Author Topic: Korg PitchBlack power out voltage drop question  (Read 10464 times)

GGBB

Korg PitchBlack power out voltage drop question
« on: January 21, 2013, 03:10:24 PM »
I put my fuzz on my pedal board the other day and it didn't sound right so I checked the bias and discovered to my horror that it was only getting about 7.7 volts from a 9v regulated supply.  An hour of troubleshooting later, I discovered that the 9v power out on the back of my Korg tuner was the culprit - the more pedals daisy chained to it, the more the voltage drop.  With no pedals actually connected, it would measure the full 9v, but I had three low current draw pedals connected to it including the fuzz.  If I daisy chained off the power supply directly, I had no voltage drop at all.  This also explained why I could never get my Boss CS-3 to work when powered from that chain.

So I assume there is something going on inside the tuner that "de-regulates" the power out (which FWIW the specs describe as 200mA max).  But what actually does that and why wouldn't they just chain directly off the power in?  Are they trying to provide some kind of protection from unregulated and/or cheap quality power supplies?  Or is there possibly something wrong with the tuner?

gcme93

Re: Korg PitchBlack power out voltage drop question
« Reply #1 on: January 21, 2013, 03:26:52 PM »
200mA is quite a lot? I guess this is turning your original power plug into a non ideal voltage source. Probably the simplest fix is to splash out on another power plug so you can have the Pitch Black powered separately? Daisy chains don't seem to be recommended by folks around here anyway, but especially not if you've got a pedal drawing that much current (Fuzz pedals are normally less than 20mA I think...)
Piss poor playing is why i make pedals.

GGBB

Re: Korg PitchBlack power out voltage drop question
« Reply #2 on: January 21, 2013, 04:10:53 PM »
Not quite what I meant - the 200mA rating is for the power OUT from the pitchblack.  The tuner itself draws maybe 30 or so.  I assume that because of the fact that they state a max current for the power OUT connector, they must have something going on to process the 9VDC signal before sending it out.

Fixing the issue isn't a problem - I'll just connect the daisy chain directly to the PS.  And although daisy chaining isn't ideal, when you've got 9 pedals (and growing) and only 6 power outlets, you don't have a choice.

GGBB

Re: Korg PitchBlack power out voltage drop question
« Reply #3 on: January 22, 2013, 08:50:42 AM »
Bump - hoping someone can explain what those "power out" jacks do.

slacker

Re: Korg PitchBlack power out voltage drop question
« Reply #4 on: January 22, 2013, 12:58:59 PM »
Sounds like there's something between the DC In jack and the DC out jack, could be as simple as a resistor, some sort of fuse or something more complicated. I took a look at the manual and it says don't try and power it through the DC out jack or it could cause damage so it's obviously not just connected straight to the DC In jack.
Have a look at the board and see if you can figure out what's in there.

GGBB

Re: Korg PitchBlack power out voltage drop question
« Reply #5 on: January 22, 2013, 01:59:41 PM »
Sounds like there's something between the DC In jack and the DC out jack, could be as simple as a resistor, some sort of fuse or something more complicated. I took a look at the manual and it says don't try and power it through the DC out jack or it could cause damage so it's obviously not just connected straight to the DC In jack.
Have a look at the board and see if you can figure out what's in there.

I opened it up and I can't really make anything out.  There are a couple of 47u caps and a few surface mount components - 2 caps, 1 resistor, one diode, and a transistor looking item with 4 connections (3 bottom, 1 on top) that is marked DA QT.  I can't really make out the traces either - some are hidden underneath the pcb mount power connectors and it's double-sided and very small so tough to follow with my eyesight.  My guess would be that the power out comes from after the filtering/regulation.

Not impressed with the quality of work in this thing - sloppy soldering and even though I've been careful, two wires have come off the board already - and I'm not sure where one of them goes.  Crap!!!  >:(

gcme93

Re: Korg PitchBlack power out voltage drop question
« Reply #6 on: January 22, 2013, 02:22:49 PM »
Show me a detailed picture and I/we might be able to help? Although after what you've just said, I'm a little reluctant to take mine apart  :icon_confused:
Piss poor playing is why i make pedals.

garcho

Re: Korg PitchBlack power out voltage drop question
« Reply #7 on: January 22, 2013, 02:23:05 PM »
Quote
Not impressed with the quality of work in this thing - sloppy soldering and even though I've been careful, two wires have come off the board already - and I'm not sure where one of them goes.  Crap!!!

