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Post by sumgai on Nov 21, 2009 23:43:36 GMT -5
..... here's a question: Would it be advantageous to have an canon(XLR) i/p instead of a jack? The one word answer? No. The reason? Because XLR connectors are meant for low-impedance balanced lines, and you're using an un-balanced line. (Look 'em up, if you wanna, but suffice it to say for now, guitars use un-balanced lines, whether they're hi or low impedance.) IOW, you're contemplating costly overkill. Where I think you're going with this is as a way to provide an additional conductor for a signal. Conducted on separate wires like that, you could do a stereo output, and that'd be cool..... but now your mantra becomes " must use a PA cable with an XLR connector", and if that doesn't happen, then you're up a creek. Even if you bring your own cable at all times, will there be an amp that will accept it, or will the House let you plug into their PA? Better to use regular cables, and be able to plug into something almost no matter where you go. And if you want stereo, you can get that and still be able to turn on/off the battery. There's a special jack that has a separate switch built-in, tailor-made for this function. Ask newey for a pointer to his thread that discusses this idea in depth, it also has a link to this "magic" jack. HTH sumgai
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Post by treguiers on Nov 22, 2009 21:18:45 GMT -5
Hi guys, have just recorded some pre-mod sound clips that i'd like to post while i get on with the mod-- only i don't know how. They're MP3s and I've saved them onto my hard-drive.
Just one more thing-- nothing to do with the mod- I'd like to stick up an avatar and the one i have in mind is also on my hard disc how do I do that?
Thanks guys
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Post by newey on Nov 22, 2009 22:14:15 GMT -5
Tres-
You have to upload the mp3s to a hosting site, and then link to it in your post. Our board software doesn't have the capability to host sound files, or photos for that matter.
As for your avatar, upload it to photobucket or imageshack. save it as "avatar size" (no more than 100X100). Copy the img code to your clipboard. Then go into your profile, hit "modify profile" and paste the avatar code into the box where it says "custom avatar".
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Post by JohnH on Nov 22, 2009 22:25:45 GMT -5
For soundclip files, Ive been putting them on Soundclick. The advantage of it over simple file sharing is that you can then post a link that leads to a streaming file - so no need for people to wait to download a whole file and temporarily save it. There's examples in my piezo thread. John
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Post by treguiers on Nov 23, 2009 9:48:47 GMT -5
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Post by newey on Nov 23, 2009 11:48:17 GMT -5
Don't take my word for it, but according to the technical data sheet on that cap, the negative leg is shorter than the positive leg.
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Post by JohnH on Nov 23, 2009 14:16:25 GMT -5
Yes, as newey said, the - lead is shorter on the electrlytic caps. Also, you should have maybe a white stripe or - symbols on the side of th ecap adjacent to the short - lead?
And you can use the 33nF cap, it will make no audible difference in this case
I suggest starting with the mag pu, getting it to run on 9V with the resitor and cap, and proving that it works. also that its signal output comes from its white lead (if its per the data). Just looking again at the diagram, I showed the red lead from the mag pu (dta shoes this to be the battery connection) being disconnected at the far end. It may need to go to ground instead, ie be connected to the outer braid.
good luck!
john
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Post by sumgai on Nov 23, 2009 14:43:13 GMT -5
tre, The real dope is that the light-blue stripe with the outline bars inside.... that's the negative lead. Sometimes there'll be an arrow head on it, particularly if the leads come out both ends, but in your case, the stripe is on the side of the case that is closest to the negative lead. The outline bar is a "minus" symbol. (And no, I have no idea who decided to use the negative lead as the chief identifier, instead of the positive one. Perhaps they were being cheap that day, and decided it was "too expensive" to spend the ink (and time) on a "plus" symbol.... who knows. ) I wouldn't go so far as to say "ignore" what the newey and John said, but many polarized components come with same-size leads, which is why there's always a real identifier. Think in terms of a robotic assembly machine, and that'll make sense. Errr, not to mention, used components that were simply "clipped" out of the circuit board, they need non-ambiguous identifiers too..... As to soldering a lead onto the ends of the 390nf cap.... Sure, you can do that. Just be careful not to use too much heat, nor for too long. If you got 'em, use a hemostat or two as a heatsink around the body. I'm not sure what size those things are, but can you not just straddle it across two strips of veroboard, and melt a (nice!) glob of solder directly between the cap-end and the copper strip? HTH sumgai
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Post by treguiers on Nov 23, 2009 17:13:51 GMT -5
Thanks guys.....well!...hi ho hi ho its off to work I go............. ;D
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Post by treguiers on Nov 23, 2009 22:26:11 GMT -5
Ok, Progress report:
Did the battery circuit and that seems to be fine. Made the blender unit, followed it to the letter.
