Yet another amp - simple inverted with 10x gain, mosfet output stage - Page 11 - 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 22nd April 2012, 10:51 AM   #101
hahfran is offline hahfran  Germany
diyAudio Member
 
Join Date: Dec 2007
Quote:
Originally Posted by mikelm View Post
Hi Hafran,

You have not yet realised the full potential of having two separate secondaries & bridges in your PSU diagram.

Whether you use cheap noisy diodes of nice schhotky ones . . . when those diodes turn off a resonance will be excited in the secondary windings of the transformer - usually in the 1meg hz region.

In your diagram you are injecting that resonance directly into the amps earth - sonic disaster !

You need to either damp that resonance with a snubber cct or filter the earth lines before you make your star earth point - or do both !
the schematic is only to show the principle not the details. In practice
an RC shunt across the secondary side of each transformer is necessary
plus an Rc across each diode. of course the electrolytics ( i have a bunch of huge Sprague computer/military grade ) are shunted with foil capacitors.
This way the far end where the two groud rails intersect to reference ground
is almost noise-free. Its not only switching diodes the power line has lots of noise. it is very advisable to run preamps , RIAA amps and such on accus.
  Reply With Quote
Old 22nd April 2012, 09:29 PM   #102
sonnya is offline sonnya  Denmark
diyAudio Member
 
sonnya's Avatar
 
Join Date: Oct 2001
Location: Denmark
Quote:
Originally Posted by hahfran View Post
But not complementary Wilson mirrors. of course one could select from a big bunch of devices those which yield a DYNAMICALLY (!!) complemnetry pair of Wilson mirrors but why? It is far more clever to follow a design rule that yields topologies insensitive to
such inevitable differences . Only ring-emitter or multi-emitter BJTs can be made dynamically complements, not simple Epi-planars. its not possible.
I cannot see why a complementary wilson should be worse than folded cascode. You will have to use complementary types in all circumstances but even the best pairs will have differences in Ft, hFE, Cre, Cob, Cib, Early voltage. So at that point i do not agree with you.

The version you have drawn is clever in the way that you use folded cascode to acces the basis instead of emitter of the input pair.

If you choose folded cascode for the VAS, i would prefer a current source instead of the emitter resistor.
  Reply With Quote
Old 23rd April 2012, 10:05 AM   #103
hahfran is offline hahfran  Germany
diyAudio Member
 
Join Date: Dec 2007
Sonnya this is more or less design philosophy. I try to keep the number of variables a minimum. I need not control what is not there. The secret of very simple topologies which quite often "sound better" than complicated is simple: they are simple. Wilson mirrors are described for DC only by a set of 5 non linear equations and these don't tell much about dynamical characteristics. I don't believe a simple simulator such as LTspice can simulate Wilsons. In general as Hiraga had noted replacing resistors with CS changes the harmonics spectrum in an undesirable manner such that odds are greater than even harmonics. Imho in terms of subjective sonic quality it doesn't matter at all whether the thd is 1% or 0.01% what matters is that the harmonics spectrum stays relatively constant to changes of load with frequency and to output amplitude.
Or put it otherwise I do not hear what I see but I might see what I hear.
  Reply With Quote
Old 24th April 2012, 06:51 PM   #104
sonnya is offline sonnya  Denmark
diyAudio Member
 
sonnya's Avatar
 
Join Date: Oct 2001
Location: Denmark
As i see it, it is all a matter of taste. You prefer simple, and i don't care if it simple or advanced as long as it does the job.

Take for example the SSA amp in the first version. The idle current in every stage was floating all over the place. We replaced the simple bias generator made of resistors with CCS. That was keeping everything in place. Some prefer it simple, but in this case simple "is not good enough!" in my world.

The TSSA is way better as the design is changed. But they are also more complex than my amps in the last version.

I use the LTspice as a tool of guidance, and until now it has not let me down. I actually has Hyperlinx Analog, LineSim, BoardSim and Thermal in my PADS ES suite package. They are only a tool for guidance and they do not replace real life measurements.

But for the tools LTspice, Hyperlynx or what they are called you would proberly have been building hundreds of amps. before getting to the results.

