Need help with understanding AN7523 amp IC

Discussion in 'General Electronics Chat' started by Stephen Flynn, Dec 6, 2017.

  1. Stephen Flynn

    Thread Starter Member

    Sep 29, 2015
    43
    1
    https://lib.chipdip.ru/126/DOC001126730.pdf - Here's the data sheet.

    Have breadboarded but can't get this to work. There's crackling and some buzzing some noise when i poke around, but signal isn't getting through. I think there are some fundamental concepts that I am missing :(

    On page 5 of the linked data sheet useage notes it says - • Please connect only the ground of signal source with the signal GND of the amplifier in the previous stage. The problem is I don't as yet have a previous stage ( i plan on building a preamp). At this point I just have phono jack and guitar lead - just trying to get some noise to come out.
    When you look at the Application example and Circuit/pcb example pattern on page 9, it shows that, especially on the pcb, that every resistor/cap on pins 5-9 are connected to GND (input) - which I interpret to definitely not be pin 3 of the chip (GND pin). I have interpreted that to mean the ground pin of my phono jack, i have just placed that on the line of my breadboard and then plugged in those resistors/caps to the same line a kind of floating virtual ground??. Also tried the ground rail on my breaboard with pin 3 of the chip connected, didn't work either.

    As for the volume pot..I'm confused about that as well (surprise surprise :) Normally I would connect the signal to centre pin of pot, run a wire to the input, and other to gnd rail. Could I still do it that way?? Or should I use pin 9 which is a dedicated volume pin. How would I use pin 9..my guess is that you only connect 2 pins of the pot, but which 2 and how?

    Could anyone tell me what I'm doing wrong here. I have 8ohm speaker attached, with a 7.9v supply, no heatsink but chip not really getting warm as yet.
    I do have a heatsink for the chip, and eventually plan to run at 12v.
    any help, much appreciated.
    cheers
    Steve
     
  2. dendad

    Well-Known Member

    Feb 20, 2016
    2,032
    522
    I've not used these before but it looks like you could connect it as follows..
    For the pot, the input from the guitar goes to one end, the shield from the guitar goes to the other end and amp chip pin 7. The wiper (center pin) of the pot will go to pin 6 via a 1uF capacitor. That is if you are not going to use the electronic built in volume control.
    On pin 9, try an LED, anode to pin 9, cathode to ground, and a 1K resistor from pin 9 to +V. That will put about 1.4V on pin 9 to turn the internal volume up to max.
    Of course, you could put a pot across the LED and the pot wiper to pin 9 and make use of the internal control.
    then just try feeding your input directly to pin 6 via the cap.
    The standby pin (5) must not be left open. I think it needs to be about 2 to 3V.
     
    Last edited: Dec 6, 2017
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  3. Audioguru

    Expert

    Dec 20, 2007
    10,590
    1,179
    ALL the grounds must be connected together.
    The datasheet shows that it works only when Standby is +5V and Volume is +1.25V.
     
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  4. Stephen Flynn

    Thread Starter Member

    Sep 29, 2015
    43
    1
    OK thanks guys. Yes it only works when everything is tied to the ground pin..i still think the datasheet is very poorly written. ...but its true I'm a moron when it come to electronics matters. I got this working a while back, and have breadboarded up a nice preamp... The preamp gives a nice clean sound and it a loosely based Fender champ style input and tone stage..the one i used is called a "vibin' champ" http://www.diystompboxes.com/smfforum/index.php?topic=47371.0.

    Currently playing around with gain/distortion channel, and some power filtering, CD/mp3 input which bypasses the preamp, and a headphone out..and wondering how on earth I'm going to be able to proto board this all up. Think I will attempt to make a pcb as I really like this little Big Amp. Running it from a 12v 2A walwart, and my speaker is a 5" 8 ohm TV speaker...which i have temporarily mounted in an upside down plastic KFC bucket.. All things considered the sound is quite pleasing. I think it will be even louder when boxed in a proper wooden cabinet, and with a better quality guitar speaker.

    thanks for assist.. <On pin 9, try an LED, anode to pin 9, cathode to ground, and a 1K resistor from pin 9 to +V. That will put about 1.4V on pin 9 to turn the internal volume up to max.> I currently using a 1uf electrolytic cap, on pin 9..not sure if getting max volume..will try as you suggest. I don't think my speaker can handle much more volume currently having to back the pickups off, or volume of the preamp down to about 75%..if I play at 100% a strange banging noise comes from the wall..it's not an electrical wiring issue, just my wife getting angry :) Looked at datasheet and it says its about 6w on 12v supply into 8ohm speaker..yes its quite a good chip. OK for battery..get a few hours playing...i used a 6 pack of AA. but...and it still outs pretty well even as battery depletes... very happy with this chip. I also have a couple of it's twin brother AN7522 which is stereo version. Thinking I may build a boom box style wood case, in stereo version of this amp and use as powered monitors for my laptop, and have the abilty to play guitar along with whatever is coming out of my laptop..should be a fun project to complete.
     
    Last edited: Dec 17, 2017
  5. Audioguru

    Expert

    Dec 20, 2007
    10,590
    1,179
    I looked at the datasheet for the Japanese power amplifier IC and see that it is WRONG.
    I guess they do not know what is inside it but I do.
     
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