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Messages - shinychrome0

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1
Preamps and Effects / Re: Custom LPF build is distorted
« on: August 13, 2010, 10:59:34 PM »
what do you mean?

2
Preamps and Effects / Re: Custom LPF build is distorted
« on: August 13, 2010, 01:59:37 PM »
Yeah.  I'm at cincinnati christian, majoring in classical guitar performance.

3
Preamps and Effects / Re: Custom LPF build is distorted
« on: August 13, 2010, 08:56:03 AM »
Ugh.  Stupid mistakes.  I'll try to get to them before i leave for school sunday.  But i can't guarantee anything.  It would be nice to get it working though.

4
Preamps and Effects / Re: Custom LPF build is distorted
« on: August 12, 2010, 04:01:30 PM »
Sorry i should have mentioned that sooner.  I used a TL082 opamp, but i just used a random opamp for drawing up the schematic.  I wish there was a cleaner wire layout, but with these stupid rat shack boards, it was the best i could figure out.  I know it sucks.  And i had already done the whole thing on a breadboard, except it was powered by a battery, and this was supposed to be the permanent build, not another troubleshooting phase. 

Here is the Schematic i've drawn up from the board.  I found and fixed two errors, one in the power supply (the 1k resistors were in series with the voltage rails, rather than with one end to ground) and another that should have stopped the whole circuit cold.  There was n connection from the output of the first opamp to the input of the second.  I have no idea how any got any sort of sound out of it before, but i don't anymore.  Fixing both of those things still has done nothing though.  nothing but hum city.

And the GE diodes were all i had around to build a bridge rectifier with.

http://www.flickr.com/photos/26826525@N05/4886278694/sizes/l/

5
Preamps and Effects / Re: Custom LPF build is distorted
« on: August 12, 2010, 02:21:27 PM »
http://www.flickr.com/photos/26826525@N05/4885957996/sizes/l/

here's the board.  I'm still working on drawing up a schematic.

6
Preamps and Effects / Re: Custom LPF build is distorted
« on: August 12, 2010, 10:11:01 AM »
its a dual package opamp.  Are those still the same pins you want voltages for?

And i'll try to get some pics and a drawing up later today if  i can manage it.

7
Preamps and Effects / Re: Custom LPF build is distorted
« on: August 11, 2010, 07:54:06 PM »
Well thats the problem.  I HAVE triple checked everything, and can find nothing wrong.  Actually, before combing the LPF and the preamp, both worked fine, except for the volume drop that was a design error, not a build error.  The only problem that i can find is that there may be too much ripple in the dc supply, but is there really any way that could harm any components?  Its only like a +/- 6v supply.  Its not anywhere near the limits of the opamp, or anything else for that matter.

8
Preamps and Effects / Re: Custom LPF build is distorted
« on: August 11, 2010, 03:29:14 PM »
Alright that didn't work.  I had everything hooked up and it sounded good for about ten seconds.  Then my signal slowly gave way to a loud hum.  I'm done.  I have no idea what happened, what fried, whatever.  And i don't have the time to find out.  I leave for college again this weekend.  So the soldering iron is off till christmas.  But i'd still like to know where the hell i went wrong.  Any ideas?

9
Preamps and Effects / Re: Custom LPF build is distorted
« on: August 11, 2010, 09:59:59 AM »
I'm going to try to salvage this by integrating it into a tube preamp i built last year.  I figure i can run it off the spare 12v secondary on the transformer if i put in a small rectifier.  The tubes will give the extra gain i need.

Will a full wave rectified signal be good enough without extra smoothing caps since they will go through the 1000uf caps in the power section anyway?

10
Preamps and Effects / Re: Custom LPF build is distorted
« on: August 10, 2010, 11:24:57 PM »
Wow.  Well thanks for mentioning that now that i have no space left on the board.  It would have been nice to know something like that a week ago.  Another project for the scrap bin.  Its useless as it is now.

11
Preamps and Effects / Re: Custom LPF build is distorted
« on: August 10, 2010, 08:54:44 PM »
Here's the updated schematic by the way.  Just the Capacitors and the power section have been changed to make use of a DC adapter.

There's a considerable volume drop when the pedal is first engaged,(even without the feedback resistors) and then it comes back up slightly after a second or two, but not back to full volume.  Isn't this supposed to be a unity gain circuit?  And shouldn't the maximum setting be pretty obvious?  With a cutoff of 2.3khz, i would think it would be.  I can tell there is a slight cut, but it sounds like its way higher up than it should be.  I'm a little lost here.

12
Preamps and Effects / Re: Custom LPF build is distorted
« on: August 10, 2010, 02:56:19 PM »
Yeah the passive filter was a good start, but its not quite good enough. 

Ok so here's where i'm at.  I just finished getting everything transferred to a board, and i must be close but not quite right.  There is a big volume drop when i kick in the filter (probably from those 68r resistors that i put in.  I'll be removing those shortly) and it does not appear to be cutting anything.  Its passing everything as far as i can tell.  It should be fairly obvious if it is cutting or not.  The cut off point should be at about 3000 hz with both knobs dimes.  Any suggestions?  I'm confused how it could be just acting as a buffer without also acting as a filter.

13
Preamps and Effects / Re: Custom LPF build is distorted
« on: August 09, 2010, 09:18:40 AM »
For the moment i've got all the tone shaping i could ask for.  I use a pod xt live as the heart of my rig, and run it through a power amp into an actual cabinet.  However, i prefer a very smooth mellow sound, Carlos santana style, and love the effect i can get with a low pass filter after the POD.  I just have a passive single pole filter i use now, with some caps on a six position switch.  I don't need much adjustability, its mostly a set it and forget it effect in my rig, but sometimes for recording i'll sweep it around while layering guitars, some with more grit, some with hardly any.  So if i can just find a cut off point that is slightly below where i want it, i can then back it down by turning the two 10k pots, and find the absolute tonal sweet spot.  So adjustability is more for the sake of having it than for any actual necessity.

14
Preamps and Effects / Re: Custom LPF build is distorted
« on: August 08, 2010, 08:47:12 PM »
ok i put  68 ohm resistors in the feedback loop to kill the feedback(and replaced the chip, which was apparently fried) and now it works great!  I'll just have to play with some capacitor values to find the right cut off point, and then i'll be ready to solder!

15
Preamps and Effects / Re: Custom LPF build is distorted
« on: August 08, 2010, 05:33:01 PM »
ok new problem now.  I layed everything out on a breadboard just to test, and i didn't have the right value caps, so i made it according to the schematic below just to test with.  Apparently, i'm getting some sort of HF oscillation, as the opamp quickly became to hot to touch and stopped making any sound.  It worked right for about 5 seconds though.  How do i fix the oscilation?

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