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richfiddler11

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4Instructables449,534Views204CommentsPittsburgh, PA, USA
I have a Masters degree in Electrical Engineering from Carnegie Mellon and have been working in the field of Automation, Robotics and Embedded Systems for over 20 years. I've always enjoyed tinkering/inventing/making things with my hands and love the Maker community, with all the openness and creativity it brings.

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  • Altoids Tin 1/8" Stereo Mixer

    If the speaker is AC powered that means it has an amp built in and it will work just fine.

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  • Altoids Tin 1/8" Stereo Mixer

    Yes, 220 ohms would be fine. My thinking/experience with this has evolved over the years since I first published. Now I’m pretty sure even 100 ohms would protect your equipment (which probably has short protection built in anyway). The worst thing that would happen is a a little distortion, but I don’t even think it would be that bad.Good luck,Rich

    Great tin!!!

    Awesome case!

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  • Disney Parks Pineapple Dole Whip

    Ah.. ok.. so that agrees with what I see locally then. Sorry for stirring up arguments here. Nicely done instructable and I'm sure it tastes great, regardless of how it came to be! Hopefully there's no such thing as bad publicity!

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  • Disney Parks Pineapple Dole Whip

    Hi Matt, I'm pretty sure Dole whip is non-dairy, so I'm a bit skeptical that this is the "official" recipe. We get it locally (not at Disney) at several soft-serve places and they all advertise it as non-dairy (and it's definitely with the Dole logo). Also, here's a Disney blog that calls it out as such: https://www.disneytouristblog.com/dole-whip/ .

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  • Altoids Tin 1/8" Stereo Mixer

    Sorry, missed this question. Higher resistance puts less load on the amplifier and reduces the distortion (in theory at least). But the little amps in portable devices are made to drive loads as low as 16-32 ohms, so over time I've lowered the resistor value with no bad effects. I suspect you could get away with a couple hundred ohms without any problem.

    Nice neat job and love the tin! Thanks for posting.- Rich

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  • Altoids Tin 1/8" Stereo Mixer

    Hi David,Good question. For the mono input, just attach 2 resistors from the tip of the mono jack (same value as the stereo inputs). Then attach the other end of one resistor to the L signal bus and the other to the R signal bus (meaning, attach to the output jack as if it were another stereo signal). Hope that makes sense.Rich

    More or less, yes. The resistors are really there to keep the output stages from fighting /damaging each other. Over the years of playing with this, I've lowered the resistance quite a bit and really you can get away with as low as a 100-200 ohms without much problem. At this point, I'd never go as high as 10k ohms.

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  • Altoids Tin 1/8" Stereo Mixer

    I posted my creepy Elvis chicken cable — you could make something similar, preferably without a face ;^)

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  • Altoids Tin 1/8" Stereo Mixer

    Here’s a very bizarre cable version I made. The original idea was to cover the resistors and sockets in that 2-part epoxy putty (comes in stick form)... I used too much epoxy to start with and let my elementary-school sculpting abilities run wild. This weird Elvis Chicken was born. I guess I could sand it’s face off, but that seems wrong too. Anyway if you can get past the creepy chicken face, you could make something less hideous looking... it is a very practical form of the mixer at least.

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  • Tuning Fork Oscillator

    Amazing what elegant circuits engineers can come up with with such basic components! Do you have a schematic and do you know what kind of motor it uses? The ultimate goal of the timebase circuit has to be to kick the motor at the right rate -- wonder if the motor is in series with the coil that drives the fork?

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  • Tuning Fork Oscillator

    In terms of practical uses: there was an electro-mechanical watch in the 1960-70’s called the Bulova Accutron, that used a tiny tuning fork as a time-keeping element. The frequency would’ve been something easily divided down to seconds... I think it was 3600Hz, but I’m not 100% sure. If you put it up to your ear, you could hear the tuning fork — the logo was even a tuning fork. These gave way to purely electronic watches that use quartz crystals for the timebase. Also, instead of using optical feedback like your circuit, the Accutron watch used the back-emf on the coil to tell when to give it a kick, otherwise the idea is pretty similar. Interesting project!

