Getting started: internal wire, power cable, connectors, casing help please!
Sep 15, 2008 at 5:59 PM Thread Starter Post #1 of 6

Omega

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Finally caught the DIY bug, and will hopefully be starting on some Twisted Pear stuff in the next week or two. For many moons, I have spent my lunch breaks reading threads here, and at diyaudio (and yes, I've read the stickies). Still have some unanswered questions!

1. Internal wiring
Suggestions? good size (AWG)? Good supplier (in USA)? I'm aware that many use navships wire, and I might try this eventually, but I'm just looking for good quality copper for now. When wiring between components, any good rules to follow? I figure signal-bearing wires should be twisted pair, while fluctuating high-power lines should be isolated.

2. Best way to get power from the wall to my transformers?
Is it recommended to find an IEC switch (with fuse and modular plug)? Which particular connectors are recommended between power cable and case? Obviously, it is good to eliminate the risk of shock from touching live leads (ran across an XLR-like plug for this, but can't seem to find it again).

3. Why does everyone use toroidal transformers? Seems to me that EI and R-core transformers offer some real advantages w.r.t. 60 Hz noise, with the only disadvantages being maybe size, weight or (marginal) cost?

4. Could anyone please recommend a good solid SE headphone jack that isn't the Neutrik locking jack? (I don't like the look of it)

5. I recognize that casing is likely to be the biggest challenge...especially considering many components will already be assembled for me. Why don't more people buy aluminum flat and put together a case like this:

My Preamp using a Darwin and a Joshua Tree.. - Project Gallery - Twisted Pear Audio Support

Clearly, that guy (Max) has done an exceptional job, and also added flourishes like rounded corners, but it seems fairly simple to tie top/bottom/lside/rside/back together using the rectangular blocks at the corners. Local metal shop says that's about $50 worth of (pre-cut) aluminum, + FPE front panel = ~$100 for a fully customized, full-aluminum case? What am I missing, having never worked with aluminum (plenty of woodworking experience)? Seems a no-brainer versus the Galaxy cases, for example.
 
Sep 16, 2008 at 4:11 AM Post #2 of 6

mwofsi

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Ok, I'll take a guess at 3:

Torroids have a lower magnetic stray field, any deficiencies they have regards to passing high frequency mains noise have been taken care of in the design of the Twisted's power supplies. They're readily available in reasonable qualities and their lighter weight helps with shipping costs. It's what TPA are happy to sell you for use with their products.

Buff' or Opus? They have their own threads you know. Russ and Brian pop in there and you get it from the horses mouth.

Fascinating post by ilimzn here:http://www.audiokarma.org/forums/arc...p/t-72273.html

Then there's the apparent paradox that torroids seem to be rarely used as audio signal transmitters despite there 'excellent' high frequency abilities?
 
Sep 16, 2008 at 6:12 AM Post #3 of 6

Uncle Erik

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Glad to see another builder starting up!

1. I use 600V Teflon coated solid core copper wire. I get it from a local place (Torrance Electronics) but I think it's worth the extra bucks for Teflon. I've accidentally touched ordinary insulation many, many times with the iron and melted a hole. Teflon won't, and if that keeps you from re-doing a wire or two, the extra money will be worth it.

2. I like IEC jacks with built-in EMI/RFI filters. Again, I pick them up over at Torrance Electronics, but I've seen them at Mouser and other places. They usually run $3-$5, and I think the filtering is worth it. You can also find them with built-in fuses and switches.

3. Not everyone uses toroids. They have their advantages, but so do the others. Look at the pros and cons and choose what works for you. If you can scrounge used iron, go for it, and work with what you have.

4. Take a look at the jacks Michael Percy Audio carries. IIRC, he sells a gold plated Vampire jack that's more of a traditional 1/4" jack. Percy has a nice selection of hookup wire and other goodies, too.

