Hi,
I've built up a Serendipity on an etched board.
Finished building the board and connected it up to my test rig to test it.
I'm getting sound - and in fact at low levels, it seems to work ok and all of the knobs seem to do as they should.
However, as soon as there is any level, from playing hard or a boost before it, I get a horrible crackle/clipping sound on top of the real sound, if that makes sense.
I've had a quick look around for shorts and I can't see anything, and it does seem to be working, so i'm wondering if it's a faulty component (capacitor??).
Anyone seen this before or have any ideas to narrow down where the problem might be?
Thanks,
Ian
That could be a bad IC, actually. I would swap it for another. If that doesn't work, check your voltages and post them here.
I agree with Brain, something similar happened to me with a faulty OPA2604, an OPA2604 for wich I paid about 5$....
Ah, cool - thanks.
I'm testing it with a JRC4558 as i've got an AD712 on order but it hasn't arrived yet.
The others i've used from the batch (of 100) have been fine, but i've got plenty so i'll try another tonight.
Ian
I tried about 4x different JRC4558's and had the same problem on them all.
I then put in an NE5532 and it seems to work fine.
Voltages with the NE5532 in:
Supply: 9.19v
1: 4.52v
2: 4.49v
3: 4.25v
4: 0.1mV
5: 4.47v
6: 4.50v
7: 4.50v
8: 9.19v
I'd say it sounds more "gritty" than "serene" though.....
Ian
Voltages look to be ok.
Thanks - anyone any idea why it doesn't work with a 4558?
No idea, but with a bit of luck I'll be finishing a Serendipity myself today or tomorrow, so I'll try some different IC's in it, including the 4558 and NE5532 (will have to borrow that from another build, I love sockets!), to see if I get the same results. What version etched board do you have? Mine is a Ver. 4, which seriously messed with my head as I had the Ver. 5 docs. Took me an hour to realise my mistake, doh!!! ::) And then another 5 minutes to locate the Ver. 4 docs ;D
Paul
Ah, cool - interested to hear your experiences.
According to the board, it's ver.4 - but actually if you look at Serendipity_ver.5.pdf, the single sided board layout still has ver.4 on.
Wonder what the difference between ver.4 and ver.5 are? - maybe it was only a mistake on the fabbed one?
Ian
I think most times when madbean came out with a fabbed version of a project, in the case of the serendipity it was ver.5, the single sided etch included in the new project file was not updated, and instead the previous version was included for those who wanted to etch. Lots of the older documents are like that. The schematic and part numbers are usually identical, and the correct layout image for the single side project is always there too, so people didn't have to track down the correct document.
Ah, ok.
Any idea what the difference was in ver.5?
Been going over both of the docs again, Ver 5 is the fabbed one, Ver. 4 is one for etching. Only thing different is the CLR, 2k2 in Ver. 4 and 4k7 in Ver. 5. Now I'm wondering why I was so confused in the first place.... Maybe I was looking at the parts layout on the wiring diagram? Dunno, good thing I don't drink anymore before/during building.... ;D
Paul
CLR?
The LED resistor you mean?
Yup, the current limiting resistor is the one included so the led won't fry.
Lots of the older projects had the clr and led on board, whereas the newer projects call for the offboard wiring of it.
I think the only difference between ver4 and ver5 is layout, and of course ver5 was fabbed. In theory they should sound identical.
Ahh, of course - Current Limiting Resistor!
Ok, thanks for that.
Ian
Both the NE5532 and JRC4558 have BJT inputs. So, why one would cause a problem and not the other, I'm not sure. Unless there's something with input offsets, maybe? I know I have used the 4558 in this circuit in the past.
On the other hand, perhaps the problem lies in the clipping portion. Depending on how involved you want to get in this: you could try temporarily shorting the two mosfets and see if the problem persists with only the BAT41s working. This might be a good guess since the crackling is layered on top of the signal.