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  • Hey, glad I could help and thanks for reporting back!Rich

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  • Hi Mark,Nice neat construction, great job. Sorry you're getting noise problems. Obviously, the best I can do is make some educated guesses as to the cause. I currently have a similar setup to you: one input is also from a chromecast audio and the other is a Raspberry Pi Zero W set up to act like an Apple Airplay receiver, but I don't think I've noticed any appreciable noise.Here are some ideas:1) max out the volume output for both devices to improve the overall signal to noise ratio and use your final output device to control the volume.2) sounds like you could be picking up noise from a switching power supply (some of the cheap USB supplies/chargers are really terrible for audio). Try swapping out different power supplies, moving them around to minimize interference, etc. Any way to powe…

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    Hi Mark,Nice neat construction, great job. Sorry you're getting noise problems. Obviously, the best I can do is make some educated guesses as to the cause. I currently have a similar setup to you: one input is also from a chromecast audio and the other is a Raspberry Pi Zero W set up to act like an Apple Airplay receiver, but I don't think I've noticed any appreciable noise.Here are some ideas:1) max out the volume output for both devices to improve the overall signal to noise ratio and use your final output device to control the volume.2) sounds like you could be picking up noise from a switching power supply (some of the cheap USB supplies/chargers are really terrible for audio). Try swapping out different power supplies, moving them around to minimize interference, etc. Any way to power both devices from the same supply?3) could be some kind of interaction between the two source devices and/or the output device (again, probably power supply related). I've never tried it, but you might get some isolation by putting low value resistors (< 100ohms) and/or ferrite beads/inductors in place of straight wire between the grounds. I'd have to think about this some more, but there could be something worthwhile in there.4) This one is grabbing at straws, but I'll throw it out there: I don't think either of your devices has a mic input (i.e. where the connector is a 4-barrel/TRRS type) but if that was the case, one of the rings carries a small DC bias voltage to power the microphone (about 1.5V). If one of the devices *did* have a TRRS jack, that could cause noise. Not very likely, but you could try swapping in a different device (preferably battery operated and for sure with TRS connector) to see which one is the culprit.Good luck and HTH.Rich

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  • Just pointing out there’s more than one way to do things... Nobody said it had to be 120 V line-level. Transformers are great at changing line voltage down (or up). I just pulled one from a dead microwave for free, and plan to rewind the secondary for a battery spot welder (or something).

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  • sorry, didn't see your comment until now. Have a look in the appendix, there are schematics showing how to add volume controls

    Nice job and thanks for posting the picture!You should be fine as long as the nuts stay tight and make/keep a good electrical contact with the case. I just like to use copper wire because A) copper is a *lot* better conductor than steel and (lower resistance/impedance) and B) because the case has coatings/paint and over time may corrode, all of which tend to insulate the connection. and C) it's not that much trouble to add a piece of copper wire.But again, the way you did it is fine and if you ever *do* experience problems (ground hum/intermittent connections) you can either add a bit of copper wire or just clean the case with fine sandpaper and tighten the nuts.Good luck,Rich

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  • Great instructable! I’ve been cleaning devices with corroded batteries for years, but never knew the chemistry. From now on I’ll definitely neutralize with vinegar.One tool I’ve found invaluable is called a “Fiberglass scratch brush” or pen. It’s a bundle of fiberglass strands in a (bulky) pen form factor and does a terrific job of removing the crystals and corrosion without damaging the surface (as would a file or sandpaper). You can find many on amazon, etc by searching for the name above, they run about $10.It’s funny, for years I hadn’t seen many leaky batteries, but within the last 5-10 years it’s been much more common. I’ve heard this attributed to the rise of inexpensive alkaline batteries that cut corners in design and manufacture to save money. I still use cheap batteries, but I …

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    Great instructable! I’ve been cleaning devices with corroded batteries for years, but never knew the chemistry. From now on I’ll definitely neutralize with vinegar.One tool I’ve found invaluable is called a “Fiberglass scratch brush” or pen. It’s a bundle of fiberglass strands in a (bulky) pen form factor and does a terrific job of removing the crystals and corrosion without damaging the surface (as would a file or sandpaper). You can find many on amazon, etc by searching for the name above, they run about $10.It’s funny, for years I hadn’t seen many leaky batteries, but within the last 5-10 years it’s been much more common. I’ve heard this attributed to the rise of inexpensive alkaline batteries that cut corners in design and manufacture to save money. I still use cheap batteries, but I try to remove the batteries from anything that might not be used for awhile.

