And a 3rd scopeshot, x: 1uS/Div y: 5v/Div
I was not able to make this measurement for longer than a few
seconds, i have not biggest 8ohm resistor, it stinked...
Obviously the amp ran into slewratelimit, so tweaking necessary !
What exactly should i check according oscillations ?
The results look even better than in sims...
Mike
I was not able to make this measurement for longer than a few
seconds, i have not biggest 8ohm resistor, it stinked...
Obviously the amp ran into slewratelimit, so tweaking necessary !
What exactly should i check according oscillations ?
The results look even better than in sims...
Mike
Attachments
Wonderfull MikeB, but let's see something more.
Mike, let me see, directly to my mail or even here if you prefer.
20 Kilohertz, sinusoidal, less 3 dB related maximum power, also the square wave in the same less 3 dB.
I will like to know when square wave started to be rounded in the corners...so, adjust to 45 Volts peak to peak and go increasing frequency, show me when start rounded.. use amplification to observe the square wave horizontal line...see if have superimposed oscilations or some damping, ringing or something strange.
Check frequency when sinusoidal turn into a triangle.
Try the less 3 dB low frequency roll of .... inject square wave first and send me picture.... and second inject square wave also.
Repeat all test with 3 volts peak to peak...but make all your testings over your 4 ohms speaker.....if cannot make noise, to the high power testings...reduce power and try to mufled your speaker.... or destruct someone old speaker removing diafragm...keep suspension and voice coil in place...and them...mufled under and over.
Well MikeB, i feel very curious to see, as using that level i do not feel too much surprised, as i already could hear your amplifier recorded by DAT, using high End AKG microphone, and sounded very nice, discounting the system losses, my PC audio card and the non special chamber to avoid reflections in your home...yes...your microphone is unidirectional, i remember.
The last time i use my Multisim was when i was testing Doctor Self Blameless amplifier..... was wonderfull simulating..... could beat the JLH that is the one that can reproduce perfect square waves in every frequency with speaker connected...using resistor as a load, you do not show us the reality, as a lot of counter forces will appear because of speaker coil moving inside magnet...really things turn worst with speaker connected.
Despite beeing wonderfull in simulation.... i gave a shot in that Blameless..... a double barrelled shot gun...boooom! over the board...so frustrated i was....one of the worst amplifier in sound quality i ever heard....before the shot i check it all.....VBE voltage correct, current correct, nothing strange...off set very low....but was terrible!
We have enormous thread about blameless, and very good people goes there and post their opinions.
That experience showed me, that a good measurement (using simulator) do not guarantee a good sound in real life hearing tests.
I concluded that this is fair, because the ones that go to shops, to buy audio amplifiers are not scopes or spectrum analisers....if some Wave form go shopping...it will return with Blameless....but humans are a little different.... we like harmonics, even some distortion is acceptable.
Your amplifier seems not oscilating, but using speaker things can be different...hehe....being very bad...... my dark side....put some 2,2 uF in parallel with your woofer...hehe
Stay with us Mike, as you have wonderfull ears...you are a very focused audiophile.... forget scopes...lets evaluate with our ears and hearts.
Of course Mike, if you have some tendence to be a "voyers".... you can have a lot of fun not hearing...just watching scope waves...ahahahaha.
regards,
Carlos
Mike, let me see, directly to my mail or even here if you prefer.
20 Kilohertz, sinusoidal, less 3 dB related maximum power, also the square wave in the same less 3 dB.
I will like to know when square wave started to be rounded in the corners...so, adjust to 45 Volts peak to peak and go increasing frequency, show me when start rounded.. use amplification to observe the square wave horizontal line...see if have superimposed oscilations or some damping, ringing or something strange.
Check frequency when sinusoidal turn into a triangle.
Try the less 3 dB low frequency roll of .... inject square wave first and send me picture.... and second inject square wave also.
Repeat all test with 3 volts peak to peak...but make all your testings over your 4 ohms speaker.....if cannot make noise, to the high power testings...reduce power and try to mufled your speaker.... or destruct someone old speaker removing diafragm...keep suspension and voice coil in place...and them...mufled under and over.
Well MikeB, i feel very curious to see, as using that level i do not feel too much surprised, as i already could hear your amplifier recorded by DAT, using high End AKG microphone, and sounded very nice, discounting the system losses, my PC audio card and the non special chamber to avoid reflections in your home...yes...your microphone is unidirectional, i remember.
The last time i use my Multisim was when i was testing Doctor Self Blameless amplifier..... was wonderfull simulating..... could beat the JLH that is the one that can reproduce perfect square waves in every frequency with speaker connected...using resistor as a load, you do not show us the reality, as a lot of counter forces will appear because of speaker coil moving inside magnet...really things turn worst with speaker connected.
