers are 4 Ohm. My BPA LM4780 amp is waiting for some parts from BianGT before I can finish it. 😉
oooh, nice job on the panelisation tobias
How much was it for everything, once you had completed your own panelisation.
How much was it for everything, once you had completed your own panelisation.
Well, first i e-mailed olimex and i thought that i had put the .brd files with the e-mail (olimex accepts .brd files directly) but of course i had forgot the file 
.
Now i'm on my 3rd e-mail attemt 🙂 hopefully i have done it right this time.
Price is $33 for a 160x100 doubleside panel + $6 shipping.
And Olimex panelize them for free, my picture is just to tell them how 🙂 I have Eagle freeware (max 80x100mm) otherwise i could have had it panelized myself
.Now i'm on my 3rd e-mail attemt 🙂 hopefully i have done it right this time.
Price is $33 for a 160x100 doubleside panel + $6 shipping.
And Olimex panelize them for free, my picture is just to tell them how 🙂 I have Eagle freeware (max 80x100mm) otherwise i could have had it panelized myself
First board done. 🙂
Thanks to Brian and n00ber and the rest of the contributers here.
Here are the pics.
Thanks to Brian and n00ber and the rest of the contributers here.
Here are the pics.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
damn that looks good
I never realised that the boards were soooo small.
Was it easy enough to assemble?
Good job Russ
Now for the good bit, get some testing done and gives us the results
I never realised that the boards were soooo small.
Was it easy enough to assemble?
Good job Russ
Now for the good bit, get some testing done and gives us the results
Well, I think a few of the pads could be a little bigger, but really it was not a bad hour or so of soldering.
particularly look at the pads on the input impedance resistor. It would be nice if they were a bit larger.
I also wonder if just making the traces a little larger may help.
Really, its an easy build though. Great work n00ber!
particularly look at the pads on the input impedance resistor. It would be nice if they were a bit larger.
I also wonder if just making the traces a little larger may help.
Really, its an easy build though. Great work n00ber!
I'll get back to work on your suggestions tommorow 🙂
Hopefully we will see some results soon, and see if any redesigning is needed.
Thx Russ
Hopefully we will see some results soon, and see if any redesigning is needed.
Thx Russ
I've found the default design rules for eagle not so suitable for DIY etching in some situations. I have changed the default distance between ground planes and traces but haven't worked out how to get the resister and small capacitor pads a bit bigger......if anyone know how then let me know 
When I was drilling the boards, I only had one size bit - couldn't find my super-tiny bit. Still, larger pads make for better soldering, and really don't take up much more room. Trace size was okay from an etching standpoint (I used photo etching), but slightly large can't hurt. Hoestly, if these boards were twice as large, they would still be small, so a slight growth wouldn;t be any problem.
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