Donovan

Yep, you're right, I missed that point. It sounds as though with a lower than matched output impedence, some power is lost. This would make sense why when I built the 18V version it sounded much better than the 9V version if it was because it was able to supply more power and make up for what was being lost. I did not measure the output current. I found a thread where someone with a similar set of circumstances found a secondary buffer on the ouptut makes a positive impact. http://www.electro-tech-online.com/electro...dphone-amp.html

Because most active guitars last thousands of hours which equates to years per battery for most people? But if you're doing something like the link below its a very cool idea. Battery life is not the only consideration, but on what are you basing the generalizations that include hours "most" people play and the gear that "most" people play? I'd agree to maybe modify that to "some of the longer-lasting systems" and "casual players". For example a system with EMG 81/85 can be expected to last about 1500 hrs (3000 per pickup). However, some single coil EMG's,like the SV, rate battery life down to about 400 hrs for a 3-pickup set. My Ghost piezo system is spec's at 500 hrs. I play somewhere in the vicinity of 2-2.5 hours per day (alone) and another 5 with band, adds up to about 7 months per battery. I'd rather not have an ugly battery compartment route on my strat, so I have to unscrew my pickguard to change the battery. Sustainiac systems are far less, rated for 15-40 hours. Folks on this forum have stated their DIY sustainer systems last a few hours at best. Let's also not forget that as battery life degrades, amplifier headroom degrades as well and signal quality/intensity degrades. The advantage of a mod like an internal charger means for DIY, you do not have to route an ugly hole for the battery compartment, and instead foregoing this through susbstitution with a tiny jack. Very stealth idea for those wishing to maintain the aesthetics of original, passive design. As well, we take the guesswork out of remaining battery life. I'd rather plug it in the night before a show and feel confident in the charge than end up with a dead guitar half way through. One might say, "well if I only need to change the battery once per year, why not just place it under the pickguard?" Sure, but every time we remove those pickguard screws, there is a little less strength in the holes than previous and we disturb the wiring,which is not designed to be disturbed over and over again without expecting failures at their terminations sooner or later. So, therein is another advantage.

i would normally have the headphone amp at the end of my pedalboard. then, i would unplug it, thus switching into battery-power mode, and velcro it to my guitar strap. at that point i would have no FX, just guitar -> patch cable -> headphone amp -> headphones. that's ultimate portability. or, if i want, i can build the headphone amp INTO my guitar, add a headphone out jack, and only use the 9v power supply to recharge the internal battery w/o removal I think it makes perfect sense to do this... plug in and charge when hanging out near an AC outlet, then go wireless when you feel like it. I actually think this would be a great option for guitars with active circuitry. You could have a setup withought having to add a removeable battery pocket. Instead of routing the big, ugly pocket, there'd just be the standard AC adapter input jack, which could be placed somewhere on the pickguard and remain very inconspicuous. When guitar is not in use, plug in and avoid having to remove pickguard screws, strings, etc., or replace batteries. We do it with cell phones, why not a guitar? That being the case, it's not actually the power supply that is the point of interest. Any above 9V'ish AC adapter will do the trick, so long as it is as "quiet" as you need it to be. What you need/want is a 9'ish volt rechargeable battery and charging circuit. There are various schematics floating about on the web for different types of batteries. A google search for battery charging circuit would be a good starting point. I found many doing this, but not many that had the necessary switching that would be necessary as the logic to control the system automatically. I suspect if you search around enough, you will find exactly what you need.

Wow, thanks. I must admit, it's messier than I'd have thought for a professional install. Notice many of the wires from the selector switch go right into the preamp PCB... this could be the "active switching" mentioned earlier. Next, go to this page on the Jackson/Sustainiac setup and pick the appropriate drawing, then review all the connections for correct placement, solder joints (fractures, bad wetting), wires for broken strands, etc., and look for any loose or poor crimps. If you have an Ohm meter, check the pots as well. Hopfeully, what you will fins is something visually obvious, else the next step would likely be the assumption the circuit board has a fried/defective component and it's time to bring in to a tech or send it back, as others mentioned. Good luck. That is a very nice guitar. The video demos show it can be very kicka$$ and fun to play.

Oh well. I'm sure all of this has been a learning experience for you to say the least. You and I are on much the same path and so I can identify with your interest, enthusiasm, confusion, disappointment, etc. No worries though, let's look at it as "right of passage". A low impedence output can handle going into a higher impedence input, but not the other way around. This is what I've learned, but it is 2nd hand knowledge from a member of the nerd herd at my employer and other threads within this and other electronics forums, for a basic bit of evidence, it's stated about 2/3 down this page... http://www.kpsec.freeuk.com/imped.htm In practical termns, if you think about how things like op amp based stomp boxes work, they are always very low output impedence and very high input impedence (this is why they're used as buffers and how they avoid "loading" the guitar circuit). They have no issues interfacing with the input of a guitar amp. If there is any issue with a low output impedence, then I'd also like to know why. Impedence is not so easily measured. It's a combination of resistance, inductance, capacitance, reactance (variation with frequency), all brought together. You would need an LCR meter to measure the individual values and use some math (that I'v enot ventured to fully understand) to come up with the impedence value. I also believe there is a difference powered vs unpowered. However, I believe that for the most part, with something as simple as headphones, you can factor it down to an estimate, based on only the resistance of the headphones. I think your biggest issue is going to be the output current, not impedence. Like I said a few posts back, I hooked this up with a TL082 driving my Bose headphones (quite high output) using dual 9V supplies and it was very nice. I do not think the dual 9V supplies change the output impedence, but the output current of the op amp does go up with increased voltage supplied to the op amp. Some of your questions are very valid and I'm not sure you're going to get the answers you really need here... notice no one else seems to be chiming in? I would recommend joining the forums at www.allaboutcircuits.com. They have a subforum ccalled "projects" and some serious nerds there that will guaranteed be able to answer your questions better than me if not fully to your satisfaction. They have helped me out recently when I was very frustrated with a project of my own and I personally will go there first for any electronics questions after that experience.

