Simple Symetrical Amplifier - Page 356 - 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 23rd October 2012, 10:46 AM   #3551
Salas is online now Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Quote:
Originally Posted by JOHN BALI View Post
Ok, thanks
So if I put 8 ohm speaker & 60W that is safe...
& good heat sink of course.

But actually I want to push it up to 75W into 8ohm if possible with only 1 pairs output
I read earlier posts & find someone who broke 4 pairs of lateral

What usually cause the Latfet "go away" anyway?
Could anyone explain, this my first lateral & don't wanna fry them
Also no one use zobel network, not need for this amp?

thanks
You should look in the many threads here and for Exicon application notes to know all about Laterals. There is no secondary breakdown so the enemies are bad thermal design and/or oscillations mainly. I have another John Linsley Hood amp that runs one pair 2SJ50 and 2SK135 at 60V and 110mA on ~0.5C/W per channel sinks for 80W for instance but I don't think it has the same capability for running full out at 4 Ohm like it does at 8 Ohm. It has a series choke//resistor Zobel. You should have the swing from driving stage to do that though and you lose about 5V for gate drive VS BJT so its about 55V utilized for real even in that example again.
  Reply With Quote
Old 23rd October 2012, 10:54 AM   #3552
Jay is offline Jay  Indonesia
diyAudio Member
 
Join Date: Feb 2003
Location: Jakarta
Quote:
Originally Posted by Magna View Post
i'd like to use Laterals for drivers, to provide suffiecient current to charge / discharge input capacitance of these Vfets. I've sucessfully used this setup in another amp which i've made about 2 years ago. I've learned somewhere else from this thread that the PSRR is not great with this kind of topology and hence i've added a Cap multiplier at the rails to power input stage.
The amp performs brilliantly in simulation. The THD20 is less than 0.015% near clipping at 4 ohms. The square wave response is good, clipping action is excellent without any clamping diodes, etc. Now the question is will this circuit work...?as shown. comments please....
I didn't check your ASC file. But yes, the base front end with cascoded VAS as designed by LC has very low distortion. But when we believe that 0.001% is hardly different than 0.0001%, I cannot see no reason why to use cascode as I have suspicious with its sound quality unless another stage is added like in yours. Your output stage is very common and has good sound reputation and has been used in similar circuit of high end amp. I think the combination will produce very good or top result.

I will be building a cascoded VAS SSA without additional driver to see how good it can be. Rail voltage is 75V, bias is around 150mA. The good thing is that all harmonics are well below -100dB and the mosfet got more than enough current for a very wide bandwidth and speed. The bad thing is that it is not stable in simulation. After all other things have been "optimized" I can only get it to be stable against 27nF in parallel with load. But it seems that in real life it will have better stability.

Surprisingly, the SSA topology works very well with darlington outputs.
  Reply With Quote
Old 23rd October 2012, 10:58 AM   #3553
diyAudio Member
 
Esperado's Avatar
 
Join Date: Jul 2011
Location: France
Quote:
Originally Posted by JOHN BALI View Post
What usually cause the Latfet "go away" anyway?
Temperature, and tension.
You will find in datasheets the"safe area" of them. You can evaluate the junction temperature, adding the case to junction thermal resistance and the case to radiator's one.
If you keep sufficient margin, you will be safe.
As other Fets, they do not suffer second breakdown, so they are very safe. Of course, and even if they are internally protected, take care the gate does not suffer from electrostatic discharge when you manipulate them.
If they are well sized, you have to be aware from HF oscillation. Amps can oscillate at a very high HF level, where dissipation, because the transition time, can be destroying, even if you are in the safe area with low frequencies. So limit the power rails current with a low power resistance or a fuse during your first power on, until you ensure your amp is rock stable.
Did i forget something ?

[edit] Yet answered by Salas, in the time i was composing this message, Sorry.
__________________
Ultimate Protection and more.The Only Source of Knowledge is experience, everything else is just information” ©A. Einstein

Last edited by Esperado; 23rd October 2012 at 11:02 AM.
  Reply With Quote
Old 23rd October 2012, 11:06 AM   #3554
naf is offline naf  Indonesia
diyAudio Member
 
Join Date: Aug 2011
Quote:
Originally Posted by Salas View Post
Went to a friend's to see and listen to his SSA build I was talking about lately.
Its based on Shaan's with the following differences:

1. No input coupling capacitor.
2. No 10K trimmers, no 1 Meg to input.
3. IR LED + 100R series trimmer output stage bias scheme instead of 2 X 1N4148. Bypassed by 470uF BGN as a whole. Gives freedom to match channels bias. Running at about 175mA in this amp's case.
4. 1.42K (1K2+220R) current feed resistor, its symmetric one is 1K trimmer + 500R in series. Does the offset trimming.
5. 270R instead of 220R as cascode load resistors. 1.5K instead of 2K2 feedback resistors. 24dB gain, 44dB OLG, 20dB FB instead of 27dB, 40.5dB, 13.5dB.

