Author Topic: Phase Inversion. Wiring?  (Read 303 times)

Offline rockdrigo

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Phase Inversion. Wiring?
« on: March 31, 2020, 09:41:19 AM »
Hi, I'm a total noob here. This is my first day with a Rhodes at home.
Plugged my oscilloscope and noticed a phase inversion (see video). Is this normal? or is it a wiring/polarity issue?
Thanks!
  --Rodrigo.

http://www.apex-telescope.org/~parrar/RHODES/RhodesPhaseInversion.mp4

Offline OZDOC

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Re: Phase Inversion. Wiring?
« Reply #1 on: March 31, 2020, 07:08:01 PM »
I can't give you a tech's answer - and hopefully one will be along shortly to help you.
But it seems to me to be a natural consequence of the way the pickups are daisy-chained together (see attached photo).
Check the Rhodes service manual to see whether this pattern of chaining is consistent from instrument to instrument or somewhat random.
David
Co-author, "Classic Keys: Keyboard Sounds That Launched Rock Music"

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Offline rockdrigo

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Re: Phase Inversion. Wiring?
« Reply #2 on: March 31, 2020, 10:13:09 PM »
Thanks for your reply.

Could be. In fact my piano has the "EARLY 73" wiring style (see below).

  --R.



Offline pianotuner steveo

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Re: Phase Inversion. Wiring?
« Reply #3 on: April 01, 2020, 06:41:45 AM »
Does it work well through an amp? If so, don't be concerned with it.
I have never heard of anyone connecting a Rhodes to an oscilloscope in my 40 years in business. I'm sure others have, but I'm not sure why unless there is a problem.

You have to remember that the signal drastically changes as a note rings out. As long as it sounds fine, you don't need to worry. One common problem with some Rhodes is dead pickups, so if you have any super quiet notes, that is likely the cause.
1960 Wurlitzer model 700 EP
1968 Gibson G101 Combo organ
1975 Rhodes Piano Bass
1979 Wurlitzer 206A EP
1980 Wurlitzer 270 Butterfly Grand
2000 Yamaha acoustic piano
2004 Hammond XK3
2009 73A Rhodes Mark 7
2009 Korg SV-1 73
....and a few guitars...

Offline rockdrigo

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Re: Phase Inversion. Wiring?
« Reply #4 on: April 01, 2020, 09:10:00 AM »
Hi,

Yes, it sounds great. I am adjusting/calibrating the tonebars and tuning. The piano had quite a trip!

I have made a recording off all the keys to graphically adjust the volume (pickup distanace) and identify potential problems (see sonogram below).

Do you recommend standard or "stretch" tuning?

  --R.


Offline pianotuner steveo

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Re: Phase Inversion. Wiring?
« Reply #5 on: April 02, 2020, 09:58:39 AM »
Most people stretch the treble tuning because human ears perceive treble notes as sounding a bit flat.
The opposite is true in the bass, we tend to hear low bass as sounding sharp. Think of early Beatle records-
Paul's bass sounds sharp on many songs. I assume the bass was tuned "perfectly" rather than lowered a little. Short scale basses (and short scale acoustic pianos, IE spinets) tend to have this issue in the bass more prominently.

No need to stretch most of the tuning in a Rhodes.
1960 Wurlitzer model 700 EP
1968 Gibson G101 Combo organ
1975 Rhodes Piano Bass
1979 Wurlitzer 206A EP
1980 Wurlitzer 270 Butterfly Grand
2000 Yamaha acoustic piano
2004 Hammond XK3
2009 73A Rhodes Mark 7
2009 Korg SV-1 73
....and a few guitars...