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C113 audio hack
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N7PXY
Some time back there was a recommendation to remove C113, between pins 1 and 8 of the LM386, to improve the audio. It didn't work well for me. In doing so one of the capacitor's end 'plates' came off. I would like to replace C113 but I am unable to decipher its value from the schematic due to the way it's printed. Other LM386 circuits I have looked at call out a value of 10uF in series with 1.2K ohm resistance for a gain of 50. Any one know what value is used/shipped with the standard kit? Thanks and 73 PJH, N7PXY |
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I believe it's a 1 UFD. 73 ken VA3ABN On Thu, Apr 13, 2017 at 1:23 PM, N7PXY <hickspj467@...> wrote:
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I did the same C113 and it fell apart a well.? I soldered in a 2.2uF. tant (what I had) (diagram indicates C113 to be a 1uF tant) and it restore LM386 back to original crummy sound Hi. I replaced the original 10k vol. pot with an audio taper 10k ?pot.? Now it's seems ?not as aggravating. but still poor output. The LM386 is a < .5W old amp. for hobby use. ? I've decided to find a TDA7052 as better amp. I removed the LM386 and installed a 8 pin DIP socket so i can vari an experimental amp using a header plugged in. The TDA7052 or TA7368P has an electronic vol. control.? My thinking is a decent AGC eventually. Another thing, I pulled out the Nano off the DDS and installed two inline header (15 pins / side). Now I can download sketches of different versions into my spare Nano but Now I just plug and play with the original. Hope that helps 73 larry WA9DOH ? On Thu, Apr 13, 2017 at 12:23 PM, N7PXY <hickspj467@...> wrote:
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N7PXY
Good idea on the 8 pin header for playing with amp chips. I did much the same thing on the volume pot; seems to sound better... but my hearing is crap. I use an short like 8" adapter cable from the raduino connector to a USB connector so it is accessible with out removing the case top then just program over whatever .ino is loaded. Tnx for the info on C113 guys. Have to look in the junk box for a replacement. PJH, N7PXY |
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That 8 pin DIP socket sounds ideal for experimenting with better audio amp IC's. ?Maybe take the original LM386 and solder a 1uF cap across the top off it between pins 1 and 8, remove the 1uF cap from C113 on the main Bitx40 board. ? Then build a daughterboard on vectorboard with 8 header pins to fit that 8 pin socket, copying Farhan's uBitx audio amp plus AGC. ?Clip back pins 1 and 8 of the LM386 so they don't go into the socket, and you can repurpose those two pins for the CW sidetone and the high side volume control pin of the uBitx. ?The uBitx volume control pot would have ground on one side, VOL-H on the high side, and VOL-M to the middle wiper pin.? ST says the uBitx's TDA2822 is obsolete, though Unisonic is selling a clone. ?The daughterboard would allow lots of different devices to be tried out. On Thu, Apr 13, 2017 at 11:15 am, Larry Smith wrote:
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