The New Hyper Balanced Amplifier - 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 18th April 2008, 11:33 PM   #1
TimS is offline TimS  New Zealand
diyAudio Member
 
Join Date: Feb 2004
Location: Auckland
Default The New Hyper Balanced Amplifier

This is an amp design that I have been working on for a while. I am now at a point where, I think, it is good enough to post on diyAudio.com It ticks most of my requirements for a good audio power amplifier: Wide Open Loop Bandwidth (>20kHz) Low-ish Distortion No more than 2 Stage design Stable while clipping What Attributes I like about this amplifier: Wide Bandwidth Medium Open Loop gain Very Stable Each Quadrant has its own feedback loop, If any pair of quadrant clips and the feed back loop goes open then there are 2 more feedback loops to keep control. Good common mode rejection. I hope you all like it. If there is any critiques or improvement let me know Cheers Tim
Attached Images
File Type: png hyperbalanced amp with cascode diff input.png (37.1 KB, 751 views)
  Reply With Quote
Old 19th April 2008, 02:20 AM   #2
diyAudio Member
 
Join Date: Nov 2004
Location: Florida
One amp to get a BTL output, cool.

Question, can you drive this amp with a regular unbalanced input source and still get the BTL output?
  Reply With Quote
Old 19th April 2008, 03:11 AM   #3
CBS240 is offline CBS240  United States
diyAudio Member
 
CBS240's Avatar
 
Join Date: Aug 2005
Location: K-town
Doubtful, since the feedback loops are a voltage divider with the input signal. The drive signals for M67/M68 will be unequal in magnitude. I have built a circuit that will convert SE signals into BL, with gain and DC control. Maybe a bit complex but it works very well. Also, there is these if you have vendetta against discrete circuits.
__________________
All the trouble I've ever been in started out as fun......
  Reply With Quote
Old 19th April 2008, 06:15 AM   #4
TimS is offline TimS  New Zealand
diyAudio Member
 
Join Date: Feb 2004
Location: Auckland
Quote:
Originally posted by EWorkshop1708
One amp to get a BTL output, cool.

Question, can you drive this amp with a regular unbalanced input source and still get the BTL output?
It will be fine. All that will happen is 1/2 of the cycle will clip earlier than the other.

Cheers

Tim
  Reply With Quote
Old 20th April 2008, 08:00 PM   #5
TimS is offline TimS  New Zealand
diyAudio Member
 
Join Date: Feb 2004
Location: Auckland
Default Frequency and Phase Response Curves

Frequency and Phase Response Curves, from the simulation
Attached Images
File Type: png hyperbalanced amp - frequency responce.png (26.8 KB, 310 views)
  Reply With Quote
Old 20th April 2008, 08:54 PM   #6
KSTR is offline KSTR  Germany
diyAudio Member
 
KSTR's Avatar
 
Join Date: Jul 2007
Location: Central Berlin, Germany
Tim, may I suggest to use more data points on these (say 200/decade)? Although not very likely here, the sim could have missed a high Q-resonance just before the roll-off.

Your plots are with plain resisitive load, I guess, no series L//R and no zobels. What happens if you hook a load cap (stepping it from 1nF to 10uF, 1-3-10 steps)?

For testing simmed stability I like to use a step voltage source of 100mV or so, with 10ns rise time, putting it into various places into the circuit (not only at the input) and then look at any overshoot/ringing, also at various places, not only the output (sometimes one can invoke hefty CM ringing which doen't show up at the output).

More elobarate stuff is the Tian method of plotting open-loog gain bode plots, which also provides much insight wrt small signal transfer function.

- Klaus
  Reply With Quote
Old 21st April 2008, 02:02 AM   #7
TimS is offline TimS  New Zealand
diyAudio Member
 
Join Date: Feb 2004
Location: Auckland
Hi KSTR

Thanks for your help.

You are right there is a resonant peak at about 1MHz and this is highlighted when I simulated the AC response with a 1uF across the output (and no series resistance).

I tried a quick brute force fix, by increasing my 3pF compensation capacitors to 30pF, which does stabilise the amplifier into 1uF but it reduces the open loop bandwidth and so increases the higher order harmonics in the distortion.

I suspect the culprit for this resonance is the input cascode, I think it is 2 mosfets too many. I have had similar performance without them but I had to use lower value feedback resistors to get the same closed loop bandwidth. Maybe I will try JFETs instead of the input mosfets and get rid of the cascode.

I ran out of time, this morning, to try anything else so I will look at the design again in the evening.

Cheers

Tim
  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
Balanced amplifier alternatives Elvee Solid State 7 1st August 2007 10:19 AM
Balanced amplifier trend? LBHajdu Pass Labs 12 29th September 2005 03:32 AM
Have you ever built this balanced amplifier aht Solid State 2 15th November 2004 07:55 AM
boss hyper fuzz honsten Instruments and Amps 0 19th May 2004 10:36 PM


New To Site? Need Help?

All times are GMT. The time now is 03:08 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