♫♪ My little cheap Circlophone© ♫♪ - Page 89 - 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 26th April 2012, 06:05 PM   #881
diyAudio Member
 
Join Date: Nov 2007
Location: Dallas
Quote:
Originally Posted by Elvee View Post
If the OP are too slow, the drivers will need to provide larger current excursions to drive them properly.
Thats stability in a nutshell...
  Reply With Quote
Old 29th April 2012, 06:57 PM   #882
diyAudio Member
 
danielwritesbac's Avatar
 
Join Date: Nov 2007
I'd like to know more about Class A preamplifier for use with this amp, and I'd also like to know more about Class A nested preamplifier for use with this amp.

Instead of running a high gain power amp, I'd like to explore running a preamplifier gain stage from regulated/capmulti power. If that is a nested preamp arrangement then the super clean signal is propagated globally.
__________________
Tools, Models & Software for DIYClipNipper boostLM1875 TurboPowerful TDA7293 kitTDA7294 pt2pt ♦ My post has opinion.
  Reply With Quote
Old 30th April 2012, 08:29 AM   #883
Elvee is offline Elvee  Belgium
diyAudio Member
 
Elvee's Avatar
 
Join Date: Sep 2006
Quote:
Originally Posted by danielwritesbac View Post
I'd like to know more about Class A preamplifier for use with this amp, and I'd also like to know more about Class A nested preamplifier for use with this amp. .
Practically all preamplifiers are class A.

Can you give an example of "nested" preamplifier?


Quote:
Instead of running a high gain power amp, I'd like to explore running a preamplifier gain stage from regulated/capmulti power. If that is a nested preamp arrangement then the super clean signal is propagated globally
Reducing the amplifier's gain will not necessarily improve quality: it will increase the GNF, which in itself might not be desirable, and will also require a heavier compensation to be stable with a higher loop gain.
__________________
. .Circlophone your life !!!! . .
♫♪ My little cheap Circlophone© ♫♪
  Reply With Quote
Old 30th April 2012, 11:57 PM   #884
diyAudio Member
 
danielwritesbac's Avatar
 
Join Date: Nov 2007
Quote:
Originally Posted by Elvee View Post
Practically all preamplifiers are class A.
Can you give an example of "nested" preamplifier?
It has its own feedback loop just like a regular preamp; but, it has an added feedback loop all the way to the speaker jack. Anything seriously out of bounds (such as that inappropriate 8khz boost or a bit of power noise or a momentary glitch) will get reeled in hard, but any power amp output reasonably matching the signal within the preamp is less affected by the added global feedback.
Quote:
Originally Posted by Elvee View Post
Reducing the amplifier's gain will not necessarily improve quality: it will increase the GNF, which in itself might not be desirable, and will also require a heavier compensation to be stable with a higher loop gain.
Details: I have build a higher voltage Circlophone that will drive my speakers; but because my source didn't automatically become larger, my power amp is running ((22/0.47)+1) 48x. The next build is scheduled to be larger yet, and I'm out of luck.

At the larger scale, it is looking attractive to use a preamplifier run cleanly from regs/capmulti. Having done so, it looks even more attractive to do a nesting preamplifier so that the global feedback loop is run from the preamp that also runs from clean power, thus "copying" the clean from end to end.
__________________
Tools, Models & Software for DIYClipNipper boostLM1875 TurboPowerful TDA7293 kitTDA7294 pt2pt ♦ My post has opinion.
  Reply With Quote
Old 1st May 2012, 06:26 AM   #885
diyAudio Member
 
Join Date: Nov 2007
Location: Dallas
Daniel, I got two words for ya: Bode Plot.

