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Old 24th October 2010, 06:02 PM   #761
hadita is offline hadita  Indonesia
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Sir, said apex B500 R27 (22ohm) I try to replace the previous 120 ohm load 4 ohm speakers at full volume and the final driver transistor hot enough after changing 120ohm & final drivers are not too hot, think about what effect the replacement of R27 is yes ... if the power is still stable at 3-4 hours usage, .. please guide

regard
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Old 24th October 2010, 08:06 PM   #762
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Quote:
Originally Posted by hadita View Post
Sir, said apex B500 R27 (22ohm) I try to replace the previous 120 ohm load 4 ohm speakers at full volume and the final driver transistor hot enough after changing 120ohm & final drivers are not too hot, think about what effect the replacement of R27 is yes ... if the power is still stable at 3-4 hours usage, .. please guide

regard
Try this output stage
Regards
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Old 24th October 2010, 11:55 PM   #763
hadita is offline hadita  Indonesia
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Originally Posted by apexaudio View Post
Try this output stage
Regards
Ok sir ,thanks a lot i will to tray this stage...
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Old 25th October 2010, 12:29 PM   #764
Djnits is offline Djnits  Philippines
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Originally Posted by apexaudio View Post
On R20/21(100R) you must have 0,5-1V, if don't replace R15/16 (1K) to get 0,5V (5mA thru VAS transistors MJE340/350), and use 1k pot instead R22(680R) for set BIAS (10mV on 0,33R/5W is 30mA per outputs)
wow! What a nice advice thanks sir...sorry 4 late reply...i had made sir what you said..thank you sir apex sharing you talent all over the world..your awesome man and rare person..thanks sir GOD bless and more power...i share my project here in tread if i fixed it

regards
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Old 25th October 2010, 01:38 PM   #765
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Originally Posted by Djnits View Post
wow! What a nice advice thanks sir...sorry 4 late reply...i had made sir what you said..thank you sir apex sharing you talent all over the world..your awesome man and rare person..thanks sir GOD bless and more power...i share my project here in tread if i fixed it

regards
I measure DC offset on some old B500 amp, and I have 1mV on left 4mV on right channel (3 pairs outputs with +/-75V rail), I am sure you can get better DC offset than 150mV.
Regards
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Old 26th October 2010, 03:44 PM   #766
mihailo is offline mihailo  Serbia
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Hi, Apex.
I am finishing ML3 tone preamp.
1.Can I use TL082CN because don't have TL072CP right now? (Pins on 082 are identic like 072).
2. Also can TL082 be in use for B500 in stead of TL072?
Will post pictures when finish in few days. Thanks
Regards
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Old 26th October 2010, 11:45 PM   #767
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Originally Posted by mihailo View Post
Hi, Apex.
I am finishing ML3 tone preamp.
1.Can I use TL082CN because don't have TL072CP right now? (Pins on 082 are identic like 072).
2. Also can TL082 be in use for B500 in stead of TL072?
Will post pictures when finish in few days. Thanks
Regards
You can use TL082 instead TL072, but TL072 is available and not expensive,
Regards
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Old 28th October 2010, 11:00 AM   #768
Djnits is offline Djnits  Philippines
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Quote:
Originally Posted by apexaudio View Post
I measure DC offset on some old B500 amp, and I have 1mV on left 4mV on right channel (3 pairs outputs with +/-75V rail), I am sure you can get better DC offset than 150mV.
Regards
hello sir apex sory for the lated replied, anayway i had only -35mv on dc offset out put trns. why it's negative 35, it's normal?.... and bias .430mv and the left side ,350mv, but sounds Good very nice,, thanks sir apex for sharing this amp..

ragards
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Old 28th October 2010, 11:43 AM   #769
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Originally Posted by Djnits View Post
hello sir apex sory for the lated replied, anayway i had only -35mv on dc offset out put trns. why it's negative 35, it's normal?.... and bias .430mv and the left side ,350mv, but sounds Good very nice,, thanks sir apex for sharing this amp..

ragards
DC offset can be positive or negative it's normal. Where you get 430mV and 350mV (points). Transistor start to conducting at 550mV from base to emitter, and go from class B to AB, than BIAS current increase and base to emitter votage is still 550mV. Use 10R instead fuses and measure voltage drop on them (about 1V). Sound is good in class B it's normal for B500 and H900.
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Old 28th October 2010, 01:47 PM   #770
sekhar is offline sekhar  India
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last but not the least i have also completed the B500. Its up and running , still in the testing phase but every thing seems ok . No heating , no buzzing just pure music , thanks a loads APEX . Will upload pics in a few days time.
i had a few queries
1. wat is the gain of this amp ?? And which set of resistors r determining them ?
2. if nsl 32 is nt used then wat value of resistor is to be used on the input side ?

regards
Sekhar
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