    Oops missed this comment and recommended the same thing above... in any case +1 for the fiberglass scratch pen/brush, it’s an indispensable tool for cleaning contacts! Pro grade electrical contact cleaner is also good to have on hand (mostly for volume controls/pots/rotary switches, etc.

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  • Hi Julien,Great idea, I like it! Nice build and nice schematic, thanks for including that and the pictures. I agree that sometimes it makes more sense to switch inputs than to mix them, and as you point out, you don't get the power loss from the resistors in the passive mixer. Also, I've come to believe that a much lower resistance in the mixer is OK. I started off building these with 10k ohm resistors, then 1k, and now I'm thinking that a couple hundred ohms (or even 100 ohms) would be fine... TBH I haven't really tested the lower limit. Given the wide range of devices that might be connected, it's best to have a reasonable resistance, say 10x the impedance of typical headphones, which would be 160-320 ohms.Thanks for sharing your work,Rich

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  • Hey, looks really great! Just be aware that if you're mixing line-level or mic-level signals, you won't get any shielding from wood, so there might be the chance of picking up interference. In that case, you could always line the inside with copper mesh or something similar. If you're mixing powered output levels from headphone jacks, the need for shielding isn't such a big deal, so you should be fine.Again, the box looks really nice!

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  • sounds like you're plugging a TRS (3-barrel) cable into a TRRS (4-barrel) jack. The Macbook for sure has a TRRS jack. Here's the problem: the sleeve (barrel closest to the cable) on a TRS/3 conductor cable is ground. The Sleeve on a TRRS/4-conductor is microphone/bias voltage.. So without an adapter, you're connecting the mic/bias voltage to ground. That's probably the source of your noise.

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  • Hi Toby, are you referring to the triangle symbols in the schematic in step 16? If so, those are just intended to represent some type of amplification or gain block. This would typically be an opamp or other amplification device.. certainly not diodes. In the past I used a board with LM4881 headphone amp chips on it, and that worked fairly well. - Rich

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  • Hi Adam, I believe mine were 5-pin as well, the trick is figuring out which ones stay connected when the plug is in the socket. To explain: 3 of the pins will stay connected whether the plug is inserted or not (gnd, left, right), but 2 of the pins (left, right) will disconnect when the plug is inserted. This is so the speaker will be cut off automatically when the headphones are plugged in. If you have a meter with a continuity beeper, this will be a lot easier. You can get them at Harbor Freighton online for under $10. Just insert a I/8" cable into the socket and "beep out" which pins are connected to the tip, ring and sleeve of the free end of the cable. Good luck, Rich

    Hi Adam, tried to respond thru app, but not sure it went through.. Short answer, 5-pin is no problem. If you look closely at the pictures, that's what i have too. Plug one end of a 1/8" stereo cable into the socket you're testing and use the continuity beeper on a volt-ohm meter (< $10 at Harbor Freight/ebay/amazon) to figure out which pins go to the tip, ring and sleeve of the other end of the cable. Make a diagram (I clipped the ones that are disconnected with the plug in).. Good luck, HTH, Rich

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  • Of course it's the author's choice whether to share his STL file or not -- I agree it would be more in the spirit of instructables to share it, but the good news is you don't need it -- there are plenty of designs on thingiverse.com that will do the job quite nicely. Just go to https://www.thingiverse.com/search?q=ryobi+18v Some even have a complete latching socket so the battery locks in place, just like in a one+ tool. Here's an example: https://www.thingiverse.com/thing:2027076

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  • ...note that some audio devices have protective circuitry that switches off the output when they see too little impedance...The solution is to add a resistor in front of the output jack ground, of course at the expense of volume drop. Hi Ralf, I couldn't agree with you more about avoiding too low an impedance load on the audio outputs/mixer inputs (lower impedance = higher power). However, I'm puzzled by your comment since the circuit here does exactly what you're suggesting:   it puts an impedance in line with each input so that the loading on them will be minimal (and it does come at the cost of reduced volume). Most headphone outputs are OK with loads as low as 8-16 ohms.. when plugged into the mixer here, they see nearly 100x that impedance (meaning on the…

