I took an arrow to the knee, I need guidance.

Discussion in 'Effects, Pedals, Strings & Things' started by PuffySlits, Jul 9, 2018.

  1. lefort_1

    lefort_1 Nuzzled Firmly Betwixt Gold Supporting Member

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    I'm going to preface this by saying, to some extent, both @Juan Wayne and @panther_king are right... and both are wrong a bit.
    (take that, Solomon!!)
    That said, I'll probably get slammed by both parties involved...let the food fight begin (j/k!!!)


    If "ideal power supplies" are connected in parallel to an "ideal load" and there is a difference in their voltage output, there will be an infinite current flow in between the power supplies and something is going to go 'poof' ... it's basic math. In the ideal world, two PSUs with identical outputs could be connected, but they'd have to remain perfectly in sync.... and nothing is that perfect in the real world.

    To avoid the smoke-scenario in the real world MOST power supplies are set up with a current limiting resistor (or some other functionality) that takes the voltage drop due to the supply-to-supply differential. In the dinky 100-600 mA supplies that we are using on our boards, the result if this goes bad isn't massive.... yes, something will smoke if the differential is big enough, but it isn't a huge physical risk. In larger supplies, tho, this can be a thing to do with caution. I used to work around 100+ amp, 5 volt supplys daily at Tek and Mentor Graphics, and when they found a reason to tie them together they'd follow a very rigorous protocol that involved setting one supply as a Voltage Master (constant voltage) and putting the other in a Constant Current mode, such that the second unit did not try to control it's own voltage output. If you get 2 100 amp supplies fighting over the voltage reference, the room is going to smell of burnt FR4 in no time flat.

    Bottom line : don't current double unless the PSU manufacturer sez it's ok, and even then get their home office number for the fire report. ;)

    I have wondered whether the 'current doubler' cables supplied from pedal-PSU makers contain a current limiter of some sort, or do they build in a limiter in their individual outputs? I sincerely doubt that plugging in one of those current-doublers triggers an automatic Master/Follower configuration of the individual supplies. That would require a little sensing circuit that I do not see when I've looked at some of their layouts.

    "Not all analogies are equal. Some are more equal than others."
    - - blatantly plagiarized, cut from the herd, butchered, and re-used from George Orwell' Animal Farm.


    Those true-all-wheel-drive vehicles have lots of feedback and controls to ensure that vehicle is going to continue on the straight and narrow. Things as simple as putting on a spare of different diameter could really mess them up if this were not the case.
    That is a very different scenario from the connecting the outputs of two power supplies. When the power in play is large and the consequences are bigger than just "I smoked my PSU", There generally are significant controls put on one or both of the power supplies, per above.

    And just to be pre-emptive, I offer that it is also different from the scenario of connecting two batteries in parallel. Batteries are (generally) subject to precepts of electrochemistry that offer some builtin tolerance of parallel connection... also, a number of batteries contain materials which tend to limit the current output.
     
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  2. kdm1218

    kdm1218 Supporting Member

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    Definitely don’t try to run your big sky and DL4 from the same outs. Not even sure how that’s supposed to be possible with the DL4’s different requirements, actually. If Big Sky was your only problem, you could use the PP2+ courtesy outlet- I did this for years with an Eventide Timefactor. But as Dave has already pointed out you are way over total ma available per port with half the stuff you are looking to power. Time to make a spreadsheet and start planning a new PSU. I recommend Strymon for plenty of ma on tap and lightweight, and fwiw I’ve run 14 pedals off an Ojai (5 500ma ports) with zero noise.
     
  3. The Captain

    The Captain Member

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    Nope. Voltage doubler, yes, current doubler no.
    And I am a know-nothing Jon Snow, yet I know this, mainly because I use one of the afore-said cables to properly power a Nova delay.
     
  4. lefort_1

    lefort_1 Nuzzled Firmly Betwixt Gold Supporting Member

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    ...well, they make'm ... and people sell'm

    https://www.sweetwater.com/store/de...r-str-y-doubler?mrkgcl=28&mrkgadid=3248788199

    Moot point for the OP tho, since it's well-established he's driving a Comby when he really needs a Road Train.
     
