Change in frequency mains - Page 5

Mikelo · 5th January 2005, 09:21 PM

I have the 'opposite' problem. I have been
using my AC motor with a 60Hz pulley for
US AC frequency, but would like to run it \
at 50 Hz with a 50 HZ pulley because it
would be quiter. Does anyone have a
schematic or drawing for such a converter?
Thanks,
Michael

EC8010 · 5th January 2005, 10:06 PM

Trust me, you don't want to do that. 60Hz is the frequency to use - even if you have to synthesize it.

Mikelo · 5th January 2005, 10:20 PM

This Pabst motor was originally built for 50Hz and
Miichell sold a power supply for it that converted 60Hz
to 50 Hz and the received wisdom was that the motor
is quieter at 50 Hz. The supply sold for $800 which
seems whacky even though it looks nicely designed
with two oscillators and two op-amps. Wish I could
get my hands on a schematic or a cheap damaged
model.
Michael

EC8010 · 5th January 2005, 11:48 PM

My mains is 50Hz, but I use 60Hz on my turntables because it's quieter.

Mikelo · 6th January 2005, 05:33 AM

This throws a wrench into my pursuit of 50Hz for
my Gyro's 24VAC Pabst motor. So what's the
argument for that it runs quieter at 60Hz?
I think the argument for 50Hz is that it runs a
little slower and hence less noise. Wish I
could compare myself.
Michael

Raka · 6th January 2005, 08:29 AM

Quote:

Originally posted by EC8010
My mains is 50Hz, but I use 60Hz on my turntables because it's quieter.

This is interesting, how did you get the impresion that the 60Hz are better? This is for all your tt? Could you please elaborate a bit on this?

After all this time working on the ps, my conclusions are that the voltage divisor MUST be avoided, and that the correct voltage is critical for low vibration.

EC8010 · 6th January 2005, 09:05 AM

Agreed, 50Hz reduces the rotational speed of the motor compared to 60Hz, but the mechanical noise of a decent sleeve bearing is minimal.

Electrically, a motor is similar to a perfect transformer in parallel with an inductor. The inductor's reactance is proportional to frequency, so the current it passes is inversely proportional to frequency. If that inductor passes too much current its core will saturate and buzz. We want our applied power to go into rotating the shaft, not saturating the parallel inductor. It's my belief that this is why 60Hz allows a lower noise floor than 50Hz. This idea seems to work for old-fashioned 4 pole motors (Garrard 301) and the more modern 24 pole synchronous motors. Remember that turntable wow is not an additive effect - it doesn't just add 0.55Hz to the audio, it's a modulating/multiplying effect that adds noise sidebands either side of each and every audio frequency.

Mikelo · 6th January 2005, 12:39 PM

Very helpful explanation! I'm going to try to test this.

dhaen · 21st July 2005, 06:59 AM

All the PCB's mentioned earlier in this thread have now gone.
A schematic can be found here
Beware its a bmp.

Onvinyl (Rüdiger), I tried to send you this, but your email was over-quota.

Cheers,

pibb · 17th January 2006, 04:59 PM

Hi: A 50 hz Pulley and power converter would get you going. I have a 50hz pulley that I would be willing to trade for yours if you are interested, let me know. ciao

Pibb

5th January 2005, 09:21 PM	#41
Mikelo diyAudio Member Join Date: Feb 2004 Location: Colorado	60HZ to 50 Hz I have the 'opposite' problem. I have been using my AC motor with a 60Hz pulley for US AC frequency, but would like to run it \ at 50 Hz with a 50 HZ pulley because it would be quiter. Does anyone have a schematic or drawing for such a converter? Thanks, Michael

5th January 2005, 10:06 PM	#42
EC8010 diyAudio Moderator Emeritus Join Date: Jan 2003 Location: Near London. UK	Trust me, you don't want to do that. 60Hz is the frequency to use - even if you have to synthesize it. __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

5th January 2005, 11:48 PM	#44
EC8010 diyAudio Moderator Emeritus Join Date: Jan 2003 Location: Near London. UK	My mains is 50Hz, but I use 60Hz on my turntables because it's quieter. __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

6th January 2005, 09:05 AM	#47
EC8010 diyAudio Moderator Emeritus Join Date: Jan 2003 Location: Near London. UK	Agreed, 50Hz reduces the rotational speed of the motor compared to 60Hz, but the mechanical noise of a decent sleeve bearing is minimal. Electrically, a motor is similar to a perfect transformer in parallel with an inductor. The inductor's reactance is proportional to frequency, so the current it passes is inversely proportional to frequency. If that inductor passes too much current its core will saturate and buzz. We want our applied power to go into rotating the shaft, not saturating the parallel inductor. It's my belief that this is why 60Hz allows a lower noise floor than 50Hz. This idea seems to work for old-fashioned 4 pole motors (Garrard 301) and the more modern 24 pole synchronous motors. Remember that turntable wow is not an additive effect - it doesn't just add 0.55Hz to the audio, it's a modulating/multiplying effect that adds noise sidebands either side of each and every audio frequency. __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

17th January 2006, 04:59 PM	#50
pibb diyAudio Member Join Date: Jan 2006 Location: Calgary	Thorens Pulley Hi: A 50 hz Pulley and power converter would get you going. I have a 50hz pulley that I would be willing to trade for yours if you are interested, let me know. ciao Pibb


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5th January 2005, 10:20 PM	#43
Mikelo diyAudio Member Join Date: Feb 2004 Location: Colorado	This Pabst motor was originally built for 50Hz and Miichell sold a power supply for it that converted 60Hz to 50 Hz and the received wisdom was that the motor is quieter at 50 Hz. The supply sold for $800 which seems whacky even though it looks nicely designed with two oscillators and two op-amps. Wish I could get my hands on a schematic or a cheap damaged model. Michael

6th January 2005, 05:33 AM	#45
Mikelo diyAudio Member Join Date: Feb 2004 Location: Colorado	This throws a wrench into my pursuit of 50Hz for my Gyro's 24VAC Pabst motor. So what's the argument for that it runs quieter at 60Hz? I think the argument for 50Hz is that it runs a little slower and hence less noise. Wish I could compare myself. Michael

6th January 2005, 12:39 PM	#48
Mikelo diyAudio Member Join Date: Feb 2004 Location: Colorado	Very helpful explanation! I'm going to try to test this.

21st July 2005, 06:59 AM	#49
dhaen diyAudio Moderator Emeritus Join Date: Jun 2002 Location: U.K.	All the PCB's mentioned earlier in this thread have now gone. A schematic can be found here Beware its a bmp. Onvinyl (Rüdiger), I tried to send you this, but your email was over-quota. Cheers,

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