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Old 3rd January 2013, 02:31 PM   #1
Aniket is offline Aniket  India
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Default 5 band equalizer, need help!!

I modded a 10 band eq circuit by omitting 5 bands to make a 5 band equalizer.
But, it didn't worked. Hum on both channels, no audio, checked the circuit and the connections several times, no errors, no mistakes, no shorts.
Kindly help, or i would start over again with a new circuit if anyone could share.

Regards,
Aniket
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Old 3rd January 2013, 02:33 PM   #2
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Some pics
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Old 3rd January 2013, 03:14 PM   #3
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Hi Aniket,
Sorry to hear that your board is not working as expected.
How did you make the power supply ? It's a dual power supply as I guessed it from your post.
Could you post your modded Power supply Section circuitry of this Eq ?

I have made a 3 band Eq following the circuit from this page below. It has a 5 band and 10 band circuits too. Their performance is really very good and simple to build as well , as I personally found.
Sam Electronic Circuits
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Last edited by csom; 3rd January 2013 at 03:42 PM.
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Old 3rd January 2013, 04:17 PM   #4
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Hi csom,
I made the psu myself, yes its a dual power supply
Its simple with a 12-0-12 V sec. transf. and bridge made using 1N4007 diodes, 10R 1W resistors and 2200uF filter caps.
Have you made this 5 band eq. using transistors as shown in the link you mentioned. //http://users.otenet.gr/~%20athsam/EQ_3.htm

Regards,
Aniket
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Old 3rd January 2013, 04:35 PM   #5
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Quote:
Originally Posted by Aniket View Post
Hi csom,
I made the psu myself, yes its a dual power supply
Its simple with a 12-0-12 V sec. transf. and bridge made using 1N4007 diodes, 10R 1W resistors and 2200uF filter caps.
Have you made this 5 band eq. using transistors as shown in the link you mentioned. //http://users.otenet.gr/~%20athsam/EQ_3.htm

Regards,
Aniket
If you are getting the desired voltages at the collectors of the transistors and the pins of the line driver opamp TLO72, then it might be a ground issue as per the symptoms you stated earlier.

Also make sure your signal is being fed correctly to the circuit and it has a proper ground connection.

If any input or output capacitor is open, then the circuit might not respond.

Also make sure the dual pots are properly soldered. Sadly I found 3 bad pots with a manufacturing defect. But that's a very rare case.

I would prefer LM317 and LM337 for the dual power supply section.



I have only built the 3 band Eq section from that site and I'm really very happy with it.
But next I'll try the 6 band one as I really love opamps over transistors, a purely personal preference.
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Old 3rd January 2013, 04:56 PM   #6
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made all the connections correctly, used shielded wires for both input and output signals, hum present on both channels, no audio with input connected to PC and output to amp.
I checked all the connections circuit several times, found no mistake according to the schematic.
Replaced TL072 with NE5532 and NJM4558 but same result, also i must tell that i used BC547 instead of 2SC1740, but both are almost identical GP transistors and all caps are fine.
'might be a ground issue' please elaborate Dear Som, i coudnt understand.

At last i removed the board from the chasis and placed my same old 5 band eq board i made 4 yrs. ago using 2 transistors per channel, still working nice.

Regards,
Aniket
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Old 3rd January 2013, 05:08 PM   #7
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Did you check if the voltages are correct at the collector, base and emitter of the transistors ?

Quote:
Originally Posted by Aniket View Post
.......
'might be a ground issue' please elaborate Dear Som, i coudnt understand.
Please have a look here.

GHOST in 3 band graphic equalizer!! SOS!
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Old 3rd January 2013, 05:12 PM   #8
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Most 2SA/B/C/D transistors has its collector at the central pin, BC's in place, has the base. Did you check it?
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Old 4th January 2013, 03:29 AM   #9
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i have gone through your whole thread Som,
there's no ground issue on my board, and voltages are fine across all transistor pins.
and i have made it on a general purpose PCB, as i said earlier no mistakes according to the schematic, and I checked transistor pins while soldering.

I have some TL072, TL074 and NE5532 opamps,
anyone could advice me a nice and working 5 band eq circuit.

Regards,
Aniket
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Old 4th January 2013, 08:34 AM   #10
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First of all, solder a wire on the metal sheet of all the potentiometers and connect it to the ground point on the filter capacitor.

Next, u have very long wires. So better make all things as small as possible. Those green and other wires r also too long.

As Oswaldo suggested, check the transistors with a fresh mind.

Gajanan Phadte

Last edited by gmphadte; 4th January 2013 at 08:34 AM. Reason: spelling
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