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  5. johnnyjj

    johnnyjj Member

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    I do find that the 'current doubling' cable, when used by the Big Sky with the PP2 on 5 + 6, hums appreciably. Not fun.
     
  6. rsm

    rsm Member

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    Get a Helix, HXFX, AX8,... o_O


    :D
     
  7. Laro

    Laro Silver Supporting Member

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    I just added a second PP2.
     
  8. The Captain

    The Captain Member

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  9. Juan Wayne

    Juan Wayne Member

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    Oh I understand that and I agree, the real explanation is way more detailed than I bothered to get into. I tend to get long winded on these topics and it ends up being pointlessly long and ignored by everyone, which isn't really helpful.

    That said, I really appreciated reading this one. I'd still stay away from those Y cables though.

    How many different ways of being a condescending, passive-aggressive douche did you need? It's not about how I think or how I feel, you boob, it's knowing my trade.

    And no, taking one output into two inputs on a cabinet is not the same as putting two outputs into one input, it basic knowledge if you've ever worked with audio at some point, let alone know anything about electronics.

    Also, a Y-cable is a Y-cable, I may not work on any company's marketing department, but I'm an electronics engineer. Maybe I should have opened with that one, that would have been classy enough, just whip out my dick to gain credibility, that gets you friends right?

    I was just trying to be helpful, but hey, feel free to buy into whatever the marketing geniuses sell you, it's your money.

    Oh, and the engine thing was also taken care of brilliantly by @lefort_1. It was a simple analogy you doofus, stop trying to be a smartass.
     
  10. Cb

    Cb Member

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    I'd try to favor the other leg.
     
  11. Juan Wayne

    Juan Wayne Member

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    I'm over here now!
    That's a cool name, especially because it returned from its ashes to become a hunk of metal which my thing somewhat resembles, and I'd probably piss off both sides of the US Civil War at the same time, so there's a plus! I just call it "La Pedalera" though, which is Spanish for The Pedalboard, but it does need a real name.

    Anyways, there's no beating required, that's actually how the concept was born. It got way more complicated down the line, to the point of becoming my engineering thesis (I graduated by playing guitar in front of the teachers, that was cool on its own), but it remains faithful to the concept of managing everything digitally without digitalizing the audio, so in the end the Phase 90 clone is still an exact copy of the real thing, and nobody could ever tell the difference (that actually came to become an issue when testing things and forgetting which circuit was on and which one not).
     
  12. soundchaser59

    soundchaser59 Silver Supporting Member

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    This is not an accurate description of the people at Voodoo Labs or MXR, just to name a couple. That being said, I don't remember seeing where it is designed to connect two outputs together to double the current. I remember seeing that some outputs could supply more current than others, and I remember seeing where a guy could use their "doubler" cord to get an 18v supply from two 9v outputs. And I'm sure it works fine, and the units are designed quite well to have that capability.

    I got rid of a lot of hum, almost all of it in fact, by never chaining my pedals in front of the amp to the same power supply as my pedals in the loop, and I keep both of those chains separate from the amp's power supply. If you shop carefully you can find decent surge suppressor power strips that have one side isolated from the other side.

    I daisy chain power and my rig is quiet, but I bought dedicated non-switching power adapters that provide 1A or 2A or even 3A. The only noise I get is when I turn on the single coils or to a lesser extent the P90's.
     
    Last edited: Jul 9, 2018
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  13. Juan Wayne

    Juan Wayne Member

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    Hey don't get me wrong, I've got nothing against either of them, all the contrary. I'm just saying that blindly quoting what a brand does or says about their own product is not a smart way to go about things. Not to have my nose up anyone's ass, but smart is finding what works for you and making it sound good and quiet like you did. Getting credibility out of throwing names on the table is just lame, as much as I respect those brands (I really do).

    The doubling of 9V into 18V is simply wiring two isolated outputs in series, and it's done often without any issues (I made a PSU wired internally that way on all pairs of outputs, not a problem). Doubling currents would be in parallel though, and it might be another kind of a headache.
     