Do you want me to post a picture of mine, for reference?

FWIW my Pitch Black has been more abused than I'd like to admit. I play in a band with LOTS of stomping, road vibration abuse, falling over, schlepping, dropping, cable yanking, beer spilling, etc., and not one problem. It's about 3-4 years old. As far as modern day 'workmanship' goes, not bad. I haven't checked out the guts, though. No problems, so I haven't bothered.

Is there a pragmatic reason that you want to use the DC out instead of chained from the adapter? Just curious. I daisy chain 5-8 pedals from a One Spot all the time, never had a problem. I know other folks have, but it seems like it's usually some Line 6 thing or some goofy DSP thing that's the culprit. Your problem sounds different, almost like a load resistor and current dropping the voltage.
"...and weird on top!"

slacker

Re: Re: Korg PitchBlack power out voltage drop question
« Reply #8 on: January 22, 2013, 02:51:59 PM »
There's a couple of decent photos online if you search for korg pitchblack schematic. I had a look earlier to see if I could get any clues as to what might be going on.

GGBB

Re: Korg PitchBlack power out voltage drop question
« Reply #9 on: January 22, 2013, 03:38:25 PM »
Thanks guys but no worries - the two boards connected by the wires have labels indicating which wire goes where.

Is there a pragmatic reason that you want to use the DC out instead of chained from the adapter? Just curious. I daisy chain 5-8 pedals from a One Spot all the time, never had a problem. I know other folks have, but it seems like it's usually some Line 6 thing or some goofy DSP thing that's the culprit. Your problem sounds different, almost like a load resistor and current dropping the voltage.

No other reason than convenience - I was using the power out as an additional power socket assuming that it was just a chain off the main in.  No big deal - I'll just have to solder another connector to the chain cable so it can plug into the pedal board supply.  I was really more interested in the how and especially why they would do that instead of just a direct split off the main power in.  It probably costs more to do it the way they did, so they must have a good reason.

gcme93

Re: Korg PitchBlack power out voltage drop question
« Reply #10 on: January 22, 2013, 05:38:29 PM »
I was really more interested in the how and especially why they would do that instead of just a direct split off the main power in.  It probably costs more to do it the way they did, so they must have a good reason.

I'm just reading through the manual online (I'm pretty interested too, in case there's a good reason for me using mine like that).

The only interesting part is that the plug requirement is 600mA minimum, despite the tuner using only 30mA max and the maximum "korg 9V out" being 200mA as you said. I can only imagine that the circuitry of the output requires the 600mA for the pedal to mimic a perfect voltage supply? I don't really know on this. Lots of hand waving and guessing on my part...
Piss poor playing is why i make pedals.

GGBB

Re: Korg PitchBlack power out voltage drop question
« Reply #11 on: January 22, 2013, 05:47:24 PM »
I don't really know on this. Lots of hand waving and guessing on my part...

Same here.

sgRED

Re: Korg PitchBlack power out voltage drop question
« Reply #12 on: January 22, 2013, 08:26:03 PM »
Every pedal on the market says it draws a small amount of current from your battery or adapter, but consider this: Three pedals???!!! Their Ampere consumption multiplies in series, that's where you get your voltage drop, and it is because of the different impedance of the different pedals, you get so much voltage drop, as if you had so many pedals. Of course, you can add one pedal after the tuner and that's it!

GGBB

Re: Korg PitchBlack power out voltage drop question
« Reply #13 on: January 22, 2013, 10:45:22 PM »
Every pedal on the market says it draws a small amount of current from your battery or adapter, but consider this: Three pedals???!!! Their Ampere consumption multiplies in series, that's where you get your voltage drop, and it is because of the different impedance of the different pedals, you get so much voltage drop, as if you had so many pedals. Of course, you can add one pedal after the tuner and that's it!

