Parts: Transformer
What does a transformer do? Essentially, it converts AC electricity from your wall outlet (120 volts) to a lower voltage (18-20 volts, still AC) that typical audio circuits require. For a more complete explanation of how transformers accomplish this, try this YouTube tutorial from The Engineering Mindset (I recommend their entire electrical engineering basics series).
So, what transformer to get? The original First Watt Aleph J used a single transformer rated at 300VA with two 18 volt secondary windings. The nearest AnTek equivalent would be this one. But if that's not in stock, you'll do equally well with one offering 20 volt secondaries (like this one, which I got). It should cost ~$40-60 plus shipping, which makes this the most expensive component other than the chassis!
This one I got. It is still for sale on Ebay.
ReplyDeletehttps://www.ebay.com/itm/254682404255
Hammond and Plitron also make excellent transformers.
ReplyDeleteAlso Toroid Corp. https://toroid.com
ReplyDeletecan you list what plitron or hammond transformer models work for this build?
ReplyDeleteSorry, I used the Antek, as seemingly have most other US builders at DIYAudio (Toroid is popular among EUR builders), so I don't have advice on other mfrs. I'm guessing any unit rated at 300-500VA with two 18-20V secondaries should work, but you might want to check in at the DIYAudio forums.
ReplyDeleteHi, thanks for doing this blog its super helpful to have one consolidate detailed guide. May I ask if I live outside of the US and the standard is 220 volts AC, 50Hz here. Where and how do I make the adjustment to this build ?
ReplyDeleteI'm afraid I'm not expert enough to answer that confidently. You should check in at DIYAudio to ask. Good luck!
DeleteTransformers with two sets of primaries (input connections for AC from the wall) will work with either 110/120 or 220/240. For 110, you connect the ac from the wall in parallel to the two sets. For 220, you essentially do this in series. The schematic here (https://i198.photobucket.com/albums/aa276/aeroplane_album/F5PSUschematic.jpg) clearly shows you the two wiring variants. The aforementioned Antek transformers have two sets of primaries. Most transformers appropriate for this usage do in order to handle both popular AC voltages.
DeletePlease be safe and make sure you understand what you are doing before actually connecting to the wall. Lots of good advice and helpful people in the diyaudio forums.
Hammond's standard range 2x18VAC transformer only goes up to 225VA, which is a bit low
ReplyDeletefor a stereo amp.
Plitron no longer sells to individuals after it was acquired by another company a few years ago.
Neither option listed above is available right now. However there is a 500VA 18v option.
ReplyDeleteWould this be a suitable substitute?
Best to ask on the "Aleph J illustrated build guide" thread on DIYAudio
DeleteAnTek has plenty of 400 VA 18V units in stock as of 7-8-2023.
ReplyDeleteIf I use an Antek AS-3225 which is 25-0-25 and 300VA will that be okay or will the voltage be too high?
ReplyDeleteNot sure, you should ask over at DIYaudio.com in the Pass Labs forum.
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