Discrete Opamp Open Design - Page 130 - 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 26th September 2012, 07:01 PM   #1291
bcarso is offline bcarso  United States
diyAudio Member
 
Join Date: May 2005
Location: Canoga Park, California
The example of a Q =100 resonance is a bit far-fetched, although perhaps useful to capture the concept. Even with a Q = 10, which is rarely encountered, feeding the output of such a resonator to a matched notch filter and switching on a sine wave at resonance produces a burst that peaks after abut 3ms and is 20dB down from the peak after 13ms.

Another observation: the presence of frequency response variations doesn't have to be due to ringing of a resonator as we tend to think of them. For loudspeaker baffles there is a transition in the radiation pattern with frequency that manifests as a gentle boost with quite low "Q". It is entirely appropriate to compensate for this with a simple bridged-T dip in the electronics.

Last edited by bcarso; 26th September 2012 at 07:05 PM. Reason: "with frequency" added
  Reply With Quote
Old 26th September 2012, 07:16 PM   #1292
gpapag is offline gpapag  Greece
diyAudio Member
 
gpapag's Avatar
 
Join Date: Nov 2002
Location: Athens-Greece
Quote:
Originally Posted by SY View Post
No, that's not minimum phase and it's also not single-valued.

We are making progress.

The two necessary conditions for a mechanical or acoustical resonance to be electrically equalizable is that the physical system that resonates should be minimum phase and expressed mathematically by a single-valued function . Is this correct?

For minimum phase, you will ask for linearity and time invariance. Say you have it.
Then causality. You have it too.
Next comes stability. Thank you, that scoops many cases out. But oops! Problem. Is there a maximum Q allowed for the stable ones?

Single-valued function.
My understanding is that a function is a single-valued one when and only when its graph contains no closed loops. Please correct me if I am wrong.


George
__________________
["Second Law is a bitch." - SY] ["The Road To Heaven:Specify the performance & accept the design. The Road To Hell:Specify the design & accept the performance"-Bruno Putzeys]
  Reply With Quote
Old 26th September 2012, 07:36 PM   #1293
diyAudio Member
 
jneutron's Avatar
 
Join Date: Jan 2004
Location: away
Quote:
Originally Posted by bcarso View Post
The example of a Q =100 resonance is a bit far-fetched, although perhaps useful to capture the concept. Even with a Q = 10, which is rarely encountered, feeding the output of such a resonator to a matched notch filter and switching on a sine wave at resonance produces a burst that peaks after abut 3ms and is 20dB down from the peak after 13ms.

Another observation: the presence of frequency response variations doesn't have to be due to ringing of a resonator as we tend to think of them. For loudspeaker baffles there is a transition in the radiation pattern with frequency that manifests as a gentle boost with quite low "Q". It is entirely appropriate to compensate for this with a simple bridged-T dip in the electronics.
You are correct, the Q of 100 was used only for concept capture.

My point was that for a chain of sequential elements from input to output, when the transfer of energy from one element to the next relies upon a resonance to build up the amplitude to a sufficient value that it achieves I/O equilibrium, that kills transient response.

I wasn't actually thinking about baffle or cone decoupling issues (but agree), but more of a reflex or 4th order bandpass kinda thing.
j
  Reply With Quote
Old 26th September 2012, 07:40 PM   #1294
RNMarsh is online now RNMarsh  United States
diyAudio Member
 
RNMarsh's Avatar
 
Join Date: May 2012
Location: 2457 Cascade Trail; Cool, CA. 95614
Quote:
Originally Posted by scott wurcer View Post
I thought we were talking MM, we have discussed virtual ground input MC before. I think John said it makes things sound like "under water".
Our discussion about spherical stylii and the use of pre-distortion on many LP's was a real eye-opener for me.
OK I thought we were talking abpout MC.... typical load was 100 Ohms. I can see JC comment working for the higher Z MM types which used 47K-ish. One thing all this brings up for ME is why I junked the whole thing relating to phonographs and LP's. Just is a big headache that never really gets cured. Esp the distortion levels and on and on. Lets just do the Line level opamp before I get sick and expel my lunch. :-)

Last edited by RNMarsh; 26th September 2012 at 07:51 PM.
  Reply With Quote
Old 26th September 2012, 07:48 PM   #1295
gpapag is offline gpapag  Greece
diyAudio Member
 
gpapag's Avatar
 
Join Date: Nov 2002
Location: Athens-Greece
Quote:
Originally Posted by Kindhornman View Post
and wouldn't this same phenomena happen with the cantilever, headshell, tonearm and gymbal mechanism?
Oh man! I had kept these same questions for my 120th post to SY.

Quote:
Originally Posted by bcarso View Post
Another observation: the presence of frequency response variations doesn't have to be due to ringing of a resonator as we tend to think of them
Brad
You are close to my asking, especially with your last sentence.
When I frequency sweep for to check the impedance of a circuit or a loudspeaker in a Bode plot, it is difficult to see if some small aberrations are indications of small resonances. I then plot the impedance in a Nyquist diagram (real part of the impedance on the X axis. The imaginary part on the Y axis. There, if there is a resonance, the plot makes a closed circle. The area of the circle is indicative of the energy stored there.

