Discrete Opamp Open Design - Page 80 - 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 7th September 2012, 02:40 AM   #791
RNMarsh is offline RNMarsh  United States
diyAudio Member
 
RNMarsh's Avatar
 
Join Date: May 2012
Location: 2457 Cascade Trail; Cool, CA. 95614
Default KOVAR

Quote:
Originally Posted by gpapag View Post
Thank you very much RNMarsh


From this paper (some will love it ) http://monarch.qucosa.de/fileadmin/d...on_Mhiaoui.pdf

page 94, the Sieebeck coeff. for Sn60Pb40 solder is –1.06 uV/K at room temperatures

So copper/Sn60Pb40 thermal EMF is 2.6 uV/K

The big problem could be with Nickel/copper (~ -19uV/K) or Nickel/Sn60Pb40 (~ -21 uV/K)

George
Also KOVAR, the transistor lead material that you solder to
the pcb. Made more for the thermal coeff of expansion compatibility with the other packaging material. So, here you have many different metals/alloys --the transistor lead metals, the pcb metals and the solder metals.

Then you must consider the thermal gradiants across the parts in the physical circuit layout so as to minimize temp diferences across a part .. like a resistor or other... you want to have same temp at each end of the resistor or part.... For example, when a pcb is mounted vertically or on its edge to conserve chassis space/size you will easliy have different temp from bottom to top of a part if it is also mounted vertically..... better to mount it horizonally. [Am I being clear?]

If you dont control all thermal factors, you wont get absolute best possible performance in terms of dc drift, noise and possibly distortion. These things are all part of making a SOTA amp from a schematic. -RNM

Last edited by RNMarsh; 7th September 2012 at 02:48 AM.
  Reply With Quote
Old 7th September 2012, 03:20 AM   #792
RNMarsh is offline RNMarsh  United States
diyAudio Member
 
RNMarsh's Avatar
 
Join Date: May 2012
Location: 2457 Cascade Trail; Cool, CA. 95614
Note a popular non lead based solder is the tin based solders -- Sn 96 and Ag 04. Compare/check its uV/K with copper.

(for audio -- you dont want any nickel in the signal path)

-RNM

Last edited by RNMarsh; 7th September 2012 at 03:23 AM.
  Reply With Quote
Old 7th September 2012, 06:11 AM   #793
diyAudio Member
 
Wavebourn's Avatar
 
Join Date: Sep 2006
Location: Pleasant Hill, CA
Send a message via Skype™ to Wavebourn
Quote:
Originally Posted by RNMarsh View Post
(for audio -- you dont want any nickel in the signal path)
Even in sockets and plugs of professional equipment used to record audiophile quality material?

My best tube amps use nickel alloy for anodes.

Also, speaking of PCBs and their orientation, it is better to orient them such a way so components are better cooled by convection. If you put it horizontally components in it's center will be heated more, and their temperature may be higher than be the PCB mounted vertically. Higher tempco have semiconductor devices, so what's the point in thermocouple effect of joints minimization maximizing overall thermal instability?

No rules of dumbs here. Everything has to be carefully designed. All pros and cons considered and calculated, in each and every different case.
__________________
"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 7th September 2012, 09:15 AM   #794
zinsula is offline zinsula  Switzerland
diyAudio Member
 
zinsula's Avatar
 
Join Date: Mar 2004
Quote:
Originally Posted by Wavebourn View Post
[...]No rules of dumbs here.[...]
__________________
If you can't trust your ears, then CLICK HERE
  Reply With Quote
Old 7th September 2012, 10:08 AM   #795
Account disabled at member's request
 
Join Date: May 2006
Quote:
Originally Posted by RNMarsh View Post
JLH didnt invent that biasing form nor feedback scheme either... used in tube circuits long, long before then. I was just pointing out that the bias scheme was used by myself earlier than was noted ... not that I invented it. I was applying it to a different topology.