You can't just randomly cram an extra stage of gain
and phase shift into an already optimized closed loop.
Won't be stable when you are done.
  Reply With Quote
Old 1st May 2012, 06:48 AM   #886
diyAudio Member
 
danielwritesbac's Avatar
 
Join Date: Nov 2007
Quote:
Originally Posted by kenpeter View Post
Daniel, I got two words for ya: Bode Plot.
You can't just randomly cram an extra stage of gain
and phase shift into an already optimized closed loop.
Won't be stable when you are done.
Not into. Around.
__________________
Tools, Models & Software for DIYClipNipper boostLM1875 TurboPowerful TDA7293 kitTDA7294 pt2pt ♦ My post has opinion.
  Reply With Quote
Old 1st May 2012, 04:58 PM   #887
Elvee is offline Elvee  Belgium
diyAudio Member
 
Elvee's Avatar
 
Join Date: Sep 2006
Quote:
Originally Posted by danielwritesbac View Post
It has its own feedback loop just like a regular preamp; but, it has an added feedback loop all the way to the speaker jack. Anything seriously out of bounds (such as that inappropriate 8khz boost or a bit of power noise or a momentary glitch) will get reeled in hard, but any power amp output reasonably matching the signal within the preamp is less affected by the added global feedback.
You can stack as many loops as you want, but as Ken reminded, they all have to comply with stability criteria, both locally and globally
Quote:
Details: I have build a higher voltage Circlophone that will drive my speakers; but because my source didn't automatically become larger, my power amp is running ((22/0.47)+1) 48x. The next build is scheduled to be larger yet, and I'm out of luck.
The CFP version has been validated by some members, and has sufficient gain spare to provide at least 40dB usable gain.


Quote:
At the larger scale, it is looking attractive to use a preamplifier run cleanly from regs/capmulti. Having done so, it looks even more attractive to do a nesting preamplifier so that the global feedback loop is run from the preamp that also runs from clean power, thus "copying" the clean from end to end.
It looks attractive, but the control theory leaves few options if the gain is inside the main loop.
An independent gain block of 20dB or so is much easier to manage.

PS

There are cases where an additional feedback path is used to manipulate the apparent output impedance of the amplifier, to suit the speakers, but that's somewhat different
__________________
. .Circlophone your life !!!! . .
♫♪ My little cheap Circlophone© ♫♪

Last edited by Elvee; 1st May 2012 at 05:03 PM.
  Reply With Quote
Old 1st May 2012, 08:29 PM   #888
diyAudio Member
 
danielwritesbac's Avatar
 
Join Date: Nov 2007
Quote:
Originally Posted by Elvee View Post
You can stack as many loops as you want, but as Ken reminded, they all have to comply with stability criteria, both locally and globally
The CFP version has been validated by some members, and has sufficient gain spare to provide at least 40dB usable gain.
It looks attractive, but the control theory leaves few options if the gain is inside the main loop.
An independent gain block of 20dB or so is much easier to manage.
PS
There are cases where an additional feedback path is used to manipulate the apparent output impedance of the amplifier, to suit the speakers, but that's somewhat different
I apologize in advance for having deleted a long post in favor of something rude, short and clear:
You can have any combination of parts causing any combination of sonic signatures resulting in a great many almost hi-fi amplifiers or you can engineer a constraint to that variety. A preamplifier can have a resistor added from inverting input to the speaker jack of the power amplifier in which case the small amount of added feedback constrains variances.

I do have some parameters. Sonic signature variance of Circlophone can be up to 8db, at most. Somehow, that tells the required extent/strength of the nesting loop. At the point of knowing the extent, then the challenge is to install about that much constraint (provided by the preamp) without hindering the stability of the power amp.

At end result, it should be possible to get hi-fi on every build without exception, even if someone happened to install a real plonker of an output device.

By same factor, the clipping performance will also be cleaner if a case exists where the power amp clips but the preamp doesn't, then the nesting loop will wash clean some of the clip.

There you have 3 big jobs done by just one preamp:
A gain stage run from super clean power
Power amp variance constraint without endless fine tuning/parts swapping
Cleaner clip performance
__________________
Tools, Models & Software for DIYClipNipper boostLM1875 TurboPowerful TDA7293 kitTDA7294 pt2pt ♦ My post has opinion.
  Reply With Quote
Old 2nd May 2012, 12:31 AM   #889
diyAudio Member
 
Join Date: Nov 2007
Location: Dallas
An amplifier with an optimized closed loop will have about 150 degree phase shift
at the point it crosses 0db, and probably roll like crazy beyond that point. If you
cascade another amp with that, even one that is perfectly linear and adds no
phase shift, the combined result will not be stable to close an all-encompassing
global loop.

