Very basic question, in the spirit of DIY:
I need a supply of +15v / -15v for a preamp.
Is there a way to modify a wall-wart type of 15v power supply to get leads of both +15v and -15v, or is it basically two power supplies? Is this a simple circuit to put together, possibly from raiding the bins of broken electronics in the house?
Or should I just order one of these from ebay?
I have an old solid state guitar amp I was fond of and the power section blew. I would like to keep the preamp section. I've tested it with the +15/-15 supply from another amp and it works. I suppose it draws very little current (?)
I need a supply of +15v / -15v for a preamp.
Is there a way to modify a wall-wart type of 15v power supply to get leads of both +15v and -15v, or is it basically two power supplies? Is this a simple circuit to put together, possibly from raiding the bins of broken electronics in the house?
Or should I just order one of these from ebay?
I have an old solid state guitar amp I was fond of and the power section blew. I would like to keep the preamp section. I've tested it with the +15/-15 supply from another amp and it works. I suppose it draws very little current (?)
Here's how you can build a +15V/-15V preamp power supply:
https://www.eleccircuit.com/power-supply-regulator-15v-15v-1a-by-ic-7815-7915/
https://www.eleccircuit.com/power-supply-regulator-15v-15v-1a-by-ic-7815-7915/
Great - thanks very much for the reply.
It seems it's cheaper to just order one. But I'm confused about whether a supply like the one I linked needs another power transformer, or whether it just takes AC directly on to the input leads?
Interesting to read up on how they work, although in this case I'll buy one.
There are linear power supplies and switch mode power supplies (smps) which each work on different principles.
The supply to which you linked is an smps and needs no additional power transformer and takes the AC directly.
A double ended linear supply usually uses a centre tapped secondary transformer which provides two low voltage outputs - a sort of double transformer in its action, but physically a single transformer.
You can't go wrong with this:
https://diyaudiostore.com/collections/power-supplies-accessories/products/super-regulator.
Just add transformer, rectifiers and electrolytics. Good up to several 100mA.
Jan
https://diyaudiostore.com/collections/power-supplies-accessories/products/super-regulator.
Just add transformer, rectifiers and electrolytics. Good up to several 100mA.
Jan
Perfect, thanks so much, I think this will work for me, and my 80s Gallien-Kreuger will live on.
https://enjon.uk/2020/07/07/dc-splitter-for-bench-psu/
(beware you need a 30V PSU though to get +15v and -15v
I think ~250mA
If ordering the smps to which you linked, be sure to select the +/-15V version.
It's capable of a peak output current of 550 mA (or so it says).
It depends on the type of wall wart. If it puts out a DC voltage, then you'll need another PSU indeed. If it's output is AC, you could build a voltage doubler type of split rail supply, as you need it.
Best regards!
It depands what sound quality you are targeting. How high noise level is acceptable. And what dimensions are your goal.
Primary question - is it important for you to make one yourself or just get it. If second option - go for something already assembled.
Jan Didden here on forum has made nice piece of super high quality power supply. You will not be dissapointed with performqance of the device he recommends.
Other options are build/buy a device:
- switching power supply - like one you linked, will work, purists say it's noisy. It is also not so simple to build PCB layout has bigh impact on noise and performance.
- something on chips 7815/7915 - very easy to build, mediocore performance in terms of noise (example here: https://www.diyaudio.com/community/threads/15vdc-7815-7915-power-supply.229503/ )
- next option is build something on LM317/LM337 - quite easy to build, acceptable performance for most audio applications (example: https://xtronic.org/circuit/adjustable-symmetrical-power-supply-using-lm317-lm337/ )
- finally something on TPS7A4701 and TPS7A3301 - highest quality power output but quite difficult to build due to surface mounted elements use (search diyaudio for details)
That one is switching power supply. May be ok for not demanding applications.
Personally I would stick with LM317/LM337.
You can download KiCAD, find chip specifications on web and create your own design like I'm doing. (I know - I could have such psu already from ALiEx... few times, but satisfaction I cannot buy). Here is what I designed so far (it may have errors, so just showing up where I went from zero):
Okay, I'm glad you told me that. If the power supply introduces noise in the audio circuit I'm going to be frustrated with that.
Are you saying there is a "LM337" version for a few bucks more that is quieter and does the same thing?
I enjoy working on this stuff, but by the time you pay $10 shipping for $1 parts and so on, it's just cheaper to buy it off the shelf.
Assembled LM317/LM337 adjustable power supply modules are readily available.
Here's one example: https://www.ebay.co.uk/itm/26467282...7779&msclkid=dbc42c9f872b117e619c4f102e0202ea
However, you need to add a power transformer with an 18V/0V/18V secondary (see circuit diagram in link and choose the input primary voltage to suit your location).
Ah so. Okay, I might have a power transformer in that range laying around. But not a small, light one, so I will consider all the variables.
I'm curious what form the introduction of noise takes? Hiss in the signal? Hum? Harmonic distortion? Are switching power supplies not used in audio, commercially?
A poorly designed switch mode supply produces electromagnetic interference (EMI) which can introduce high frequency noise to your preamp.
A well designed (read expensive) one will not.
P.S. Make sure when selecting a power transformer for a linear supply that it has a sufficient current rating.
A well designed (read expensive) one will not.
P.S. Make sure when selecting a power transformer for a linear supply that it has a sufficient current rating.
I see. Perhaps it would help to move it away from the preamp - like the distance that a laptop power supply is separated from the machine with say, a meter of lead from the amp...
Since it's a bass amp, I wonder if there is a way to filter HF noise with a capacitor.... It's not for a high-fidelity purpose. I'll probably experiment with the cheap one.
I'm learning a lot. Cheers.