Regarding DIY audio gear safety

[Overmann]

Hello,

I hope this hasn't been asked to death, but my searches didn't find anything at this level of noob regarding the subject. Most of what I found went slightly over my head, I'm afraid.

I am wondering how safe it is to build DIY audio gear like the kits sold by Sound Skulptor, Seventh circle audio, JLM audio, Hairball and PCBgrinder. I have always loved fiddling with things and have done some soldering repairs on old computers before. Form what I've seen many of these kits look fairly simple (like extremely complicated legos). However, I've read alot of posts regarding safety and DIY, and the words deadly and death seem to crop up a lot. Most of these statements seem to regard things that don't seem related to what I would like to do (build some preamps and perhaps a compressor and EQ or two), but I thought I'd ask here.

How dangerous is it to build some of these kits. Are some kits completely safe and are some kits a deathtrap for someone like me? Where can I find information directly related to this kind of project? Will I end up killing myself? I like my life..

Disclaimer: If you end up killing myself trying to build a $199 preamp, you are not responsible, hopefully.

EDIT: I also posted this on gearslutz, but realized that this forum probably would be a better place to ask this question.

 

[joaquins]

With the proper safety precautions in mind you should be able to survive those kind of projects, I think the instructions of the kits have safety recommendations.

If you start with low voltage projects (avoid tubes for example) and get a prebuilt power supply so you don't need to deal with mains you are pretty much away from lethal stuff, unless you start to eat tantalum caps, those are bad for you, don't eat them  :-\

I don't know how well documented each of the kits are, I don't want to say you are safe off all risk with this, I don't know where a good list of safety precautions for this activity could be found, but there sure is one around. I started with 13yo or so, I just powered my projects with 9V batteries and I survived enough with that to get to know things before start to work on higher energy projects, till I got to the big stuff now working on industrial mains with 100kW+ installations.

JS

Edit: Be safe!  ;D

 

[JohnRoberts]

You probably need to ask the people selling you the kits. If they can't give you a good answer, thats the answer.

JR

 

[Overmann]

Thank you for the replies.
Sound skulptor sells assembled external PSU's for their 19" units, so I guess that should work fine for me (as long as I don't attempt to build the tube pre-amp). If I go for seventh circle audio I can by an assembled chassis (with PSU) and build and fit the pre-amps/compressors in the chassis. I guess that should work fine as well. That might be a good place to start.

I really want to have a go on PCBgrinder's MSPQ76, but I guess I would have to build the internal PSU myself and the assembly guide makes no sense to me. Better leave that project for when I have already built some  preamps and/or compressors.

And thanks, joaquins; I won't eat the tantalum caps, alltough they do sound delicous. :-X

 

[pucho812]

Anything dealing with electronics can be hazardous, even on units you buy at the store, there is potential.... Just go slow,  and follow  safety precautions.  Start with simple like building a cable, then a di box, then move up and up and up....

 

[dirtyhanfri]

Good advices here...

I started with DIY like 5 years ago, even I knew anything about electronics then (I worked as electrician apprentice before, so that gave me a little feedback about AC), my only accidents are some burned fingers and just a few (light) electrical shocks, and always was my fault by not being safe enough.

Start slowly, build some passive devices, then move to bigger circuits with pre assembled psu, and then build something starting with it's psu, and always keep in mind the potential damage. And don't fully trust safety devices, test before needing them.

This said, I have to confess my first build was a stand alone mic preamp, actually the first part I built and tested was the PSU...everything went  right, but that's not the way.

This made me remember the day I tested that PSU  ;D, I used a long extension cord as a remote switch to be far away from it when firing up for first time, just in case it explodes or something... funny days ;D ;D

 

[tmuikku]

Jeah get your workbench tidy and practise using the tools, soldering iron, tweezers etc. Even if you are aware of the hazards and carefull not to work on unit that is powered up but cannot hold the tool in hand or touch a wrong point it might give you en electric jolt Also, if your hands are shaking (coffein?) don't work on the unit. Minimize the risk of humanly error.