George
__________________
["Second Law is a bitch." - SY] ["The Road To Heaven:Specify the performance & accept the design. The Road To Hell:Specify the design & accept the performance"-Bruno Putzeys]
  Reply With Quote
Old 26th September 2012, 08:12 PM   #1296
forr is offline forr  France
diyAudio Member
 
forr's Avatar
 
Join Date: Dec 2004
Location: Next door
Quote:
Originally Posted by Wavebourn View Post
I found one more interesting discrete opamp. Looks like an instrumental amp loaded on output transformer. V/I converters drive controlled by current common cathode stages with deep feedback by voltage. However it is power amp, but can be used as line level output stage with smaller tubes. Thanks to transformer output can be balanced, for professional studio usage.
Click the image to open in full size.

This was published in Electronics World, author Jeff Macaulay, if I remember well.
  Reply With Quote
Old 26th September 2012, 08:29 PM   #1297
gpapag is offline gpapag  Greece
diyAudio Member
 
gpapag's Avatar
 
Join Date: Nov 2002
Location: Athens-Greece
Quote:
Originally Posted by jneutron View Post
Is 20 khz triangular realistic? I would have expected sine for this derivation. Are the peak G's representing slew max or where the stylus hits the vinyl wall?

jn
I was expecting that objection.
Jneutron, I had to do it in my primitive way for to be able to understand it. I used only elementary geometry
Grooves
Acceleration is on part two that is to be published sooon together with an Excel spreadsheet trimmed for SnMs

Of course, there are readily available equations for calculating velocity and acceleration for sines, but these are for normal people. (this is that Jan has not understood about me and asked for new glasses)

Comparing my triangular peak values with the sinus values gives the nice number 1.41…

George

>Edit: Here is a nice method to actually measure acceleration : http://www.luckydog.demon.co.uk/images/Baxandall.pdf
Attached Images
File Type: jpg sin.jpg (127.1 KB, 258 views)
__________________
["Second Law is a bitch." - SY] ["The Road To Heaven:Specify the performance & accept the design. The Road To Hell:Specify the design & accept the performance"-Bruno Putzeys]

Last edited by gpapag; 26th September 2012 at 08:46 PM.
  Reply With Quote
Old 26th September 2012, 08:55 PM   #1298
diyAudio Member
 
jneutron's Avatar
 
Join Date: Jan 2004
Location: away
Ah, so you are using the zero crossing straight line portion for the calculation?

The first derivative (velocity) of the triangular wave I was thinking of is a square wave, the second (acceleration) is infinite at the transitions.

I thought you might be calculating based on the stylus mass,contact area, vinyl modulus, and vinyl density at the abrupt transition in direction.

j
  Reply With Quote
Old 26th September 2012, 10:10 PM   #1299
diyAudio Member
 
Wavebourn's Avatar
 
Join Date: Sep 2006
Location: Pleasant Hill, CA
Send a message via Skype™ to Wavebourn
Quote:
Originally Posted by forr View Post
Click the image to open in full size.

This was published in Electronics World, author Jeff Macaulay, if I remember well.
My respect to Jeff!
__________________
"Our youth [...] have bad manners, contempt for authority; they show disrespect for their elders, contradict their parents, [...] and tyrannize their teachers. -- Plato, 447-367 BCE
  Reply With Quote
Old 26th September 2012, 11:37 PM   #1300
diyAudio Member
 
Chris Hornbeck's Avatar
 
Join Date: May 2011
Location: Little Rock
Quote:
Originally Posted by gpapag View Post
For a tip with an effective mass of 0.27mg (Denon DL-103)following a theoretical groove with an 20KHz triangular 5cm/sec modulation, the resulting peak acceleration is 10,000m/sec^2 (1020G).
The inertial force due to this acceleration btn tip side and wall land would be 0.0027N.

Increasing by 20db the modulation velocity to 50cm/sec, these numbers are multiplied by 10.

In a more common case (1KHz at 5cm/sec) acceleration drops down to 500m/sec^2 (51G) and force is at 0.0000135N

I am sure that calculations based on tip dynamics will give wild peak temperatures but wouldn’t published images prove any thermal induced evidence at the groove lands, if that high temperatures were really occurring?
Wow. Thanks, George. That's enough to get into the right order of magnitude, for sure. From here, I'd need to know whether the vinyl acts like a liquid or not, rate of heat transfer, temperature rise due to pressure, effective contact area, and (I'm sure) a dozen other things. It's just too far over my head, and I'm not sure I'd believe anything on these tiny size scales without a measurement to keep me honest. Here's a few references if anybody's interested:

Turntable Forum • Frictional heating of vinyl revisited

but their arguments are not my own. They're interested in tip temperature and friction and I'm interested in vinyl temperature and pressure.

Anyway, I've failed, and need to retract my claim of 400 F instantaneous temperature, pending a measurement.

Thanks,
Chris

ps: Thanks for the great link. I have some photos made for Stanton Corp back in the 70's, but they're matted and framed, so difficult to scan to share. I really need to do it anyway.
  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 11:01 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