I promise I've finished now.
This pertains to the Fig A variation of SOAR. It just may generate some comment.
Brian.
This pertains to the Fig A variation of SOAR. It just may generate some comment.
Brian.
AndrewT said:
You're right! I was half asleep. I was off by order of magnitude here and there. 🙄 Thanks Andrew. I thought it looked a little (a lot) extreme.
..Todd
Hi Pingrs,
post1225, any chance you could redo that with a log scale on both axes?
You're Email is off.
First comment,
why 10uF for C20&21?
what would happen with 1uF and maybe even lower at 100nF.
Transient currents will pass at much higher levels than the DC protection trigger values even with a small cap here.
post1225, any chance you could redo that with a log scale on both axes?
You're Email is off.
First comment,
why 10uF for C20&21?
what would happen with 1uF and maybe even lower at 100nF.
Transient currents will pass at much higher levels than the DC protection trigger values even with a small cap here.
Hi Andrew T,
Sorry for the delayed reply - I've lost internet access at home.
As requested, reproduced as log-log.
Sorry, I didn't realise e-mail was off. On now.
I think I need some further insight into what you mean regarding the comment. Would you PM me please?
Regards,
Brian.
Sorry for the delayed reply - I've lost internet access at home.
As requested, reproduced as log-log.
Sorry, I didn't realise e-mail was off. On now.
I think I need some further insight into what you mean regarding the comment. Would you PM me please?
Regards,
Brian.
precision-I gets hot, need help.
Hi,
This is about precision I. at first my amp was operating very well but this few days it’s showing me some abnormal Hot. Sometimes any one of the channel gets very hot, I have measured 106c was today. This problem is not having every time. Only sometime and suddenly without any reason. Sound still good as before. If I turn it off and on it again this will operate normal again but don’t know when will hot again. It’s not all time showing, only some times like two days later or may be next day.
Anyone can have comment on it.
Thank you
michael
Hi,
This is about precision I. at first my amp was operating very well but this few days it’s showing me some abnormal Hot. Sometimes any one of the channel gets very hot, I have measured 106c was today. This problem is not having every time. Only sometime and suddenly without any reason. Sound still good as before. If I turn it off and on it again this will operate normal again but don’t know when will hot again. It’s not all time showing, only some times like two days later or may be next day.
Anyone can have comment on it.
Thank you
michael
It might be going into oscillation intermittently.
The phase margin may be too low.
The phase margin may change with varying PSU supply voltage (as the mains voltage changes).
The phase margin may change with changes in ambient or component temperature.
As a short term sticking plaster add a temperature switch to each heatsink and connect that to a warning lamp/LED.
Investigate the phase margins by doing more thorough testing.
The phase margin may be too low.
The phase margin may change with varying PSU supply voltage (as the mains voltage changes).
The phase margin may change with changes in ambient or component temperature.
As a short term sticking plaster add a temperature switch to each heatsink and connect that to a warning lamp/LED.
Investigate the phase margins by doing more thorough testing.
Reduce your stand by current to a level you will measure
a very small voltage (1 milivolt) or something alike over the emitter resistances...into the power transistors.... do that with your input shorted and after 30 seconds of warm up..... do that fast, as the warm up may turn your adjustment wrong...if excess of bias, the transistors will warm very fast and you will be adjusting it warm.... this will result underbiased when cold.
Increase your Miller capacitor value to 100pf.
Have you measured AC voltage into the output, without audio signal entering?
It may be oscilation..... or the combined effect of thermal drift triggering oscilation.
Are those amplifiers exactly the same.... say.... where they built the same way...same kind of construction, same boards?
The differences you have may be the reason.... check that.... watching one board check the one is unstable... the differences you have into the unstable one should be modified.
regards,
Carlos
a very small voltage (1 milivolt) or something alike over the emitter resistances...into the power transistors.... do that with your input shorted and after 30 seconds of warm up..... do that fast, as the warm up may turn your adjustment wrong...if excess of bias, the transistors will warm very fast and you will be adjusting it warm.... this will result underbiased when cold.
Increase your Miller capacitor value to 100pf.
Have you measured AC voltage into the output, without audio signal entering?
It may be oscilation..... or the combined effect of thermal drift triggering oscilation.
Are those amplifiers exactly the same.... say.... where they built the same way...same kind of construction, same boards?
The differences you have may be the reason.... check that.... watching one board check the one is unstable... the differences you have into the unstable one should be modified.
regards,
Carlos
Attachments
Value of emitter resitors
Carlos and P1 friends,
How sensitive is P1 to the value of the emitter resistors (R24-39)? What side effects could occur if one uses 0R47 instead of the specified 0R33, other than taking into account the measurement of bias current across the higher value resistors?