It did not show more than 10-15mVDC offset after many hours of play. No turn on thud, no turn off thud. Just a mute woofer pump maybe 1 or two 2mm pk-pk travel for less than 1sec at power off.

No noise no hum, built on iterated matrix boards, AC ground lifted though.

Smooth detailed expressive sound. Very good timing and presence. Maybe a bit softer than life IMHO in the brilliance region but it kinda shouted ''Latfet" to me about that trait. Fully retrieving though, just a slight tonal characteristic rather helpful with the many bit strident recordings or happier tweeters etc.

All in all, finally a current feedback rather simple 40-50W Mosfet amp you can expect it to succeed as a build when with typical DIY instruments and knowledge. Not too hot, not too big, but with a generous musical heart. Kudos to Shaan for arriving to a workable basic SSA with common semis example and sharing it, congrats to my friend Michael for keeping it stable when he reduced it to even less parts.
Kudos to you Sir to inform in this thread.
how much supply of this SSA version?
  Reply With Quote
Old 23rd October 2012, 11:12 AM   #3555
Salas is online now Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
28-30V per rail depending on mains.
  Reply With Quote
Old 23rd October 2012, 11:17 AM   #3556
diyAudio Member
 
Esperado's Avatar
 
Join Date: Jul 2011
Location: France
Quote:
Originally Posted by Salas View Post
Maybe a bit softer than life IMHO in the brilliance region but it kinda shouted ''Latfet" to me about that trait. Fully retrieving though, just a slight tonal characteristic rather helpful with the many bit strident recordings or happier tweeters etc.
Salas, i'm not sure of that (softer than life). I believe that is an effect of the speed quality of closed loop amps, to reduce the HF distortions witch gives slower amps a brighter character than expected.
I had noticed the same effect on my amp, after SSA modification of it. Because it uses exactly the same active components, i'm pretty sure the components sonic characters were not involved.
__________________
Ultimate Protection and more.The Only Source of Knowledge is experience, everything else is just information” ©A. Einstein

Last edited by Esperado; 23rd October 2012 at 11:22 AM.
  Reply With Quote
Old 23rd October 2012, 11:24 AM   #3557
Salas is online now Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
That's what I heard but take it with a pinch of salt in the context of a full system. I remember it again in the previous less DC behaving attempts of that config still. That was remedied with the CCSs then, this example did not take them in his first attempt though, it latched to one rail fully biasing one half, so he reverted to resistive current feed. But he is the persisting kind of fellow, I am sure he will attempt it again. In any case of revision I will report.
  Reply With Quote
Old 23rd October 2012, 12:39 PM   #3558
diyAudio Member
 
Esperado's Avatar
 
Join Date: Jul 2011
Location: France
Quote:
Originally Posted by Salas View Post
That's what I heard but take it with a pinch of salt
Salas, take my remark with a pinch of pepper, as it address half of the situations we need to compare.
Misses the comparison with the same topology between different power devices (BJT, Lateral, HEX vertical). Only way to figure out what can be the part of the topology, and what can be the one of any device's sound.
I believe that, with enough open loop gain and current feedback, distortion is low enough to erase any typical distortions (color) due to components non linearity.
I believe L.C. can say more about that, because his D amps is supposed to have *no analog sound*, means no 'color' influence of the switching device technology.
__________________
Ultimate Protection and more.The Only Source of Knowledge is experience, everything else is just information” ©A. Einstein
  Reply With Quote
Old 23rd October 2012, 12:41 PM   #3559
Salas is online now Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Surrealistically enough I got a phone call 15mins ago that he attempted 2 BF245C 14mA free IDSS matched equipped with source leg trimmers and prepared for 10.5mA this morning. He dropped them in instead of the current feed resistors and it looked it did OK. More monitoring and some listening in the evening he said.
  Reply With Quote
Old 23rd October 2012, 12:51 PM   #3560
diyAudio Member
 
Esperado's Avatar
 
Join Date: Jul 2011
Location: France
Salas, i was in my morning brain frog. My last remark applies as well with different CCS as well as CSS vs resistance, etc... Any stage configuration as well as they are linear enough...
__________________
Ultimate Protection and more.The Only Source of Knowledge is experience, everything else is just information” ©A. Einstein
  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
Symetrical schematics are alike plague in Brazil, do you like them? destroyer X Solid State 151 1st July 2010 03:09 PM
Symetrical out low Zout karsten21 Tubes / Valves 5 1st February 2010 11:19 PM
going balanced/symetrical - what benefits? weissi Solid State 15 20th October 2007 09:06 AM
Symetrical field, is this? Raka Multi-Way 6 14th September 2003 02:21 PM
Non-symetrical SMPS output cm961 Parts 4 21st August 2003 11:27 PM


New To Site? Need Help?

All times are GMT. The time now is 06:05 PM.


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