I understand about voltage drops and current draw but I'm not sure I get what your point is - can you explain further?  If I hook three pedals to the tuner power out and the tuner to the 9V regulated power supply, the three pedals all have a voltage drop (less drop with two or one pedals) but the tuner has 9V.  If I hook the same four pedals up to the power supply directly using the same daisy chain cable, no voltage drop (because it's regulated).  What I want to understand is how does a regulated power supply get unregulated - what is in the tuner pedal to "unregulate" the power supply?

sgRED

Re: Korg PitchBlack power out voltage drop question
« Reply #14 on: January 23, 2013, 12:01:16 PM »
Quote
I understand about voltage drops and current draw but I'm not sure I get what your point is - can you explain further?  If I hook three pedals to the tuner power out and the tuner to the 9V regulated power supply, the three pedals all have a voltage drop (less drop with two or one pedals) but the tuner has 9V.  If I hook the same four pedals up to the power supply directly using the same daisy chain cable, no voltage drop (because it's regulated).  What I want to understand is how does a regulated power supply get unregulated - what is in the tuner pedal to "unregulate" the power supply?

OK, i see your standing point now.
First: You cannot "unregulate" a power supply that has been regulated already. it is just not possible and also is wrong word for it (electrically and literally)!
Second: Your tuner simply cannot provide enough juice (mA) for itself and 2 or 3 more pedals = VOLTAGE DROP (and it doesn't mean something is "unregulated")
Third: If you have for example, a 5A regulated power supply for your pedals with 5 outputs. That means that every power (let's say 9V) output has it's special and unique voltage regulator/capacitor/diode/etc. circuit. Every circuit on it's own is connected to the output of the transformer that gives let's say 20V and 7A. That transformer alone has 2, 4 or 6 (or something) isolated outputs with dedicated COIL of that transformer that sends current to only one separate regulator. Every output goes to a regulator, gets regulated (ironing or cutting the peaks in the transformer's voltage and gives a steady voltage without ups and downs) for 9V or 12V or even 18V (depending on the possibilities of the manufactured supply and players needs). That's what basically voltage regulator and pedal power supply does.
Fourth: A tuner pedal with extra power output can NOT and simply will not, have the power to supply regulated 9V or any, to one pedal or separate chain of effect boxes. Why? Because it is not meant to do. It is just what the guys in commercials say it can do. Why? It's obvious. Some customers will connect 1, 2 or even three pedals that will somehow (small current draw) work, and they do not complain. You on the other hand complain. Why? Because Korg tuner is a great tuner, a power outlet is just a backup thing, it may power your wah for example, not a whole chain man. :) It probably has a IC (chip) that gives you power, not a separated isolated power outlet. And my best guess after this is, that it has only a "drive trough" connection that leaves you with FOUR pedals in one chain, not 3!!!
Further so, everything i'm saying is that you'll always need those adapters, power supplies etc., to and power up your pedals, and not rely on a manufacturers promise. Here's a example: A manufacturer says that it can power up to a 30 pedals at the time: http://www.diago.co.uk/pedal-power/diago-powerstation.html go there and see this one! it says: 9V 3000mA and it can power up 30 pedals. Now let's calculate. If you got a 30 pedals that go from 30mA to 300mA or even higher, what it can do and what does it means? It means that every pedal has to be "weaker" than 100mA to do this because 3000 divided by 30 is 100mA! Decide for your self! And Korg pitch black, i am surprised it can do one at the time properly! Why??? Because it's meant just as a backup, it's a production gimmick, not a regulated supply. Now go and see: http://www.voodoolab.com/pedalpower_2.htm and specially a section thet says: "What’s good for charging a cell phone is NOT good for your pedals.", and "custom designed, ultra-low noise toroidal transformer, with separate balanced windings for every output."! That is probably the best answer for you on that page!
HOPE IT HELPS MAN! CHEERS, AND HAPPY PLAYING (AND TUNING ALSO)

