The MONGREL (supersym II) - Page 4 - 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 6th July 2010, 05:34 AM   #31
diyAudio Member
 
ostripper's Avatar
 
Join Date: May 2008
Location: Albany , NY (smallbany)
Quote:
By bigun - Do I understand right - the outputs don't switch off ? And this thing sounds as good as a pure Class A amp ? - then this is great !
Let me clarify , this op stage exhibits non-switching tenancies to a much higher power level than a standard class B type 2 EF. All class B stages work in class A at low power levels , this one carries the effect to a higher level even without the feedback to the CCS's.

One note , this was done in simulation.

At 1/2 power the amp goes true B with full switchoff , but still with reduced Xover distortion (especially H5,7,9,11). With Keen's super low noise floor these higher order components are 125 - 140 db down! GONE I have used both the standard models from ON and Andy c.'s special ones , SAME RESULTS. All the other amp OPS's (EF2 ,triples) ,do not exhibit this behavior.

BTW , the krill's non- switching behavior also degrades with level/load. IF you want FULL non-switching get a couple of LT1166's (IC below) link: http://cds.linear.com/docs/Datasheet/lt1166.pdf
I might add this as an add-on to this amp , VERY easy to implement.
OS
Attached Images
File Type: gif buffer.gif (33.0 KB, 1356 views)
  Reply With Quote
Old 6th July 2010, 10:43 AM   #32
Account disabled at member's request
 
Join Date: May 2006
Linesource has a point, there is a cascode so other LTP trannies can be used, mpsa18 for instance has lower noise and higher hfe. In 99 percent instances the max hfe figures given in datasheets are never reached so you will be lucky finding 992/1845 at 600, while its common finding mpsa18 at 800, lucky when you finding them at 1000. There are offcourse many other transistors having high hfe, some even reach 10 000, darlingtons. For these type applications I use a tranny having common hfe around 1000 and cob is only 1.8pf (not that it matters that much when its cascoded), only slightly higher than 1845, noise figures will be much better too. I think those BC parts will have better noise figures than the fairchilds in general, but because noise figures is a complex subject Id rather not get into it here but for optimizing a circuit for noise youll see the benefits of having high beta parts around although this is not the only important parameter.

Os for us to be able to compare we need more detailed parameters than say, half power, give us a frequency too. Use say 20 volt swing at 20KHZ plz, I would just like to make a interesting comparison with a amp of mine. My amp displays lower THD than yours Im pretty sure using quite a few less active parts but what Im interested in is to see how the distortion figures compare but the ones of most interest is the ones from 7th onwards. The idea is to see how much the frontend influences these higher harmonics ie Im gonna be surprised if my amp displays lower distortion figures for 7th and up, although not for the THD. In my amp I just use a common triple in class ab biased at 60 ma. I cannot have so much complexity in a amp used in cars, so I rather design around very fast, very linear circuits, optimize the operating current of each active part and parts selection to get high performance.
  Reply With Quote
Old 6th July 2010, 11:03 AM   #33
wahab is offline wahab  Algeria
diyAudio Member
 
Join Date: Nov 2009
Location: algeria/france
2SA872A/2SC1775A are of great quality...if you can find some.
Very low noise, very high HFE , linear at will...
  Reply With Quote
Old 6th July 2010, 04:27 PM   #34
diyAudio Member
 
ostripper's Avatar
 
Join Date: May 2008
Location: Albany , NY (smallbany)
Quote:
Use say 20 volt swing at 20KHZ plz
Do you mean 20V p/p or +-20 (40V p/p) ???

Here is all the 20k output...

Simulation is included last.

OS
Attached Images
File Type: gif 20kthd.gif (32.5 KB, 1280 views)
File Type: gif 20k_1kFFT.gif (26.4 KB, 1151 views)
Attached Files
File Type: zip mongrel_Ksim_final.zip (7.0 KB, 84 views)
  Reply With Quote
Old 6th July 2010, 04:42 PM   #35
diyAudio Member
 
keantoken's Avatar
 
Join Date: Aug 2006
Location: Texas
Blog Entries: 2
The MPSA18 has higher gain, but more Cob.