You have to have power on when checking out the voltages with multimeter. Don't rush, think at least twice what you are doing before actually committing if there is power involved. Also be aware there might be voltage for surprisingly long time in capacitors after you have shut down the mains. Always check with multimeter, or have one always hooked to psu rails.

 

[Overmann]

All right, I might be able to do this if I start with passive and low voltage stuff and work my way up. But this all seems a litle more risky then I expected it to be. I've been fiddling with electronics since I was a kid and only once or twice electrecuted myself. Harmless but uncomfortable. This summer I was removing a wall socket at my moms appartment because I was helping her set up new walls and it turned out I had turned of the wrong fuse. That was more then just uncomfortable.. I made sure all fuses were off after that..  :-[

I'll obviously have to do some reading as I can hardly deciphre the safety advice that I'm being given. Some of the kits probably have detailed explenations of some of these things but I'd like to get a head start. I read somewhere on this forum that one guy knew someone that had killed himself just by getting close to the tube with something (I didn't understand what he had been doing and to what he had been doing it), so I won't go anywhere NEAR a tube!

Can you guys recomend something to read (or watch) that explains the basic workings of a small project like this and the risks involved. Most of the litterature I'm finding is 500 page textbooks on electrical engineering, it seems. Is there an "audio DIY handbook" or something similar?  :

 

[thermionic]

Buying a secondhand bench power supply can be a 'life saver' in more ways than one:

i) It means you can test and debug your projects without them being connected to the mains.

ii) You can limit the current, so that you won't damage a project if it has an error

iii) You won't keep blowing fuses if the aforementioned project has an issue (very frustrating)

iv) You can test the project psu and project itself independently

There are probably about another 10 reasons why a bench PSU is a good thing to have that I haven't written here. It saves stress and makes for safer debugging / tweaking*

*Unless you're making Valve projects, in which case a bench PSU will be pretty lethal in itself!

 

[PRR]

> removing a wall socket ... it turned out I had turned off the wrong fuse.

Put a loud radio in the socket you will work on. Then you can (probably) hit the right fuse.(*)

There's also 2-part tracers. Put the plug in the outlet to be worked on. Take the probe to the fusebox and rub the breakers to find the strongest beep. This is not perfect. Sometimes you can't tell which of two adjacent breakers beeps the loudest. The loud radio is somewhat more sure.

Still beWARE! The outlet may be on fuse 10, but the overhead light may be on fuse 11 yet spliced-through in the outlet box.

Be very wary. Properly made working wiring is supposed to be reasonably safe. But we don't work on working wiring, we work on wiring which has gone bad. A broken neutral can make the white wire "live". In particular, it used to be common to wire two circuits going the same place with two hots and one neutral in the same cable. If the neutral has come loose, and you don't know, and shut-off just one breaker, that neutral is still "live" through the still-on breaker and load. (In recent years a 2P breaker is required for such runs.)
---

(*)I once did that, turned off breakers one at a time, and the radio never stopped! I already knew there were no pre-fuse taps (my father's house had that). And turning off most of the breakers killed the radio. Turning-on one-by-one, I found two breakers powering the one circuit. Argh! The wiring in the fusebox looked right. Then I had to go around and open EVERY box in the two rooms. Found a lot of bad connections. Undid most of them. One of the first boxes turned out to have two hot wires from two breakers which had been spliced together.

If they'd fed from opposite sides of our 240/120V feed, they woulda popped instantly. I suspect that happened, and they moved the breaker-ends around until the popping stopped.

With *two* 20A breakers feeding to the splice, it would be possible to pull 39+A anywhere in the kitchen (a place where you might have multiple large loads). As the wires were 15A rated, this could have been very bad.

 

[CJ]

non contact tester  $4.99  make sure it works!

maybe i should get one, 

had to quit posting in this thread, people thought i was promoting electro-shock therapy,

http://groupdiy.com/index.php?topic=59084.msg750665#msg750665

since i quit posting i have been zapped about 100 more times, 5 times in one day, yeah i know, explains a lot, don't it? 