GGBB

Re: Korg PitchBlack power out voltage drop question
« Reply #15 on: January 23, 2013, 02:20:57 PM »
OK, i see your standing point now.
First: You cannot "unregulate" a power supply that has been regulated already. it is just not possible and also is wrong word for it (electrically and literally)!
Second: Your tuner simply cannot provide enough juice (mA) for itself and 2 or 3 more pedals = VOLTAGE DROP (and it doesn't mean something is "unregulated")
Third: If you have for example, a 5A regulated power supply for your pedals with 5 outputs. That means that every power (let's say 9V) output has it's special and unique voltage regulator/capacitor/diode/etc. circuit. Every circuit on it's own is connected to the output of the transformer that gives let's say 20V and 7A. That transformer alone has 2, 4 or 6 (or something) isolated outputs with dedicated COIL of that transformer that sends current to only one separate regulator. Every output goes to a regulator, gets regulated (ironing or cutting the peaks in the transformer's voltage and gives a steady voltage without ups and downs) for 9V or 12V or even 18V (depending on the possibilities of the manufactured supply and players needs). That's what basically voltage regulator and pedal power supply does.
Fourth: A tuner pedal with extra power output can NOT and simply will not, have the power to supply regulated 9V or any, to one pedal or separate chain of effect boxes. Why? Because it is not meant to do. It is just what the guys in commercials say it can do. Why? It's obvious. Some customers will connect 1, 2 or even three pedals that will somehow (small current draw) work, and they do not complain. You on the other hand complain. Why? Because Korg tuner is a great tuner, a power outlet is just a backup thing, it may power your wah for example, not a whole chain man. :) It probably has a IC (chip) that gives you power, not a separated isolated power outlet. And my best guess after this is, that it has only a "drive trough" connection that leaves you with FOUR pedals in one chain, not 3!!!
Further so, everything i'm saying is that you'll always need those adapters, power supplies etc., to and power up your pedals, and not rely on a manufacturers promise. Here's a example: A manufacturer says that it can power up to a 30 pedals at the time: http://www.diago.co.uk/pedal-power/diago-powerstation.html go there and see this one! it says: 9V 3000mA and it can power up 30 pedals. Now let's calculate. If you got a 30 pedals that go from 30mA to 300mA or even higher, what it can do and what does it means? It means that every pedal has to be "weaker" than 100mA to do this because 3000 divided by 30 is 100mA! Decide for your self! And Korg pitch black, i am surprised it can do one at the time properly! Why??? Because it's meant just as a backup, it's a production gimmick, not a regulated supply. Now go and see: http://www.voodoolab.com/pedalpower_2.htm and specially a section thet says: "What’s good for charging a cell phone is NOT good for your pedals.", and "custom designed, ultra-low noise toroidal transformer, with separate balanced windings for every output."! That is probably the best answer for you on that page!
HOPE IT HELPS MAN! CHEERS, AND HAPPY PLAYING (AND TUNING ALSO)
Wow - that's a lot of information.  I guess I haven't been expressing myself clearly - sorry.  I realize all that you are saying, but I don't see how it answers my question.  So let me try to elaborate a bit further.  I'm not asking why does the voltage drop when you connect multiple pedals to same unregulated power supply.  The Korg doesn't create power from nothing, so the power that comes from the power out is power that originally comes from my regulated supply (9V 400ma from only one transformer output into 5 isolated jacks).  The Korg is getting 9V, the other 4 pedals connected to the supply (via their own connectors) are all getting 9V.  If I daisy chain another three pedals off of any one of the 5 power sockets including the one used by the Korg so that there are a total of 4 pedals connected to that one power connector, they still all get a stable 9V.  However, if the three extra pedals are connected to the Korg's power out, there is a voltage drop proportional to the number of pedals connected to the Korg power out.  So only when the Korg power out is used do I get any voltage drop, but the power coming in to the Korg is a stable 9V.  There's regulated power going in to the Korg, and unregulated power coming out.  I am trying to understand how that happens (electrically) and why Korg would design their power out that way instead of just a direct split off of what is coming in to it (which it definitely is not).

gcme93

Re: Korg PitchBlack power out voltage drop question
« Reply #16 on: January 23, 2013, 02:41:39 PM »
I'm going to try hitting this with a bit of theory (electronics is part of my degree but I know I'll make a silly mistake here)

The way to make sure each pedal receives the same voltage (9V) is just to branch the power line so that effectively, each pedal is connected to the power in parallel. Anything connected simply in parallel to something else, SHOULD receive the same voltage. Kirchhoff was the don behind that one.

