Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Analogue Source Turntables, Tonearms, Cartridges, Phono Stages, Tuners, Tape Recorders, etc.

Phono cartridge self resonance
Phono cartridge self resonance
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 28th January 2019, 07:49 AM   #31
luckythedog is offline luckythedog  United Kingdom
diyAudio Member
 
Join Date: Nov 2009
Location: London, UK
Quote:
Originally Posted by PRR View Post
The cartridge winding C is in there too, but I suspect it is not-large compared to cable and tube C.
Yes, I accept that empirically too. The reason for interest is because, in alternate topology preamps with ultra-low input Z, cable and input stage C effects are avoided. One is just left with, and relies on, coil impedance.

LD
  Reply With Quote
Old 29th January 2019, 02:42 AM   #32
PRR is offline PRR  United States
diyAudio Member
 
PRR's Avatar
 
Join Date: Jun 2003
Location: Maine USA
Low-Z inputs short-out capacitive effects.

Coil capacitance is a lot about its Surface Area. Bigger coils, more C. This needs clarification: there is a C to "free space", nothing near the coil. In many practical cases there is C to a core or shield and this will be larger than the free-space C.

More reading: Transformers For Electronic Circuits, Grossner, "The wideband transformer Synthesis".

The C of guitar pickups is moderately well known. 123pFd may be a typical value. The phono pickup coil is much smaller than a guitar pickup coil, so the C would be much-much less. I'm thinking under 25pFd. Which is clearly the smallest C in a typical phono system.
  Reply With Quote
Old 29th January 2019, 04:49 PM   #33
luckythedog is offline luckythedog  United Kingdom
diyAudio Member
 
Join Date: Nov 2009
Location: London, UK
Thanks that's more than interesting. So self-C is pretty much for the coil as a lumped body to the universe as a whole or the ground of the circuit involved whichever is nearer

All I can think is that as a lumped body the inductor behaves as a single turn. I can sort of get that since the mutual inductance of all turns sums. It has to be something like that.


LD
  Reply With Quote
Old 29th January 2019, 05:50 PM   #34
Bonsai is offline Bonsai  Europe
diyAudio Member
 
Bonsai's Avatar
 
Join Date: Jul 2003
Location: Europe
I think Pyramid has a good suggestion - get it on a VNA. Also look at the screen and audio lines wrt ground.

I've been fiddling with some crude models on LTspice and its very easy to get a peak between 10k and 20k Hz of 6-8 dB with a 47k load. If you set the load at 100k or 200k, the resonant peak is 15dB (all figures ref 1 kHz). Quite how some carts are showing peaks of 20dB with a 47k load beats me though.
  Reply With Quote
Old 29th January 2019, 07:20 PM   #35
billshurv is offline billshurv  United Kingdom
diyAudio Member
 
billshurv's Avatar
 
Join Date: Mar 2014
Phono cartridge self resonance
The peak is indeed easy. It's the trough that's an issue.



Bump in the input C to 400pF and you'll see that peak grows.
  Reply With Quote
Old 29th January 2019, 09:35 PM   #36
luckythedog is offline luckythedog  United Kingdom
diyAudio Member
 
Join Date: Nov 2009
Location: London, UK
Quote:
Originally Posted by Bonsai View Post
I think Pyramid has a good suggestion - get it on a VNA. Also look at the screen and audio lines wrt ground.
Yes, that'll be interesting.

Quote:
Originally Posted by Bonsai View Post
I've been fiddling with some crude models on LTspice and its very easy to get a peak between 10k and 20k Hz of 6-8 dB with a 47k load. If you set the load at 100k or 200k, the resonant peak is 15dB (all figures ref 1 kHz). Quite how some carts are showing peaks of 20dB with a 47k load beats me though.
Well, after years of figuring out how best to avoid the LCR resonance was born the ultra low Z preamp. And I sort of forgot all about the LCR hump. If the wind is blowing the right way, and with the right cart choices there need not be a lump, dip, bump in the audioband.

A few things are falling right for low Z preamps lately.....

LD
  Reply With Quote
Old 31st January 2019, 06:44 AM   #37
Bonsai is offline Bonsai  Europe
diyAudio Member
 
Bonsai's Avatar
 
Join Date: Jul 2003
Location: Europe
Was the mid-range dip single channel with needle up or down?

If it’s there in normal use, I’m wondering if there’s some coupling (mechanical or inductive) causing cancellation and then further up the in the top octave, the resonance peak.

I’ll have a play a bit later. Interesting problem.
  Reply With Quote
Old 31st January 2019, 07:49 AM   #38
billshurv is offline billshurv  United Kingdom
diyAudio Member
 
billshurv's Avatar
 
Join Date: Mar 2014
Phono cartridge self resonance
Putting the AT oddity to one side for a moment and looking at the dip in general. If Ortofon is right and the dip is eddy currents can anything be done to prevent them bar having a laminated core? Given LD does not seem them in his OM measurements (not sure if he has tested his S120 as well) does a low-Z load on the cartridge reduce the eddy current effects?


I've forgotten all I knew about this area of EM but if there is a plausible mechanism them that is one loose end, if not tied and least tagged for dealing with
  Reply With Quote
Old 31st January 2019, 09:07 AM   #39
Bonsai is offline Bonsai  Europe
diyAudio Member
 
Bonsai's Avatar
 
Join Date: Jul 2003
Location: Europe
We need JN here on this one.
  Reply With Quote
Old 31st January 2019, 09:36 AM   #40
billshurv is offline billshurv  United Kingdom
diyAudio Member
 
billshurv's Avatar
 
Join Date: Mar 2014
Phono cartridge self resonance
well LD has a FizzX background.
  Reply With Quote

Reply


Phono cartridge self resonanceHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
WTB : New phono Cartridge/stylus Ilianh Swap Meet 4 1st July 2019 04:44 PM
WTB: Phono Cartridge Rodeodave Swap Meet 6 18th April 2018 03:12 PM
Philips GP 390 phono cartridge? msdin Analogue Source 1 9th January 2016 11:26 AM
measuring tonearm/cartridge combination resonance neuperg Analogue Source 2 25th June 2009 08:32 AM
a little help with phono cartridge bferjanc Analogue Source 1 22nd March 2009 04:25 PM


New To Site? Need Help?

All times are GMT. The time now is 02:03 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki