Hi guys!
I need schematic of a transistors audio amplifier with damping factor >200 and output for RMS power Po = 50...100W/4ohm, with power supply Ucc=+/- (35....40)Vdc.
Thanks for your help!
I need schematic of a transistors audio amplifier with damping factor >200 and output for RMS power Po = 50...100W/4ohm, with power supply Ucc=+/- (35....40)Vdc.
Thanks for your help!
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For speaker impedance of 4ohms (Bass speakers 8"/4ohms with Qts=0.8)! 😉
Audio amplifier should be the damping factor> 200 and frequency range at (+/-3dB) 30 ... 20000Hz!!🙂
thank you!
Surely Qes would be the important one here. If most of the speaker's damping in mechanical, the amplifier is less relevant. Also, the speaker's inductance will dominate at 20000Hz, so the damping factor will have no effect up there.
Sounds like I'm being picky, but if your specs can relax a little to match your actual requirements, it gives you more amplifier designs to choose from.
HTH,
Brian
Hi brig001!
Bass driver (speaker) has Qts=0.64!😉
Cabinet is bass reflex box with Qt = 0.9
See measurements with a professional CLIO!
Bass driver has the following parameters:
Qms = 4.13
Qes = 0.75
Qts = 0.64
Vas = 27.60 l
Fs = 41.38Hz
Re = 3.50
Attachments
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Unless you include the speaker leads in the feedback loop you'll never approach anywhere near that damping factor "at the speaker". Add a tenth of an ohm (or less) cable/terminal etc resistance and that alone swamps the result.
Try to include a long speaker cable within the feedback loop and then get it to be unconditionally stable.....that's a tough one. 
Thicker gauge with smaller strands for the speaker cable is good, but every transistor has an inherent Gm that is in series (plus ballast resistors) with the output "voltage source". What’s more is the Gm becomes non-linear at the high current conduction and the low current conduction around the current crossover region. IMO, higher current gain will not necessarily get you a lower output Z. A global loop with higher feedback factor may help but there are side effects to having too much feedback. That old horse has been beaten to a pulp around here for years. If a low driving Z is desired, nested loop(s) around the output stage can help to create a load dependent dynamic output Z that does not depend on the global loop for control. There are many ways to do this, some being more complex than others and with different degrees of accuracy.
Still, unless you use HUGE wire it is difficult to get mOhm output Z at the speaker in any situation. Extremely low output Z is not so good for some higher efficiency speakers.
Thicker gauge with smaller strands for the speaker cable is good, but every transistor has an inherent Gm that is in series (plus ballast resistors) with the output "voltage source". What’s more is the Gm becomes non-linear at the high current conduction and the low current conduction around the current crossover region. IMO, higher current gain will not necessarily get you a lower output Z. A global loop with higher feedback factor may help but there are side effects to having too much feedback. That old horse has been beaten to a pulp around here for years. If a low driving Z is desired, nested loop(s) around the output stage can help to create a load dependent dynamic output Z that does not depend on the global loop for control. There are many ways to do this, some being more complex than others and with different degrees of accuracy.
Still, unless you use HUGE wire it is difficult to get mOhm output Z at the speaker in any situation. Extremely low output Z is not so good for some higher efficiency speakers.
The underlined was practiced by Kenwood it called Sigma Drive.Try to include a long speaker cable within the feedback loop and then get it to be unconditionally stable.....that's a tough one.
Thicker gauge with smaller strands for the speaker cable is good, but every transistor has an inherent Gm that is in series (plus ballast resistors) with the output "voltage source". What’s more is the Gm becomes non-linear at the high current conduction and the low current conduction around the current crossover region. IMO, higher current gain will not necessarily get you a lower output Z. A global loop with higher feedback factor may help but there are side effects to having too much feedback. That old horse has been beaten to a pulp around here for years. If a low driving Z is desired, nested loop(s) around the output stage can help to create a load dependent dynamic output Z that does not depend on the global loop for control. There are many ways to do this, some being more complex than others and with different degrees of accuracy.
Still, unless you use HUGE wire it is difficult to get mOhm output Z at the speaker in any situation. Extremely low output Z is not so good for some higher efficiency speakers.
Those driver parameters don't look too unusual, my woofers are
Qms 3.2
Qes 0.54
Qts 0.46
and I don't have any problems with conventional amplifiers. Even tried a SET, and no problems.
HTH,
Brian
Qms 3.2
Qes 0.54
Qts 0.46
and I don't have any problems with conventional amplifiers. Even tried a SET, and no problems.
HTH,
Brian
It is quite unusual to use a Qts=0.46 driver in a vented enclosure.
This medium Qts better suits a sealed enclosure.
Your software for modeling the speaker should have an input for the speaker leads and amplifier source impedance.
If it does not, then it is virtually useless, because it can never model speakers on sensible length leads.
This medium Qts better suits a sealed enclosure.
Your software for modeling the speaker should have an input for the speaker leads and amplifier source impedance.
If it does not, then it is virtually useless, because it can never model speakers on sensible length leads.
Not really, i've designed & built quite a number of BIG beasties over the years, with higher than .4 Qts & they All turned out fine 🙂
Qts>0.45
It is OK if is Qts>0.45 .... Qts<0.8 for bass reflex box!?🙄😉
Only it gets softer poorly defined bass as opposed to when the subwoofer is Qts <0.45 where the bass is solid and well-defined!🙂
cheers!
It is OK if is Qts>0.45 .... Qts<0.8 for bass reflex box!?🙄😉
Only it gets softer poorly defined bass as opposed to when the subwoofer is Qts <0.45 where the bass is solid and well-defined!🙂
cheers!
Anyway, the original question: I don't know of any designs, but to help, you need to be looking for something with high open loop gain, so I would guess that chip amps would be likely candidates. I'm building a 2W diamond output stage amplifier that uses an opamp for the gain and feedback, and this will easily get down to < 20 milli ohm. I have however used an output choke which then makes it more like 100 milli ohm at the output. So, I would look for high open loop gain (lots of feedback) and no output choke for starters. You might need some care with speaker leads though, because lots of feedback and no output choke could easily be affected by RFI. Good luck.
Brian
Brian
In addition to the ideas above by brig001, will it be possible to put the amplifier [e.g. one channel] physically close and/or attach it to the loudspeaker; maybe like a powered subwoofer.
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