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    ...note that some audio devices have protective circuitry that switches off the output when they see too little impedance...The solution is to add a resistor in front of the output jack ground, of course at the expense of volume drop. Hi Ralf, I couldn't agree with you more about avoiding too low an impedance load on the audio outputs/mixer inputs (lower impedance = higher power). However, I'm puzzled by your comment since the circuit here does exactly what you're suggesting:   it puts an impedance in line with each input so that the loading on them will be minimal (and it does come at the cost of reduced volume). Most headphone outputs are OK with loads as low as 8-16 ohms.. when plugged into the mixer here, they see nearly 100x that impedance (meaning on the order of 1/100th the power required). Perhaps you should take a closer look at the schematic. In all the years this project has been up, most folks have questioned the need for the resistors, but you're the first person to ever say that it doesn't go far enough in protecting the outputs of the devices plugged into it!! Cheers, Rich

    Hi Ralf,re: a line output needing higher impedance, yep OK, I get what you're saying... hmm.. you might be better off with an active buffer of some kind.. unity gain op-amp follower or something like that. I'm afraid that the signal reduction due to higher impedance and the need to boost the gain later on will aggravate the ground noise problem you're having otherwise. The isolation transformer might help, but an active boost on your projector output might be the way to go. If you can find an old NTSC video distribution amp/splitter, those have an audio buffer and people pretty much throw them away these days because of HDMI... just a thought.. good luck!Rich

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      • Wooden Spokeshave
      • Sanding Saw
      • Router Plane
  • As someone who clearly appreciates hand woodworking, you'd enjoy using a scraper plane (or even just a hand scraper ). Have a look at the no. 80 Stanley Scraper plane and you'll see why I thought of it looking at your spokeshave.. here's a good article.. https://www.popularwoodworking.com/woodworking-blogs/chris-schwarz-blog/cheap-thrills-the-no-80-cabinet-scrapercheers and thanks for the nice insructable.. -Rich

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  • Beautiful workmanship on the piece and very nice Instructable. I like the beech and brass look. I think you need a matching handmade scraper plane!

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      • Table Saw Class
      • Easy Table Saw Sled
      • 5 Ways to Remove a Stripped Screw
      • Make Your Own High Quality CO2 Lasercutter! With Touch Control!
      • Make a Z-axis for Your Laser Engraver!
      • Arduino Laser Engraver Wood Design!
  • richfiddler11 commented on mikeasaurus's instructable Best Ginger Beer

    wow, I suddenly have a craving for a spicy ginger beer... will have to give this a try!

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  • ha ha, yeah I hear you on that... my family has a strong packrat streak too. BTW, I found a tutorial on sharpening a handsaw http://workshopcompanion.com/KnowHow/Tools/Sharpening/8_Sharpening_Hand_Saws/8_Sharpening_Hand_Saws.htmmight be worth a try. I've refurbished old hand planes and they're a joy to use.

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  • nicely done instructable but I can't help but feel bad about destroying an old tool like that. I've restored some old tools with great results and have no idea how you'd sharpen a big handsaw saw like that, but I guarantee if it lasted this long, the steel and wood are much better than what you can buy today. It looks nice though and I'd do it if the saw handle didn't have to be modified... maybe join the handle to the shoe with a steel plate or similar.

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      • Universal Mini OMTP ↔ CTIA Adapter - Convertendo
      • Handheld PCB Drill
      • ATmega8 As Arduino (using Internal 8Mhz Crystal)
  • Utkarsh Verma -- No!! Please don't remove it! There are often many ways to solve a problem and I don't think having a switch there is foolish at all. It was clever of you to think of it on your own and you did a very nice write up. It may not be the absolute simplest solution, but that doesn't mean that it's not a valid and useful solution, and it may have some advantages. So look at the tradeoffs of the 2 different solutions:- With your switch solution, the user commits (more or less) to having your adapter plugged into the phone all the time. The advantage is that whatever headset they choose to plug into their phone can be made to work. - With the simple cross-wiring adapter I mentioned, the advantage is that if the phone and headset match, you don't need an adapter at all (same applie…

