hello,do you like OTL amplifier?
using MOSFET as output devices?
suitable output power for your room?
hi-fi sound?
I read some old audio book,looking for a easy to build and sounds good's amplifier circuit...I choose the classical OTL amp.
so I do simulating with the BJT output stage version!the result isn't well,too large of the distortion...I know the reason is simple circuit construction has no more driver stage to offer more driven current...I think of MOSFET power device,haha...
after many times I do simulation and adjusting the parameter of the electrical devices,I got more satisfying result:
50V single power supply,class-AB,input sensitive is 850mV(RMS),22W(RMS,8ohm load) output power,from 20Hz~20KHz THD=0.023%(full power output).
well,let's see the circuit schematics:
Attachments
Re: Old audio book
yes,I know that...but I don't feel the new audio book has new and good idea,few years ago,I order a lot of audio book from the post,but now I don't do that again,lost interesting,too little readable knowledge,so I would like to read old book...
regards!
WINCO
Upupa Epops said:Read also new audio books - with five devices you can't make miracle, although many people claim it.
yes,I know that...but I don't feel the new audio book has new and good idea,few years ago,I order a lot of audio book from the post,but now I don't do that again,lost interesting,too little readable knowledge,so I would like to read old book...
regards!
WINCO
Upupa Epops said:Winco, knowledges aren't about feeling, but about knowledge of theory and about practical experiences. Sure, old books are good too, but not in all
ok,Upupa Epops:
I understand your meaning!I will try my best to chase up the times development! a old word:"men live to old and lean to old!"
is it?
thank you!
regards!
WINCO
Hi Darkhorse,
When you go from bipolar to Mosfet you don't need the biasing resistors to be so low.
Try R6 and R7 at 1k each + readjust RP2
Try 2N5551 for BD139
Try increasing R2
Increasing the R2/R8 ratio increases the open loop gain to limit of Q2 loading
this can decrease closed loop distortion - find optimum
This type of input stage needs a low source impedance
preferably 50 ohms, not more than 600.
Enjoy your dabbling.
Cheers ......... Graham.
When you go from bipolar to Mosfet you don't need the biasing resistors to be so low.
Try R6 and R7 at 1k each + readjust RP2
Try 2N5551 for BD139
Try increasing R2
Increasing the R2/R8 ratio increases the open loop gain to limit of Q2 loading
this can decrease closed loop distortion - find optimum
This type of input stage needs a low source impedance
preferably 50 ohms, not more than 600.
Enjoy your dabbling.
Cheers ......... Graham.
Graham Maynard said:
hello,Graham:
in fact,I don't agree with you in "Try R6 and R7 at 1k each ",the power MOSFET need high Iq of driver stage,because of it's input capacitor is about 1400~1700pF...
but I will try with your suggest ,thank you!
I will show you the simulating result tomorrow...
regards!
WINCO
edl said:
haha...It doesn't matter at all!
but I don't prefer JLH BJT's version,because I have done some simulation with 2N3055 as output device,at about 15KHz or more higher the waveform goes so freakish...so I give up!
hi,Graham Maynard:
I come back,lastnight's simulation result:
(1)as your suggest,increast R6 & R7 at 1K each,R2 at 5.1K,
driver stage Iq=10.6mA,THD=0.0238%...(23W output)
I modify R6/R7 ratio,R6 at 200R,R7 at 1.8K,THD=0.0208%(
)(2)no change of my schematics,driver stage Iq=37mA,THD=0.0225%(23W output)
from the results, you right 50%,that is to say R6 & R7 not demand at same value!
I don't know,perhaps high Iq let voltage stage and driver stage increast distortion more than high Iq decreast MOSFET output stage's distortion...I think so!
regards!
WINCO
Hi Darkhorse,
Okay, so source followers can manage with less current drive at audio frequencies.
You have completed ratio tests on R6 / R7 for THD, but it may be best to determine their ratio by observing 10 to 20kHz squarewave response, instead of extracting lowest possible THD.
I also wrote;- >Try increasing R2, and
Increasing the R2/R8 ratio increases the open loop gain to limit of Q2 loading
this can decrease closed loop distortion - find optimum<
I forgot to mention the corollary ( not a word I could say or even think of using after a bevy), try adding another R8 and C2 in parallel in an attempt to almost *halve* the distortion.
When you construct it, keep C5 as low as possible. There is also no reason why the single rail psu voltage cannot be upped to 70-80 Volts with this kind of circuit to obtain 50W-8ohm / 100W-4ohm capability. Increasing C9 limits loudspeaker thump to a big sigh !
Cheers ......... Graham.
Okay, so source followers can manage with less current drive at audio frequencies.
You have completed ratio tests on R6 / R7 for THD, but it may be best to determine their ratio by observing 10 to 20kHz squarewave response, instead of extracting lowest possible THD.
