[edit: new link as old one is dead]
http://members.rennlist.org/lt_texan/GarrardPowerSupply.pdf
[/edit]
I don’t know if this is the right forum, but here goes:
I’m in the UK and I’ve purchased a Garrard 401 turntable. It is a UK model, so it runs on 240VAC/50Hz.
But it looks like I might need to use this in the US, so I need to convert 115VAC/60 cycles to the UK standard.
I found Dr. Imbabi’s DIY power supply that fits the bill:
http://www.eng.abdn.ac.uk/~eng289/401/401ps.jpg
I figure mains transformers with 115/230 primaries will get me what I want.
Does anyone have experience with this design? I can’t find anything in these archives (except a reference to the above site).
I also don’t understand a couple things, so I’ll toss these out and see if I get a bite:
1. Any ideas on what capacitance should be on each of the “back to back” caps at the output of the LM3886?
2. T1 and T3 rectification looks drawn to be full wave with centre taps to ground, but the voltages calculate as if it is bridge rectification (where CT would not go to ground).
BTW, I know I can convert the 401 to run on 115VAC/60cycles, but I would have to:
1. buy a new motor pulley
2. buy a new strobe lamp
3. buy a new turntable platter (yikes!)
Bet the psu is cheaper, and then I have clean power too.
Thanks much in advance,
Dan
http://members.rennlist.org/lt_texan/GarrardPowerSupply.pdf
[/edit]
I don’t know if this is the right forum, but here goes:
I’m in the UK and I’ve purchased a Garrard 401 turntable. It is a UK model, so it runs on 240VAC/50Hz.
But it looks like I might need to use this in the US, so I need to convert 115VAC/60 cycles to the UK standard.
I found Dr. Imbabi’s DIY power supply that fits the bill:
http://www.eng.abdn.ac.uk/~eng289/401/401ps.jpg
I figure mains transformers with 115/230 primaries will get me what I want.
Does anyone have experience with this design? I can’t find anything in these archives (except a reference to the above site).
I also don’t understand a couple things, so I’ll toss these out and see if I get a bite:
1. Any ideas on what capacitance should be on each of the “back to back” caps at the output of the LM3886?
2. T1 and T3 rectification looks drawn to be full wave with centre taps to ground, but the voltages calculate as if it is bridge rectification (where CT would not go to ground).
BTW, I know I can convert the 401 to run on 115VAC/60cycles, but I would have to:
1. buy a new motor pulley
2. buy a new strobe lamp
3. buy a new turntable platter (yikes!)
Bet the psu is cheaper, and then I have clean power too.
Thanks much in advance,
Dan
Last edited:
Build it. The 401 sounds a lot better run off this PS than the wall.
1. Probably around a 1000uF. I never saw much point including these caps - the 3886 has negligible offset and really doesn't mind working into a very low dc load.
2. I don't understand your point. It is centretapped as both opamp and 3886 need a bipolar supply.
I played with this circuit almost 10 years ago so memory is a bit sketchy. The oscillator produced lower distortion with a better opamp; i think i measured about 0.05% with a 5534 after fine tuning. The biggest contributor to distortion was the step-up transformer.
You need a decent heatsink on the 3886 - it gets quite hot, probably due to the inductive load.
1. Probably around a 1000uF. I never saw much point including these caps - the 3886 has negligible offset and really doesn't mind working into a very low dc load.
2. I don't understand your point. It is centretapped as both opamp and 3886 need a bipolar supply.
I played with this circuit almost 10 years ago so memory is a bit sketchy. The oscillator produced lower distortion with a better opamp; i think i measured about 0.05% with a 5534 after fine tuning. The biggest contributor to distortion was the step-up transformer.
You need a decent heatsink on the 3886 - it gets quite hot, probably due to the inductive load.
Dan,
I've build this desig, but deviated a bit.
The parts around the LM3886 are basically a gainclone. If you look in the chip-amp forum you'll find a lot of info. I've build that part it according to
http://dogbreath.de/Chipamps/GainCardCopy/GainCardCopy.html
These pages give very clear instructions.
I used an old switchmode power supply which i ripped out of a broken dvd player as the ps for the opamp. As opamp I used the ne5534. (cheap and good).
