Discrete Opamp Open Design - Page 171 - 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 15th October 2012, 02:52 PM   #1701
Waly is offline Waly  United Kingdom
diyAudio Member
 
Waly's Avatar
 
Join Date: Jan 2011
Location: London
Quote:
Originally Posted by KBK View Post
The problem I have with SMT is not that they can sound uniform. They can sound uniform, but on the wrong side of the equation. Choked, is how they sound. Uniformly choked, wide-band, under all loading, from micro to macro.

to-92 and similar is a good balance between thermal sinking and transient function. Too big and too much '3d material' can mess up field effects and their associated path-connectivity, and so on.

Since the ear hears via transient function, in all parameters.... micro linearity in transients, and specifically as compared to one another wide-band, in all moving and living complex harmonic function ---this becomes the critical point. (this is the part that 'few-to-none' in the audio industry understand is the primary critical function for all circuitry)

It's not just the measurement, it's signal development in the physical sense that becomes the primary function, here. Heck, it undeniably is the primary issue, here. Unavoidably so.

SMT could be good (might, as it reaches it's own stability and stays there -depends on use and execution) for thermal tracking, but not for primary signal development and expression.
I may be dense this afternoon, can anybody translate this?
  Reply With Quote
Old 15th October 2012, 02:55 PM   #1702
qusp is offline qusp  Australia
diyAudio Member
 
qusp's Avatar
 
Join Date: Oct 2009
Location: Brisbane, Australia
Quote:
Originally Posted by Waly View Post
I may be dense this afternoon, can anybody translate this?
sorry I cant be of any help, it just reads like a heap of psuedo-scientific phrases strung together to me. sorry KRK youve lost me
  Reply With Quote
Old 15th October 2012, 03:12 PM   #1703
KBK is offline KBK  Canada
diyAudio Member
 
Join Date: Dec 2003
Location: The Wilds Of Canada
Quote:
Originally Posted by qusp View Post
SMT sound 'choked' I guess its because theres less air around them? does this apply with the devices that are exactly the same device in a different package?
I'm no critical expert here. Jneutron is one of the guys here who has the goods on a lot of this stuff, having done direct work in these areas. he and I have a history, but I never fail to listen closely. meaning, I do not have his specific background...but I do understand the issues, though.

it's a trade off of thermal dissipation of transient function, and also pathway sizing as we traverse the delta of core to skin (and other 'stuff'), as compared to the physical shape and complex impedance of the given materials set -under said 'excruciatingly complex wideband' load.

This is why they say that to hear an op amp for the first time, is to hear an original NE5532, one that is in a true ceramic dip package.

When you get to hear that differential (nearly a perfect single cause analysis), you finally begin to get a chance to hear the coloration involved in case materials, due to dissipation and signal development/flow.

Last edited by KBK; 15th October 2012 at 03:15 PM.
  Reply With Quote
Old 15th October 2012, 03:17 PM   #1704
rsavas is offline rsavas  Canada
diyAudio Member
 
Join Date: Aug 2012
Location: Ontario
Other possible candidates to try out, for jfet's ,2SK2394,2SK3557, in SOT23 pkg
from JFET - Junction Field Effect Transistors
http://www.onsemi.com/pub_link/Collateral/EN4839-D.PDF
http://www.onsemi.com/pub_link/Collateral/2SK3557-D.PDF
  Reply With Quote
Old 15th October 2012, 05:33 PM   #1705
EUVL is offline EUVL  Europe
diyAudio Member
 
Join Date: Oct 2003
2SK3557 is essentially identical to BF862, except for a touch less Yfs and higher capacitances.
So BF862 is IMHO the better part.


Patrick
__________________
xen-audio.com
  Reply With Quote
Old 15th October 2012, 05:35 PM   #1706
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: cambridge ma
Did some quick sims of the split/bootstrapped compensation (jcx). I found with an even split (2-200pF in series) with the center bootstrapped was an improvement, however the bootstrap had to be derived at the output of the emitter followers just before the output pair or the thirds were worse. The distortion numbers start getting silly.

Indeed the settling time is very compromised by this.

Hi Ken, I'm honored. There is very little signal current in any resistors but the feedback network.
__________________
"The question of who is right and who is wrong has seemed to me always too small to be worth a moment's thought, while the question of what is right and what is wrong has seemed all-important."

Last edited by scott wurcer; 15th October 2012 at 05:38 PM.
  Reply With Quote
Old 15th October 2012, 05:53 PM   #1707
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: cambridge ma
Quote:
Originally Posted by KBK View Post
This is why they say that to hear an op amp for the first time, is to hear an original NE5532, one that is in a true ceramic dip package.
Believe it or not when you remove the plastic with fuming nitric acid the devices still work.
__________________
"The question of who is right and who is wrong has seemed to me always too small to be worth a moment's thought, while the question of what is right and what is wrong has seemed all-important."
  Reply With Quote
Old 15th October 2012, 05:55 PM   #1708
bcarso is offline bcarso  United States
diyAudio Member
 
Join Date: May 2005
Location: Canoga Park, California
Quote:
Originally Posted by scott wurcer View Post
Believe it or not when you remove the plastic with fuming nitric acid the devices still work.
Except for that "nitride haze"
  Reply With Quote
Old 15th October 2012, 06:07 PM   #1709
bcarso is offline bcarso  United States
diyAudio Member
 
Join Date: May 2005
Location: Canoga Park, California
Actually, short of repackaging the chips on a high-thermal conductivity substrate, I suspect the attachment via the gate lead to a heatsink as close to the package as possible ought to do very well, considerably better than a TO-92.

However, if thermal changes, with their myriad time constants and heat capacities, were as devastating as suggested, the combination of operating the device(s) at the zero tempco point and perhaps as well servoing the dissipation by actively adjusting the drain-source voltage would remove those effects. Unfortunately that procedure will be replaced with others, including higher distortion from the Vds manipulation, although this could in principle be backed out later on.
  Reply With Quote
Old 15th October 2012, 06:17 PM   #1710
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: cambridge ma
We might be getting carried away with these thermal issues. A simple potting in the right stuff might be enough.

Diamond filled epoxy?
__________________
"The question of who is right and who is wrong has seemed to me always too small to be worth a moment's thought, while the question of what is right and what is wrong has seemed all-important."
  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 05:02 PM
discrete opamp help blackpowderaudio Parts 0 16th December 2009 04:46 PM
THAT transistor headphone amp (250ma discrete opamp) design sanity check. Russ White Headphone Systems 19 13th December 2007 01:52 PM


New To Site? Need Help?

All times are GMT. The time now is 04:41 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