Dr. Imbabiís DIY Power Supply? - diyAudio
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Old 30th June 2008, 03:30 PM   #1
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Default Dr. Imbabiís DIY Power Supply?

Hi there

Dr. Imbabiís DIY Power Supply?

I searched all over for a link to this PSU and the only one I found here is a dud!

Anybody have the schematic or a live link to it?

I am looking into building a similar PSU but would like to check it out.

It is for a Lenco L75 turntable (with a shaded pole motor)

T-I-A

D
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Old 30th June 2008, 04:04 PM   #2
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I have a copy of his design for the Gerrard 401.
PM me your email address.
I too have a L75 and would be interested in your build.
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Old 30th June 2008, 04:11 PM   #3
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Cromodora - you've got mail...


What do you think of this?

http://www.norre.dk/TTPSU/TTPSU.html#Downloads|outline

D
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Old 1st July 2008, 03:38 PM   #4
kevinkr is offline kevinkr  United States
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Quote:
Originally posted by GlidingDutchman
Cromodora - you've got mail...


What do you think of this?

http://www.norre.dk/TTPSU/TTPSU.html#Downloads|outline

D
Interesting design, one concern is the issue with distortion of the output sine, I am not sure whether that is actually an issue or not, but I would probably replace the first order LPF with a 2nd or 3rd order filter if I were concerned.
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Old 1st July 2008, 03:56 PM   #5
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Quote:
Originally posted by kevinkr


Interesting design, one concern is the issue with distortion of the output sine, I am not sure whether that is actually an issue or not, but I would probably replace the first order LPF with a 2nd or 3rd order filter if I were concerned.
Hi Kevin

Distortion is not really an issue here - as long as the output signal is an appoximate sine wave with a stable frequency.

I wonder if there is simpler crystal oscillator diagrams somewhere without a complicated PIC and display...

D
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Old 1st July 2008, 04:57 PM   #6
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Distortion is most definitely an issue but this approach delivers reasonably low distortion. A few years ago i did a very similar exercise using a 90S8515 and measured a second and third harmonic within 0.1%, pretty much on par with a good Wien bridge. I used a proper 8-bit dac but accurate resistors are probably fine. Reshaping a square wave is not likely to produce similarly low distortion.

A Wien bridge is certainly a great 5-minute solution, perfect if you don't need fine tuning or two phases.
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Old 1st July 2008, 06:51 PM   #7
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Quote:
Originally posted by analog_sa
Distortion is most definitely an issue but this approach delivers reasonably low distortion. A few years ago i did a very similar exercise using a 90S8515 and measured a second and third harmonic within 0.1%, pretty much on par with a good Wien bridge. I used a proper 8-bit dac but accurate resistors are probably fine. Reshaping a square wave is not likely to produce similarly low distortion.

A Wien bridge is certainly a great 5-minute solution, perfect if you don't need fine tuning or two phases.
Ja - an issue but not that big an issue... you're not going to pump music throught the thing... he-he!

Man - I am looking for a single phase VFO that enables you to set two seperate freqs for 33.3 and 45 rpm but still allow fine tuning of about +/-20%. Two fine tune pots plus a toggle-sw between the speeds. Thats all - no need for a display... one can check the speed with a strobe on the platter.

Wien-bridge is allright but isnt there a "digital" solution? Will certainly be the only digital in my analogue front-end - he-he!

D
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Old 1st July 2008, 07:15 PM   #8
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Quote:
Originally posted by GlidingDutchman


Ja - an issue but not that big an issue... you're not going to pump music throught the thing... he-he!

Man - I am looking for a single phase VFO that enables you to set two seperate freqs for 33.3 and 45 rpm but still allow fine tuning of about +/-20%. Two fine tune pots plus a toggle-sw between the speeds. Thats all - no need for a display... one can check the speed with a strobe on the platter.

Wien-bridge is allright but isnt there a "digital" solution? Will certainly be the only digital in my analogue front-end - he-he!

D
The way i see it the main point of aftermarket AC power supplies is the low distortion. At least in synchronous motors it obviously affects the vibration of the motor and the sound. Even with a Garrard induction motor i hear obvious difference in sound depending upon the oscillator quality. But then again i also clearly hear the mains cable to the motor...


A simple digital solution (no micros) won't have easy trimpots. And it will definitely generate a lot of RF noise which will have to be filtered or else will mess with the rest of your system. A micro is the easiest way, especially if you are just repeating an existing design. Even easier is to buy one of Mark Kelly's boards and just solder the parts. I hear they are excellent.

A Wien bridge can do all that you require. Why complicate things?
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Old 1st July 2008, 08:16 PM   #9
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Quote:
Originally posted by analog_sa

A Wien bridge can do all that you require. Why complicate things?
Vra ek ook - ask I also...

These thingys could be an option? >> http://www.maxim-ic.com/appnotes.cfm/an_pk/3846

D
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Old 1st July 2008, 09:13 PM   #10
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A great idea. No experience with these particular pots but they seem quite simple to implement. Even simpler is the DS1802 - you just need two pushbuttons. In any case it's a much better solution than ordinary pots.
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