For R* I used little pots, so I could vary the frequency so that my turntable (Thorens TD160) runs at exactly the right speed (I think the frequency needed for this was 47 Hz).
Be sure to check that the waveform produced is a nice sine. Use an oscillioscoop or the soundcard of your computer (that's what I did). The produced waveform depends on setting of all 3 pots.
The pot which is in the diagram is used to let the thing oscillate right. If you put it to low it won't oscillate, to high and the wave get's distorted.
The other two pots (R*) determine frequency, but if you set them to different values you'll distort the wave form (the setting is not too critical).
As you need only very small adjustments for R* you'll have to find appropriate series and parallel resistors to get a nice set up. You can calculate these from the given formulas.
succes, MArco
I've build this desig, but deviated a bit.
The parts around the LM3886 are basically a gainclone. If you look in the chip-amp forum you'll find a lot of info. I've build that part it according to
http://dogbreath.de/Chipamps/GainCardCopy/GainCardCopy.html
These pages give very clear instructions.
I used an old switchmode power supply which i ripped out of a broken dvd player as the ps for the opamp. As opamp I used the ne5534. (cheap and good).
For R* I used little pots, so I could vary the frequency so that my turntable (Thorens TD160) runs at exactly the right speed (I think the frequency needed for this was 47 Hz).
Be sure to check that the waveform produced is a nice sine. Use an oscillioscoop or the soundcard of your computer (that's what I did). The produced waveform depends on setting of all 3 pots.
The pot which is in the diagram is used to let the thing oscillate right. If you put it to low it won't oscillate, to high and the wave get's distorted.
The other two pots (R*) determine frequency, but if you set them to different values you'll distort the wave form (the setting is not too critical).
As you need only very small adjustments for R* you'll have to find appropriate series and parallel resistors to get a nice set up. You can calculate these from the given formulas.
succes, MArco
Thanks much for the responses and the advice.
On the psu, I think I am confused as to taking a secondary centre tap to ground.
I took a look at my copy of Morgan Jones and saw his example of a “typical” transistor amp power supply. This used 8 diodes across 2 bridges.
I attach a picture.
Also I see the one on the dogbreath site. One bridge.
I expect both will work.
Also, looks like I’ve now got the excuse to get an oscilloscope
Dan
On the psu, I think I am confused as to taking a secondary centre tap to ground.
I took a look at my copy of Morgan Jones and saw his example of a “typical” transistor amp power supply. This used 8 diodes across 2 bridges.
I attach a picture.
Also I see the one on the dogbreath site. One bridge.
I expect both will work.
Also, looks like I’ve now got the excuse to get an oscilloscope
Dan
I'd use a soundcard, because you then also assess the wow and flutter when you digitize sine waves from a test record.
In
http://www.diyaudio.com/forums/showthread.php?s=&threadid=33479&perpage=10&pagenumber=5
you'll find how I distilled the wow and flutter signal from a soundcard recording.
In that thread you'll find more info on a PSU for your turntable.
succes, MArco
In
http://www.diyaudio.com/forums/showthread.php?s=&threadid=33479&perpage=10&pagenumber=5
you'll find how I distilled the wow and flutter signal from a soundcard recording.
In that thread you'll find more info on a PSU for your turntable.
succes, MArco
okay, driving the motor with 60Hz makes sense to me.
But to build a second power supply for a 50Hz strobe sounds like a pain.
Would a 5534 provide enough grunt to drive the LED? Would I need a higher power amplifier to drive a setup xformer for the neon lamp.
Sorry, but one more question on Imbabi's design - what rating in necessary on the 12-0-12 xformer for the oscillator? I'm thinking real small. I found a 6 watt in RS. (Maybe that's enought to drive two 5534's - one 50Hz, another 60Hz?)
thanks,
Dan
But to build a second power supply for a 50Hz strobe sounds like a pain.
Would a 5534 provide enough grunt to drive the LED? Would I need a higher power amplifier to drive a setup xformer for the neon lamp.
