500W PA amplifier with Limiter

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
 
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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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
 
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
 
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
 
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
 
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.
Regards
 
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
 
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

R12(1k) and R19(22k) determining amp gain, OP amp work as AC buffer and DC servo, first OP amp work with gain R1,R2 and R4 determining gain of this stage, and with different resistor value instead NSL32 you can detrmining amp input sesitivity (use 33k or any value from 1k to 100k).
Regards
 
as i type this msg i am currently asssembling the protection circuit for the b500. One thing came up to mind cant i use a single supply source for the protection board , may be a single 15-0-15 TF. Use a small sugar cube relay of 12V and drive 12V DC fans for cooling.
What changes need to done to incorporate a single TF.

regards
Sekhar
 
@ apex
i would load the b500 with higher rail voltage bec. i want to drive it for sub woofer two 1000watts speaker 4ohms. what would be aproximate no. of power transistor per rail at 140 vdc. do i need to changed the pre- driver transistor?

thanks alot sir