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Just noticed it's unregulated, may be noisy...
Feedback Score 0 Anybody out there know of a Canadian website where I can buy a replacement wall wart ( 24 Volt 100 ma ) for an Electro-Harmonix Deluxe Memory Man? I find several U.S. sites that carry it. Just curious if there is a Canadian web supplier that's under the radar.
Thanks,
Bob
Feedback Score 0 http://www.sayal.com/ActionIndexP.asp?ID=26770
Just noticed it's unregulated, may be noisy...
Feedback Score 0 Thanks for the lead.
My original adapter makes noise and emits a loud hum in my amp, making the effect unusable. If I can't find an original adapter, I'll give the generic one a try.
Bob
Feedback Score 2 (100%) The original is an AC supply. The conversion from AC to DC is done in the pedal itself. ANY 24v supply that provides 100-300ma or so will be fine. With AC, there is no positive or negative side to the plug as there is with DC. So, as long as the plug is the right size, or you're able to solder on a new one of the right size, you're homefree.
Feedback Score 0 Correct me if I'm wrong. Polarity does seem to matter. And output seems to be DC.
Feedback Score 2 (100%) My humblest of apologies. I called up this document - http://www.ehx.com/assets/instructio...memory-man.pdf - and read the "Warning" too quickly for my own good, and yours. Yes, it says "Your unit comes equipped with a 24 Volt/100mA AC external power adapter." But then a few sentences below, it also says "Connect the included 24DC/100mA AC Adapter...".
I have to work on my reading, and EHX has to work on their documentation.
Given that it needs to be 24vDC, yes you have to be mindful of polarity (or be willing and able to reverse it on your own), mindful of plug size, and mindful of quality of regulation. Not all DC supplies are created equal, and it does not take very much at all for a supply to meet the bare minimum criteria for "DC".
I find it often useful to make what I call power-distribution blocks. This is simply a small plastic chassis with an in and some out jacks of relevent size, a status LED, and some on-board smoothing to supplement what the supply already provides. A nice 1000uf/35v cap between hot and ground can do the trick and further reduce any residual ripple. That way, one can use supplies that are less than perfect without having to endure annoying hum.
Feedback Score 6 (100%) Would you use the same value of cap (i.e., 1000uF) for 12 volts?Originally Posted by mhammer
If not, how do you calculate the value of cap required for 9 volts and 12 volts?
Not intending to derail the thread
Thanks
Dave
Feedback Score 1 (100%) I gather from your comment that the original still powers things up fine, but is noisy as a kindergarten after sugar hour.
Pardon the expression :D but it could be Hammer Time.
It could be all you really need do is replace the existing filter cap in the unit you already have. IF you are committed to its replacement then all is good, take a hammer, and crack the seal around it. Usually these things end up having 2 diodes and 1 capacitor inside. It may be cheaper or more expedient to replace that cap first.
Following that, I like the idea of a good power-bar for the 9/12/18/24 volt systems overall. Would make life a fair deal simpler to deal with each makers design set-up :)
Hey, just to throw this out there too, is house hold door bell systems and humidifiers still run from 24 volts? Those transformers should be easily available and not over pricey too if you were to build a power-bar :)
// scriptio in pace
// pax lineamenti
"How to build a cigar box guitar - Free Plans at www.cigarboxnation.com."
Feedback Score 0 
Yes, it does power up the effect, the delay works fine, however the hum is hideous and delay regeneration makes it worse.
I just might crack it open and see what value the cap is, possibly replacing it. If it doesn't work, no biggie...I'll find a new one eventually.
Good tips from both you and mhammer....Thanks guys.
Bob
Feedback Score 2 (100%) Okay, a few things.
1) You don't have to replace anything in the wallwart itself, so don't crack it open. If it is a device that has 120V involved, the more sealed it is from your fingers, the better. Fortunately, power supplies are the sort of thing that you can supplement and improve completely outside of the black box.
2) The reason why I like the idea of a power-distribution box is because you can: a) install a power indicator LED and know if its the pedal or the wallwart source, b) replace the cumbersome daisy-chain cables that are so popular with custom length individual cables that go from a jack on the box to a jack in the pedal. Daisy-chains are fine if your pedals are all one brand or made in the same size/style chassis (e.g., EHX Nano and MXR), but they do not gracefully handle a wah beside a big-box pedal.
3) Every microfarad of smoothing helps. There is no specific value of cap required for supplies of different voltages, other than one with an appropriate rating. So, if the supply provides 9v, you'd want a cap rated at 16v or better, and if the supply is putting out 15v, you're going to want a 25v-rated cap, or better.
AC adaptors convert AC to DC by retaining/passing only one half cycle of the alternating current they receive from the wall (AC swings in both directions, remember). Once it meets the criterion of being something which is ONLY more positive than zero volts, and never negative, it "counts" as DC. But there can be many degrees of smoothing or degrees of regulation. remember that the ideal DC is a battery, which involves no processing, but is merely a steady-state chemical current source. Simply keeping the positive swing from wall current, and sticking a 470uf cap on the resulting output inside the black cube provides the sort of DC which is suitable for a broad range of purposes, like powering an appliance or vintage calculator, but is nowhere near as stable/constant as a battery. There is enough ripple still in there (i.e., 120hz fluctuation between some voltage less than the rated output, say 9vdc, and slightly more) to be heard as a loud hum in audio circuits.
It is best to think of power-supply hum as being like really, REALLY low hiss. because that is essentially what it is: noise. And the same way you would attempt to minimize audible hiss by turning the treble way down, you can reduce hum in a supply by turning the treble so far down that you are cutting the "treble" on the supply at below 60hz. That is, the added capacitor serves the same role as the tone control on your guitar, only lower down.
When calculating simple filters, one uses the formula F = 1 / (2 * pi * R * C), where R is in megohms and C is in microfarads. If I had a 10-ohm resistor in series with the positive lead, and ran a 470uf capacitor from the resistor to ground (on the plug side of the resistor, not the wallwart side), that would provide a 6db/oct high-cut filter whose rolloff started around 33.9hz. Bump that 470uf cap up to 1000uf and the rolloff starts around 15.9hz. Since the filter that creates has only a 6db octave rolloff, by the time you get up to 120hz, you would have around 18db of hum reduction/smoothing introduced (if you think of the supply voltage as being like a super-low audio signal).
Note that multiple capacitors can be placed in parallel to achieve more combined capacitance. So, 220uf plus 470uf gets you 690uf total.
Ideally, one would use an actively regulated supply, with either a discrete transistor circuit or else a standard 3-pin regulator. These work great, but they typically demand 2VDC coming more than what they can put out. That is, you cannot feed a 9V regulator 9v in and get 9v out. It would need to see at least 11v coming in. So, if you had a decent 12V or even 15V wallwart, you could feed THAT to a little power-distribution box containing not only a status LED, but a 9V regulator, and additional capacitance for smoothing. That would provide nice smooth hum-free power for your pedals.
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