Sorry, but one more question on Imbabi's design - what rating in necessary on the 12-0-12 xformer for the oscillator? I'm thinking real small. I found a 6 watt in RS. (Maybe that's enought to drive two 5534's - one 50Hz, another 60Hz?)
thanks,
Dan
It does, but beware, There might be a capacitor involved which provides the phase shift for 2 of the 4 poles of the synchronous motor.
If so, it will be either suited for 50Hz or 60 Hz, but not both. The motor will run noisy/vibrating or not at all when the wrong cap is used.
Of course you can change the cap, but you'll have to find out to which value..
succes, MArco
Original post edited by moderator (by prior agreement with post author) because of safety concerns - see his later post.
So, what you now need to do is instead set the speed control to MAX and now use a variac to set the speed using a strobe disk
(you can buy one here http://www.dedicatedaudio.com/analog?start=20)
If you're clever with an art program and have a good quality printer you can make your own strobe disk!
For a light, get a set of LED Christmas tree lights or decorative lights. (IKEA USA and Canada stock such things).
One interesting side effect of the lower voltage on the Garrard turntable is that it quiets down and the rumble from the motor decreases!
You can print a strobe disk from here ...
http://www.soundexchangehouston.com/table/strobe.html
I tried it with a halogen lamp and it was still clear enough to know you were matched up with the mains.
http://www.soundexchangehouston.com/table/strobe.html
I tried it with a halogen lamp and it was still clear enough to know you were matched up with the mains.
I just don't know why you want to generate a sine wave with a wien bridge and feed that signal to the gainclone, then feed the amplified signal to a stepup transformer. Why don't you construct a wien bridge with a single power opamp like the LM3886 or TDA7294, and feed that sine wave signal to a stepup transformer?
Advantages:
1) save space
2) low part count - you need only 2 transformers and less a single opamp
3) short, point-to-point soldering possible
Advantages:
1) save space
2) low part count - you need only 2 transformers and less a single opamp
3) short, point-to-point soldering possible
honinbou said:I just don't know why you want to generate a sine wave with a wien bridge and feed that signal to the gainclone, then feed the amplified signal to a stepup transformer. Why don't you construct a wien bridge with a single power opamp like the LM3886 or TDA7294, and feed that sine wave signal to a stepup transformer?
Advantages:
1) save space
2) low part count - you need only 2 transformers and less a single opamp
3) short, point-to-point soldering possible
Disadvantages:
1) How do you accurately set output amplitude?
2) No low-pass filter at output possible (reduces harmonics)
It's easy to avoid the separate transformer/rectifier for the oscillator anyway.
honinbou said:I just don't know why you want to generate a sine wave with a wien bridge and feed that signal to the gainclone, then feed the amplified signal to a stepup transformer. Why don't you construct a wien bridge with a single power opamp like the LM3886 or TDA7294, and feed that sine wave signal to a stepup transformer?
Advantages:
1) save space
2) low part count - you need only 2 transformers and less a single opamp
3) short, point-to-point soldering possible
Disadvantages: More difficult to implement AGC properly. The Wien is an inherently low distortion oscillator, the AGC is its main source of distortion. It is much easier to implement decent AGC at low voltage and current than at full power.
Hi
I built a power supply for a rock turntable about 10 years ago. I wanted to use an ac motor but wanted to try and see if genereting the sine wave would produce a better sound than relying on the mains supply. I was amazed how much improvement it made. It really cleaned up the sound and made notes clearer.
I used oscillators to produce the sine wave and used a different oscillator to set 45 and 33 speeds. I do not remember the circuit details at this moment ( I will check ) but the circuit I designed looked a little like the one in the first post with the frequencies generated by crystals.
I recommend your project - you will be amazed by the results.
Don
I built a power supply for a rock turntable about 10 years ago. I wanted to use an ac motor but wanted to try and see if genereting the sine wave would produce a better sound than relying on the mains supply. I was amazed how much improvement it made. It really cleaned up the sound and made notes clearer.
I used oscillators to produce the sine wave and used a different oscillator to set 45 and 33 speeds. I do not remember the circuit details at this moment ( I will check ) but the circuit I designed looked a little like the one in the first post with the frequencies generated by crystals.
I recommend your project - you will be amazed by the results.
Don
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