Discrete Opamp Open Design - Page 286 - 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 17th March 2013, 06:09 PM   #2851
RNMarsh is offline RNMarsh  United States
diyAudio Member
 
RNMarsh's Avatar
 
Join Date: May 2012
Location: 2457 Cascade Trail; Cool, CA. 95614
Quote:
Originally Posted by dadod View Post
But somewhere we have to start when design, and then do the measurement on the built amp. I hope you do not advocate to design without simulation?
Damir
I dont know about that. Hewlett and Packard didnt design thier first instrument on a computer SIM. ETC. I have never designed any audio circuit by doing a SIM. I designed one complex filter (which won the patent prize) on a SIM and had it built and shipped many to customers... about a year later, I measured it and it was exactly as the SIM predicted. The patent was based on SIM.
But audio isnt that complex. If you know your goal and you know how to get it, then just do it and make it. A hand held calculator is all I use. I have a lot of test equipment over the years... they teach me and books teach me what others did. I am most interested in exploring ideas and concepts. Now if you had to make an IC, then SIM is the best way and now the only way. But experience still plays a large role as to what to do on the SIM.

Accumulated knowledge and mentoring goes on... whether IC or descrete. It's not unlike a Medical Doctor who, after years of study, mentoring and experience gets really good at what he does. As I see it, this forum is a lot about mentoring and ought to be doing more of it.

Thx-RNMarsh

Last edited by RNMarsh; 17th March 2013 at 06:32 PM.
  Reply With Quote
Old 17th March 2013, 06:20 PM   #2852
diyAudio Member
 
Kindhornman's Avatar
 
Join Date: Aug 2012
Location: Los Angeles, California
RNM arsh,
I think that you would have to add that the sim is only as good as the information input into it. As the saying goes, garbage in garbage out..... If the models being used do not contain all of the variables necessary to get an accurate result is the result worth the time? This is no different from a mathematician rounding off all the steps in a formula and wondering why his rocket missed the moon, accuracy is in the inputs.
  Reply With Quote
Old 17th March 2013, 06:55 PM   #2853
dadod is offline dadod  Croatia
diyAudio Member
 
dadod's Avatar
 
Join Date: Apr 2006
Location: Zagreb
Quote:
Originally Posted by RNMarsh View Post
I dont know about that. Hewlett and Packard didnt design thier first instrument on a computer SIM. ETC. I have never designed any audio circuit by doing a SIM. I designed one complex filter (which won the patent prize) on a SIM and had it built and shipped many to customers... about a year later, I measured it and it was exactly as the SIM predicted. The patent was based on SIM.
But audio isnt that complex. If you know your goal and you know how to get it, then just do it and make it. A hand held calculator is all I use. I have a lot of test equipment over the years... they teach me and books teach me what others did. I am most interested in exploring ideas and concepts. Now if you had to make an IC, then SIM is the best way and now the only way. But experience still plays a large role as to what to do on the SIM.

Accumulated knowledge and mentoring goes on... whether IC or descrete. It's not unlike a Medical Doctor who, after years of study, mentoring and experience gets really good at what he does. As I see it, this forum is a lot about mentoring and ought to be doing more of it.

Thx-RNMarsh
I am completely with you in that, but it was a time ago when spice was not available free of charge as now. I am talking about DIY not professionals circuit designer were spice was available much earlier. I worked in telecommunication and electronic was my whole life hobby and I started to use and learn spice simulator less then two years ago and I am 68 old, so its never to late to learn new staff. For the skill electronic designer its enough to use a hand held calculator, but then you have to build the thing to see if it work as it suppose to work and with simulator you can tray many different combinations and fast by it. I know a simulation is good as the one using it is good and as the models are good, but it fascinate me now as I can try many new ideas with no need to built it all.
BR Damir
  Reply With Quote
Old 17th March 2013, 06:59 PM   #2854
RNMarsh is offline RNMarsh  United States
diyAudio Member
 
RNMarsh's Avatar
 
Join Date: May 2012
Location: 2457 Cascade Trail; Cool, CA. 95614
Quote:
Originally Posted by Kindhornman View Post
RNM arsh,
I think that you would have to add that the sim is only as good as the information input into it. As the saying goes, garbage in garbage out..... If the models being used do not contain all of the variables necessary to get an accurate result is the result worth the time? This is no different from a mathematician rounding off all the steps in a formula and wondering why his rocket missed the moon, accuracy is in the inputs.
You are talking details... I was talking concept. but I did address your detail..... experience goes into a successful SIM. Could I do what Scott W. does at his level of detail where he works. No way.

