Designing and selling mains (240V) audio equipment UK - Hobbyist / low quantity

[andyowenwest]

I am currently researching and designing electrical audio equipment, example devices:

Tube and solid state guitar amplifiers
Guitar effects pedals
Mixing / filtering units
Synthesizers
Some of these devices will be mains powered and some low voltage.

For context I am in the UK and hold a Masters' degree in Electrical and Electronic Engineering.

I have had friends, relatives etc approach me about buying the amps / pedals that I design

Mainly focusing on the mains tube amps I wish to design:

• What safety testing is required?
• Do I need EMC testing If I use a linear / transformer based PSU design (presumably I would if I designed SMPS)
• Should I have product liability insurance? - if so, how long is this required for, if someone is killed by my product 20 years down the line am I still liable?
• What is the approx cost of getting a home built product into a sell-able state?
• Could I draw up a disclaimer to reduce my liability in the event of injury?
• Could selling the tube amps as a 'parts kit' be a way around all this?
• Should I setup a limited company or similar to start selling these?

In short, what i'm faced with is wanting to sell my guitar amps, pedals etc for fun on the side but not face my house being repossessed in event of an accident. I'm also not intending this to be my main line of income which makes compliance testing into the £1000s prohibitively expensive. I see homemade 'clone' tube amps that people build from schematics on hobbyist forums up for sale on ebay and I cant imagine they would have gone through compliance testing but this makes me wonder how open they are to prosecution?

[bd139]

I've done some research on this as I am developing a product to bring onto the UK market.

> What safety testing is required?

http://www.legislation.gov.uk/uksi/2016/1101/pdfs/uksi_20161101_en.pdf defines what is required. It's a superset of EU regs but basically you will need to self-certify it as CE approved. Start here, do lots of research: https://www.gov.uk/guidance/ce-marking. Sometimes it's better to pay someone else to do this so you can point at them if it's wrong or sue them.

> Do I need EMC testing If I use a linear / transformer based PSU design (presumably I would if I designed SMPS)

Yes. EMC directive covers this. This is enforced by Ofcom and trading standards. See: https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32014L0030 ... strictly you don't need to do this and can defer it but if Ofcom are called out or investigate a product of yours which has a negative EMC situation then you're up shit creek and are going to court.

> Should I have product liability insurance? - if so, how long is this required for, if someone is killed by my product 20 years down the line am I still liable?

Hell yes you definitely need insurance. See later.

> What is the approx cost of getting a home built product into a sell-able state?

Depends how much you do yourself. CE cert is paperwork and marking. EMC will most likely require a third party and cost ££££.

> Could I draw up a disclaimer to reduce my liability in the event of injury?

See later

> Could selling the tube amps as a 'parts kit' be a way around all this?

Yes the EMC directive and CE legislation only applies to finished products. This is a common workaround!

>Should I setup a limited company or similar to start selling these?

Definitely a limited company.

Key point: You need abstraction of liability even if you're doing face painting these days. Look up public liability insurance. Hide behind a limited company. It's not a perfect layer of protection but if you screw up then it seriously limits the damages, not that you intend to screw up based on these questions which are all sensible and good to hear being asked. Disclaimer doesn't really supercede the law. Be clear how the product is intended to be used in documentation and you are covered though if someone does something stupid later on. It won't stop someone suing you but it'll stop them from being successful. You would still have to pay to defend yourself so make sure all paperwork is in order.

Low voltage stuff is probably easiest to abstract responsibility away. Sell it with a CE approved wall wart as a self assembly kit and you're done.

Tubes and mains. Pfft I'd run a mile these days.

[mikeselectricstuff]

> Do I need EMC testing If I use a linear / transformer based PSU design (presumably I would if I designed SMPS)

Yes. EMC directive covers this.

You do not necessarily need testing. You just need to be confident that it meets the required level of performance,
For a linear amp with a transformer PSU, it would be totally unnecessary to do EMC emissions testing as it is obviously not going to be a problem ( assuming it's not oscillating, which you could confirm in a few seconds with a scope).

Mains powered valve stuff introduces a whole new level of potential risks ( electrical and thermal - touch hazard) , however a lot of these can be mitigated by good design and construction, especially if it's all enclosed. If your market would accept it, kits are one way to go but introduces potential support headaches, and doesn't necessarily avoid liability if someone makes a mess of building it.
Using ready-made approved PSUs is a good way to avoid a lot of the issues with mains, though may not fix all EMC issues as pre-approved units are always tested with quiet, resistive loads.

