Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Pass Labs This forum is dedicated to Pass Labs discussion.

Recommendation for 5-10W amp.
Recommendation for 5-10W amp.
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 4th May 2014, 12:37 PM   #31
mos57 is offline mos57  Italy
diyAudio Member
 
mos57's Avatar
 
Join Date: Apr 2006
Location: Catanzaro - Italy
Quote:
Originally Posted by Bigun View Post
with such simple topologies you can have poor PSRR, is there a way to improve it ?
Yes Garreth, at expense of simplicity.

Differential input stage and CCS might be one solution.
  Reply With Quote
Old 4th May 2014, 01:12 PM   #32
mos57 is offline mos57  Italy
diyAudio Member
 
mos57's Avatar
 
Join Date: Apr 2006
Location: Catanzaro - Italy
Schematic with dual power supply, revised in some small parameters to optimize its performance.

With these small changes we have obtained:

An extended and flat frequency response, an overall lower distortion.

(in particular, 3rd harmonic is decreased by almost an order of magnitude).
All this by biasing the final stage with a value less than the original circuit.
Attached Images
File Type: png FIG_13_Yuma_Mosfet_Bal_2.png (19.9 KB, 533 views)
File Type: png FIG_13_Yuma_Mosfet_Bal_2_Transient.png (18.8 KB, 517 views)
File Type: png FIG_13_Yuma_Mosfet_Bal_2_AC.png (20.4 KB, 489 views)
File Type: png FIG_13_Yuma_Mosfet_Bal_2_Distortion.png (28.8 KB, 486 views)
  Reply With Quote
Old 4th May 2014, 01:47 PM   #33
juma is offline juma  Germany
diyAudio Member
 
juma's Avatar
 
Join Date: Nov 2005
Location: Berlin
Quote:
Originally Posted by mos57 View Post
...The result is very clear to me: ...
I took some time to look into this charade and it's clear to me too: it's a fake - you used 6.8k resistors to limit the current through BJTs to about 1.5mA and since the feedback loop is absent and the BJTs' parameters are unequal, one of them stays current hungry and of course you'll get unsymmetrical signal at the output. So your thesis still lingers in the fairy land...
  Reply With Quote
Old 4th May 2014, 01:52 PM   #34
Bigun is offline Bigun  Canada
diyAudio Member
 
Bigun's Avatar
 
Join Date: Jan 2009
Location: Waterloo, ON or Herefordshire UK
Recommendation for 5-10W amp.
Quote:
Originally Posted by mos57 View Post
Yes Garreth, at expense of simplicity.

Differential input stage and CCS might be one solution.
You could try a dual differential with a low impedance feedback network ?
__________________
"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 4th May 2014, 04:41 PM   #35
dobrivoje is offline dobrivoje  Serbia
diyAudio Member
 
Join Date: Aug 2009
Location: Smederevo, Serbia
Until now, I've made a few Juma's amps. All of them are exellent. So I plan to make some more.
Juma knows to design amps. Also, he makes them, not just simulate. If he is satisfied with sound, he publish them. For free. It's more than enough, isn't it?
  Reply With Quote
Old 4th May 2014, 05:02 PM   #36
mos57 is offline mos57  Italy
diyAudio Member
 
mos57's Avatar
 
Join Date: Apr 2006
Location: Catanzaro - Italy
Quote:
Originally Posted by juma View Post
I took some time to look into this charade and it's clear to me too: it's a fake - you used 6.8k resistors to limit the current through BJTs to about 1.5mA and since the feedback loop is absent and the BJTs' parameters are unequal, one of them stays current hungry and of course you'll get unsymmetrical signal at the output. So your thesis still lingers in the fairy land...
Yuma, I do not tell lies, I'm not trying to discredit your work, it's just my passion which brings me to investigate the audio topologies: the search for the best, as I think everyone here.

Perhaps the value of 6.8k has remained of one of the many iteration I've done on the circuit, but it does not change. As you can see, I brought that value to 3k so as to allow a current in the input transistor of about 3.7 mA, while the bias of the MOSFET greatly exceeds 1 A, but the result does not change.

See attached images.
Try doing simulations by yourself and you will be convinced, otherwise post here your result
in the absence of feedback the lower MOSFET works in the CE, while the upper MOSFET in CC. This is the reason of the imbalance.

