Which inverter for this record player?

[mascip]

Hi,

this is the back of a record player that I want to install on a boat (with 12v lead acid batteries). Do I need a pure sine wave inverter to get it to work properly, or would a modified sine wave inverter do the job appropriately.



It's only 45W so I assume I could power it with this 100W "quasi sine wave" inverter for example, but will "quasi sine wave" be enough? Or do I need "pure sine wave"?

I cannot find any 100W pure sine wave inverters: the minimum I can find is 300W and it's more expensive (£130).

Any input very welcome

 

[amlu]

go for pure sine wave if you have a choice. not a problem if rated for more watts, it will take as much as connected equipment needs, not whole 300 or something watts all the time. you will have some spare capacity to power a mixer or laptop etc.

if it will work with modified sine cannot be known without checking or knowing electronics and looking on schematic for it, hard to say how is wired up, possibly with vintage circuits to control speed etc.

edit: have a look in tlc wholesalers, 300watt pure sine inverters for 60 quid

 

[mascip]

Thanks a lot for your answer amlu

For £60 can I really trust this inverter? It might be a mistake, but I would rather stick with a reputable brand than have to replace the inverter in a year or two.

I'm going to think about what I would do with a cheap (£37) 100W "quasi sine wave" if it didn't power the record player properly: could be a present for a friend, or I could sell it to someone else for £30. That might be the way to go: for £37, just try it and see ;-)

I wish the answer had been "it will work for sure, no worries", but it's good to have the information that it might not work

 

[mascip]

Oh, another question: if it didn't work properly with a "quasi" sine wave it wouldn't damage the record player, right?

 

[amlu]

Thanks a lot for your answer amlu

For £60 can I really trust this inverter? It might be a mistake, but I would rather stick with a reputable brand than have to replace the inverter in a year or two.

I'm going to think about what I would do with a cheap (£37) 100W "quasi sine wave" if it didn't power the record player properly: could be a present for a friend, or I could sell it to someone else for £30. That might be the way to go: for £37, just try it and see ;-)

I wish the answer had been "it will work for sure, no worries", but it's good to have the information that it might not work

tlc are quite reputable wholesalers, should not be selling generic chinese crap (but everything is chinese this days anyway)
and you should be able to return it if something goes wrong. unlike some ebay deals etc.

installed a 12v 600watt cheapo ebay inverter for a friend, in a off-grid caravan, all connected up, measured 260v on the output!. told him to get it replaced (import from china, not easy). He instead contacted the seller, they advised him to open up the unit and adjust the trim-pot. It works now as far as I know (caravan went to Spain).

 

[Lucien Nunes]

I would use a true sine wave interter, buy a 300W one if you have to. That is a valve record player; the impedances of signal circuits in valve equipment are much higher than in solid-state and it makes them more prone to pick up buzz from the power delivered by a 'quasi-sine' unit. In truth 'quasi sine' is not sinusoidal at all, it is a 3-step rectangular wave that has a specific mathematical relationship to a sine, namely that the peak / RMS ratio is the same. So it produces the correct voltages inside equipment, but is not much better than a square wave as far as radiating interference is concerned. The record deck motor will be an induction motor so the frequency needs to be correct. Most units are pretty good in that regard though.

measured 260v on the output

What meter did you measure that with Amlu? Because of the non-standard waveform of a Quasi-sine model, some meters will give an incorrect reading. The whole idea of quasi-sine is that the peak voltage is correct for the benefit of switched-mode PSUs but the RMS is also correct for resistive and transformer loads. To do this it has to output peak voltage for some of the time and none at all for the rest of the cycle, which can fool a non-true-RMS meter. If you set it to 230V on such a meter, a motor or light bulb will 'see' the wrong voltage.

 

[mascip]

Thanks a lot Lucien. So the lesson is:

"anything that processes sound (or any other type of signal / data) should be wired only on a true sinewave inverter"

Because they are prone to damage by current spikes.

Right?

 

[mascip]

One last question: does anybody know any 100W pure sine wave inverter?

 

[Lucien Nunes]

Right?

No, not quite. Spikes aren't the issue here - by spikes we normally mean abnormally high voltage peaks, which should not occur with a properly functioning inverter. And I wouldn't equate data processing i.e. computing / all-digital equipment with analogue sound. Most digital devices are powered via switched-mode power supplies, which use similar technology to inverters themselves, and digital circuitry is inherently fairly tolerant of background electrical noise. Therefore a normal desktop or laptop computer will usually work 100% OK on quasi-sine, as the power is converted and filtered before it leaves the power supply unit or charger.

Audio / analogue circuitry can be up to 1,000,000 times more sensitive to the undesirable harmonics on non-sinusoidal power, which usually causes at least an audible background buzz, if not a loud one. Your case of the valve radiogram is unusual, because people don't often power vintage equipment from inverters. The circuitry of an AM radio or phono amplifier is especially sensitive to electrical noise, and you would be very lucky not to get annoying buzz from a quasi-sine. The harmonic-laden AC will be present in the main power transformer, turntable motor, switch wiring etc, and to a lesser extent on the valve heater circuit which is AC and visits all parts of the chassis. FWIW many vintage valve car radios were powered by a dedicated electro-mechanical inverter in a separate box, and they had to go to some effort to suppress the interference it created.

I don't know of such a small pure sine, but if you get a larger one, it will be more useful for other things, and will run cool and have a long life. You lose a little in slightly higher idle consumption.

 

[mascip]

Ok, I get how analogue circuitry would expect a pure sine wave, and how digital equipment is generally made to withstand imperfect sine waves. Thank you for such an in-depth explanation

300W inverter it is, then. Again, thank you!

 

[mascip]

I found a smaller one: pure sine wave 200W, Victron Phoenix Inverter 12/180

 

[amlu]

I found a smaller one: pure sine wave 200W, Victron Phoenix Inverter 12/180

go for it, quality bit of kit.

 

[Lucien Nunes]

I don't know where the smaller Victron stuff is made these days as it's ages since I used to install them, but they were always one of the best. Should outperform and outlast no-name bargain basement alternatives.