Fast mains electricity tonight?

[Rave]

My best friend has decided to start adding LPs to his massive collection of Frank Sinatra CDs. He emailed me tonight asking about a turntable upgrade because, in his words, his current turntable is giving him 'reedy treble and thin bass'.

That's not a problem I've ever had with vinyl, even with the cheap Bush MTT1 that I've been using since I knackered the cartridge on my Linn LP12 and then moved into my own place where I didn't have the space for it, or the money for a new cart. So I invited him round tomorrow to have a listen to my MTT1 to see if buying one (they're still £50, as they have been for years) would sort his problems.

Of course I decided to have a listen of my own tonght to make sure that my MTT1 still sounded alright....and it didn't really- a bit reedy, with thin bass. It didn't take me long to realise that that was because the turntable was running fast. Sure enough, after busting out my CD copy of Abba Gold and my Vinyl copies of Voulez Vous and Super Trouper, I established that the turntable was playing about a semitone high. Dragging my finger on the record label got it slowed down enough to lose a semitone and sound pretty good.

I'm pretty sure the MTT1 is tuned to run at a multiple of mains speed. I've notice 45s running fast before, but never 33s. By my unscientific reckoning, a semitone is equivalent to about 2% fast running, which means the mains must be up around 51Hz tonight.

That's pretty fast right? What's going on? Anyone got an oscilloscope to see if I'm just being paranoid?

Really must sort the LP12 out I guess, since apparently the Valhalla power supply has it's own 50Hz oscillator.

[MadduckUK]

[kalniel]

Mains frequency does vary sometimes to counteract supply/demand irregularitys - if they slow it down then they always speed it up for an equal proportion afterwards.

[Steve]

The way I understand it they regulate the frequency of the grid rather strongly - they have quite small acceptable tolerances, and will play with the voltage of the grid in order to maintain 50Hz.

[G4Z]

That is some really rubbish bit of equipment if that really is the cause, wouldn't think it was possible on my technics.

[TheAnimus]

for some reason, i'm going to have to stick my fluke into the wall when i get home tonight!

[Moby-Dick]

that could hurt - I suppose this is the only argument I can see for connecting equipment via a UPS

G4Z - mains powered digital clocks used to take their time form 50Hz AC signal ( I remember building the circuit for it in A Level Electronics , but that was 1000 years ago !)

[Steve]

mains powered digital clocks used to take their time form 50Hz AC signal

What idiot ever thought it'd be a good idea to produce a timer from mains?

[kalniel]

that could hurt - I suppose this is the only argument I can see for connecting equipment via a UPS

G4Z - mains powered digital clocks used to take their time form 50Hz AC signal ( I remember building the circuit for it in A Level Electronics , but that was 1000 years ago !)

Most bedside clocks still do It's quite neat actually because it is so regular - and the fact they do catch up with an descrepancies means you're not likely to be out for too long.

[TAKTAK]

for some reason, i'm going to have to stick my fluke into the wall when i get home tonight!

So that's what they call it nowadays

[Zak33]

Lets get thias straight in my feeble brain.

The main voltage might have been a tad higher than 240v at 50hz last night, making motors spin fractionally faster? So George Michael sounded like Michael Jackson, Michael Jackson sounded like Mickey Mouse, Mickey sounded like Mini and Mini sounded like she was on helium?

I think you've got a point, cos I was watching an old film on VHS video early in the evening last week, and it finished at 5:30 am, and it was only supposed to be 90 minutes long

[TheAnimus]

Yes.

[Howard]

Shouldn't the voltage regulators in these devices counteract fluctuations?

Maybe you've both got a cold or something and it's playing with your hearing

[Rave]

I'm not talking about the voltage. I'm talking about the frequency.

[TheAnimus]

you can get nasty frequencies because of some industrial gear such as air-conditioning etc.

Modern UPS's will actually tell you this input data, yet another reason, if you don't already have one for your main desktop!

[Rave]

Turns out there's a speed adjuster on the motor. Once I'd figured out what tool to poke in there (a 2mm flathead screwdriver as it turns out) I got it running bang on. I had to pull a bunch of foam out with tweezers first though.

However there's no digital circuitry anywhere inside the turntable that I can see so I'm pretty sure the overall speed is dependent on the speed of the mains. I shall watch out for it going off again in future. Meanwhile I think it's long overdue a new stylus....

Oh and because google was no use at all in trying to figure out how to adjust the speed, I'm just going to bung in some keywords so that if anyone else comes looking in the future, they can come here, and avoid the irritation of pulling a load of foam out a tiny bit at a time.

Bush MTT1 turntable record player speed adjustment adjuster adjusting changing motor platter tool