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    Utkarsh Verma -- No!! Please don't remove it! There are often many ways to solve a problem and I don't think having a switch there is foolish at all. It was clever of you to think of it on your own and you did a very nice write up. It may not be the absolute simplest solution, but that doesn't mean that it's not a valid and useful solution, and it may have some advantages. So look at the tradeoffs of the 2 different solutions:- With your switch solution, the user commits (more or less) to having your adapter plugged into the phone all the time. The advantage is that whatever headset they choose to plug into their phone can be made to work. - With the simple cross-wiring adapter I mentioned, the advantage is that if the phone and headset match, you don't need an adapter at all (same applies for your switch too). The *disadvantage* is that when you need the adapter, you might not be able to find it.I didn't mean to discourage (sorry if I did) but I did want to make sure you understood my point. I hope you keep coming up with ideas and writing instructables. If you ever want to bounce ideas off someone, I'd be glad to discuss more with you (I am an electrical engineer).Take care,Rich

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  • I do understand your switch adapter 100%: In one switch position It's passing all 4 connections straight through and in the other position it's swapping the sleeve and ring2. It's up to the user to figure out which switch position works for their particular headset/phone combination. This is very simple to understand.I'm simply pointing out that you can get the *exact* same functionality with a simple CTIA-OMTP adapter (crossed sleeve and R2). It's up to the user to decide if the adapter is required or not. This is in fact what I've been doing for years now.Here's a commercial CTIA-OMTP adapter on Amazon https://www.amazon.com/dp/B01I507X4W/

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  • Universal Chat Mic -- DIY Gaming/Comm Headset

    Hey UtkarshVerma: No need to autodetect, add circuitry or a switch. To solve the problem of adapting a headset of one type (OMTP/CTIA) to a phone of a different type (OMTP/CTIA) you only need a simple adapter that swaps the Sleeve and R2 (Tip and R1 are passed straight thru). There are really only 2 cases: * Case 1: headset and phone use same standard (OMTP or CTIA). Solution: No adapter needed, plug headset straight into phone.* Case 2: headset and phone don't match. 2 possible sub-cases (omtp->ctia and ctia->omtp) but both are solved with the same adapter.Solution: Swapping Sleeve and R2 works for both. Wiring chart in the pic below. Map it out with OMTP on the input, CTIA on the output and vice versa and you'll see it works for both (unless I've *really* missed something).BTW, I …

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    Hey UtkarshVerma: No need to autodetect, add circuitry or a switch. To solve the problem of adapting a headset of one type (OMTP/CTIA) to a phone of a different type (OMTP/CTIA) you only need a simple adapter that swaps the Sleeve and R2 (Tip and R1 are passed straight thru). There are really only 2 cases: * Case 1: headset and phone use same standard (OMTP or CTIA). Solution: No adapter needed, plug headset straight into phone.* Case 2: headset and phone don't match. 2 possible sub-cases (omtp->ctia and ctia->omtp) but both are solved with the same adapter.Solution: Swapping Sleeve and R2 works for both. Wiring chart in the pic below. Map it out with OMTP on the input, CTIA on the output and vice versa and you'll see it works for both (unless I've *really* missed something).BTW, I don't have any problem with arguing (discussing, debating, whatever you want to call it) as long as it's fact-based and not personal. If someone can show me a better way to do something, a different point of view or a flaw in my reasoning, I'm open to that.

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  • Yeah, no problem. It is relevant and might help somebody. Nicely done instructable, BTW! One point on your adapter: couldn't you get the same effect without the switch? i.e. if the headset and device are of the same type (OMTP or CTIA) you don't need an adapter. OTOH, If they're not compatible, wouldn't a fixed adapter that swapped the sleeve and the ring closest to the sleeve handle both cases? Just seems like that would be easier.

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  • I do cover OMTP vs CTIA in the instructable already. Seems like you're really just promoting your own instructable here, but at least it is relevant and if somebody doesn't want to buy a commercial adapter then at least your project is a good alternative. Good luck with that.