DIY is safer than climbing PG&E towers in the rain like we used to do,

had a friend throw a loop of wire around a 60 KV line, formed a 1 turn current transformer, tried to run his house off it, worked, but only when the load was high, safer than flying a chopper in Viet Nam i guess,

 

[JohnRoberts]

I bought a NCVT and mine is too sensitive. it beeps within inches of a hot wire, so too sensitive to parse hot and neutral lines in outlets. Great for finding wires behind walls.

I added an always on (blue) LED in my outlet tester for determining that the outlet is cold (fuse or breaker properly disconnected) before working on it. Even if the outlet is horribly mis-wired so that ground is hot, the ground LED will light up still indicating power present.

JR

 

[PRR]

> a 60 KV line, formed a 1 turn current transformer

If doing a current-transformer, he is liable to get as much power from the 2,300V lines on the street as the 60KV lines through the fields. There's practical limits how much current you can put in a wire. Just making it fatter increases cost as d^2 but surface-area (heat dissipation) only as d^1, so a fat wire at current density equal to a small wire will burn-up. Also you want something not too stiff to roll/unroll.

Mostly they pick a "reasonable" voltage, upsize the wire to a "reasonable" diameter, *then* up the voltage (and towers and hangers) at roughly the same current. If they make a significant jump in voltage (next available model, or planning ahead) the 60KV line may work at lower current than a lower-Volt line.

Not that 2KV is much safer than 60KV, but you don't have to throw so much wire so high up.

 

[PRR]

>> non contact tester
> I bought a NCVT and mine is too sensitive. it beeps within inches of a hot wire, so too sensitive to parse hot and neutral lines in outlets. Great for finding wires behind walls.

Sperry VD6505 isn't $5 but gets fair/good comments about the adjustment range.

You need to have a brain. On max setting, it will tell you that a pile of paper is "live". Of course inside an electrified room there is sure to be some capacitive coupling to both the paper and to the user's body, so this is correct, if meaningless. For wall-scanning, you'd turn down until most of the wall was silent but a strip below/above outlets/switches beeped, then you can scan your zone of interest with some discrimination. For poking bare wire/screw, minimum sensitivity is probably what you want.

 

[G-Sun]

I recommend a build with a good manual,
and see if the person selling them offer support.

 

[JohnRoberts]

>> non contact tester
> I bought a NCVT and mine is too sensitive. it beeps within inches of a hot wire, so too sensitive to parse hot and neutral lines in outlets. Great for finding wires behind walls.

Sperry VD6505 isn't $5 but gets fair/good comments about the adjustment range.

You need to have a brain.

That must be my problem...

On max setting, it will tell you that a pile of paper is "live". Of course inside an electrified room there is sure to be some capacitive coupling to both the paper and to the user's body, so this is correct, if meaningless. For wall-scanning, you'd turn down until most of the wall was silent but a strip below/above outlets/switches beeped, then you can scan your zone of interest with some discrimination. For poking bare wire/screw, minimum sensitivity is probably what you want.

I'm so stupid I can't find the sensitivity adjustment...  Still can't find it...  :-[

JR

 

[PRR]

> I can't find the sensitivity

Some of the other products reviewed worse. One had no batteries, no manual, no clue that it needed batts (of course- but may not be universally obvious), and the battery door was difficult to even find.

 

[JohnRoberts]

> I can't find the sensitivity

Some of the other products reviewed worse. One had no batteries, no manual, no clue that it needed batts (of course- but may not be universally obvious), and the battery door was difficult to even find.

There is no battery door but a plastic snap that needs to be released so it can slide apart.

Took it apart again... (I had to install the batteries when it was new)...  Still no evidence of a sensitivity trim... It does have a flashlight mode though.... I found that before.. 

This was cheaper than dirt so not really complaining, I got what I paid for (not much).

JR