Despite beeing wonderfull in simulation.... i gave a shot in that Blameless..... a double barrelled shot gun...boooom! over the board...so frustrated i was....one of the worst amplifier in sound quality i ever heard....before the shot i check it all.....VBE voltage correct, current correct, nothing strange...off set very low....but was terrible!
We have enormous thread about blameless, and very good people goes there and post their opinions.
That experience showed me, that a good measurement (using simulator) do not guarantee a good sound in real life hearing tests.
I concluded that this is fair, because the ones that go to shops, to buy audio amplifiers are not scopes or spectrum analisers....if some Wave form go shopping...it will return with Blameless....but humans are a little different.... we like harmonics, even some distortion is acceptable.
Your amplifier seems not oscilating, but using speaker things can be different...hehe....being very bad...... my dark side....put some 2,2 uF in parallel with your woofer...hehe
Stay with us Mike, as you have wonderfull ears...you are a very focused audiophile.... forget scopes...lets evaluate with our ears and hearts.
Of course Mike, if you have some tendence to be a "voyers".... you can have a lot of fun not hearing...just watching scope waves...ahahahaha.
regards,
Carlos
Hi Cortez !
These will be next tests, it was late yesterday...
Hi Carlos !
Don't misunderstand the results, the corners are always rounded,
completely independent of the frequency. It's just that the amp
needs ~2uS to settle. So, depending on the timescale you can
see the round corners just better...
This means even with a 1hz squarewave, the result is identical,
if using the same timescale.
The frequency is the same on all 3 shots.
I can't make your suggested test with higher frequencies on sinus...
I don't have a functiongenerator, for these tests i've constructed
a squarewavegenerator with fixed frequency...
Mike
These will be next tests, it was late yesterday...
Hi Carlos !
Don't misunderstand the results, the corners are always rounded,
completely independent of the frequency. It's just that the amp
needs ~2uS to settle. So, depending on the timescale you can
see the round corners just better...
This means even with a 1hz squarewave, the result is identical,
if using the same timescale.
The frequency is the same on all 3 shots.
I can't make your suggested test with higher frequencies on sinus...
I don't have a functiongenerator, for these tests i've constructed
a squarewavegenerator with fixed frequency...
Mike
That's OK Mike!..those multiple questions is to call you to show us more waveforms.
And not beeing guilty....as Carlos was the one that asked..hehe
Bandwidth, you understand those things more than I, as you are expertise in Computer Programing....was reading.... you are humble my friend..... one of the 4 best programer in Deutschland. I am deeply honored Mike, i am very lucky with friends...very lucky.
CONGRATULATIONS!
Mike, some conscient misunderstandings can be helpfull to push friends to publish things.... some are driven by pride..... you are diriven by challenges...this way...hehe...show me the worst side of the moon.
But if you prefer...send direct to me....please!
regards,
Carlos
And not beeing guilty....as Carlos was the one that asked..hehe
Bandwidth, you understand those things more than I, as you are expertise in Computer Programing....was reading.... you are humble my friend..... one of the 4 best programer in Deutschland. I am deeply honored Mike, i am very lucky with friends...very lucky.
CONGRATULATIONS!
Mike, some conscient misunderstandings can be helpfull to push friends to publish things.... some are driven by pride..... you are diriven by challenges...this way...hehe...show me the worst side of the moon.
But if you prefer...send direct to me....please!
regards,
Carlos
Hi MikeB,
I have followed your project silently with pleassure!
On the third oscilloscope picture you attached I interpret the slewrate to be around 15V/uS, it's not "ultrafast" so I wonder is this correct?
Have you checked the rise/fall time of the flanks on the pulses from the generator when connected to the amplifier input?
Also how does the signal look at the base of diff input?
Edit: 100 Hz square wave is enough to trace with the scope and study rising/falling flanks of your amplifier in the beginning.
A tip for all DIY:ers
BTW, we all have 100/120 Hz unsmoothed from our full way rectifiers from the mains transformers, it's easy to build with fast comparator a simple squarewave generator built in the amplifier.
Regards Michael
I have followed your project silently with pleassure!
On the third oscilloscope picture you attached I interpret the slewrate to be around 15V/uS, it's not "ultrafast" so I wonder is this correct?
Have you checked the rise/fall time of the flanks on the pulses from the generator when connected to the amplifier input?
Also how does the signal look at the base of diff input?
Edit: 100 Hz square wave is enough to trace with the scope and study rising/falling flanks of your amplifier in the beginning.
A tip for all DIY:ers
BTW, we all have 100/120 Hz unsmoothed from our full way rectifiers from the mains transformers, it's easy to build with fast comparator a simple squarewave generator built in the amplifier.
Regards Michael
Hi Michael !
I'm not sure if the amp is limited to 15v/us, but it's not an impressive
value. With speed i thought more of delay, avoiding feedbackcaps.
The tripledarlingtonversion had much higher slewrate...