When I wired the whole thing up the piezo is on all the time with no mag pup. i.e the blender isn't blending. I've a few things to check, but i think it was in the wiring up of the whole thing, I've a feeling fatigue may have been setting in at that point.
I will go over it tomorrow thoroughly, but if any of you have any inkling as to what it might be then please jump right in!
talk soon
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Post by JohnH on Nov 23, 2009 22:51:12 GMT -5
Hey well done, you may not be far off. Nothing ever works first time (oops, should have mentioned that before!)
So in summary, the mag pup is now running off 9V? and if connected directly to an amp, working fine?
The piezo is coming through the blender, but not the mag pu. It would be good to confirm that the blender circuit is actually working (even if not actually blending) rather than just being bypassed in some way.
If you disconnect both In1 and In2, you should then then be able touch either one and get a hum, or feed a signal into either one. Try just the mag pu on its own onto either In1 or In2, and similarly the piezo pup., Check the wire colours to In1 and In2.
You have to find ways to break it down to isolate a problem. Can you confirm that the mag output comes from the white wire?
On the board, make sure there are no small shorts between copper traces or blobs of gunk. You can run a fine blade along between copper strips to make sure
Also, Id be grateful to know a couple of voltages: First, just to confirm the voltage that the mag pup is getting across its old battery terminals - we were targeting about 3.5V with a new battery, or down to maybe 2.8V if a depleted one. Second, on the blender board, can you measure the voltage across the 33k resistor, it should be about 4.5V to 5.5V. Also, measure the battery voltage itself.
John
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Post by treguiers on Nov 24, 2009 7:12:14 GMT -5
I don't know if you are allowed to swear on this site .....THE GUITAR IS *@#$%*! AMAZING!!!!!!
I sorted the problem. I was working into the early hours and had connected the o/p of the piezo directly to the tip. Sorted that put everything back....it works like a charm.
A question; it seems on initial testing that the buffer circuitry has improved the general quality of the piezo. Would you have predicted that? As luck would have it a few gigs have come in for that particular guitar. I have every intention of giving a full evaluation, including soundclips, but I feel that I'd be in a much better position to do that the far side of those gigs....so I would ask for your patience, although you strike me as a patient lot!
I can't thank you all enough(I tried clicking the exalt button but that just got me to your individual profiles)
Cheers to you John especially you are a genius.
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Post by JohnH on Nov 24, 2009 7:16:47 GMT -5
Hey congratulations! I'm stoked that you got it working. +1 to you and you deserve it.
John
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Post by newey on Nov 24, 2009 7:17:22 GMT -5
Clicking the exalt button adds a karma point, and does take you to the user's profile. But, if you check the count, it should go up by one.
If memory serves, JohnH's original piezo thread discusses exactly that as a reason to buffer the piezo.
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Post by D2o on Nov 24, 2009 15:54:49 GMT -5
And you don't have to be directly involved to hand out an exalt either. I was impressed with your enthusiasm over this and so kyle is in my head exalted you ... and that's saying something, right there, that is! Well done, one and all!
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Post by JohnH on Dec 5, 2009 22:24:34 GMT -5
TG thanks for posting those - I had a quick listen and the piezo seem does seem to be more lively. I hadn't expected that from adding a buffer to an already active pickup, but its a bonus. A few questions I have:
what is your recording set up? how long is the chord from guitar to input? (its related to how the mixer might have improved the tone) Could you measure the battery voltage and the voltage at the mag pickup? That will help answer the question about increasing mag output, and is a check on the estimate of 12k for that resistor. If that means you need to remove strings to get to that place however, fine to wait until you are ready of course.