What I can do well, is look at topologies, figure that a certain class (differential) is best and there are three versions of it. exploring which was best lead me to what is now called the current mode fb circuit topology. And, part of that decision was the desire to have constant gnfb at all freqs. It turned out that it has other benefits ... more in HF and RF. But within it's pro-con for audio, it has solutions. In IC form it is hard to do and isnt the best for many apps. The results you get with any of the differentail family of circuit topologies is always in the details.

So I went into R&D technical management side of things where I could explore concepts and ideas and do problem solving on that level and leave the details to the specialists.

Thx-RNMarsh

Last edited by RNMarsh; 17th March 2013 at 07:08 PM.
  Reply With Quote
Old 17th March 2013, 07:43 PM   #2855
diyAudio Member
 
Kindhornman's Avatar
 
Join Date: Aug 2012
Location: Los Angeles, California
Richard,
I agree with what you are saying and you do have much more experience than most with our without the simulations. On the point of the current mode NFB circuit Doug Self just flamed that completely as a non starter on his thread asking questions about added topics for his book. He was adamant that it was a lost cause and had no hope of competing with a voltage mode feedback topology. Check that thread out, you may find it interesting.

Steven
  Reply With Quote
Old 17th March 2013, 07:55 PM   #2856
RNMarsh is offline RNMarsh  United States
diyAudio Member
 
RNMarsh's Avatar
 
Join Date: May 2012
Location: 2457 Cascade Trail; Cool, CA. 95614
I know he says that in his books... and thus doesnt cover it in detail... just acknowledges its existence and moves on. C-Mode fb is an option that has its pro-con like all other topologies. It has found a home in the IC opamp arsenal of the opamp makers especially in higher freqs and higher speed amps and interfaces.... like adc/dac and RF. All analog IC makes have them now as an adjunct to their line of VFb amps. It needs to get optimized for audio... too bad he doesnt explore its potential more. Other noted designers have done so and they have also written books. He is also against MOSFETs while others find them better for output stage. Doesnt like jFEts on input either. So, get all the sides and try them for yourSelf. Like Bob Cordell. Outside of audio and at higher freqs is the nitch for current-mode. Thats where its strengths gain ground.

It all depends on your design goals and thier technical priorities as to what you think is more important for the best sound. The diff input VFB is probably the best known, the best understood and offers the most bang for the buck. And, you can get tightly matched devices.

Thx-RNMarsh

Last edited by RNMarsh; 17th March 2013 at 08:13 PM.
  Reply With Quote
Old 17th March 2013, 08:31 PM   #2857
RNMarsh is offline RNMarsh  United States
diyAudio Member
 
RNMarsh's Avatar
 
Join Date: May 2012
Location: 2457 Cascade Trail; Cool, CA. 95614
Take a look at Bob Cordells book to help get a total overall balanced view. "Designing Audio Power Amplifiers" [McGraw-Hill).

And, there are many excellent developed cmfb circuits here in the DIYAUDIO forums. Truely excellent work being done to optimize them.

With these are Diamond buffers and Diamond amp configurations and complimentary push-pull and similar cmfb topologies.

Thx-RNMarsh

Last edited by RNMarsh; 17th March 2013 at 08:40 PM. Reason: Current-mode feedback -
  Reply With Quote
Old 17th March 2013, 08:42 PM   #2858
diyAudio Member
 
Kindhornman's Avatar
 
Join Date: Aug 2012
Location: Los Angeles, California
Richard,
I do have that book and I have seen that Cordell does talk about the subject. Even in the thread I mentioned Bob pops in from time to time and the two of them do disagree about certain things, it is rather interesting to see the interaction between them. High Performance Loudspeakers by Martin Colloms is another very good read to go with these two authors.
  Reply With Quote
Old 19th March 2013, 05:37 AM   #2859
diyAudio Member
 
Join Date: Nov 2011
Location: Cooktown, Oz
Quote:
Originally Posted by Kindhornman View Post
On the point of the current mode NFB circuit Doug Self just flamed that completely as a non starter on his thread asking questions about added topics for his book.
Where is this thread please?
  Reply With Quote
Old 19th March 2013, 05:46 AM   #2860
diyAudio Member
 
abraxalito's Avatar
 
Join Date: Sep 2007
Location: Hangzhou - Marco Polo's 'most beautiful city'. 700yrs is a long time though...
Blog Entries: 109
Send a message via MSN to abraxalito Send a message via Yahoo to abraxalito Send a message via Skype™ to abraxalito
Audio Power Amplifier Design book- Douglas Self wants your opinions
__________________
There is surely nothing quite so useless as doing with great efficiency what should not be done at all - Peter Drucker
  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 11:04 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