Wow, I spent some time searching and was not able to locate anything either. Sorry. Is the standard pickup a piezo? Did you wire the new piezo to the Ovation preamp?

That could very well have done it. Another thing that could have done it is an ESD (electrostatic discharge) event... a shock transferred from your body or an object to the device during handling which causes damage in the form of frying an internal pathway,either partially or fully. We often neglect this phenomena in the DIY world as it's not really given much attention in the standard tutorials. It's the very reason why you get electronic circuit boards for PC's packaged in silver metallized bags. They're static shielding, designed to protect, until the consumer gets their hands on them. In the industrial world, we spend thousands of dollars on bench setups designed specifically to reduce and neutralize static buildup and discharge around sensitive devices. They constantly monitor the operator for proper grounding to keep the operator, the bench, and the product at ground potential to avoid static. Op amps are among these sensitive devices, as are most semiconductor devices. When an ESD event occurs and damages a component, it is all but untraceable without using specialized X-ray equipment with very high magnification. Yes, I agree on using sockets, but why can't you just remove the chip and try replacing it? No matter what you've done, it is always removeable,even if you've clinched the leads over. Get yourself some wicking braid and liquid flux on your next visit to the electronics shop. You flux the braid, lay it across your joint and apply heat to both braid and solder joint. When the solder melts, the braid sucks it up. When you have enough sucked up, the chip should be easily coerced out of the holes. It's at least an opportunity to give it a try.

Both the Sustainer and the middle pup have a strong pull. The bridge is very weak, almost no pull at all (but there still is SOMEthing).... So, maybe just a shi**y pup..? edit: Note that the sustainer and the pup also have some pull (maybe just as strong) when tapped even when they are not selected. (not sure if this is normal--please excuse my ignorance). They are permanent magnets, so yes, they should always have pull. The tap test is to determine if there is sound output. You should be able to tell a difference in volume of sound if the pickup is working vs one that is not. Can you post a pic of what the setup looks like beneath the pickguard? Many of uas have been dying to see a closeup and it may help solve your issue.

Yep, you're right... sorry, my bad. Gain is as you said in your "noninverting" configuration. I had it confused with the inverting gain circuit, which gain can be unstable in that configuration. Back to your problem... If you've not changed anything from your test setup and your test setup was working fine, then I can think of only two things as possibilities. You've either made a wrong connection or have a damaged/defective component. Use your meter to trace through the circuit. Any of your components could have failed or be on the verge of complete failure, without visual evidence.

Pete's comment was exactly my point. Everyone (including me) knows a JB is passive. The point is the switching may not be passive. This could be your issue, unless of course, you've checked it out and are sure it is not. I would not assume that since the pickups are passive, that the switching is as well.

That's your latest configuration? I thought you said before that your gain pot was where the 1K resistor is and that what you're showing as a 100K log is actually a 100k resistor. I think that is where it should be, not where it is shown in that drawing. The way it is now, it will try to go to gain <1, which will make it unstable. I also think it should be a linear pot when you're working gain. Making that a linear pot and moving it will help with the jumpiness.

May be a tupid question but... is the battery new or has it possibly passed its useful value? Their life is not astronomical in those circuits.

No problem. If you do any more of these things, get a socket so you can change the chips out to try different ones. They usually follow a standard pinout so they are "plug and play" in a sense. What are you using as an enclosure?

You'd need a multimter with a sample and hold peak detector. Pickup manufacturer's sometimes post this information, but it's a big window at best. That's unfortunate. I'd really hoped to see this worked out. Have you tried playing with capacitor values? As we said in the beginning, the TL082 is better than an LM741. The TL072 is a lower noise version of the TL082. Still, all of these are general purpose "penny" chips because they are outdated by newer technology and you can buy them on the penny. Here's an interesting page, though it's 5 years old. Even then, the TL082 was outdated. http://tangentsoft.net/audio/opamps.html Take a look at this and order yourself some free samples... http://www.linear.com/pc/productDetail.jsp...009,C1026,P1293 This one looks just right for you IMO... it should be more output, less noise, and, you can get free samples... http://focus.ti.com/docs/prod/folders/print/opa627.html

You can try DIYstompboxes site. You will need to research a lot in order to understand what you need to design and how to do it, unless you can get someone to do it for you or find one pre-drawn on the web, though my experience with the pre-drawn web stuff shows they are not trustworthy and can cause a lot of confusion/disappointment, particularly as a lot of them are designed for dual power supplies which is misleading for those of us guitar enthusiasts. Just make sure you look for SINGLE SUPPLY circuits in your hunt. It does not matter how many pickups you are going to have as you'll be pulling off the line after they're already mixed/switched. You will need: A gain stage (boost) if so desired... desire it, at least some. An active filter for each frequency band, so 1 for lows, 1 for highs... you pick the frequency bands. A mixer to blend the 2 two to your delight. They do not need to be in that order necessarily. All in all this means a battery, a board, 3 op amps, and a bunch of resistors/caps to support them. Should you go the complete DIY route and have a vague grasp on electronics, I'd recommend you start by reading these: http://www.allaboutcircuits.com/vol_3/chpt_8/1.html http://courses.cit.cornell.edu/bionb440/da...ingleSupply.pdf http://focus.ti.com/lit/an/sloa093/sloa093.pdf http://www.all-electric.com/schematic/simp_mix.htm If you come up with a basic drawing as a starting point, help will be here to assist in refining it. Good luck.