Powering pedals with daisychain. Understanding mA

[solarplexus]

Hi guys,

I am trying to power all my pedals with a daisychain and I'd like to understand better how to calculate the mA draw.  Thing is, I am powering through a Boss TU-2 that says: MAX current 200 mA (This unit + other effects).  I have many pedals.  Some go from 7mA to 265mA.  What would be the ideal current output for a 9V adaptor for all those pedals?  Here is the list with mA's.  Some are ballparks as I couldn't find the values online.

Strymon Lex:  250mA
Small Stone:  50mA ?
Fl-9:  50mA?
GE-7:  7mA
TU-2:  55mA
Whammy:  265mA
Microsynth:  55mA
Iron Lung:  55mA?
Holy Grail:  55mA?
Rebote delay:  50mA?
Tech21 Liverpool:  50mA?
DOD 440:  50mA?

Right now I have a Boss adaptor and a Harman that came with the Whammy.  The Boss is 500mA and the Harman is 1.3A.  Will I fry my TU-2 if I use the Harman?

Please help and thank you so much!

Matt

[R.G.]

"Ideal" may be tough to find. I think you're actually looking for "cheapest that's enough".

First - are the all 9Vdc, not AC or some other voltage? This is an important point.

Second, are some of them heavy-current digital devices instead of analog pedals? I'm being a little ingenuous, as I'm sure the Strymon is one of these, and the Whammy. Heavy current digital devices almost uniformly have internal switching power supplies of their own inside the box, and may or may not play well with other pedals on the daisy chain.

Third, the quoted figures are probably maximums, except for actual measured values.

I would go about this by saying that the lowest safe power is to add them all up. That's 992ma. **IF** they are all rated for 9V*DC* at the listed current drain, you can be pretty sure that a power supply that says it will supply at least 1A has a chance.

Chance. It could be that the pedals don't all use their maximums all the time. And it could be that especially the heavy-current digital ones don't play well with others on a single daisy chain. I've seen that before.

[solarplexus]

Thanks for the reply.  Am I safe to use the 1.3A with the Boss TU-2?  If so, I will try with all the pedals altogether.  I tried with the Boss adaptor and the Lex gave me a faint high-pitch whine, so I tried with the stock PSU and everything was good.  I am suspecting it is not getting enough current from the Boss PSU. 

[R.G.]

Got a pointer to the Harman specs online?

[solarplexus]

Can't find anything online other than "will power up jamman, etc, etc."  On the PSU though there is:

input: 100-240V-50/60hz (it has the adaptor for European outlets)
max. 3A

Output: 9V -  1.3A

[mistahead]

As RG said there is a first check that everything there is running on 9Vdc - If I recall correctly the whammy uses a 12vac and there are some others there which are ringing vague alarm bells... while I cannot for the life of me remember how to "summarise" is 9vdc positive GND vs. negative GND is also something to check (Fuzz Face, true Rangemaster clone  from my board cannot be chained if memory serves).

Soooo - assuming you take those incompatible pedals out, and don't push all your stomps to max all at the same time and the total mA looks to be under or around the sum of the draw you should be fine.

Plus - and RG (as well as others) will slay me for suggesting this - a quarter of an amp over rating can be supplied by a lot of the kit we have lying around our homes, I was once (in my early days) forced to run a specialist scanner off of a significantly under rated (in terms of mA) unregulated supply as the manufacturer had decided to make their device draw some really out-there value and I wasn't capable/budgetted to custom replace. Ran hot and sketchy but I got the scanner to proper EOL!

[R.G.]

I just looked up a picture of the Harman power supply.

DO_NOT DO_NOT DO_NOT DO_NOT DO_NOT DO_NOT DO_NOT DO_NOT DO_NOT DO_NOT DO_NOT DO_NOT DO_NOT DO_NOT DO_NOT  try to power your 9Vdc pedals from that.

It will kill them dead. It puts out 9V....AC.... and that is deadly to most pedals, even if they are nominally polarity protected.

