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Old 26th July 2009, 09:40 AM   #1
Stee is offline Stee  Italy
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Default Boost your amplifier

Good day to all

the booster that you see attached is a project that sees the CFP renewed because using the same components as driver like final

this method compensates for differences in absolute gain of the complementary devices
making the stage of current gain stable
and with natural sound

This simple solution allows you to abandon the EF output type
notoriously slow and lacking in vitality

an idea that soon will generate the enthusiasm of the fans
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Old 27th July 2009, 01:53 PM   #2
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Hi Stee,

I really like your enthusiasm

However, I don't really see the advantage in your approach. If you use high power outputs also for drivers, you will need a pretty powerfull VAS or, again, a driver to drive them. Also hfe between upper and lower bjts is not matched, so variations are always possible.

Why not simply use high beta CFP-drivers, such that the product of the CFP-hfe's is almost independant of the output bjts?

Have fun, Hannes

PS: by the way, the 'simple' operation of dividing numbers is not commutative. Neither the multiplication of matrices.
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Old 27th July 2009, 02:19 PM   #3
Bigun is online now Bigun  Canada
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Interesting, I have been thinking along similar lines for a current amp where differences between complementary sides is holding back the performance.

Anyhow, it seems to me that you need to set up the CFP so that all the devices are experiencing the same conditions to achieve a good match - same current flow through both the 'master' and 'slave' devices of the CFP. Unfortunately it does move the onus back to the drivers to provide enough current but again, the drivers can also be designed to minimize differences by using CFP ! Obviously you then need to use a single ended VAS.
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Old 27th July 2009, 03:02 PM   #4
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Quote:
differences between complementary sides is holding back the performance.
Which case would be that? I would be very curious about this as in my experience distortion cancellation in complementary circuits is nice, but not extremely effective.

Have fun, Hannes
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Old 27th July 2009, 03:30 PM   #5
Bigun is online now Bigun  Canada
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Quote:
Originally posted by h_a
Which case would be that? I would be very curious about this

I made a topology for a current amplifier in my simulations that had very low distortion when using the ideally matched default spice models it doesn't work nearly so well when the complementary devices are mismatched.


http://www.diyaudio.com/forums/showt...48#post1887648
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Old 27th July 2009, 04:03 PM   #6
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Quote:
the 'simple' operation of dividing numbers is not commutative. Neither the multiplication of matrices.
Why not?
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Old 31st July 2009, 07:57 PM   #7
Stee is offline Stee  Italy
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Default Matching devices

you will need a pretty powerfull VAS or, again, a driver to drive them:
see the new self-biased current drive

match same PNP (for example 97 and 97) and same NPN ( 43 and 43)
it's easy
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Old 31st July 2009, 08:47 PM   #8
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Default Re: Boost your amplifier

Quote:
Originally posted by Stee
Good day to all

the booster that you see attached is a project that sees the CFP renewed because using the same components as driver like final

this method compensates for differences in absolute gain of the complementary devices
making the stage of current gain stable
and with natural sound

This simple solution allows you to abandon the EF output type
notoriously slow and lacking in vitality

an idea that soon will generate the enthusiasm of the fans

That circuit will suffer from crossover distortion.
It really needs a good bias stage.
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Old 3rd August 2009, 05:59 PM   #9
Stee is offline Stee  Italy
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Default distortion is a resulting problem

for bias it's possible connect one NTC resistor between second base's copule
distortion in CFP come from different absolute gain between two rails
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Old 4th August 2009, 07:35 AM   #10
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Default Very usefull booster Stee..thank you.


I have several nice audio chips...and they sounds very good and can produce the needed voltage to drive your circuit.

This is very usefull, a very helpfull style of circuit... this way we can use our toys and your booster will produce the needed punch...exactly were those chips fails.

Their small case to dissipate heat limits the power, also the protections they use to overcurrent and peaks are a problem too... we can use them without drive the protections..as all that stuff kill chip amplifiers quality...adding the booster you suggest, we can use them in more safe way..loading them lightly and avoiding them to operate into the distortion levels..and even this way we gonna have a nice power to the speaker.

This is creativity...new simple solutions to the daily problems... to offer things we can use... my respect and congratulations fratello Stee.

regards,

Carlos
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