Francesco
Attached Images
File Type: png FIG_17_Yuma_Mosfet_2.png (22.8 KB, 486 views)
File Type: png FIG_18_Yuma_Mosfet_2_Transient.png (18.2 KB, 150 views)
  Reply With Quote
Old 4th May 2014, 05:04 PM   #37
e_fortier is offline e_fortier  Canada
diyAudio Member
 
e_fortier's Avatar
 
Join Date: May 2001
Location: Eastern Canada
Recommendation for 5-10W amp.
Quote:
Originally Posted by dobrivoje View Post
Juma knows to design amps. Also, he makes them, not just simulate. If he is satisfied with sound, he publish them. For free. It's more than enough, isn't it?
+1

Do not forget, we also have the PCB layout.

I will built the one from Juma. Thanks for sharing your design Juma

Regards,
Eric
  Reply With Quote
Old 4th May 2014, 05:19 PM   #38
mos57 is offline mos57  Italy
diyAudio Member
 
mos57's Avatar
 
Join Date: Apr 2006
Location: Catanzaro - Italy
Quote:
Originally Posted by Bigun View Post
You could try a dual differential with a low impedance feedback network ?
Work is in progress. But why is the reason for low impedance feedback?
In this case the FB signal enter in the second base of differential pair.
  Reply With Quote
Old 4th May 2014, 07:18 PM   #39
juma is offline juma  Germany
diyAudio Member
 
juma's Avatar
 
Join Date: Nov 2005
Location: Berlin
Quote:
Originally Posted by mos57 View Post
....
See attached images.
Try doing simulations by yourself and you will be convinced, otherwise post here your result
in the absence of feedback the lower MOSFET works in the CE, while the upper MOSFET in CC. This is the reason of the imbalance.
I did some additional simulations (absent feedback loop) and I succeeded to get the result similar to yours (see attachment) by making LatFETs have very different gm (KP) and Vto parameters and the imbalance is clearly a product of different gain of LatFETs and not because of topological error.

So obviously, the imbalance you get is due to the erratic sim model you use for LatFETs which both work in Common Source mode.
Attached Images
File Type: gif sim5.gif (56.9 KB, 121 views)
  Reply With Quote
Old 4th May 2014, 09:13 PM   #40
mos57 is offline mos57  Italy
diyAudio Member
 
mos57's Avatar
 
Join Date: Apr 2006
Location: Catanzaro - Italy
Quote:
Originally Posted by juma View Post
I did some additional simulations (absent feedback loop) and I succeeded to get the result similar to yours (see attachment) by making LatFETs have very different gm (KP) and Vto parameters and the imbalance is clearly a product of different gain of LatFETs and not because of topological error.

So obviously, the imbalance you get is due to the erratic sim model you use for LatFETs which both work in Common Source mode.
Your reasoning does not convice me for two reasons mainly.
  1. given that all the complementary pairs have more or less the same problem, one could not build amplifiers using pairs of devices.
  2. The same couple indicted, when simulated in the schematic with two batteries does not show these large discrepancies.

In the attached scheme to avoid overlap operation of the two devices, I deliberately under-biased the final stage where you can see a bit of cross-over distortion.
The appearance evident that it captures is that here the positive half-wave is amplified to the same level or even slightly greater than the lower one.

So the difference with your original circuit seems topological
Attached Images
File Type: png FIG_19_Yuma_Mosfet_Bal_2.png (19.1 KB, 146 views)
File Type: png FIG_20_Yuma_Mosfet_Bal_2_Transient.png (18.7 KB, 105 views)
  Reply With Quote

Reply


Recommendation for 5-10W amp.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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Tiny PAM8610 10W+10W board problems trevmar Class D 29 6th May 2016 02:05 AM
my 10W POWER AMP. NEED HELP'' desertstorm Solid State 8 12th December 2013 11:19 AM
10W amp help Dprasad97 Chip Amps 2 13th April 2012 12:37 PM
10W suitcase amp famousmockingbird Tubes / Valves 16 20th August 2011 05:56 PM
Best possible 10W from chip amp Robert_66 Chip Amps 14 2nd November 2004 11:43 AM


New To Site? Need Help?

All times are GMT. The time now is 06:53 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki