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Post by ashcatlt on Mar 4, 2012 20:27:06 GMT -5
You should extend the analysis out to higher frequencies. Does that curve just keep heading toward infinity? You might not hear the oscillations at their fundamental frequency, but the can cause other issues. Basically I think you need something to tame that super high frequency boost. It has to happen in the feedback loop, but I don't understand these inverting opamp things quite well enough to tell you how to do it.
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Post by darkavenger on Mar 4, 2012 20:56:13 GMT -5
Done. It seems to level off till about 100k then starts rising again. soundclick.com/share.cfm?id=114844444.7nf cap with 300k resistor in parallel then 10k and 2.2nf parallel. Sounds nice, I had to stop for the moment, I'll add more clips soon, I wanted to get the 300k turned down to 47k in the same setup among some other things.
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Post by JohnH on Mar 5, 2012 3:21:40 GMT -5
I really like that sound - sort of blue-grassy banjo rather than Dreadnought. I say keep that and work on a system to blend in some mag - great stuff!
If you want to curb frequencies above dog-hearing range, a small resistor in series with the pickup will do so in this case - try 560 Ohms.
John
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Post by darkavenger on Mar 5, 2012 17:26:40 GMT -5
150 Ohms 47ohms looks good too. I like the way this setup sounds as well, but my personal preference would be to get a bit more zing. Edit: NEW MP3 uploaded soundclick.com/share.cfm?id=11486715Part one is 47k + 5nf and 10k + 2.2nf Second is back to 250-300k ish Third is 0 + 5nf, I think I like 2.2k caps better though the resistance is too low. Edit2: Update, I've added a 1k trim pot for volume. This may be replaced with a fixed resistor in the final version.
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Post by darkavenger on Mar 8, 2012 18:31:11 GMT -5
Ok, so blending options.
There is the option of using a 100k blend pot to mix the two buffered signals, it's looking pretty good. What are the down sides of using this with no added buffer? What would the output impedance be? When turned completely one way or the other, does the impedance even change by much?
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Post by JohnH on Mar 8, 2012 22:15:27 GMT -5
Ok, so blending options. There is the option of using a 100k blend pot to mix the two buffered signals, it's looking pretty good. What are the down sides of using this with no added buffer? What would the output impedance be? When turned completely one way or the other, does the impedance even change by much? If you are talking of using a 100k linear pot, with each end connected to a buffer output, and the centre lug going to output, then it is a good simple way to go. Output impedance will be max at mid blend, at just over 25k. This will be fine for gping into a guitar amp, guitar pedal or processor, but a bit high to go into a mixer line in. Its good to have that option, but you could achieve that by putting a non-true-bypass pedal, such as anything by Boss, after the guitar. J
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Post by darkavenger on Mar 8, 2012 23:16:34 GMT -5
100k pot it is! I'm going to order my parts.
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Post by darkavenger on Mar 11, 2012 19:21:50 GMT -5
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Post by darkavenger on Mar 15, 2012 0:06:38 GMT -5
Well... 4.7nf and 2.2nf together ended up being the best combo. Next up is mounting, then blending. I'll update with recordings through the stages.
Edit: triple post FTW
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Post by darkavenger on Apr 12, 2012 12:50:12 GMT -5
Hey there, I have an update.
I forgot to order a 100k blend pot in my last order to mouser, so blending coming soon with my next order.
I did get my new bridge after a bit(a lot) of hassle with two vendors, so the mounting stage is up next.
I did have an interesting development with the circuitry, the power consumption has jumped to 1.3mA and I have been unable to figure out why. Everything appears to be the same as the simplified version that used 0.09mA and I've taken out different parts in the different sections of the preamp trying to figure out what's causing the drain, but no luck. I've removed the feedback loop capacitors, various resistors, and still 1.3mA is being used. Is it possible this could be from damaging the chip somehow, I may have miss connected something at one point, or had two wires contact by accident. It is also possible the breadboard is shorting somewhere as it has done this once before. I would expect that any of that would stop the circuit from functioning... however it still works as it should. Any thoughts?
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Post by darkavenger on May 22, 2012 23:20:56 GMT -5
Update time. I've gotten everything ready for a full install. I've tested out the new bridge on my jag and the under bridge install and everything seems good so far. The whole thing fits under the bridge and is minimally visible after a bit of trimming. The circuitry is small enough to fit on the back of the 100k blend pot. Power consumption is back down to 0.1mA, figured that one out.
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