I have difficulty finding metal oxide resistors below 0R47. I could use 0R33 wire wound resistors but they cost more and could be inductive (does that matter?).
If anyone has a good source for the .33 metal oxide resistors please let me know.
Thanks,
Francois
Carlos and P1 friends,
How sensitive is P1 to the value of the emitter resistors (R24-39)? What side effects could occur if one uses 0R47 instead of the specified 0R33, other than taking into account the measurement of bias current across the higher value resistors?
I have difficulty finding metal oxide resistors below 0R47. I could use 0R33 wire wound resistors but they cost more and could be inductive (does that matter?).
If anyone has a good source for the .33 metal oxide resistors please let me know.
Thanks,
Francois
The lowest those resistance values the better will be your bass...and
the power equalization will be worse.....so... a matter of decision...and this depends the power you gonna use and how different are your power transistor gain.
My suggestion is 0.22 ohms or lower than that, already knowing you will not use the amplifier hard..... lower because will not use hard.
Higher values than the suggested into the schematic will clearly, without any doubts, affect your bass reproduction...better not to use emitter resistances..but we are forced when we used more than one pair into the output.
The local feedback advantages do not compensates the sonics losses...better without that local feedback...also output coil is a hell...needed because some folks use complex loads..speakers with crossovers that has coils, resistances and capacitances inside...and together long cables turns the output coil needed.
But..if you have speaker simple... a woofer connected directly into your amplifier output, and a single tweeter with its capacitor...then do not use even coils for better sonics results.
People much more experienced than i am (John Curl) already told those coils are from stone age and not more used...but this is under "controled" sittuations...if the guy has terrible speaker crossover and long special cables...then.....problems!
Do not install resistances into the audio patch, in special into the power audio patch...you see that you gonna face 4 ohms from the speaker (or 8 ohms) some from the cable and it is better not to have resistances into the amplifier output not to waste power and quality....of course... each case is a different case.
We want resistances into the speaker... nothing more to waste energy.... together resistances there are inductances and capacitances..all this is annoying... if we can avoid...better for us.
regards,
Carlos
the power equalization will be worse.....so... a matter of decision...and this depends the power you gonna use and how different are your power transistor gain.
My suggestion is 0.22 ohms or lower than that, already knowing you will not use the amplifier hard..... lower because will not use hard.
Higher values than the suggested into the schematic will clearly, without any doubts, affect your bass reproduction...better not to use emitter resistances..but we are forced when we used more than one pair into the output.
The local feedback advantages do not compensates the sonics losses...better without that local feedback...also output coil is a hell...needed because some folks use complex loads..speakers with crossovers that has coils, resistances and capacitances inside...and together long cables turns the output coil needed.
But..if you have speaker simple... a woofer connected directly into your amplifier output, and a single tweeter with its capacitor...then do not use even coils for better sonics results.
People much more experienced than i am (John Curl) already told those coils are from stone age and not more used...but this is under "controled" sittuations...if the guy has terrible speaker crossover and long special cables...then.....problems!
Do not install resistances into the audio patch, in special into the power audio patch...you see that you gonna face 4 ohms from the speaker (or 8 ohms) some from the cable and it is better not to have resistances into the amplifier output not to waste power and quality....of course... each case is a different case.
We want resistances into the speaker... nothing more to waste energy.... together resistances there are inductances and capacitances..all this is annoying... if we can avoid...better for us.
regards,
Carlos
Francois,
www.partsconnexion.com have Mills MRA5 Non-Inductive 0.33R, which I will use. They are 5 watt, 1%, but small.
www.partsconnexion.com have Mills MRA5 Non-Inductive 0.33R, which I will use. They are 5 watt, 1%, but small.
Not only because induction Billa.... the resistance is a big problem too
Even reducing the inductance...the resistance will remain
When we have different gain transistors, we have to use them...but in the reality if we could find matched transistors.... a good idea is to supress.... the difference is listenable.
regards,
Carlos
Even reducing the inductance...the resistance will remain
When we have different gain transistors, we have to use them...but in the reality if we could find matched transistors.... a good idea is to supress.... the difference is listenable.
regards,
Carlos
billabong said:
Digi-Key also carries Mills resistors, listed under the Huntington brand (parent company): part number: MRA05-.33-ND
..Todd
hi,
i have changed bias setting for now. testing the amp it is looks operating well....see next what hpns...
thanks for vlble information spc DX..
i want to add tharmal sensor but i dn't know how to make circuit for it. i have tokin OHD3-80m tharmal sensosor.
best regards
michael
i have changed bias setting for now. testing the amp it is looks operating well....see next what hpns...
thanks for vlble information spc DX..
i want to add tharmal sensor but i dn't know how to make circuit for it. i have tokin OHD3-80m tharmal sensosor.
best regards
michael
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