  14. panther_king

    panther_king Member

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    If I'm not mistaken, alot of PSU manufacturers (for the products we are discussing) are *required* to limit the current on a per output basis by law. Something regarding the limit of each output having to be a certain value of the overall available current from the entire supply. I don't have the exact terminology of the requirements off the top of my head, but I remember because it's something that Tru Tone seems to 'flaunt' as bypassing with their own supplies, which offer the entirety of their current across all taps, as long as the total draw from all taps do not exceed the maximum for the unit. They just labelled them what they are labelled 'because they have to' (that quote paraphrased from their own product demos and videos). I don't know what specifically they're doing to keep the taps isolated at the point, because it just sounds like a big daisy chain to me, but they are isolated (they say). So in the circumstance of the Tru Tone devices, running two taps in parallel is stupid, because the technology renders it unnecessary.
     
  15. Mark Robinson

    Mark Robinson Member

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    One tidbit to know is if signal ground is connected to power ground in specific effects you use. Use a multimeter from signal sleeve to each power conductor and see. When they are tied, then you can lift either the tied DC, or the signal shield, and then share power for paired effects, like wired, provided they are not power pigs. Boss pedals seem to be able to be chained. I try to avoid it, cause oops high gain, and Wah on board and in use, and the low level hum and hiss of some of my stuff is quite enough, without inducing more hum.
     
  16. lefort_1

    lefort_1 Nuzzled Firmly Betwixt Gold Supporting Member

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    I've been out of the biz for 20 years, but I am not aware of regs that require current limits OTHER than ones that prevent safety problems from happening, i.e. Fire and OSHA regs that aim to prevent the overloading of power equipment... there are design-limits for upstream common components (e.g. the input transformer) and the sum of the output current should never exceed that current capability... thus, the manufacturer is suppsed to 'limit' the individual taps to a sum that stays within the safe-design range for the common components. Apparently, the 'limit' can be in the form of a written warning on the device, rather than a hard-wired, curret-limiting resistor (otherwise, TruTone could not do what they are doing).

    The ARE other regs for efficiency of power supplies (e.g. EISA2007, US DOE Level VI, CEC Tier 2, NRCan, etc) that have mandated Efficiencies for PSUs when under minimal/no load.
    But that it to prevent gross waste of energy on unused taps/PSUs that happen to be plugged in... which have been a huge waste of energy in the past. But that isn't what we are talking about.

    As long as the individual taps do not put an unsafe burden on the common-to-all-taps components, I don't know of a rule that states they can't make a, say, 900 mA tap.
    As I said before, I worked on systems where 100 AMPS was barely sufficient. Those kind of systems remain in use today, and they are totally legal and not limited to lower mA output. Outlets like Digikey, Allied and other are full of power supplies rated in the tens of amps. Many have multiple taps as well. (our PSU had 4, including a -5.2V for ECL logic, bitd). As far as I know, there are no current-limiting regs in place for consumer vs industrial designs (which is different from FCC radiated/conducted regs).
     
  17. The Captain

    The Captain Member

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    Since you are in Australia, I suggest you talk to the guys at Pedal Empire in Brisbane, but make sure you check the numbers you need carefully. I bought a Hot Stone recently, assumed it would run my EQD Avalanche Run, which PW assured me it would, but it's 15Ma short, needing 415, and each output maxes out at 400. The included power supply is 1 amp, so 585 mA of headroom. The PE guys said it would just draw whatever it needed off another tap, which it DOES NOT because each output is ISOLATED. Duh !!! And I fell for that.
    That's OK, it works fine on the power supply it came with, but I did have plans to put together a small board running a few things off the one brick.
     
  18. Purple_Plexi

    Purple_Plexi Member

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    Interesting, my experience is the opposite: I have no problems daisy-chaining analog pedals (dirt, which is normally early in the chain), but have learned to give digital pedals (delay/reverb, which is normally late in the chain) their own outputs.

    The Avalanche Run works fine off of a 400 mA Voodoo Lab output :dunno
     
  19. eclecticsynergy

    eclecticsynergy Member

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    Do not dismount until after the battle is over.
     
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  20. DanSimon

    DanSimon Member

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    hmm somehow im using one of these non existent current doublers to power my strymon off a PP2+. Its been fine with no noise for 2 years.

    i didnt read the entire debate, hopefully i misunderstood. this is definitely 9v , mA doubler. Not voltage doubler. Strymon= 9v.
     

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