Garrard 401 PSU

[Primalsea]

I'm looking into a psu for the garrard.

So far I have only 2 ways of generating a 50hz sinewave:

5mhz crystal and 5 divide by 10 circuits to give 50hz square wave. This can then be put through a filter to change it to an approximation of a sine wave.

This method ends up with a sea of circuits and I'm not 100% convinced by it.

MP3 player with un compressed wav file of 50hz sinewave. This can be put through a bandpass filter before being amplified to 240V.

At the moment this seems an elegant solution.


Any other ideas?? I have a funny feeling that many of the PSUs for the Linn Sondeck use the first method. Pro-Ject PSUs use a microprocessor but I suspect that the output is not as good as a wav file out of a MPS player.

[pre65]

Hi Paul-i remember reading about all sorts of ideas regarding 401 power supplies but in the end the standard Garrard supply won out.

It may have been in the early days of WD so check back in the archives.


Philip.

[Primalsea]

Thanks Phil,

How do I look into the WAD archives?

I looked at other posts on WD but only saw talks about PSUs not doing a better job than the mains.

I only skimmed through them but it looked like the PSUs didn't meet all of the designs requirements (as I see fit).

These would be:
Clean sine wave, cleaner than the mains.
Output impedance which is the same as the mains.
Same voltage as mains.

[Black Stuart]

Primalsea,
I would persevere with this idea.

Apparently the still in production Technics SL1200 benefits mightily from an external PSU, available from a company in the USA.

If it works for one TT, why not for another.

[Mike G]

Hi Paul,

"How do I look into the WAD archives?"

I'm not sure the WAD archive is publically available, but i think Richard has access to them. Maybe he can search out the required posts, and place them in this thread - I think that has been done before.

Mike.

[pre65]

Hi-the discussions i remember were in this forum so consult the archive (link at bottom of the home page) probably in the "source" section.



Philip

[pre65]

Hi Paul-so have you got yourself a 401 now ?


Philip

[david counter]

here's one
http://www.wduk.worldomain.net/forum...read.php?t=769

[Primalsea]

Thanks guys,

Phil I do have a 401 now and sort of happy with it. It need more work, a proper clean up and oiling and the plinth needs finishing. Once these are done I think I will be content with it, apart from the PSU that is.

I've think I have read all of the posts on this forum (including the one kindly linked to)
The problem as I see is that the PSUs were inferior to the mains, thats why they didn't seem to work.

The best wave form generator I can see so far is the MP3 player playing uncompressed files. I like this idea for several reasons.

Its cheap and easy.
The sine wave will be very good (once filtered)
The MP3 player screen can say 33.33 or 45RPM which will look cool
The track length can be limited to the maximum that a record will be expected to play for. This means that when I fall asleep the deck will stop itself!

I'm looking into rectifiying the mains which then running it through an amp circuit that will handle the voltage. I'm not keen on using a isolation Transformer as this will increase output impedance. You dont use one for the garrard anyway and I guess that as long as the bulid standard is good it's not needed.

If theres any posts that someone knows of that is along the same lines as my thinking please advise.

Cheers

[Primalsea]

Found an interesting web page on this topic thats worth reading.