Episode 81 - Soldering Your Own Headphone Amp [Discussion]

[sembazuru]

I just finished watching this episode and thought it had a lot of good tips for beginning solderers. Even the out-take with Patrick's burned thumb.

One thing that I think Dave should have covered is the importance of tinning stranded wires before attempting to insert into the board holes. It can be extremely frustrating to insert stranded wires (I assume he used stranded hookup wire for the jacks, switch, & LED) when they start fraying. A quick twist between your fingers on the stripped and and applying just enough solder to fuse them together would keep headaches to a minimum.

Also, while I like is idea to have the input as a captive cable and male plug, I think he forgot an important step of assembly. The metal of the altiods tin is very thin and over use will cut through the wires causing random shorts. At the bare minimum he should have put a couple layers of e-tape over the wires where they pass through the wall of the tin. Even better would be to use a rubber grommet (also should be available at jaimco, mouser, digikey, newark, allied, etc). These grommets (also sometimes called bushings or strain reliefs) are donut shaped with a slot cut all the way around the perimeter. See this photo: http://media.digikey.com/photos/Keys...Photos/740.jpg You have to cut a slightly larger hole, but then you just slide the wire through and the thick rubber will protect your wires from being eaten at by the sharp edges of the hole.

Darn... one more note... A quick and simple way of twisting wires together (both for noise reduction and easier cable management) uses a drill and a desk clamp. Clamp one end of all the wires together in the clamp, and then tighten the chuck of your drill around the other end of the wires. (For best results, pull the wires so they are straight and make sure they are all at roughly the same tension. This also works best for lengths 1 foot and greater. But if all you need is a couple inches, do a couple feet and save the twisted wires for another project.) Pull the wires tight (so they aren't drooping, you don't need guitar-string tight) and run the drill until the wires are twisted to your satisfaction. Release the drill chuck and remove from the clamp. Cut the lengths you need and, voila, less wire-management headaches. This also makes the wiring look neater, and as we say here "If it looks good, it works good".

[ghostwolf]

Nice episode, Now I need see if TI will send me two OPA2132P ICs through their free sample service. I think I am going to add a Acoustic Simulator to my amp and use it with my RIAA amp and record player. (RIAA was made to distribute a standard for vinyl records audio levels and amplification http://en.wikipedia.org/wiki/RIAA_equalization. I don't think any lawyers was present at that time :-)

[freakazoid12]

Originally Posted by Sembazuru

At the bare minimum he should have put a couple layers of e-tape over the wires where they pass through the wall of the tin.

He did, look for when he's holding the completed version back in the studio. (under his iphone I think) It's more obvious in the HD version but the cable's gone from black & red of the raw wires to the pure black of electrical tape or some sort of other covering.

[fishtoprecords]

Originally Posted by Sembazuru

At the bare minimum he should have put a couple layers of e-tape over the wires where they pass through the wall of the tin. Even better would be to use a rubber grommet

Grommet is really needed. Rather than just e-tape, I like to put shrinkrwap tubing on it, perhaps two layers. Looks better than e-tape

[eugovector]

So, I haven't googled yet, but I'm hoping someone has modded the instructions to include a circuit for rechargable batteries. I'll have to see if I can get all the pieces in time to assemble this over the holidays, but I just don't do disposable batteries anymore.

[skoles]

I like this episode.

- An easily approachable DIY project
- Useful end product
- Cheap
- Geek factor

I'm never going to build a robot, tho it was cool to see. Mag boots, meh but interesting. Oragami? DYI Segway was cool albeit way out of the price range of something to try.

A cool episode would be on making your own vacuform table or molding your own plastic parts using a pour-in kit.

[haku]

Originally Posted by Skoles

A cool episode would be on making your own vacuform table or molding your own plastic parts using a pour-in kit.

I like that idea and way of thinking - episodes on how to build/modify useful tools to make bigger/better end projects without needing deep pockets would be most welcome.

[freakazoid12]

Originally Posted by eugovector

So, I haven't googled yet, but I'm hoping someone has modded the instructions to include a circuit for rechargable batteries. I'll have to see if I can get all the pieces in time to assemble this over the holidays, but I just don't do disposable batteries anymore.

"modded"? rechargable 9V batteries exist, no modifications of the circuit are needed.

[sembazuru]

Originally Posted by Freakazoid12

"modded"? rechargable 9V batteries exist, no modifications of the circuit are needed.

I think he was referring to actually having a charge controller built in so the batteries don't need to be removed in order to charge them.

@eugovector
I haven't seen any circuits for that yet (but I haven't looked that hard). You may have to do your own modifications to the schematic to do this. To get started, check out this data sheet for two of the many charge controller IC's that are available: http://datasheets.maxim-ic.com/en/ds/MAX712-MAX713.pdf Remember that 9V batteries are actually 6 cells all in series, so two 9V batteries in series (like what is used in this amp) is actually 12 cells in series. Make sure when choosing the controller IC for your charging circuit that it can handle at minimum of 12 cells and is appropriate for the chemistry of the batteries you want to charge. The Maxim chips that are in the above data sheet are able to handle up to 16 cells in series and can charge both NiCd and NiMH, so either chip should work unless you want to use any Lithium based 9V battery. I just don't know about availability for the chips as that has always been one of the downsides of designing around Maxim chips in the past.

Because of the extra required parts and circuitry for safely recharging batteries, you may need to use a larger case (even up to using a project box), or do all your circuitry as surface-mount.

Good luck.

[alecf]

I'm finally getting around to watching this episode - I've been living vicariously as a watcher of Systm for a while, wishing I had even close to the chops to build robots, hack my car etc.. I've been writing software in a many languages on many platforms for more than 15 years (google me...) and still hardware hacking is totally daunting.

This was the first episode where I said "Ah ha! I could actually do that!" I really really loved all the soldering tips, explanation of how to clean the soldering iron, why not to solder directly onto chips, etc. Really basic stuff that I'm sure most viewers know really well, but were a total mystery to me. I don't even need or want a headphone amp but I'm going to make this just because it was such an approachable project

Anyway, I don't even have any specific questions or anything (I'm still gathering parts to try this) I just wanted to say how awesome this episode was!