5. Flat aluminum? I think it's a good idea, too.

DSC_0007.JPG


This is the most extensive work I've done with aluminum, though I've also done woodwork for years. You can work it much the same way, but it is harder and you can't steam dings out of it.
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Be sure to get bits, blades, etc. that are meant for metal - it will chew up woodwork stuff fast. Also, invest in a set of files. Unless you have a milling machine, you won't get perfect cuts and will need to square/round them up with files. A bench with a vise or two is very helpful. When you drill aluminum, be sure to use an auto centering punch because bits wander more than they do on wood. Drill pilot holes with a small bit, then work your way up. Bigger bits will still wander even after you punch the aluminum if there isn't a pilot hole.

Be sure to wear safety goggles and maybe gloves. I wear glasses, so I always have that covered, but took 4-5 nicks on my hands this weekend from the aluminum. When you drill, you'll get long, thin strands of tinsel flying out of the hole. These are usually sharp-edged, so plan accordingly and clean up.

Another good source for aluminum is eBay. Go to the Business & Industrial listings and run searches for "aluminum plate -diamond" and you should get plenty of offcuts and odd pieces for fair prices. Searching for "aluminum bar" will turn up useful stuff, too.

As for that amp, I should be able to get everything cut, drilled and fitting together right on Saturday and proceed to final filing, rounding over the edges and sanding it smooth on Sunday. Then, with any luck, off to the powdercoater on Monday or Tuesday morning. Look into your local powdercoaters for a finish. Getting a powdercoat is a whole lot easier than painting or polishing and it's tough. I considered anodizing, but I've read that it changes the size of aluminum. Since I count on the holes lining up, etc., I ruled it out.
 
Sep 16, 2008 at 4:00 PM Post #4 of 6

mwofsi

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Quote:

1. Internal wiring
Suggestions? good size (AWG)? ..... .... When wiring between components, any good rules to follow? I figure signal-bearing wires should be twisted pair, while fluctuating high-power lines should be isolated.


I've seen 22awg recomended as a good useful size for audio work, ( as large as you can go and still get it through pcb holes). For TwistedPear stuff you could probably go a little larger because of their handy terminal blocks. Power supply wiring would be a good place to use larger sizes (18awg maybe) depending on application.

A commonly suggested wiring method is to arrange ground wiring in a form of star ground ( not necessarily attached to the chassis) to avoid ground loop noise. Choose a convienient point as being the only place that all ground wires meet.

If you just want to do a quick wire up, stripped out household electrical cable will do fine, probably available from your local hardware for a few cents a foot. 3-6amp should be fine.
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Sep 16, 2008 at 5:31 PM Post #5 of 6

Omega

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Thanks for the suggestions!

I would not have thought to use star ground or EMI/RFI filters on the power inlet, but after the recommendations, it seems the obvious solution
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. Sounds like I'll have to plan my aluminum construction a bit more carefully as well...currently don't have the space or tools for a proper drill-press style rig for making holes in aluminum without slippage...if the simple punch-pilot-drill won't cut it.

Was lucky enough to get in on the most recent round of Buffalo orders. My overall objective is (conceptually) a digital pre-amp. All my sources have decent digital output, so I see no reason to continue using their sub-par analog output stages > analog preamp > amp. The dual input (S/PDIF and I2S) and good jitter handling of the Buffalo made it a good match for digital preamp duty. The added bonus is getting true balanced source path "for free!"
 
Sep 16, 2008 at 5:46 PM Post #6 of 6

Uncle Erik

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You can do the aluminum without a drill press. Use a T-square and a scratch awl to scribe lines on the aluminum. Where scribe lines intersect, you can feel out the center with the point of a punch or auto-centering punch and mark it. Thin bits won't wander from that point. Once you have a hole, you can use progressively larger bits. It takes time, but you can get away with a hand drill and a little filing for cleanup. You should get good results and you'll be happy with your work. If you've done woodwork, you can do this.
 

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