You will have to severely overcompensate the nested amps. Preferrably lowering
gain to extend bandwidth, than by rolling them off early. Cause its roll that adds
to a problem. You can stack the flat part of flat Bode plots to a higher open. But
one and only one pole must roll, and far earlier than the rest. You also have to
relocate your pre-clip, to get its phase shift out of the new loop. You could not
nest amps, both optimized to roll at the usual rate and place in the usual manner...

The circlophone's compensation would have to change, as well as the pre-amp.
I would not mess Circlophone's proven stability. So easy to make an oscillator...
Follow my thread if you want oscillators. I am trying to add a stage of class A
balanced, prior to injection of the quadrature feedback. Because balanced A
is a candidate for cross coupled neutraliztion of Miller to extend bandwidth.
After mixing QFB, you can't do that trick anymore, so I want to mix QFB as
close to the output as possible... again, my theories usually make oscillators.

I think you would do better to take the +40dB open loop boost offered by CFPs,
Set the closed loop to whatever gain suits you, and still come out ahead.

Last edited by kenpeter; 2nd May 2012 at 12:56 AM.
  Reply With Quote
Old 2nd May 2012, 04:00 AM   #890
diyAudio Member
 
Join Date: May 2010
First the honest disclaimer: I am no technologist to get into the nitty gritty of design. Still I wish to comment on a few points.
Here a new topology has been presented--for the vary first time, so far as my limited knowledge goes-- with a bunch of advantages and flexibility, quite beyond the finicky precision of audio design and setup as most of us know it.

Hooray!

But I guess in our enthusiasm, we shouldnt "tweak it beyond recognition" and end up with the proverbial camel, which originally was planned as a horse, until the committee decided to chip in with mods and tweaks. No offence meant to anyone, but the collective aim of discussion and debate should be, IMHO, to take the design forward along its declared path and to devise testing methods etc to validate/improve the design. Perhaps some of the more knowledgeable should move to man the rudder!

As an enthusiastic follower of the "audible difference" camp, I must perhaps at this point recall the move by many Japanes audio majors towards the quasi-complementary output topology in the late 1970's or thereabouts. Many Japanese amps of the era used custom designed output transistors with large die sizes and large double and triple-sized 'bodies', and many of these were audibly superior to other designs. This was before the craze for "super symmetry" and before the MOSFET invasion. Many of the designers of the time favoured the quasi-complementary output stage with robust NPN devices, and as a result, one of the favourite stunts in our DIY group was to build almost identical power amps, one with fully comlementary devices and the other with a quasi-complementary stage and do some serious listening comparisons. As I remember, the devices of choice were the 2N 3055/2955 series or the 'clones' TIP or MJ series. I still have some of those PCBs in the 'junk box'! Frankly many of us thought (and I still believe!) that the quasi sounded 'better', all said and done.

All the greater reason for me to want to jump in and finish the Circlophone, and have a listen! But even before I come to that (thrilling!) milestone, I dare say, Elvee, you are the best that has happened to DIY in a long while, if only it is for the reason that yours is a highly tolerant design and lends itself to implementation by the hobbyist with limited knowledge, resources and test equipment, while at the same time it takes him/her to a higher level of audio 'nirvana' with considerable ease and confidence!
  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
Need help with OB design - cheap, cheap, cheap djn Multi-Way 38 30th May 2010 07:26 AM
Scosche SPL meter: Cheap find with potential, or cheap junk? theAnonymous1 Everything Else 5 11th October 2006 04:40 AM
Alpine cda-9831 vs. 9833 vs. 9835 cbecker33 Car Audio 3 10th December 2004 01:47 PM


New To Site? Need Help?

All times are GMT. The time now is 09:05 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