Moving magnet phase shift

0 Members and 1 Guest are viewing this topic. Read 37388 times.

neobop

  • Full Member
  • Posts: 3448
  • BIRD LIVES
Re: Moving magnet phase shift
« Reply #120 on: 12 Jun 2014, 10:31 pm »
I may be sorry I'm entering into this thread but I have a few things to say.

Phase shift is boldly in the topic, and there has been a request for an EE to respond. Let it be known that the RIAA EQ in every preamp I know of is a simple RC network which simply reverses the EQ that was supplied in making the recording. Therefore, there are not phase problems. The phase shift in the recording is undone by the phase shift in the playback resulting in no phase shift at the end of the process.

However, If the cartridge has an untamed resonance  in the audio band all bets are off, but this has nothing to do with the phono preamp and the imagined phase shift in it.

Any discussions in the Audio Asylum are best ignored.

PS. 99% of what we call MM cartridges are actually VR (variable reluctance).  GE told the truth with their VR series, where did we get off the track. Pardon me, but i just like to call a spade a spade.

I was thinking about this statement and how it might apply to a strain gauge system with no RIAA correction. 

1. Doesn't correct relative phase?

2. No need, maintains phase integrity from midband up, therefore moot? 

3. All of the above?

4. none of the above?

5. who cares?

neo

*Scotty*

Re: Moving magnet phase shift
« Reply #121 on: 12 Jun 2014, 11:41 pm »
If the response curve is flat when it comes out of the preamp, then this may be a case where amplitude error equals phase error.
If the strain gauge cartridge can accurately reproduce a square wave then there are no phase errors.
Scotty

neobop

  • Full Member
  • Posts: 3448
  • BIRD LIVES
Re: Moving magnet phase shift
« Reply #122 on: 13 Jun 2014, 01:21 am »
I don't think lack of amplitude error proves encoded phase error is corrected.

If there is encoded phase error, then it would be encoded on the square wave track.  I think you're right.

Lets look at the test report.   :dunno:

neo

dlaloum

  • Full Member
  • Posts: 710
Re: Moving magnet phase shift
« Reply #123 on: 13 Jun 2014, 02:51 am »
Most natural phenomena are minimum phase.

If the strain gauge cartridge is also minimum phase (why wouldn't it be!) - then a flat F/R implies correct phase, as the relationship between amplitude and phase in a minimum phase system is symmetrical....

As long as you are not using digital linear phase or maximum phase filters, any mechanical adjustment or standard electrical filtering/EQ will be minimum phase, hence the simple old fashioned flat frequency response is a valid measure of phase correct behaviour.

It sounds too simple to be true, but in this case stick with occams razor....

The strain gauge test report does not look at phase....

But they are measuring an analogue system using analogue (which implies minimum phase) systems...

neobop

  • Full Member
  • Posts: 3448
  • BIRD LIVES
Re: Moving magnet phase shift
« Reply #124 on: 13 Jun 2014, 04:12 am »
That seems right.  I was looking at it as a system and the preamp RIAA should be the inverse of cutter head encoding.

The reverse curve is theoretically applied using time constants at 75us, 318us, and 3180us.  [2122Hz, 318Hz, 50Hz]

http://sjostromaudio.com/pages/index.php/hifi-projects/147-the-riaa-curve#.U5p4KlIU8dU