|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
96.255.43.35
In Reply to: RE: What is the rationale for 120Hz? posted by Awe-d-o-file on March 24, 2016 at 17:43:09
Because the filter capacitance is in parallel between hot and ground, the lower impedance at 120Hz vs 60Hz permits a given capacitance to double its filtering action at 120Hz vs 60Hz. "More" of the AC is sent back to ground at the higher frequency. Earlier, I had not taken into account the parallel connections of the capacitance. Personally, I would rather just double the capacitance, if I felt that was needed. That said, I do like the effects of my P300 putting out plain old 60Hz/120V.
You wouldn't want to do it into an AC synchronous TT motor, because that is designed specifically for 60Hz input. Possibly the result of putting 120Hz AC into such a motor would double or halve its speed, or burn it up. (I'd have to have another think on this.)
Follow Ups:
Yes, assuming the same loading, the 120Hz sine will allow for half the voltage ripple on the unregulated rail since the cap gets refreshed twice as often.
Yes, that is why. Shunt caps shunt more efficiently as the frequency is increased. Series inductors are also more effective at blocking higher frequencies. Also, a higher frequency is easier on the iron of a transformer, as saturation is also less likely to occur - that's why transformers rated for 60Hz don't work well at 50Hz, but transformers rated for 50Hz work fine at 60Hz.
Twice the pulses of balanced AC is a good thing. Here is info onsynchronus AC motors.
ET
"""Some P300 users have discovered that these devices are a splendid source of pure AC for running their AC synchronous turntable motors. Indeed, the more expensive Walker motor-drive, designed by Dan Fanny of AHT, works on the same principle though it has a lower power output and it can't be used for powering multiple components.
For the 33.3 RPM speed the Power Factor (line frequency) must be set to the 60 Hz default setting. Some turntable manufacturers such as Walker, Basis, VPI and Rega make turntables with AC synchronous motors that are stable when used at a higher line frequency. This means that dialing in 80 Hz, or 81 Hz to be more precise, will result in an increase to the 45 RPM speed. However other turntables with synchronous motors that use a certain type of speed control circuitry could be damaged by prolonged operation above 80 Hz. Among these are Roksan, Merrill and others, which can still be operated safely at the 60 Hz setting. Of course turntables using DC and non-synchronous motors won't be affected (and the speed won't change) by altering the line frequency. Likewise CD players and transports should not be affected. When in doubt, ALWAYS consult the manufacturer.
In current P300 units, there is no way to set the Power Factor to exactly 81 Hz. Some users have found the 80 Hz setting to be close enough to suit them. The good news is that all Power Plants manufactured after October '99 will be programmable to 81 Hz, for exact 45 RPM turntable speed, though it won't be fine-tunable like the Walker unit."""
I use a Walker on my Lenco, and all my other turntables (4) are vintage Japanese direct-drive types which have internal speed control mechanisms of one kind or another. So I feed the DD turntables good old 120V/60Hz, or 100V/60Hz from a step-down transformer for those built to the Japanese standard. My P300 is, however, one of the later ones that would allow adjustment of frequency, up to a point. (I thought it worked in 5-Hz increments, but I have never played with that adjustment.)
Mine goes from 50-120 one Hz at a time. 120 really widens and focuses the image and it's easy to notice the life lost if you will if the power gets interrupted where it resets to 60.
ET
if only because so many report a positive result. (The "idea" being to raise the AC frequency from 60 to 120Hz.) Is there something magical about doubling the frequency from 60 to 120, or do you hear a gradual improvement if you increase the frequency in small jumps, stopping at 120? And on what types of gear? (preamplifier, cdp, etc)
Thanks.
Edits: 03/26/16
I imagine it increases little by little. Much easier to hear when you jump from 60-120.
Again these are subtle but pretty easy to hear. I get the best improvement in image which I consider the final frontier if you will in sound improvement.
ET
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: