Preamp concept - Page 3 - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 24th September 2005, 04:04 PM   #21
diyAudio Moderator Emeritus
 
lumanauw's Avatar
 
Join Date: Oct 2002
Location: Bandung
Send a message via Yahoo to lumanauw
Hi, PMA,

This one seems not coming from you. Lack of PMA characteristic
You dont use differential or CCS for the first stage?

Is this better than your openloop I/V converter?

Hi, all,

I have a question about Diamond buffer used as power amp output stage. From some examples, I see 2 kind of DB used for power amp. One is CCS feeding (like the one here and also Walt Jung), the other is only R loading, like this one I attach. It comes from a respectable sounding Marantz. Using 7W 8K2 plain resistor, even without bootstrapping.

What is the pro/con between using CCS and R for feeding diamond buffer?

2nd. Is it necessary to put Capacitance between upper and lower diamond buffer? The Marantz has 2 x 10uF cap around DB, while Walt Jung uses none. Again, what is the pro/con between these 2?
Attached Images
File Type: jpg marantz.jpg (55.1 KB, 3316 views)
  Reply With Quote
Old 24th September 2005, 04:26 PM   #22
anli is offline anli  Russian Federation
diyAudio Member
 
Join Date: Oct 2004
Well, I must mention, cited preamp was inspired by Kingwa's amps (audio-gd.com).
  Reply With Quote
Old 24th September 2005, 05:46 PM   #23
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
By the time I have built (not only simulated) the amp shown here in http://www.diyaudio.com/forums/showt...220#post730220

The amp is pretty fast, F(-3dB) = 3MHz. It does not need the output RC correction as shown. It is stable, drives pure 1500pF load without problem, with square signal tr = 10 ns at the input. Step response is without overshoot, with 1500pF load the overshoot is about 20%. Sine wave of 3MHz is pure at the output, undistorted. Output impedance is low, about 4 Ohm. It drives even 50 Ohm load. I will give it a chance and will make a preamp based on this circuit. Simplicity makes sense.
  Reply With Quote
Old 24th September 2005, 05:52 PM   #24
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
Quote:
Originally posted by lumanauw
Hi, PMA,

This one seems not coming from you. Lack of PMA characteristic
You dont use differential or CCS for the first stage?

I wanted to build quite fast and very stable stuff for now, for this reason I did not use global feedback, CCSs, mirrors etc. I am interested in sound result of this approach. I kept class A. The circuit has quite a lot of gain if needed, this is set by resistors between emitters of the input differential stage. DC is set by resistor between collector of the 2nd transistor and ground.
  Reply With Quote
Old 24th September 2005, 06:27 PM   #25
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
Quote:
Originally posted by lumanauw


I have a question about Diamond buffer used as power amp output stage. From some examples, I see 2 kind of DB used for power amp. One is CCS feeding (like the one here and also Walt Jung), the other is only R loading, like this one I attach. It comes from a respectable sounding Marantz. Using 7W 8K2 plain resistor, even without bootstrapping.

What is the pro/con between using CCS and R for feeding diamond buffer?

2nd. Is it necessary to put Capacitance between upper and lower diamond buffer? The Marantz has 2 x 10uF cap around DB, while Walt Jung uses none. Again, what is the pro/con between these 2?
David,

as you know, I also built a diamond buffer based power amp with R feeding, see http://www.pha.inecnet.cz/macura/next.htm. Though CCS should be superior due to maintaining the constant current even for large output swings, the results do not seem to be that different. The capacitor between bases in my circuit reduces distortion and helps the transition to class AB, if needed.
  Reply With Quote
Old 24th September 2005, 06:31 PM   #26
anli is offline anli  Russian Federation
diyAudio Member
 
Join Date: Oct 2004
Quote:
Originally posted by PMA ... Simplicity makes sense.
I don't like plenty of parts too, capacitors especially But - what is your opinion about thermal distortions importance (I mean active parts outside global NFB loop, as in your case, as you have not global NFB )?
  Reply With Quote
Old 24th September 2005, 06:34 PM   #27
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
Quote:
Originally posted by PMA
It is stable, drives pure 1500pF load without problem, with square signal tr = 10 ns at the input. Step response is without overshoot, with 1500pF load the overshoot is about 20%.
I made a mistake here, I was speaking about 15 000 pF load. Verified also for 47 000 pF, no problem.
  Reply With Quote
Old 24th September 2005, 06:36 PM   #28
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
Quote:
Originally posted by anli
I don't like plenty of parts too, capacitors especially But - what is your opinion about thermal distortions importance (I mean active parts outside global NFB loop, as in your case, as you have not global NFB )?
I know what you are speaking about and I have read those articles. Frankly speaking - I do not know.
  Reply With Quote
Old 24th September 2005, 06:44 PM   #29
anli is offline anli  Russian Federation
diyAudio Member
 
Join Date: Oct 2004
I have read an artcicle by russian author also, unfortunately, in Russian only:

http://www.aml.nm.ru/reasons.htm
  Reply With Quote
Old 24th September 2005, 06:46 PM   #30
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
Quote:
Originally posted by anli
I have read an artcicle by russian author also, unfortunately, in Russian only:

http://www.aml.nm.ru/reasons.htm
Thank you Andrej, russian is no problem for me.
  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
Help with a concept the joz Subwoofers 14 26th February 2009 07:22 AM
FS: Gain Concept No.X kirc Swap Meet 0 7th December 2007 09:40 AM
AV OB concept Geoff H Multi-Way 2 4th February 2007 06:31 PM
Another ESL Concept just.sounds Planars & Exotics 2 15th February 2006 10:35 AM
New speaker concept SY Multi-Way 3 15th September 2004 02:41 PM


New To Site? Need Help?

All times are GMT. The time now is 11:54 AM.


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