I also wrote;- >Try increasing R2, and
Increasing the R2/R8 ratio increases the open loop gain to limit of Q2 loading
this can decrease closed loop distortion - find optimum<
I forgot to mention the corollary ( not a word I could say or even think of using after a bevy), try adding another R8 and C2 in parallel in an attempt to almost *halve* the distortion.
When you construct it, keep C5 as low as possible. There is also no reason why the single rail psu voltage cannot be upped to 70-80 Volts with this kind of circuit to obtain 50W-8ohm / 100W-4ohm capability. Increasing C9 limits loudspeaker thump to a big sigh !
Cheers ......... Graham.
ok,Graham,I will do more simulation and observing 10 to 20kHz squarewave response.
and I don't understand "try adding another R8 and C2 in parallel in an attempt to almost *halve* the distortion.",can you give a sketch map to let me know it's meaning,thank you!
and you also say:"There is also no reason why the single rail psu voltage cannot be upped to 70-80 Volts with this kind of circuit to obtain 50W-8ohm / 100W-4ohm capability. "
I think IRF540/9540 as output device is can't load too heavy dissipation(hight voltage load 4ohm)!so I decide using about 50V~60V is suitable to load 8ohm or 4ohm...
cheers!
WINCO
Upupa Epops said:For this output power you need 250*100*40 mm heatsink, which is not so large ( for class AB ).
ok,notice to the quote who want to add 70~80V voltage PS...
thank you ,Upupa Epops !
oh,I forget to ask you this dimension suitable to one channel or stereo channel???
regards!
WINCO
Old guys, with old ears, with old vinyl discs could have fun with those old things .
So, this is very good...old style circuit...and that thopologie sounds good because of.....hehe...cannot say, because is not my intelectual property...but this thopologie always sounds good.
There are some critics that came from the "modernist" we have, some of them pops out as Epupa, always remembering us that we must walk ahead and no backwards.
He is rigth...but not completely..... as the real thing is that Digital is already developed...and in technologie is advanced related the circuits we make....so....Epupa pops is delayed also.... alike all of us...using conventional analogic designs and discrete components.
Hey guys, there are room to every circuit... and some people loves to hear her father sound...remember her father or already loosen mother..... there are tubes, they are romantic alike candles... tollerance is more adequate...to have many things...if not...have to erase solid state, as this is old.... and order all guys to run to Class D.....class T...class Epson....Class Sigma.
And some of us, feel those old designs as better than new double or triple simetrical, dual cascode, 4 CCS, mirrored many times, with four darlington, double assemetrical triple error correction, and i discovered someone that made a very good sounding amplifier with classes A, AB, and B working same time....sounded very nice!
If we want really to make the better..... we can turn the world better too..... returning 300 years back...everyone could have some work, some income, no computers making all job to us....no machines sending hundreds to feel unhappy because nobody needs them anymore.
This is not a coded message.... Epupa Popcorn...this is for you my dear....jump 10 foot high nervous with me, if i could touch you...but remember after that, i am a very nice guy, and not your enemie...but sometimes, in this life....our ideas can make some separation...each one pushing his rope end...alike young children game.... a with strip in the ground... a long rope.... 10 boys one side...other 10 boys the other side...and putting strength to move in one direction.... sometimes we can be in the same group dear Popcorn.... and sometimes we are in opposite sides.
just that...no more than that...quite simple.
Carlos
So, this is very good...old style circuit...and that thopologie sounds good because of.....hehe...cannot say, because is not my intelectual property...but this thopologie always sounds good.
There are some critics that came from the "modernist" we have, some of them pops out as Epupa, always remembering us that we must walk ahead and no backwards.
He is rigth...but not completely..... as the real thing is that Digital is already developed...and in technologie is advanced related the circuits we make....so....Epupa pops is delayed also.... alike all of us...using conventional analogic designs and discrete components.
Hey guys, there are room to every circuit... and some people loves to hear her father sound...remember her father or already loosen mother..... there are tubes, they are romantic alike candles... tollerance is more adequate...to have many things...if not...have to erase solid state, as this is old.... and order all guys to run to Class D.....class T...class Epson....Class Sigma.
And some of us, feel those old designs as better than new double or triple simetrical, dual cascode, 4 CCS, mirrored many times, with four darlington, double assemetrical triple error correction, and i discovered someone that made a very good sounding amplifier with classes A, AB, and B working same time....sounded very nice!
If we want really to make the better..... we can turn the world better too..... returning 300 years back...everyone could have some work, some income, no computers making all job to us....no machines sending hundreds to feel unhappy because nobody needs them anymore.
This is not a coded message.... Epupa Popcorn...this is for you my dear....jump 10 foot high nervous with me, if i could touch you...but remember after that, i am a very nice guy, and not your enemie...but sometimes, in this life....our ideas can make some separation...each one pushing his rope end...alike young children game.... a with strip in the ground... a long rope.... 10 boys one side...other 10 boys the other side...and putting strength to move in one direction.... sometimes we can be in the same group dear Popcorn.... and sometimes we are in opposite sides.
just that...no more than that...quite simple.
Carlos
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