[If you dont understand the significant differences of the two topologies, there are plenty of books about the circuit and how it would differe from JLH design. One is: Emerging Techniques for High Freq BJT Amplifier design: A Current-Mode Perspective (1994) by C.Toumazou, J.Lidgey, A.Payne. Covers it so well, its in my reference library I keep. [ International Conference on Electronics Circuits and Systems, Cairo, Egypt.] But there are more contemporary books. -RNM
So what you are saying is add on a cascode and that makes it a different topology ?? I think not. So if I add on a cascode to a LTP its not a LTP anymore ?? Strangely enough another member here experimented with the particular circuit and found that the cascode can actually do more harm than good in the case of BJTs. JLH did invent and was the first to use it in line and phono stages back in 1968. I am too young for the tube era but could you explain how complementary tube circuits were made ??
  Reply With Quote
Old 7th September 2012, 10:23 AM   #796
diyAudio Member
 
jacco vermeulen's Avatar
 
Join Date: Oct 2004
Location: At the sea front, Rotterdam or Curaçao
Send a message via Yahoo to jacco vermeulen
Quote:
Originally Posted by Wavebourn View Post
Also, speaking of PCBs and their orientation, it is better to orient them such a way so components are better cooled by convection.
No rules of dumbs here.
http://www.diyaudio.com/forums/attac...gbt-hp-pcb.jpg

(sorry Anatoliy, I live to tease)
__________________
No More Mr Nice Guy
  Reply With Quote
Old 7th September 2012, 03:02 PM   #797
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
You walked into that one, Richard. Of course, I agree that nickel is a lousy connector material. However, Wavbourn don't know that yet. '-)
  Reply With Quote
Old 7th September 2012, 03:50 PM   #798
diyAudio Member
 
Wavebourn's Avatar
 
Join Date: Sep 2006
Location: Pleasant Hill, CA
Send a message via Skype™ to Wavebourn
Quote:
Originally Posted by john curl View Post
You walked into that one, Richard. Of course, I agree that nickel is a lousy connector material. However, Wavbourn don't know that yet. '-)
I know John that nickel, no matter how lousy it is, was widely used in connectors of pro equipment used to record concerts that you enjoy. '-)
__________________
"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 7th September 2012, 04:31 PM   #799
Account disabled at member's request
 
Join Date: Oct 2008
I finally got time to simulate Scott's (ggggggggg (9XG) i think) posted here somewhere. I used BF861B instead of BF862.
Attached: the schematic I used, BF861B datasheet and the results.

Cheers
Stein
Attached Files
File Type: pdf Schematic SW discrete opamp BF861B.pdf (27.8 KB, 146 views)
File Type: pdf BF861A_BF861B_BF861C.pdf (121.4 KB, 62 views)
File Type: pdf THD 1k.pdf (129.2 KB, 55 views)
File Type: pdf THD 20k.pdf (43.1 KB, 46 views)
File Type: pdf 20k square.pdf (31.3 KB, 34 views)
File Type: pdf HARMDIST 1k 10m-1.5V in.pdf (100.4 KB, 41 views)
File Type: pdf SNR vs Vout.pdf (45.9 KB, 33 views)
File Type: pdf THD vs Vout.pdf (43.9 KB, 41 views)
File Type: pdf THD+N vs Vout.pdf (44.2 KB, 55 views)
  Reply With Quote
Old 7th September 2012, 05:21 PM   #800
bcarso is offline bcarso  United States
diyAudio Member
 
Join Date: May 2005
Location: Canoga Park, California
Quote:
Originally Posted by stinius View Post
I finally got time to simulate Scott's (ggggggggg (9XG) i think) posted here somewhere. I used BF861B instead of BF862.
Attached: the schematic I used, BF861B datasheet and the results.

Cheers
Stein
Interesting. Although the harmonic structure is pretty clearly mostly 2nd with a little 3rd, how many harmonics are accounted for in the later plots?

Does your simulator have an option for log scaling?

Brad
  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 08:52 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