Bear in mind that the system is complaints driven. If you're selling small quantities, unless you kill someone or set their house on fire, you're 99.9%likely to get away with doing nothing more than slapping a CE mark on. Up to you how worried you are about that 0.1%

[bd139]

Yeah totally agree - see my edit above.

To note my father sold a product for 20 years without even a CE mark on it and no one complained to give you an idea how lax everything is.

[andyowenwest]

Thanks for the links, will have an in-depth read when i'm home tonight

With rgs to CE marking and EU regs, who is best to consult: trading standards, citizens advice, lawyer?

Perhaps for the number of units im planning to sell the SELV products with a pre approved CE psu is the way to go

Will EMC testing still be required for an effects pedal using a micro controller? as although its classed as an 'unintentional radiator' its oscillator will be well above the 9kHz limit

Certainly a minefield for a hobby!

[andyowenwest]

So it looks like the cheapest way to go about the amp design is to use a transformer / linear PSU removing the need for EMC, self-certify for CE and sell under limited company


Providing i keep well documented paperwork and regularly update / revise the CE documentation in the event of a claim what insurance do I need

Would public liability or product liability be more suitable? and any recommendations where to look as so far the product liability cover I have found seems to be geared at businesses with more than one employee!

[bd139]

I just checked mine. I have combined public liability and professional indemnity insurance in one. Costs £53 a month from Axa

Edit: honestly when I think about this, I'd make sure you have a marketable product available and customers lining up before even committing to this.

[AndyC_772]

It is indeed a minefield - and the problem is there's no low volume exemption. It really is a major barrier to entry, though arguably where safety is concerned, that's no bad thing if it keeps dangerous amateur projects off the market.

One of the noisiest power supplies I ever saw tested was a linear design. In a simple linear PSU the rectifier diodes can start and stop conducting very quickly indeed, peak currents can be huge, and the RF spectrum that results can be horrendous. The idea that linear mains PSUs automatically "are quiet" is total BS.

You may escape some compliance requirements if you sell a kit, but customers will still quite rightly complain if they build a kit correctly, according to your instructions, and then manage to injure themselves.

One of the professional services I offer is forensic analysis of failed products. Companies occasionally send me their customer returns, and I analyse them to determine the root cause of what went wrong. Sometimes I also get to see a copy of any email conversations which have occurred between the supplier and customer.

For obvious reasons I can't go into specifics, but please be aware, some people do *incredibly* stupid things with electrical products, then look for *any* way they can possibly find to blame other people for the consequences. This includes "the instructions didn't say NOT to do <x>, so I assumed it was OK to do <x>" (which, of course, is why so many products include ridiculous safety warnings).

FWIW: the insurance industry regards product liability as quite separate from public liability and professional indemnity. You might need all three.

[mikeselectricstuff]

Thanks for the links, will have an in-depth read when i'm home tonight

With rgs to CE marking and EU regs, who is best to consult: trading standards, citizens advice, lawyer?

None of the above are likely to have the first clue about it

Perhaps for the number of units im planning to sell the SELV products with a pre approved CE psu is the way to go

Absolutely - start simple and build up from there. Get PSUs from someone reliable like Stontronics.

Will EMC testing still be required for an effects pedal using a micro controller? as although its classed as an 'unintentional radiator' its oscillator will be well above the 9kHz limit

Testing is never actually required, but it is often the most certain way of demonstrating compliance.
For a simple small MCU device that's not doing fast digital I/O, EMC is unlikely to be an issue and personally I probably wouldn't bother with any testing - just add damping resistors to limit output slew rates, and ensure decoupling and groundplanes are good . The clock requency isn't a big issue, it's more about edge rates. Although emissions regs start at 9khz, it's very hard to actually radiate at low frequencies due to teh long wavelengths.

[bd139]

One of the noisiest power supplies I ever saw tested was a linear design. In a simple linear PSU the rectifier diodes can start and stop conducting very quickly indeed, peak currents can be huge, and the RF spectrum that results can be horrendous. The idea that linear mains PSUs automatically "are quiet" is total BS.

Very true. I have had to add snubber diodes across the rectifiers in a linear power supply to get them to shut up. Third iteration of one linear supply at the moment now which has schaffner filter on inlet, snubber diodes, RF chokes in it just so it doesn't splatter noise all over the amateur radio bands. The Meanwell SMPS it replaces was actually quieter.

[mikeselectricstuff]

Back in the days when I repaired cheap clock-radios, they always had 10nf caps across the diodes in the rectifier to avoid noise on the AM radio.

[m3vuv]

what if you built them,sold them to a friend then brought them back off of him to then sell as secondhand?