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Old 26th September 2012, 05:08 AM   #31
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Hi all is that any Chang in sound if i use large size output capacitor with same value with i used but distortion start very low volume
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Old 30th September 2012, 09:16 PM   #32
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A large capacitor in the output should help with low frequency performance. If you are noticing some distortion it must be coming from something else, such as mains hum; oscillation (do the transistors get hot?); crossover distortion (is the quiescent current right?); or clipping if the mid-rail voltage is wrong.

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Old 30th September 2012, 11:25 PM   #33
wahab is offline wahab  Algeria
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There was many iterations of this topology at the time ,
i built the one on a Motorola application note and frankly
it was a fairly good amp considering its simplicity.

As another exemple , the Black Devil was a german iteration.

Anybody have scan of AN-483B (Motorola)?
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Old 2nd December 2012, 02:11 PM   #34
abbe is offline abbe  India
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renjish Download

Link to IP infringing material removed by moderation.
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Old 8th January 2013, 02:09 PM   #35
Udayami is offline Udayami  India
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Default Philips 40w Amplifier with universal preamplifier

I have done what exactly stated at the book by M.D. Hull both preamplifier and Amplifier ckt but there is motorboting sound in no signal condition please give me a remedy.......
Is there any problem with BD139 & BD 140 matching hfe?????????
I use 2N3055 as output
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Old 8th January 2013, 09:00 PM   #36
JMFahey is offline JMFahey  Argentina
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It's very probably a grounding problem, you'll have to be careful on how and where you ground different parts of the amp.
One general purpose solution is using separate ground return wires, at least for the speaker, main amp and preamp, all going to the PSU main capacitor negative.
It's more complex than that, but at list this is a first step.
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Old 9th January 2013, 08:48 AM   #37
Udayami is offline Udayami  India
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Default Philips 40w Amplifier with universal preamplifier

I also make an arrangement for separate grounding but the problem persist.
Finaly i notice that if i replaced the capacitor C7= 27 pf by a 180pf capacitor then there is no motorboting sound but there is a broken BASS problem in FULL BASS condition.
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Old 8th March 2013, 06:45 AM   #38
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Hey Amp builders!!! Does anyone have a scan of the entire book by mr md hull?
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Old 8th March 2013, 08:30 AM   #39
pdul is offline pdul  Denmark
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This thread makes me remember those old Philips amps used in many of their apparatus, based on AD149 outputs
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Old 8th March 2013, 02:14 PM   #40
kevinkr is offline kevinkr  United States
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I'll word it more strongly, scans of in copyright material are nothing more than theft. Please go out and buy a legitimate copy somewhere. Further links to infringing material will be removed when encountered, and their posters will receive an infraction.
"To argue with a person who has renounced the use of reason is like administering medicine to the dead." - Thomas Paine
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