Ib at all frequencies needs to be considered, since while the MPSA18 might have higher gain at 1KHz, it might be worse at 20KHz, etc. For sure, the MPSA18 will have greater phase shift.

- keantoken
  Reply With Quote
Old 6th July 2010, 04:51 PM   #36
Bigun is offline Bigun  Canada
diyAudio Member
 
Bigun's Avatar
 
Join Date: Jan 2009
Blog Entries: 2
Quote:
Originally Posted by keantoken View Post
The MPSA18 has higher gain
how does it have gain ? it only exhibits gain when it's in a circuit and the gain is determined by the components around it ?

hfe - is not gain, it's the input impedance of the base, and it's not constant.
__________________
"The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.
  Reply With Quote
Old 6th July 2010, 05:00 PM   #37
diyAudio Member
 
keantoken's Avatar
 
Join Date: Aug 2006
Location: Texas
Blog Entries: 2
Higher voltage gain no, current gain yes. Hfe is known as static current gain.

- keantoken
  Reply With Quote
Old 6th July 2010, 05:07 PM   #38
Bigun is offline Bigun  Canada
diyAudio Member
 
Bigun's Avatar
 
Join Date: Jan 2009
Blog Entries: 2
Quote:
Originally Posted by keantoken View Post
Higher voltage gain no, current gain yes. Hfe is known as static current gain.

- keantoken
I'm just causing trouble for the sake of it aren't I ? - but my newbie way of keeping things simple is to treat BJTs as voltage controlled devices and hfe just doesn't fit into that narrow way of seeing things. I think hfe is misleading, it's a curve (not a straight line) on a graph that gets interpreted as a 'current gain' and I prefer to see it instead like this: a BJT is a voltage controlled device, the voltage is between base and emitter. To maintain this voltage you need a voltage source that can provide current into the base. This is really another way of saying you have an input impedance. It is a non-linear function of several variables. If you draw a graph of base current against emitter current you get a curve - if you squint at the curve you can draw a straight line somewhere and call the gradient a 'gain' and then you get to complain that the behaviour goes non-linear when you move away from the part of the curve you tried to fit a line against. Yuck.
__________________
"The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.
  Reply With Quote
Old 6th July 2010, 05:08 PM   #39
diyAudio Member
 
ostripper's Avatar
 
Join Date: May 2008
Location: Albany , NY (smallbany)
Quote:
By homemodder- pretty sure using quite a few less active parts
TOO MANY PARTS !
I am using
Click the image to open in full size.
http://www.diodes.com/datasheets/ds30304.pdf

Whole input pair/cascode/2 CCS's will take up less room than the input cap , no stupid matching ,either.
OS
  Reply With Quote
Old 6th July 2010, 05:27 PM   #40
Account disabled at member's request
 
Join Date: May 2006
Thanks Os thats perfect, It still seems to me that getting absolute low thd figures is the way to go. Ill show some plots and the output stage which is common but the input and vas I will cover sorry. I wont bother showing 1K plot figures they are just too small but i can include a 50khz or 100 khz plot to show what the circuit is capable of.

Kean, Id say yes and no, depends where the part is used, in Os circuit the ltp transistors are cascoded, so theres no cob problem. Now think about early voltage and what effect the higher hfe is going to have on various parameters,(common mode distortion, noise, dc offset, PSRR) and it will become clear why the mpsa18 will outperform the 1845, not to mention that its noise figure is lower too.
  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
Symasym - the next generation (supersym) ostripper Solid State 260 26th June 2014 09:23 PM
Supersym patent Rescue Toaster Pass Labs 6 22nd January 2008 09:49 PM


New To Site? Need Help?

All times are GMT. The time now is 07:26 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