Kirchoff's complimentary law is that if the current of electricity hits a branch, no current is lost, it's merely split between the two paths according to the resistance of each.

SO
You have 400mA, of which, the Korg uses 30mA and has the rest available if needed. The manual says it needs a 600mA supply which seems like a lot. I'm thinking this is a clue to your problem.

You know already that it isn't a simple parallel branching between the power in and out. My theory put simply is that for some reason, that small filter/circuitry/whatever it is inside needs a certain amount of current to make it's effective output voltage ~9V, and your 400mA supply doesn't quite hack it.

Therefore, when you have extra things in the chain from the power out, the output resistance (impedance) of the "power out" socket isn't as insignificant as it needs to be, and you get this annoying ratio of output voltage decrease when you add another pedal. The output resistance is added in to the equation as a voltage divider, the limiting factor being the current available.

Ultimately it's just not a very clever extra for a pedal, I guess Korg added some protection stuff in so they couldn't get sued for power surges etc.
Piss poor playing is why i make pedals.

slacker

Re: Korg PitchBlack power out voltage drop question
« Reply #17 on: January 23, 2013, 02:44:23 PM »
First: You cannot "unregulate" a power supply that has been regulated already.

Not true, you can do this very easily, all you need to do is stick a series resistor between the output of the supply and what ever you are powering. The voltage drop across this resistor is then proportional to the current draw of the device V = IR so the voltage available to the device being powered drops as current draw increases, therefore the voltage is no longer regulated.
This is what the Pitchblack is doing, there's something between the DC in and DC out jacks that limits current. This is fair enough, it's probably designed to protect the pitchblack but according to the specs it should allow 200 mA before limiting and it clearly isn't.

sgRED

Re: Korg PitchBlack power out voltage drop question
« Reply #18 on: January 23, 2013, 03:11:17 PM »
the output resistance (impedance) of the "power out" socket isn't as insignificant as it needs to be, and you get this annoying ratio of output voltage decrease when you add another pedal. The output resistance is added in to the equation as a voltage divider, the limiting factor being the current available. Ultimately it's just not a very clever extra for a pedal, I guess Korg added some protection stuff in so they couldn't get sued for power surges etc.
This guy (gcme93) is right, and yes it does act as a divider, you get smaller amount of Volts adding each pedal. So why not buy something stronger as a supply, read a little more about regulating voltages and that's it!?
P.S. Regulated, unregulated... that doesn't mean that you get strictly 9V. You can also get 8,89V, and it's good as long it doesn't oscillate!!!
Oscillation of the electric potential of the source makes the pedal go "brrruuummm", voltage divider further cuts the peaks of the oscilations so you get a smoother  potential, and from that electrons direct flow goes smoother (DC). It doesnt mean it just makes it 9V fom 12, 13, 18 etc.! It'l get ya all kinds of voltages and you think you bought a LM7809 for example.
Cheers

sgRED

Re: Korg PitchBlack power out voltage drop question
« Reply #19 on: January 23, 2013, 03:22:39 PM »
Quote
Not true, you can do this very easily, all you need to do is stick a series resistor between the output of the supply and what ever you are powering. The voltage drop across this resistor is then proportional to the current draw of the device V = IR so the voltage available to the device being powered drops as current draw increases, therefore the voltage is no longer regulated.
This is what the Pitchblack is doing, there's something between the DC in and DC out jacks that limits current. This is fair enough, it's probably designed to protect the pitchblack but according to the specs it should allow 200 mA before limiting and it clearly isn't.
It's true. The rule you are mentioning is called dividing, that means cutting the amount of electrons depending on the resistor value. This is what happens when this guy connects his pedals: http://en.wikipedia.org/wiki/Voltage_divider
Regulator: http://en.wikipedia.org/wiki/Voltage_regulator
And also check out this simple stabilizer: http://img.bhs4.com/5b/1/5b18114b29a5db2d5c1deeaafe7bd44ce6190958_large.jpg
He just has too many pedals in a chain, and believes the current draw specifications
P.S. Impedances are not matching so the voltage drop isn't exactly expected as it should be in a perfect situation, it is always so!
« Last Edit: January 23, 2013, 03:26:56 PM by sgRED »