The master volume: theres a few possibilities, I will think about it - one way involves another identical mixer circuit, this time with one input grounded and the other coming from the current mixer output. Other possibilities are a dual gang pot of about 50k per section with each half between a pickup and the mixer input. You might also get away with just a single pot of 100k or 50k after the whole output. Theres a risk to the tone with that last one, but you can test it outside the guitar first.
John
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Post by sumgai on Dec 6, 2009 1:12:35 GMT -5
tre, Good Job, a big +1 for you! ;D The final answer to your first question is, pretty much any component you add to a circuit will somehow change the overall sound. The trick, of course, is to make that change either un-noticible, or else make it enhance your tone even more. So, the mixer/pre-amp is all set, right? Then all you need to do/want to do for a Master Volume is insert a high-resistance pot between the output of that mixer/pre-amp and the output jack. The value can be anywhere from John's suggested 50KΩ up to 1MΩ. Why such a large range? Two reasons: 1) The lower the amp's input impedance (and make no mistake, the volume pot plays a part in determining this number), the more you risk distorting the overall sound. Normally, when you turn down the guitar's output, you also lower the impedance, but in that case (a passive guitar), you aren't sending out nearly as much signal, hence there's not as much chance of distortion. Here (an active circuit), you can easily exceed the amp's design spec, in terms of expected signal input strength versus the impedance, and that's not good for one's tone; and 2) Even in an active circuit, the volume control will have affect the highs in your signal. Lower pot values tend to bleed more highs off your tone, higher values tend to reduce that effect. Both points lead one to try for a higher pot value to start with, and that's a good thing. I'd go for maybe a 100KΩ unit, with either a linear ("B") or an audio ("A") taper, that'd be your choice. If the tone has suddenly dropped in clarity, then move up to 250KΩ, or even 500KΩ, and see what happens. Query #2: So far as battery supply voltage to the pickup goes, I'd try to stay within the design parameters published by the manufacturer. There's no reason to go overboard, you've got other avenues open to you for making more volume. And if the thing is under warranty.... But John's correct, you need to measure that voltage - you don't want to starving the pickup, either. HTH sumgai
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Post by JohnH on Dec 6, 2009 1:48:51 GMT -5
So, the mixer/pre-amp is all set, right? Then all you need to do/want to do for a Master Volume is insert a high-resistance pot between the output of that mixer/pre-amp and the output jack. The value can be anywhere from John's suggested 50KΩ up to 1MΩ. Why such a large range? Two reasons: sumgai My concern with that one is that this guitar, like many electro-acoustics, serves time plugged into a PA system. Line inputs to PAs have low impedance, maybe 20k, so the output impedance of the guitar needs to be a good factor lower again, as it has been so designed here. Even with a 50k pot, the output imedance, at mid pot turn could be 12.5k (rather than maybe 2k or 3k as currently) or more which is enough to start losing signal strength into that line input. Can be tried though. John
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Post by sumgai on Dec 6, 2009 3:50:04 GMT -5
John, Your point is duly noted. A simple DI box takes care of any potential issues. Built-in or external, all bases are then fully covered. sumgai
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Post by ashcatlt on Dec 6, 2009 4:41:47 GMT -5
Higher supply voltage may buy you more headroom before clipping, but if you're not getting distortion out of it now (even when cranked), I don't think you'll get much more volume.
Did anybody else notice the horrible high pitched (like, dog-whistle range) noise that overwhelms every one of the clips which include the mag pickup? It's extremely loud in comparison to the rest of the signal, even when you're playing. If it's masked by your tinnitus or your poor monitoring situation, you should try running it through some frequency analysis (Voxengo SPAN is free).
I don't know what the Hell that is, but you must fix it!
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Post by treguiers on Dec 6, 2009 15:00:55 GMT -5
In answer to ashcatlt, i threw on a set of headphones and did hear what he was talking about. i am reasonably confident though it's a shortcoming in the system i used to record the clips..........
