power supply help

I don’t have one, but this looks pretty groovy.


www.rocktronusa.com/powertap-pedal-power-supply.html

Even throttling back the voltage, the pedals will still draw the same amount of current. So take a look at all your pedals and add up the current draw for each pedal. They should have a label like this; the pedal draws 100mA:



mA = milliamps.

For example, you have three pedals on the board.  One draws 100mA, one draws 200mA, and the other one draws 150mA.  That's a total of 450mA.  Make sure to get a power supply that delivers at least 500mA (that little cushion of 50mA is good). 

The power supply doesn't have to match the total current draw; rather, it has to supply at least the amount of total current draw.  This means a power supply that provides 1A, or 2.5A, or 5A will work fine as well.  But larger power supplies cost more and are bigger. 

If you use a power supply that cannot deliver the current needed, the pedals may not sound very good, or they may not work at all.

Last consideration: if the possibility exists that you might add more pedals to the mix, go bigger on the power supply.

You'll need a second power supply then.

Digital stuff will NOT like 7.5 generally - I would expect the tuner to likely not work.

Is your Boss wall wart actually a switching type power supply with universal input of 100-230VAC?
The Amazon link above takes you to a universal switching type supply that has input/output specs as "Universal AC/DC Adapter - AC Input:100-240V 0.25A 50/60Hz, DC Output:3V/4.5V/5V/6V/7.5V/9V/12V"

For something like an adapter, it'll convert the wall current even if it's lower than anticipated because the stepdown is so drastic - it's like taking drops from a firehose.

Looks like the Boss PSA-120T is a regulated output, step-down transformer based wall wart. If schematic on the internet is correct, there is a 7809 voltage regulator in the circuit keeping the output at 9V despite variation on the input side. Google "Boss PSA120T schematic"

I tested a similar one of these today at the 7.5v selection. My multimeter said it was 12.35v.

Then I set the selector to 6v and got 9.86v.

To verify that this was probably close to standard, I found a 6v wall wart and my multimeter said it was 8.68v.

The 6v wall wart was rated 100ma. The selectable wall wart was rated 500ma, which is probably why there is such an apparent jump.

Why the jump at all ? It's not regulated and the Voltage selector might be a "guess" for an average "load" expected.

This behavior is pretty typical of all wall warts I've tested.

What is really needed is "regulated" 7.5v that can be selected up or down to match the amount of voltage starvation needed for each device(which probably differs).

Since that is rare or non-existent, failing batteries were used. Alas, failing batteries seem to drop voltage extra fast at the end in my experience, but even if they didn't, one would always be chasing a relatively small window where the battery was at 7.5v because it's not going to stay there for long.

And if one isn't really getting 7.5v or 6v when using a wall wart, isn't tested battery voltage more accurate ?

But like I said, it seems like falling voltage levels at the end of a batteries life seems to fall faster than the early discharge curve voltage changes.

And is the best voltage for a ts9 really 7.5v...or 7.7 or maybe 7.7 to 7.1 ?

If the battery in question was tested at 7.5v and you played it for 10 minutes before deciding it was the sound you desired, I'd have to suspect that 10 minutes ago it was really at 7.8 or so.

And a ts9 might act differently than another ts9 or ts9dx.

One thing to try is to set the selector to 4.5v and see what voltage that tests at, and if the pedal still works.

But note that when I used batteries at 7.5v in my test pedal, the indicator light was so dim it looked like it wasn't on.

I tried the 4.5v once and may have just thought it didn't work at all if the indicator light was that dim.

So that might get closer to 7.5v and still work, but chances are the EXACT value needed might not be there.

I'm going to approach this issue with multiple battery 7.5v "top voltage" instead of the 7.5v "bottom voltage" of a dying battery.

In short, I'm hoping for a longer run time in the range of 7.8v to 7.3v using batteries at the top of their charge.

And for grins, I'll test the 4.5v selection and see what shows up.

Nothing better than smoother sound, right ?

Yeah, revs gizmo sounds best...IF it provides enough current at each setting. There is the vexing issue of waning current flow with lower voltage I've found.

Anyway, I tested 4 things today, with the goal of finding the fastest and cheapest way to 7v or so, and the results were mixed.

I tested two voltage adaptable wall wart from different manufacturers and found that the 4.5v selection produced 6.96v and 7.20v. The 7.20v produced nearly the same dim light I got when my batteries were at 7.5v so it's close, but not exact. Both gismos were rated 300ma. Surprisingly, settings of 1.5v and 3v produced a 10.5v reading ! I think this extra voltage was a clue to the unknown relationship between current flow and voltage that I've never figured out completely. A curse on my high schools for not having an electronics class in an electronic world !

Next I tested two AA battery rigs to harness the 2000ma + capacity(10x the standard 200ma of a 9v battery).

The first was using 7 rechargeable batteries in an 8 battery holder with one slot dummied out. This produced about 8.28v of power and took a couple of hours to get down to the 7v area. I suspect this rig will produce 7v for 2-4 hours but didn't take time to test it in real life.

I thought there must be a faster and cheaper way to get 7.5v and there is ! Using cheap Harbor Freight carbon batteries and 5 AA batteries in a 6 slot battery holder, it starts at about 8.23v and gets to the 7v area in a little over an hour. I estimate it could then take a couple hours of more to drop below 7v.

Sorry. That's as far as I plan to go at the moment. I'm supposed to be focusing on something else, and just wanted to see if I could get 7.5v for when I explore my pedals again in the future.

So, one voltage selectable wall wart might work, and two AA battery rigs that might work for a couple of hours.

And I'm pretty sure every voltage selectable is going to vary as to it's "fixed" rate. Maybe test a bunch and find one that's spits out exactly the voltage you want.

I'm also sure that every wall wart that claims a certain voltage that "isn't regulated", is going to test at a higher voltage than given.

But this suggests another avenue of research. If a 6v wall wart produces 8.68v, what does a 5v produce ? There are a ton of 5v wall warts for cell phones laying around to try. Are they regulated ? Maybe. Well, how about a 4.5v wall wart or a 4v wall wart. I used to go to a local thrift store and buy handfuls of wall warts for a buck each. Sadly, I was after higher voltage wall warts at the time. So check garage sales and thrift stores or maybe buy some cheap electrical product that includes a small wall wart.

Or find the gizmo rev was talking about. That sounds pretty interesting for all sorts of things, if the voltages are matched with adequate current flow.

For instance, when someone selects a "high input" pad on an amp or device, a little volume is often lost. And when you turn up the "distortion" on a chip on your pedal or floorboard, a little volume is often gained. Much like what a change in voltage might do. And the frequency mix often changes. So how is this being done ? Are the frequencies being modified with a resistor or cap that also varies the voltage ? Is there a digital map of new frequencies being changed in a programmed way as distortion values are turned up ? Whatever is being done, it's not without side effects. Like I said, electric music is COMPLEX. So what happens with almost ANY distortion chip that is starved of voltage ? I've not seen any claim for a RAT for instance. Just assorted fuzzes and a ts9. But maybe a whole lot of other pedals might do something interesting with low voltage. Last I fiddled with this was 20 years ago, with 20 to 30 year old pedals. Now there are 20 years more pedals that remain to be explored ! I'll leave that to the distortion nerds of the world. Hopefully they'll report back...

If ya wanna get gnarly with it here's some info.

www.learningaboutelectronics.com/Articles/How-to-reduce-voltage-with-resistors.php