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  • Hi Ferkijel, you're fine. The outer sleeve on the RCA is common (ground) as is the case, so having them touch is not a problem at all. Post a picture when you're done! Rich

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  • Hey, nice work and glad you liked it! Thanks for sharing the pictures. I love the "Tin-tin tin" but it seems like you should make some kind of divider so you can store cables or something in the extra space! Nice job! -- Rich

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  • Couch KBM (keyboard/mouse on the Couch)

    Hey, I'm sorry I missed your comment for so long! (busy lately) Not sure if you built anything or not yet, but I use a double keyboard setup every day (attached some pictures). It looks pretty funky, and is a bit heavy, but it definitely does the job! A few comments:- This is 3rd or 4th iteration, it keeps evolving over time. - two pieces of thin, light board separated by a 3.25" riser - masonite pegboard is nice because you can easily use cable ties to capture wires, etc, but the 1/4" luan plywood is lighter- wide enough to span the outside width of my recliner- there's a small USB hub hidden between the layers. - lower keyboard/mouse attached to hub - a 10-ft heavy-duty USB extension cord that acts as a detachable tether. (this and another wire with power for a USB LED li…

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    Hey, I'm sorry I missed your comment for so long! (busy lately) Not sure if you built anything or not yet, but I use a double keyboard setup every day (attached some pictures). It looks pretty funky, and is a bit heavy, but it definitely does the job! A few comments:- This is 3rd or 4th iteration, it keeps evolving over time. - two pieces of thin, light board separated by a 3.25" riser - masonite pegboard is nice because you can easily use cable ties to capture wires, etc, but the 1/4" luan plywood is lighter- wide enough to span the outside width of my recliner- there's a small USB hub hidden between the layers. - lower keyboard/mouse attached to hub - a 10-ft heavy-duty USB extension cord that acts as a detachable tether. (this and another wire with power for a USB LED light are covered in light-blue woven cable jacket)- top keyboard/mouse is wireless, but could have a used 2nd USB hub/extension cable- top design allows swapping out keyboard/mouse easily for other computers- small black plastic frame on left is a 3D printed phone holderBTW, I didn't feel the need to modify the recliner arms in any way. This rig sits there rock solid on its own, just had to make sure the bottom was smooth so it didn't rip up the fabric in the chair.If you made something, please share a picture, I'd love to see your ideas!Rich

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  • I'd build it as-is, but replace one of the 3.5mm stereo input jacks with two mono 1/4" jacks (L+R). On the two 1/4" jacks, the ground/sleeves are tied together, the tip of one goes to the tip of the 3.5mm stereo jack, the other tip goes to the ring (middle) of the stereo jack. You shouldn't have to change anything else. Make sense?

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  • Diodes will waste a lot of power (0.7V * 1A= 700mW per cell, for example). This article suggests that parallel connection is not a problem per se, but sometimes large parallel packs will have fuses in line with each cell in case one develops a bad short: http://batteryuniversity.com/learn/article/serial_...

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  • Hi Marc, if everything is built correctly, the cables are all good and the outputs of all 4 synths are good then you should hear all 4. I would suggest the troubleshooting method of changing 1 variable at a time, for example: for each cable in turn, test each one with Synth #1 and input #1. If all 4 cables are good run through the inputs in turn, then the synths. If all of those single combinations are good, start working on pairs, etc, until you can reproduce the problem. Not much fun, but that's how I troubleshoot.. if you're patient and methodical, you'll eventually find the issue. Rich

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  • As long as the total impedance of the outputs is high, practically you can have as many outputs as you want. No need for a switch. Remember, the output loads are seen in parallel, meaning that 1 low impedance output load (like headphones) will kill the sound for all of them. But you could drive many pre-amp inputs without a problem.

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  • Honestly, it's not that critical as long as they're all the same value. Lower resistor values will result in less signal loss, but at some point there will start to be some degree of distortion (when you start to get down below 10x the output impedance of the devices, for example), but that depends on a lot of factors. I think 1K ohm is plenty high enough and you could probably get away with half that -- say 470 ohms or higher, and be fine.

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  • Nice instructable, but in the statement "P / V = I 500 watts / 120 volts = 4.16 ampere hours (at 120 volts)" you're actually solving for Amps, *not* amp-hours. The two are *extremely* different -- Ampere is the unit of electrical current flow and Amp-hours is a measure of battery capacity. This may seem like a picky detail to some, but getting your units wrong can mean the difference between something working well vs having it catch on fire/blow up.

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