Discrete Opamp Open Design - Page 121 - diyAudio
Go Back   Home > Forums > Source & Line > Analog Line Level

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

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 25th September 2012, 12:45 PM   #1201
diyAudio Member
 
Join Date: Apr 2003
Location: Eastern Pennsylvania
Quote:
Originally Posted by janneman View Post
You know, I'm not really a phono guy but reading all these phono pre articles in Linear Audio makes me start to think about it.

What I wonder: assuming that the hf ringing comes from mechanical ringing of the cantilever system. If we then damp the coil output to get rid of the ringing/overshoot, that's electrical damping, correct?
Meaning, the cantilever system merrily rings along, except we now don't see it in the electrical output? Or is my assumption incorrect?

jan
I'm going to make a logical guess about this, but I should think that the mecahical system would also be damped. I say that because if you electrically load down the output of an rotary electrical generator, the generator itself becomes a greater mechanical load for whatever is turning it. A phono cartridge, essentially being an reciprocating electrical generator, should experience the same sort of mecahnical loading or damping as a result of being electrically loaded or damped.
__________________
Ken
  Reply With Quote
Old 25th September 2012, 12:49 PM   #1202
expert in tautology
diyAudio Member
 
bear's Avatar
 
Join Date: Apr 2002
Location: New York State USA
I do not know, but it seems likely to me that there is no "electrical damping" merely EQ when a small capacitive load is applied to flatten an HF peak... consider that it could be series inductance as well?
__________________
_-_-bear
http://www.bearlabs.com -- Btw, I don't actually know anything, FYI -- [...2SJ74 Toshiba bogus asian parts - beware! ]
  Reply With Quote
Old 25th September 2012, 12:57 PM   #1203
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
Quote:
Originally Posted by Ken Newton View Post
I'm going to make a logical guess about this, but I should think that the mecahical system would also be damped. I say that because if you electrically load down the output of an rotary electrical generator, the generator itself becomes a greater mechanical load for whatever is turning it. A phono cartridge, essentially being an reciprocating electrical generator, should experience the same sort of mecahnical loading or damping as a result of being electrically loaded or damped.
That sounds perfectly logical. Is that indeed the case? Somehow intuitively I can hardly imagine that tiny coil damping those mechanical vibrations - but my intuitions often are wrong.
Anybody has expertise about this?

jan
__________________
If you don't change your beliefs, your life will be like this forever. Is that good news? - W S Maugham
Check out Linear Audio!
  Reply With Quote
Old 25th September 2012, 01:00 PM   #1204
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
Quote:
Originally Posted by bear View Post
I do not know, but it seems likely to me that there is no "electrical damping" merely EQ when a small capacitive load is applied to flatten an HF peak... consider that it could be series inductance as well?
I understood we were talking about damping by loading with a (relatively) low impedance, sort of brute force.

jan
__________________
If you don't change your beliefs, your life will be like this forever. Is that good news? - W S Maugham
Check out Linear Audio!
  Reply With Quote
Old 25th September 2012, 01:23 PM   #1205
diyAudio Member
 
Joachim Gerhard's Avatar
 
Join Date: Mar 2009
Jan, i think you talked about damping electronically IN THE CIRCUIT ( like Bob did ) and not loading the cartridge AT THE INPUT. That could be done too, i do that with loudspeakers all the time where i tame metal cones for example with series and parallel traps. I have not seen that done with MC cartridges though besides simple RC loading.
By the way, i think i will try it, good idea.
  Reply With Quote
Old 25th September 2012, 01:58 PM   #1206
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
I believe Steven van Raalte did it in his Linear Audio Vol 3 article, loading the cartridge with 10.7k to dampen the response and electrically compensating later in the chain.

If I look at Bob's VinylTrak article in Vol 4 he appears to do the same.
He suggests a 6.7k load so that the roll-off with the cartridge inductance falls at the 75uS RIAA, so you have that EQ right at the cartridge.

jan
__________________
If you don't change your beliefs, your life will be like this forever. Is that good news? - W S Maugham
Check out Linear Audio!
  Reply With Quote
Old 25th September 2012, 02:57 PM   #1207
expert in tautology
diyAudio Member
 
bear's Avatar
 
Join Date: Apr 2002
Location: New York State USA
Most of us doing vinyl these days are using MC cartridges, they want a low R load, usually between say ~10ohms and ~100ohms... it seems to that while this load effects the HF response, it's hardly big rolloff, and in addition dropping the load down too low will also drop the already low output lower, so maybe not a good idea?

But, I am more interested in the ground discussion...

_-_-bear
__________________
_-_-bear
http://www.bearlabs.com -- Btw, I don't actually know anything, FYI -- [...2SJ74 Toshiba bogus asian parts - beware! ]
  Reply With Quote
Old 25th September 2012, 03:05 PM   #1208
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: cambridge ma
Quote:
Originally Posted by Joachim Gerhard View Post
I was not talking about the coil damping the cantilever. The cantilever is suspended on a wire that goes into the cartridge body. That gives the cantilever the opportunity to move
and gives a restoring force. That suspension is damped by a rubber ring.

Joachim do you have any references on this stuff (I'll check the patent)? I would take the suspension to primarily damp the 8.5 Hz arm/cart resonance. I still don't believe the tip mass resonance gets any benefit of motor "braking".
__________________
Silence is so accurate.
  Reply With Quote
Old 25th September 2012, 03:20 PM   #1209
bcarso is offline bcarso  United States
diyAudio Member
 
Join Date: May 2005
Location: Canoga Park, California
Quote:
Originally Posted by janneman View Post
I believe Steven van Raalte did it in his Linear Audio Vol 3 article, loading the cartridge with 10.7k to dampen the response and electrically compensating later in the chain.

If I look at Bob's VinylTrak article in Vol 4 he appears to do the same.
He suggests a 6.7k load so that the roll-off with the cartridge inductance falls at the 75uS RIAA, so you have that EQ right at the cartridge.

jan
Jan, although he does discuss the example of 500mH and 6.7k*, Bob stops short in his actual preamp design of realizing the 75us entirely at the cartridge. Last sentences of 4th paragraph pg. 137 LA #4: "There is also a S/N penalty. Perhaps a compromise is in order."

Based on the model presented for the V15, 370mH in series with 830 ohms, the appropriate value for an external resistor to realize a 75us tau would be 4.103k ohms (a total R of 4.933k ohms). That value using a real resistor adds significant thermal noise, particularly at high frequencies, and also causes some attentuation.

Cordell's compromise is a load of 18k ohms, and he compensates in the stage response.

Brad

*Note that the article does not mention that the 6.7k is the total resistance, as the example is just for 500mH with no internal resistance.
  Reply With Quote
Old 25th September 2012, 03:20 PM   #1210
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
I really don't know for sure. I never really care about max gain. Just optimum design for low distortion.
  Reply With Quote

Reply


Hide 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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Discrete OPAMP audio-gd Vendor's Bazaar 27 20th September 2012 04:02 PM
discrete opamp help blackpowderaudio Parts 0 16th December 2009 03:46 PM
THAT transistor headphone amp (250ma discrete opamp) design sanity check. Russ White Headphone Systems 19 13th December 2007 12:52 PM


New To Site? Need Help?

All times are GMT. The time now is 01:38 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2