solid state with output transformer - 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 8th January 2013, 09:40 AM   #1
Stee is offline Stee  Italy
diyAudio Member
 
Stee's Avatar
 
Join Date: Jul 2005
Location: milan
Default solid state with output transformer

I have invented a method to sound the amplifier in the solid state as a valvular, so reduce to a minimum the negative feedback with a rule called 1:100
Take a simple amp

Ie without cascode in the input stage, without cascode stage voltage and with unity gain in the output stage (without Darlington)
The open-loop gain will be approximately 27dB
Set the closed-loop gain to a gain much greater 40dB
(set NFB resistor's ratio one to hundred)
This means doing the opposite of the traditional approach

You will get a sound but not distorted, but no EQ
This is because there is no longer a residual gain sufficient to correct the waveforms extensive (low frequency)
In short you are listening to the real sound of your amp
And you realize that the impedance matching the speaker load is scarce

My solution is to adopt an output transformer more powerful than that required
With very low transformation ratio (7:1)
So as not to inflict emphasis on the acoustic scene and at the same time allow the device to an internal resistance adequate

The result is excellent (tested on diagram Rotel RA-02 with toroidal transformer 230/32 +32 V 300VA)
http://www.esafono.it/Esoter%20Evoqu...0Amplifier.pdf
Attached Images
File Type: png QUASI ZERO FEEDBACK.PNG (77.4 KB, 297 views)
File Type: png next project4.png (58.8 KB, 293 views)
__________________
Please download my best audio idea https://www.facebook.com/DiyAudioHiEnd

Last edited by Stee; 8th January 2013 at 09:45 AM.
  Reply With Quote
Old 8th January 2013, 11:06 AM   #2
oshifis is offline oshifis  Hungary
diyAudio Member
 
Join Date: Mar 2004
Location: Budapest, Hungary
I would suggest to study a high school textbook on linear systems and negative feedback. You will find a formula on the first few pages how the closed loop gain can be calculated.
  Reply With Quote
Old 8th January 2013, 11:17 AM   #3
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
Stee,

The feedback factor is the difference between open loop and closed loop gain.
If you wish to lower the feedback factor so that you can listen to the amp non-linearity better, you can just lower the open loop gain and save the cost of the xformer.
Loading T1 collector would be a convenient place.
You coulkd even put a pot there for continuous control of open loop gain and feedback factor.

jan
__________________
I won't make the tactical error to try to dislodge with rational arguments a conviction that is beyond reason - Daniel Dennett
Check out Linear Audio Vol 7!
  Reply With Quote
Old 8th January 2013, 01:35 PM   #4
Stee is offline Stee  Italy
diyAudio Member
 
Stee's Avatar
 
Join Date: Jul 2005
Location: milan
Default closed loop gain

If you wish to lower the feedback factor so that you can listen to the amp non-linearity better because lose equalization

the attenuation factor of the feedback(and viceversa the correction factor) does not behave as you think

is difficult to set a dime with potentiometer - better to add a resistor in parallel
Attached Images
File Type: png NFB envelope.PNG (16.3 KB, 217 views)
__________________
Please download my best audio idea https://www.facebook.com/DiyAudioHiEnd

Last edited by Stee; 8th January 2013 at 01:53 PM.
  Reply With Quote
Old 8th January 2013, 02:49 PM   #5
wahab is offline wahab  Algeria
diyAudio Member
 
Join Date: Nov 2009
Location: algeria/france
Congratulation for the never lacking originality.....
  Reply With Quote
Old 8th January 2013, 02:55 PM   #6
Stee is offline Stee  Italy
diyAudio Member
 
Stee's Avatar
 
Join Date: Jul 2005
Location: milan
Thanks
I speak about equalization because the negative feedback is a system of dynamic attenuation
This system attempts (up where he space of action) to correct the deficiency by the load current increasing the voltage
This happens on the frequencies of large amplitude that the bass
where there is no output stage is really capable (large parallel end devices es.TIP35)
__________________
Please download my best audio idea https://www.facebook.com/DiyAudioHiEnd
  Reply With Quote
Old 8th January 2013, 03:23 PM   #7
GoatGuy is offline GoatGuy  United States
diyAudio Member
 
Join Date: Dec 2012
Location: SF Bay Area
Redacted by author

Last edited by GoatGuy; 8th January 2013 at 03:50 PM. Reason: Being wrong... should be corrected.
  Reply With Quote
Old 8th January 2013, 03:47 PM   #8
diyAudio Member
 
Osvaldo de Banfield's Avatar
 
Join Date: Dec 2011
Location: Barrio Garay,Almirante Brown, Buenos Aires, Argentina
Goat, I believe you are wrong. The anode of the led is wired to GND via a 22K resistor, and the cathode to -42V, so it really has about 20 mAcurrent in it.

Although, I canīt understand how this circuit warranties or ensures an idle output voltage less than the famous 25 milliVDC though the load, and prevents temperature drift of this output voltage. (???)
__________________
LW1DSE
  Reply With Quote
Old 8th January 2013, 03:50 PM   #9
GoatGuy is offline GoatGuy  United States
diyAudio Member
 
Join Date: Dec 2012
Location: SF Bay Area
I redacted my note. You are right, Osvaldo. It is early here in San Francisco CA. The "coffee isn't working" ... is true.
  Reply With Quote
Old 8th January 2013, 03:52 PM   #10
Art M is offline Art M  United States
diyAudio Member
 
Join Date: Oct 2010
Location: SF Bay Area
Quote:
Originally Posted by GoatGuy View Post
Stee...

Ummm... hate to call it what it is, but "********", brother.

The "Quasi-zero feedback amplifier" in the original PDF cannot work. It has at least 4 design errors. One is significant enough to prevent operation of the long-tailed differential pair up front, completely.

Specifically, the resistor R8 is connected to ground, which prevents the current source Q1 from conduction, at all. The LED will never light, as there is no V+ path to it. Now... go find the other 3 errors ... they're not as significant, but just as important.

GoatGuy
Please point out the other 3 errors on this proven design.

300/500W Subwoofer Power Amplifier

Last edited by Art M; 8th January 2013 at 03:56 PM. Reason: Repeating the known
  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
output transformer for on solid state dual channel for THD reduction muddasirwaheedmalik Solid State 12 23rd May 2012 02:49 PM
What Solid State Amps with Output Transformer do you know of? Onvinyl Solid State 27 27th April 2010 10:41 PM
Solid State Replacement of Ribbon Transformer? tmblack Pass Labs 5 31st January 2010 04:49 PM
Solid State amp with output transformers vizion Solid State 31 10th November 2007 03:23 PM
Transformer output solid state lumanauw Solid State 34 3rd April 2007 02:14 PM


New To Site? Need Help?

All times are GMT. The time now is 08:47 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright Đ1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2