So I bought a Yuan Jing Burr-Brown PGA2311 remote volume control preamplifier and refuse to pay too much money for a wall wart.
The hard part is finding wall warts that convert to low AC voltage...
I picked up a few wall warts from a Thrift store for $1 each. I managed to find a 15v, and a 12v. But the Preamp is listed that it requires 6-9v... so I wouldn't want to try it with the 12v wall wart.
SO, my question is... Can I take the 12v wall wart and and some resistors or something to drop it down to 9volts?
The hard part is finding wall warts that convert to low AC voltage...
I picked up a few wall warts from a Thrift store for $1 each. I managed to find a 15v, and a 12v. But the Preamp is listed that it requires 6-9v... so I wouldn't want to try it with the 12v wall wart.
SO, my question is... Can I take the 12v wall wart and and some resistors or something to drop it down to 9volts?
According to Parts Express it requires a 6-9 VAC supply. This is an easy find at any Electronic Parts store or contact them because they are supposed to carry a supply.
There's a store called Jameco Electronics on the freeway about 10 miles south of San Francisco International Airport. They do a lot of internet business too. Below is a snippet from one of the pages in their catalog; it shows 115VAC input, 9VAC output, adaptors (red box). Maybe one of these might work for you.
Attachments
Wow. A lot of bad advice above. Try to ignore.
The board has built-in regulators, so you can use a higher AC voltage to supply it. The main concerns then will be increased heat in the regulators (which I don't think is an issue; the PGA2311 doesn't use much current), and the voltage rating of those capacitors.
What is the voltage rating of the 2 large 3300 uF electrolytics? Use an AC transformer with rated at up to 1/2 of this voltage. The peak value of the AC will be 1.41 * the RMS AC voltage, but wal-warts also tend to run high in voltage unless loaded with the rated current, so assume that the peaks will be roughly double the nominal rated AC voltage. Or you can measure the AC voltage, and calculate the peaks at 1.41 * measured voltage. It is OK to use if less than the voltage rating of those capacitors.
The board has built-in regulators, so you can use a higher AC voltage to supply it. The main concerns then will be increased heat in the regulators (which I don't think is an issue; the PGA2311 doesn't use much current), and the voltage rating of those capacitors.
What is the voltage rating of the 2 large 3300 uF electrolytics? Use an AC transformer with rated at up to 1/2 of this voltage. The peak value of the AC will be 1.41 * the RMS AC voltage, but wal-warts also tend to run high in voltage unless loaded with the rated current, so assume that the peaks will be roughly double the nominal rated AC voltage. Or you can measure the AC voltage, and calculate the peaks at 1.41 * measured voltage. It is OK to use if less than the voltage rating of those capacitors.
2 back to back 8V zener diodes, with a resistor in between them, and connected across the secondary, will clamp the output at about 9VAC.
Get regulator that can take 18VDC input. Get cap that can also do that on the input side. Jam this combination between the bridge rectifier and the rest of your amp.
My description left something to be desired. The idea is not unlike the ac regulator found in the LM317 datasheet.
I agree the only good advice here is getting the proper xformer.
Your description would either blow something up or the current-limiting resistors would limit the diodes' ability to clamp voltage in which case it would still blow something up. Shunt regulators are different from series (that LM317 example quoted) and more difficult to get right.
I am going to by a transformer from the Yuan Jing website, since that's the manufacturer of the board, they have transformer sized to fit. ..
Thanks for everyone's opinion!
Thanks for everyone's opinion!
Since there's built-in rectification and regulation, I was going to suggest to simply use the 12 V wall wart.
But then I had a look at the pics and the specs and these show that a dual voltage is needed. I can only see a single bridge rectifier and a three pin connector, and those imply the use of a centre tapped transformer as in the example below.
The specs confirmed this.
" Operating voltage: Dual AC6V ~ 9V
- Recommended Voltage: AC 6V-0-AC 6V / 10W "
You wouldn't really need to go to Yuan Jing's website as a 6-0-6 V or 9-0-9 V centre tapped transformer should be easily available closer to home and perhaps of better quality, safety wise (UL-listed).
But then I had a look at the pics and the specs and these show that a dual voltage is needed. I can only see a single bridge rectifier and a three pin connector, and those imply the use of a centre tapped transformer as in the example below.
The specs confirmed this.
" Operating voltage: Dual AC6V ~ 9V
- Recommended Voltage: AC 6V-0-AC 6V / 10W "
You wouldn't really need to go to Yuan Jing's website as a 6-0-6 V or 9-0-9 V centre tapped transformer should be easily available closer to home and perhaps of better quality, safety wise (UL-listed).
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Instead of using resistors you must go for the regulator option. You may use the 78XX series regulators or Zener diode if suitable voltage.
The unit probably has a 3-pin power connector (6/0/6 Vac). Assuming the unit uses a bridge rectifier/dual caps/regulator at its power input, it would run off of dc as well as ac. So take two 12 volt wall warts, connect them as a center tapped 12-0-12, bridge rectify, filter and regulate down to +/-9 volts, and feed into the unit.
Two 12V warts in series is ok but you can use as is. 9V~ rectified gives 9x1.4=12.6V, almost the same.If you bring it down to 9V the unit will get only 9-(2x0.6)=7.8V , the voltage drop of the bridge rectifier.
Mona
I just peeked at the unit's picture on Amazon. Just get a 12.6 v ct transformer from radio shack and hook it up.
Mostly HORRIBLE advice with just 1 or 2 good suggestions.
1) all 78xx or whatever regulators apply to DC , not to AC .
Go study some very basic Electricity (let alone Electronics) to understand the difference.
2) shunting a high power high current capability voltage source such as a transformer to bring its voltage down is a sure fire (literally) recipe to BURN it.
3) The proper answer as given by a few is to get the proper rated transformer.
4) series Zeners to *chop* some voltage down at least will not burn the transformer but will give you a lot of chopping (duh!!) "hash" noise.
Considering we are in DIY Audio where people go to pains to replace regular supply diodes by ultrafast/FRED/Schottky/whatever to reduce radiated switching noise (and that with gentle 50/60 Hz sinewaves) or place .1uF ceramics in parallel with them for the same purpose, it should be anathema to add series clipping zeners which introduce transients 10 or 100 times higher .
Just sayin'
1) all 78xx or whatever regulators apply to DC , not to AC .
Go study some very basic Electricity (let alone Electronics) to understand the difference.
2) shunting a high power high current capability voltage source such as a transformer to bring its voltage down is a sure fire (literally) recipe to BURN it.
3) The proper answer as given by a few is to get the proper rated transformer.
4) series Zeners to *chop* some voltage down at least will not burn the transformer but will give you a lot of chopping (duh!!) "hash" noise.
Considering we are in DIY Audio where people go to pains to replace regular supply diodes by ultrafast/FRED/Schottky/whatever to reduce radiated switching noise (and that with gentle 50/60 Hz sinewaves) or place .1uF ceramics in parallel with them for the same purpose, it should be anathema to add series clipping zeners which introduce transients 10 or 100 times higher .
Just sayin'
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I sure regret my, uhhh, contributions to this thread. Why is this #@$&* thing still kicking?🙂
Anyhoo, I thought 9vac wallwarts weren't too uncommon, for telephone stuff and 2-way radio chargers. For cheap units, I depend on the local Goodwill store, Marlin P Jones Co., and All Electronics
Anyhoo, I thought 9vac wallwarts weren't too uncommon, for telephone stuff and 2-way radio chargers. For cheap units, I depend on the local Goodwill store, Marlin P Jones Co., and All Electronics
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