I connected the head of a PA system to my sound card, and used Audacity to record. I saved them as MP3 files. The rec. signal was quite low to begin with so everything was cranked up. Even at that i had to amplify the recording in audacity before saving it. I will check it but I'm thinking it picked some noise along the way and amplified it.
The length of cable from guitar to PA head was 10 feet and was a high quality cable(Klotz LaGrange)
With regard to the voltages at the battery terminals, it's 9.22v at the piezo and 3.15v at the mag.
With regard to the master volume, I do have some latitude to recover lost tone from the EQ section of the original piezo pre-amp.
Getting back to the sound-clips. If it turns out they are compromised, I can call on some friends with proper studio facilities to do better sound-clips.
cheers guys
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Post by ashcatlt on Dec 6, 2009 17:43:01 GMT -5
In answer to ashcatlt, i threw on a set of headphones and did hear what he was talking about. i am reasonably confident though it's a shortcoming in the system i used to record the clips.......... I hope for your sake this is true. I'm only hearing it on the clips that include the mag pickup, though, and it seems a bit quieter/different in the clips where the mag is blended in. This leads me to fear something more serious. Did you change anything between the various clips?
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Post by JohnH on Dec 6, 2009 17:57:50 GMT -5
I use Audacity too, and you can probably go straight from guitar to pc line input, to cut down on intermediate steps - it would be good to check the pure output from the guitar. All the rest seems in order, the voltages are just right as is, I dont see any mileage in tweaking them further.
John
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Post by treguiers on Dec 6, 2009 20:13:04 GMT -5
Right! it's 1 o'clock in the morning here, you could hear a pin drop. I've just plugged in my guitar into my Aer Compact 60. I've turned the master up to 8 and the gain to 5( i didn't play a note because it would be enough to knock lumps out of a concrete wall) The piezo is the quietest, followed by the mag. the noise level seems to increase during the blend process, but all within very acceptable levels, considering how loud I had it. If i touch the metal part of the blend pot during the blend process the noise level seems to increase, leading me to believe that there may be some sort of earth issue At no point did i hear that high pitched signal on the sound clips, and I would like to reiterate that all seems within very acceptable limits I am going to scrub the sound-clips and record some more.
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Post by JohnH on Dec 6, 2009 21:55:45 GMT -5
OK thats encouraging! I think mag pickups, even humbucking ones, do pick up more electrical noise than piezos. If you want to address the bit of extra buzz when touching the pot, then grounding the pot case would do it. If you dont want to heat up the pot enough to solder to the back, with all the circuit board already there, a small grounded wire soldered to a washer and slipped over the pot shaft will do it.
John
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Post by treguiers on Dec 7, 2009 5:57:34 GMT -5
just deleted the post with the sound clips, but I'll record some more very soon.........
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Post by D2o on Dec 7, 2009 13:48:27 GMT -5
I had a chance to listen before you took it down. Good job!
D2o
P.S. Yes - I heard the high pitched squealing as well - good job all the same
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Post by treguiers on Dec 7, 2009 20:59:07 GMT -5
OK now I'm rather curious, went to record the guitar again and found that the high frequency was present: It's definitely coming from the mag pup. I used a small powered 4 channel mixer into my sound card via audacity. A high freq on the mag, none on the piezo.
Plugged the guitar into the aer amp(set very high), no high freq on the mag or piezo.
Gonna earth the pot and try going directly into the sound card, but any thoughts would be more than welcomed.
Ash, I get the feeling you have some thoughts as to what it may be.
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Post by sumgai on Dec 7, 2009 21:22:02 GMT -5
Ash, I get the feeling you have some thoughts as to what it may be. ash has not only been there and done that, his groupies bought him the T-shirt, whereupon he promptly spilled coffee all over it! He'll have the straight poop/dope/horror stories/skinnie for ya in just a moment or two, so hang tight......
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Post by treguiers on Dec 7, 2009 22:05:19 GMT -5
Earthing the blend pot seemed to reduce the high freq a bit. going in directly via the sound card meant some serious amplification(around 30dBs). It picked up some noise. I faintly heard the high freq, but not sure whether it's just paranoia and fatigue. Sounds tip top thru an amp
I'll await wisdom from the elders! 3am here, I'll catch you guys tomorrow.
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