[GGBB]

If it's for the Whammy, the Harman 1.3A supply is probably 9VAC so don't use it with any DC powered pedals.  It should say on the supply what it is.

The TU-2's max 200mA rating is the maximum amount of current that you can safely draw in total with the TU-2 and all pedals connected to it's power out.  I would be careful with chaining that many pedals and almost 1A off the TU-2 when it specifically says 200mA max.  I tried chaining a few pedals off my Korg Pitchblack which has a similar setup to the TU-2 and also says max 200mA.  I wasn't even drawing 100mA from a 9V 400mA regulated supply and I had problems because of the way the power out from the Korg was configured.  The more pedals I added, the lower the voltage was into them - going down to below 8V with only three pedals plus the Korg.  All four pedals running straight off the power supply worked fine.  A closer look inside the Korg revealed that it's power out was not merely a split off the power in, but instead it was passed through some filtering and protection circuitry so that what came out of the Korg was no longer stable regulated 9V.  If the Boss is anything like the Korg, I don't think you'll have any luck chaining your pedals out of it no matter which power supply you use.  Chain off the supply directly and forget about the TU-2's power out jack.

EDIT - I type too slow.

[mistahead]

Ouch - my response at least assumed 9vdc out such as Voodoo, one spot (I think) etc.

I also should have noted the DC connector sheath/pin orientation of each pedal chained - most use Boss style these days, but not all, good way to ruin your day there (I really have to remember to put protection diodes in my test amp before I run out of LM386 chips hahah).

[solarplexus]

It is the Whammy 5, which is true bypass and runs fine with the boss PSU.  I checked the manual.  9VDC.

[slacker]

The reason the TU2 says max 200ma is because Boss want you to use their power supply and that can only supply 200ma.
The two DC jacks on the TU2 are just wired in parallel there's no circuitry in between them.

[solarplexus]

The reason the TU2 says max 200ma is because Boss want you to use their power supply and that can only supply 200ma.
The two DC jacks on the TU2 are just wired in parallel there's no circuitry in between them.

Cool.

So... I guess a pedal can still work with less V than optimal charge, but what about current?  Can a pedal still work with less A or there is a breaking point where it just won't light up?  If I use the 1.3A PSU, I believe each pedal would have it's optimal current needed?

[R.G.]

So... I guess a pedal can still work with less V than optimal charge, but what about current?

Pedals expect a power supply to be a pretty-well-fixed voltage source, and to let them have as much current as they want. They will only take what current they need.

Regulated DC power supplies (and DO NOT use anything else, for a number of reasons) make a more-or-less fixed voltage that can supply total outgoing currents from zero up to some maximum. When the sum of loads on the output exceeds what they can do, they generally sag to lower voltages, sometimes pretty fast.

The bottom line here is to never put loads on a power supply adding up to more current than the power supply is rated for. Less is fine, they'll all be OK. As an example, a power supply rated at 9Vdc and 1A can supply any number of pedals as long as the total of all the pedals' current doesn't go over 1,000 ma.

Can a pedal still work with less A or there is a breaking point where it just won't light up?

If the pedal demands more milliamperes than the power supply is rated for, the voltage will sag. There will come a place where it just won't light up.

If I use the 1.3A PSU, I believe each pedal would have it's optimal current needed?

Let me say this again.
DO NOT DO NOT DO NOT DO NOT DO NOT DO NOT DO NOT DO NOT DO NOT DO NOT DO NOT DO NOT DO NOT DO NOT DO NOT DO NOT DO NOT DO NOT use that HARMAN 1.3A 9V ***AC*** power supply to power your pedals. It will almost certainly kill one to all of them. 9VAC is deadly to most pedals.

If you had some theoretical 9V***DC*** power supply rated at 1.3A, yep, it could probably supply all the power your pedals need.

AC and DC are different. This is important. If you miss this distinction, you'll be asking us how to fix your pedals.