+/-7V power supply from 16VAC

Started by marksmartus, November 02, 2017, 11:46:45 AM

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marksmartus

Hi all.
I searched and couldn't find any posts in the forum about this. I am going to try making a +/-7V power supply driven by a 16VAC wall wart. I was thinking, rectify it, filter it, run it through an LM317 set up to make 14 volts DC, and then split the supply using the resistor voltage divider trick like they do on guitar pedals to turn +9V into +/- 4.5V for the audio. Has anyone done this before?

I just made a breakout box that sends out the audio for the individual strings, but it just goes in between the guitar and the synth (in my case a GR-55) and needs the synth for power. I want to make a standalone box without having to use 2 adapters. I might try making a hex fuzz using Tube Screamer type circuits.

Mark Smart
Mark Smart
mark@marksmart.net

admin

#1
this is a good reference  - uses a 9-16VAC power input and a charge pump to achieve clean bipolar power rails 
Alesis Quadraverb schematic
http://www.ampl.nl/quadraverb/images/Quadraverb%20service%20manual.pdf

this works using an external  9VAC-16VAC  "wal-wart" as power input

Omit the +5VDC Output ( i.e all parts after D12) if you  do not need it.



replace the 7812/7912 fixed DC regulators with adjustable output  type

LM117 for +7VDC
http://www.tij.co.jp/general/jp/docs/lit/getliterature.tsp?baseLiteratureNumber=snvs774&fileType=pdf

LM137 for -7VDC
http://www.ti.com/lit/ds/symlink/lm337-n.pdf



FWIW - since 2007 , 16VAC power adapters are becoming more rare - due to global "green" power saving mandated laws 

marksmartus

OK, thanks! I have a bunch of these 16VAC wall warts around that I bought for various old equipment, so I might as well use them.
Mark Smart
mark@marksmart.net

admin

#3
QuoteOK, thanks! I have a bunch of these 16VAC wall warts around that I bought for various old equipment, so I might as well use them.

same here - surplus Telco modem Power supplies
Alesis Quadraverb schematic  circuit above still works with 16VAC as input

marksmartus

#4



Initial tests indicate that this circuit works. I'll keep you posted as I test it more.

Mark
Mark Smart
mark@marksmart.net

mooncaine

Quote from: admsustainiac on November 02, 2017, 11:53:03 AM... and a charge pump to achieve clean bipolar power rails
Oooh, I love it when you folks talk dirty.

gumbo

Quote from: mooncaine on November 03, 2017, 06:20:03 PM
Oooh, I love it when you folks talk dirty.

...I've had my suspicions about you for a while, moonie....    :o
Read slower!!!   ....I'm typing as fast as I can...