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 April 2013, 10:48 AM   #501
Banned
 
Join Date: Oct 2010
Location: Chigwell, Essex
Quote:
Originally Posted by jxdking View Post
Here is the simulation.
There is plenty phase margin and gain margin. It could be quite stable.
I think what you have is the forward path frequency response, and, in any case, looking at the zero dB crossing you have no phase margin or gain margin at all.
  Reply With Quote
Old 6th April 2013, 11:38 AM   #502
dadod is offline dadod  Croatia
diyAudio Member
 
dadod's Avatar
 
Join Date: Apr 2006
Location: Zagreb
Quote:
Originally Posted by michaelkiwanuka View Post
I think what you have is the forward path frequency response, and, in any case, looking at the zero dB crossing you have no phase margin or gain margin at all.
That was Opel Loop Gain, you can't just look at the zero crossing, Close Loop Gain should be detracted first.
  Reply With Quote
Old 6th April 2013, 01:03 PM   #503
Banned
 
Join Date: Oct 2010
Location: Chigwell, Essex
What he really needs is a plot of the loop gain frequency response.
  Reply With Quote
Old 6th April 2013, 01:10 PM   #504
dadod is offline dadod  Croatia
diyAudio Member
 
dadod's Avatar
 
Join Date: Apr 2006
Location: Zagreb
Quote:
Originally Posted by michaelkiwanuka View Post
What he really needs is a plot of the loop gain frequency response.
Like this one?
Audio Power Amplifier Design book- Douglas Self wants your opinions
  Reply With Quote
Old 6th April 2013, 11:10 PM   #505
diyAudio Member
 
Join Date: Nov 2011
Location: Cooktown, Oz
dadod, would you let us have the LTspice *.asc file as well as your device models?
  Reply With Quote
Old 7th April 2013, 05:18 AM   #506
dadod is offline dadod  Croatia
diyAudio Member
 
dadod's Avatar
 
Join Date: Apr 2006
Location: Zagreb
Quote:
Originally Posted by kgrlee View Post
dadod, would you let us have the LTspice *.asc file as well as your device models?
Here it is.
Attached Files
File Type: zip TPC-TMC.zip (18.5 KB, 30 views)
  Reply With Quote
Old 7th April 2013, 06:39 AM   #507
diyAudio Member
 
Join Date: Nov 2010
Default Re Thermal Trak

Quote:
Originally Posted by Waly View Post
...I hate them with a passion, they create more problems then they solve (due to the poor diode choice ....
The diode choice certainly does not provide a convenient match with the transistor, so there is extra work.
But they still better coupled with vastly superior response speed to an add on temperature sensor, so why do you hate them?

Best wishes
David.
  Reply With Quote
Old 7th April 2013, 08:23 AM   #508
hahfran is offline hahfran  Germany
diyAudio Member
 
Join Date: Dec 2007
Quote:
Originally Posted by Dave Zan View Post
The diode choice certainly does not provide a convenient match with the transistor, so there is extra work.
But they still better coupled with vastly superior response speed to an add on temperature sensor, so why do you hate them?

Best wishes
David.
Well these devices are discontinued. However the focus on thd is imho of some academical interest it doesn't have so much value for the connoisseur of music.
If the spectrum of harmonics matches the spectrum of acoustical musical instruments not even trained musicians can hear a difference between 0.01% thd ( very few if any amp at all will accomplish that with real reactive loads) and 2% thd. What is equally important the harmonics spectrum must not change versus frequency and must be constant over a wide range of power.
These are really important design objectives. Whether or not speakers qualify
is another question.
Above this a third objective the "dynamics resolution" .
This term is not to be confused with dynamic range or dynamic headroom.
Especially in this class of descriptive sound quality tube amps, the QUAD 303,
and amps with Thermal Track excel but you don't see it in any measurement,
but you hear it, and that is exactly what only matters.
  Reply With Quote
Old 7th April 2013, 09:20 AM   #509
matze is offline matze  Germany
diyAudio Member
 
Join Date: Sep 2012
Location: Dresden
(post #500)
Quote:
I think that TPC-TMC has a potential to be quite stabile and with very low THD. With this simulation THD20k is very low, 0.2ppm at 80W//8ohm.
[ thumbnail with Bode plot ]
Hi Damir,

the low gain margin at about 6 to 7 dB looks a bit suspicious to me.
I took a look onto your Spice model in a later post. Maybe it is wise to also consider different load capacities behind the output coil, leaving the speaker resistance high (speakers often have a high impedance at high frequencies). The series resonance between the output coil and the load capacitance will influence your gain and phase margins.

Furthermore, building the beast up you may have additional loss of stability margins.
The difference between theory and practice is larger in practice than in theory.

Very interesting is the phase behaviour below the unity gain crossover. At around 50 kHz, the negative feedback seems almost to turn into positive feedback. Here, the loop gain amounts to 60 dB. I know that theory completely allows this and so the circuit really should be stable. Nevertheless it looks unusual.


Good luck,
Matze


(If you are interested in compensation techniques, this thread might also be interesting for you:
Amplifier with nested Miller compensation
)
  Reply With Quote
Old 7th April 2013, 10:59 AM   #510
dadod is offline dadod  Croatia
diyAudio Member
 
dadod's Avatar
 
Join Date: Apr 2006
Location: Zagreb
Quote:
Originally Posted by matze View Post
(post #500)
Hi Damir,

the low gain margin at about 6 to 7 dB looks a bit suspicious to me.
I took a look onto your Spice model in a later post. Maybe it is wise to also consider different load capacities behind the output coil, leaving the speaker resistance high (speakers often have a high impedance at high frequencies). The series resonance between the output coil and the load capacitance will influence your gain and phase margins.

Furthermore, building the beast up you may have additional loss of stability margins.
The difference between theory and practice is larger in practice than in theory.

Very interesting is the phase behaviour below the unity gain crossover. At around 50 kHz, the negative feedback seems almost to turn into positive feedback. Here, the loop gain amounts to 60 dB. I know that theory completely allows this and so the circuit really should be stable. Nevertheless it looks unusual.


Good luck,
Matze


(If you are interested in compensation techniques, this thread might also be interesting for you:
Amplifier with nested Miller compensation
)
Hi Matze,
Thank you for your interest and suggestion. I know that 6-7dB of the gain margin is quite low, but that simulation was just my exercise to see what is possible with the combination of TPC and TMC. Original TT amp, I used for this simulation, uses TMC only and it is playing music for more then year and it’s very stable and nice sounding. You can look at this thread for more info.ThermalTrak+TMC amp I am not sure if I ever try this TPC-TMC staff in real amp, but who knows.
Thanks
Damir
  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
Comments on Audio Power Amplifier Design Handbook by Douglas Self Samuel Groner Solid State 68 16th March 2013 10:26 PM
The design of active crossovers- Douglas Self wants your opinions DouglasSelf Analog Line Level 282 7th December 2012 01:56 PM
Douglas Self's Active Crossovers book forr Analog Line Level 8 31st December 2010 05:20 PM
New Douglas Self Book blmn Solid State 7 22nd July 2009 06:00 PM
book-audio power amplifier by Douglas Self mikee12345 Solid State 8 16th November 2003 01:16 AM


New To Site? Need Help?

All times are GMT. The time now is 07:59 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