I checked output from squarewavegenerator, rise/fall was barely
visible on scope. I will check more details the next days.
A comparator to make squarewave ? My generator uses 3 bjts...
Michael
I'm not sure if the amp is limited to 15v/us, but it's not an impressive
value. With speed i thought more of delay, avoiding feedbackcaps.
The tripledarlingtonversion had much higher slewrate...
I checked output from squarewavegenerator, rise/fall was barely
visible on scope. I will check more details the next days.
A comparator to make squarewave ? My generator uses 3 bjts...
Michael
Hi MikeB,
I've not had a chance to look over your design closely or read the entire thread, but generally raising the Ic provides more class A current to charge device capacitances and increase the slew rate as you probably know. This of course assumes that there's nothing fundamentally wrong with the design.
You need a function generator? - I've only tried these quickly on my PC and they seem to work, a function generator and scope using a basic sound card, obviously the bandwidth is highly limited by the sound card but it's free. I believe it will work on even an early Pentium PC, there is just an exe file no installation required, fftscope is the download that's needed it has the scope and function generator in one program:
http://duncan.rutgers.edu/physicsfreewares.htm
After a very quick look I have to wonder if the early stages have enough current gain? Also, have you looked at the open loop voltage gain?
Enjoy!
Pete B.
I've not had a chance to look over your design closely or read the entire thread, but generally raising the Ic provides more class A current to charge device capacitances and increase the slew rate as you probably know. This of course assumes that there's nothing fundamentally wrong with the design.
You need a function generator? - I've only tried these quickly on my PC and they seem to work, a function generator and scope using a basic sound card, obviously the bandwidth is highly limited by the sound card but it's free. I believe it will work on even an early Pentium PC, there is just an exe file no installation required, fftscope is the download that's needed it has the scope and function generator in one program:
http://duncan.rutgers.edu/physicsfreewares.htm
After a very quick look I have to wonder if the early stages have enough current gain? Also, have you looked at the open loop voltage gain?
Enjoy!
Pete B.
Hi !
Darkfenriz, principally the LTP is already cascoded, the voltage
at the collectors keeps nearly constant.
PB2, with the PC i can only generate frequencies within the
audioband, this excludes already a 10khz squarewave.
But for measuring with audiofreqs this tool shood be very handy !
And yes, increasing the Iq increases the slewrate, but with FC
it also lowers the gain, which is already a bit too low.
To avoid this, i have to increase current in LTP also, which gets
difficult with to92-devices. So i am considering to go back to
tripledarlington, or use CFP-LTP...
Mike
Darkfenriz, principally the LTP is already cascoded, the voltage
at the collectors keeps nearly constant.
PB2, with the PC i can only generate frequencies within the
audioband, this excludes already a 10khz squarewave.
But for measuring with audiofreqs this tool shood be very handy !
And yes, increasing the Iq increases the slewrate, but with FC
it also lowers the gain, which is already a bit too low.
To avoid this, i have to increase current in LTP also, which gets
difficult with to92-devices. So i am considering to go back to
tripledarlington, or use CFP-LTP...
Mike
Yes, of course the rise time is limited but you can "square up" or increase the square wave rise time by using a high speed comparator at the output. At least it gives you variable frequency and the other functions. There's also an FFT as you probably noticed, but I've not tried it. Of course you also need a high speed scope to look for oscillations.
Pete B.
Pete B.
MikeB,
I skimmed through but did not red carefully the entire thread, checked and noticed your second schematic in Post #17 and still there is a missing pulldown resistor from the LED cathode setting the FC transistors to a "fixed" cascoding voltage level, do you have anything there in your real circuit not shown on the schematic?
I do understand that in your schematic the pulldown resistor is not needed as it is a voltage source instead of a LED.
Regarding speed, yes you are right, it can also be interpreted as well as delay!
Cheers
I skimmed through but did not red carefully the entire thread, checked and noticed your second schematic in Post #17 and still there is a missing pulldown resistor from the LED cathode setting the FC transistors to a "fixed" cascoding voltage level, do you have anything there in your real circuit not shown on the schematic?
I do understand that in your schematic the pulldown resistor is not needed as it is a voltage source instead of a LED.
Regarding speed, yes you are right, it can also be interpreted as well as delay!
Cheers
What a thread!.... a perfect selection of wonderfull people.
Very good to ready...very instrutive.... and Mikeks soft!...my God!...
Hey Mike.... have you see the Mikeks girl friend in the avatar picture?...secret...don't tell anybody......hummmm ...good!
I love the wave forms....and Ultima here too....more wave forms please!
Carlos
Very good to ready...very instrutive.... and Mikeks soft!...my God!...
Hey Mike.... have you see the Mikeks girl friend in the avatar picture?...secret...don't tell anybody......hummmm ...good!
I love the wave forms....and Ultima here too....more wave forms please!
Carlos
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