Hiragas papers are good no doubt about it, but he did not have the tools we have today. And maybe he had made som changes and come to another conclusion. I dont say it is the case but he proberly would have.

It is a fact that the the footprint the distortion leaves has an impact on how we perceive the "painting" the system delivers us.

Some might like the high distortion that valve amps produce. I am not fan of it as i like it uncoloured. Actually Pix from Sweden which build my Mirand sold it as he wanted experiment with valve amps. He told me that the Valve amp produced a sweet sound but it was not as precise and uncoloured as the MIRAND A1. He does like both types of amps but it is down to the taste of the person listining to it.

Back to my designs. The actually measures as they simulate within a margin.

I do not want to tell you how you should design. But i think my knowledge for using the wilson current is very well proven both in simulation and in real life.. Not in 2 hours of work but several month!

I welcome design idears or changes but it should be documented. Or at least why it is done and not because we think so.... If we think so, it is better to say "should we try this instead?".

It is not a closed thread, dont get me wrong. But please say why you have changed it instead of saying it is stupid to use the "wilson current" mirrors.
  Reply With Quote
Old 8th June 2012, 06:08 AM   #105
Jay is offline Jay  Indonesia
diyAudio Member
 
Join Date: Feb 2003
Location: Jakarta
Quote:
Originally Posted by sonnya View Post
See the difference to my version. There is 30dB less on second and third harmonic.
That is an awsome chart, Sonnya. Which circuit was it? Possibility is that the mosfet lacks sufficient drive to not sound boring. If it doesn't then this is a must build amplifier.
  Reply With Quote
Old 24th October 2012, 05:37 PM   #106
lineup is offline lineup  Sweden
diyAudio Member
 
lineup's Avatar
 
Join Date: Dec 2005
Location: the north
It is a remarkably good amplifier you have there, Sonnya.
I hope more people can find it and enjoy building it

Quote:
Originally Posted by sonnya View Post
Updated schematic with buffer.
Per sim it is stable into 8R||10uF.
The bandwidth is hitting 2MHz.
But to be that fast, a perfect layout is very important.
Here is the latest schematic posted by Sonnya, attached
Attached Files
File Type: pdf simpleamp v11 noninverted 290312.pdf (16.3 KB, 221 views)
__________________
lineup
  Reply With Quote
Old 29th October 2012, 12:05 PM   #107
mikelm is offline mikelm  England
diyAudio Member
 
Join Date: May 2003
Location: England
Send a message via Yahoo to mikelm
Hi Sonny, I was wondering . . . . when you say you have measured the bandwidth up to 2meg hz with this design are you referring to the -3db point ?

p.s. and would that be half power of half voltage ?

cheers

mike

Last edited by mikelm; 29th October 2012 at 12:14 PM.
  Reply With Quote
Old 29th October 2012, 06:24 PM   #108
sonnya is offline sonnya  Denmark
diyAudio Member
 
sonnya's Avatar
 
Join Date: Oct 2001
Location: Denmark
Yes, it is the -3dB point.

But mike, The Mirand A1 and TSSA is way better.
  Reply With Quote
Old 29th October 2012, 06:57 PM   #109
mikelm is offline mikelm  England
diyAudio Member
 
Join Date: May 2003
Location: England
Send a message via Yahoo to mikelm
Thx Sonny,

Yes, the TSSA made me realise that a few things in my SE CFB design needed some attention - but those things are more or less fixed now so I can do an preliminary comparison - final comparison can only be done when both amps have optimised PSUs - and that may take a few months.

I'll post it over in TSSA builders thread soon.
  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
Simple stereo gain stage ss007 Analog Line Level 156 23rd August 2013 03:52 PM
Wanted: Zero feedback 2-10x gain line stage...prefer symmetrical Ric Schultz Analog Line Level 14 26th February 2011 07:26 PM
Voltage gain stage for Non-NFB MOSFET current amp gripracer Solid State 50 23rd October 2009 02:37 AM
AMP with inverting output stage mosfet fab Solid State 112 28th January 2007 04:32 AM
Elektor op-amp front-end with mosfet CF output stage Dusk Elektor 1 5th April 2006 04:09 AM


New To Site? Need Help?

All times are GMT. The time now is 03:50 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