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Urumiko

Any am techs on here?

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Im just curious. ive been learning to tweek and build valve amps for a while now, i keep thinking i need to join a forum to get help with thiso, I was just wondering if there are any techies on here.

I was also wondering if there would be much appetite for breaking the electronics section of the forum in to 3 sections, in guitar electronics, pedals and outboard effects, and amps?

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Probably a little beyond the scope of Projectguitar. We do get the (veeeeeeeeeeeeeeeeeeeeeeery) occasional thread popping up relating to effects and amps, but not frequently enough to justify their own section. My gut feel is there are other forums out there (Music Electronics Forum, AX84, EL34 World, DIY Stompboxes etc), that do it better than we could, and we do guitar building better than they can, however I'm open to suggestion if there's enough concensus and interest.

You'll need to get the idea past our resident server room dungeon master @Prostheta too ;)

 

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I'd like to add that fiddling with AC isn't allowed for us mere mortals in many countries, it's for trained electricians only.

 

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For domestic fixed wiring (power points, house wiring, light sockets, switches etc), yes. In many countries the law is quite explicit regarding who can and cannot perform electrical work. Wierdly, here in Australia I can go down to the local hardware store and buy as many cables. light switches, mains outlets and electrical fittings as I can carry, but as soon as I want to install it in my home I need a licenced A-grade electrician. And paradoxically, just across the ocean in neighbouring New Zealand, I would be able to do my own wiring despite both the Aus and NZ electrical regulations being administered under the same standard, AS/NZ3000.

For building your own device that plugs into a mains wall outlet for personal use things get a bit more murky and grey. A guitar amp is probably legally considered an 'appliance', which in many countries probably just needs to be assembled by a 'competent person'. However the design and construction itself will probably come under the scrutiny of all sorts of legal requirements in order to be certified as safe to be commercially sold in a country.  Essentially confirming if the construction and/or end use of the product is or is not likely to cause harm or damage.

But you're not selling your amp commercially. And as a DIY-er no-one can assess you as being competent to design and assemble such a project. For all I know there are no legal restrictions in DIY-ing your own tube amp, but if you sell it on to someone and they get injured using it because it was improperly designed or assembled. then what?

Pedals? No problem. The only nasty certifiable part that plugs into the wall will be a plug pack, which you won't be building from scratch and are not responsible for certifying it complies with local regulations.

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You can do your own wiring in the UK, but it has to be inspected, signed off and ultimately taken responsibility for by a qualified electrician so it's not common to do ones own DIY electrics, however my dad was an electrician so I've been enjoying free labour in that regard :D I don't know about the rest of the world, but electricians are terrible at making good here though, especially when they aren't getting paid.

 

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2 hours ago, curtisa said:

here in Australia I can go down to the local hardware store and buy as many cables. light switches, mains outlets and electrical fittings as I can carry, but as soon as I want to install it in my home I need a licenced A-grade electrician.

Same here. Also, if a DIY guy makes it and something goes wrong, the insurance won't cover the damages, at least not fully.

Pedals and such are DC devices which can be operated by a battery or a factory made AC/DC converter so they're free to DIY.

Which leads to an interesting question: Is it possible to build a small battery/converter powered tube amp with a spring reverb?

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8 hours ago, Bizman62 said:

Pedals and such are DC devices which can be operated by a battery or a factory made AC/DC converter so they're free to DIY.

There is one extra caveat surrounding DIY pedals. There are also regulatory bodies in most countries that look after radio interference, and electronic products that have the potential to generate radio emissions that cause interference with other products and services must also be certified. In the DIY pedal world that would include anything that needs a high frequency clock to operate - anything with a built in CPU or an analogue chorus/flange/delay. As a non-commercial individual you're probably unlikely to get sprung for such a thing, and the anecdotal reports I've seen floating around is that you'll only be issued a cease and desist notice if you are, but even so...

 

8 hours ago, Bizman62 said:

Which leads to an interesting question: Is it possible to build a small battery/converter powered tube amp with a spring reverb?

Depends. It's entirely possible to build tube gear that only runs on 12V. 'Starved plate' designs are reasonably common but tube purists will argue that they don't have that sound and are a pale imitation of the real deal. But they'd be entirely safe to DIY.

It's also possible to build something that takes the street-legal 12V and produce hundreds of volts for 'proper' tube operation inside the box, but that may also open a can of worms regarding how 'safe' your product is. A device that can generate enough volts to kill, despite being powered from a low voltage wall wart may raise some eyebrows with the pen pushers if you're ever asked to explain its operation. If the method used to generate the HV involved DC-DC conversion, you'd also fall under the requirements for radio emissions (above).

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Thanks, @curtisa. Never thought about the radio emissions until you mentioned them. Then again, doesn't the metal box of a pedal create a Faraday cage which should keep most of the radio noise within?

Gotta love your way of criminal thinking! It only vaguely occurred to me that one could plug an inverter to a 12V converter for 240V AC. As you said, it will be a can of worms regarding safety. Again, no fire insurance might cover the damages caused by such a monster. And yes, as I've noticed how easy it is to make a radio receiver just by chaining some extra devices between the guitar and the amp, accidentally creating a radio transmitter would be equally easy.

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3 minutes ago, Bizman62 said:

Thanks, @curtisa. Never thought about the radio emissions until you mentioned them. Then again, doesn't the metal box of a pedal create a Faraday cage which should keep most of the radio noise within?

Generally that's the idea, and chances are it's probably fine. But if it isn't certified and tested, how do you know it's sufficient? There's other ways RF can get in and out - how about via the input and output jacks? How about radiated from the DC socket?

 

4 minutes ago, Bizman62 said:

Gotta love your way of criminal thinking! It only vaguely occurred to me that one could plug an inverter to a 12V converter for 240V AC.

It's hardly a 'criminal' way of achieving high plate voltages. A DC-DC step up converter is nothing special. You can even use two back-to-back mains transformers to do the same thing. One to go from 240V mains to something safe (ie, the plug pack), which then feeds another transformer wired backwards to take something safe and step it back up to lethal. That's exactly how it's done in the Mesa Boogie V-Twin pedal.

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I could be entirely wrong but i was led to believe by a veteran  amp tech that you can sell on home brew electronics if you get them PAT tested.

I'm not sure how we got on to home wiring but changing ones own light fittings and switches etc is fairly common practice in the UK. Its nigh on impossible to prove who did what anyway.

 

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6 hours ago, Urumiko said:

changing ones own light fittings and switches etc is fairly common practice in the UK. Its nigh on impossible to prove who did what anyway.

It became legal in Finland too a few decades ago. The basic idea is to allow replacing switches or lamps or covers into an existing inspected  and approved wiring. Redoing the wiring in the fuse panel isn't allowed. Same goes for changing the functionality of the wiring, i.e. adding a wall plug to the radiator cable and such.

For any electric devices the CE certificate sets the requirements.

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