GT Rack Effects Power

The power scheme for our modules not only makes powering a wide variety of effects very easy, it is also designed to protect your investment in effects from the most common "pedal killer" - accidental connections to an incorrect power source.

In Modules, we covered how to power GT modules.  Now we'll cover two parts of the overall power solution in more detail.

Power Supply

You can choose to use our 18V Power module or third party power supplies that meet the power specs our modules require.  Done properly, either approach will work fine. 

Third Party Power Supplies

We don't test any third party power supplies.  As long as they meet a few requirements, numerous third party power supplies should work fine.  Here's what you need (or don't need) in third party power supplies:

  • DO NOT USE A SWITCHING POWER SUPPLY.  They are a common source of extreme levels of power noise that can make your effects unusable.  This noise is very difficult to filter out and will happily make its way throughout your entire chain.  Unfortunately, the general trend in power transformers is to build switching transformers.  They are cheaper, smaller, and lighter than old style transformers.  They work fine for a wide variety of consumer electronics, but are a disaster when used with audio equipment.  We repeat DO NOT USE SWITCHING TRANSFORMERS - THEY CAN DESTROY YOUR TONE.  They won't damage your equipment, just add so much noise you can't use it.  If a transformer isn't heavy enough to double as a light dumbbell, it is probably a switching transformer.  You want heavy metal.
  • Use a regulated power supply.  Regulated means that it produces about the same voltage no matter how much load is on it (within its spec of course).  Unregulated transformers will produce much higher voltages with light load and voltages near its rated voltage under full load.  The modules will tolerate a considerable amount of excess voltage, but it is recommended that you not operate them that way.  It will likely result in eventual overheating and failure of components on the module's power board.
  • Use a transformer that produces DC voltage, not AC.  Our modules will tolerate and perhaps even work fine with AC power, but AC voltage and DC voltage of the same size won't work the same.  There's some math involved to calculate the AC voltage that would work in place of our DC voltage requirement, but it's much better to just use the proper DC voltage and keep it simple.
  • Our modules are designed to be supplied +18V, DC.  The circuits in the modules run at a wide variety of voltages, just like pedals.  Some effect circuits might run on -1.5V, -3V, -9V, -15V, 3V, 6V, 9V, 12V, 15V, 18V, 24V or perhaps a few other voltages.  We have modules that use all those voltages.  One of the functions of the power board in each module is to convert +18VDC to whatever voltage is used by the circuit.  This keeps everything simple - all our modules use the same +18VDC.  A couple also plug directly into wall power 120/240V AC, we'll get to that in a minute.
  • Center positive or center negative doesn't matter.  Either work, but we always use center positive because that is what our 18V Power module produces.  That is different from the normal center negative power, so be careful if you use our 18V Power module to power your 18V effects.  Center negative means the outside of the DC plug is positive.  That can lead to short circuits if an unused daisy chain jack comes in contact with metal, like a rack rail, enclosure, or anything else.  Center negative seems like a bad idea to us, so we put the power in the center and ground on the outside.  To use our power supply with third-party center negative effects, check the polarity your effects expect.  You'll likely need a cable that swaps the polarity.  These often come with pedalboards and pedalboard power supplies.
  • You'll have to calculate how many milliamps you need.  Our module descriptions provide information about power consumption.  Those are guidelines that should get you reasonably close, but the actual power requirements can vary depending on specifically how the module is built and its configuration.  Use as many or as few power supplies as you need to meet the needs of your selected modules.  If you cable everything up and they don't power on, disconnect a few modules to see if your capacity is too low.  If you don't have enough power, the modules won't power up or they may sound awful.  That shouldn't hurt anything, but don't use them that way.

In summary you need some number of quality, heavy, non-switching, regulated, +18VDC power supplies that will provide the number of milliamps you need.  Pedal power bricks should be good candidates, if they provide enough +18VDC capacity.  YOUR TONE WILL BE AWFUL IF YOU USE NOISY SWITCHING POWER SUPPLIES.

GT 18V Power Module

18V Power module - Front
18V Power module - Rear


Naturally, if you use our power supply module, you don't have to worry about the noise or meeting the specs above.  It is designed for this one specific purpose.  It also has a few nice features:

  • Voltage display.  On the front panel it displays the voltage being produced on both channels, +18VDC +/- about 10%
  • Amperage display.  On the front panel it displays the milliamps being used on each channel so you know how much more capacity you have available
  • Blackout operation.  If the displays for volts and amps are too bright or distracting, there are switches to turn them off.
  • Safety fusing.  It has a fuse on the incoming wall power feed, as well as fuses on both output channels
  • 120VAC, 240VAC untested.  The module can be supplied with 120V or 240V AC (need to change fuses!).  We have only limited ability to test 240V operation, but it tests OK in those limited tests.  HOWEVER, WE DO NOT SUPPORT 240V OPERATION.  Our tests don't change the frequency of the power when it changes the voltage.  We have not tested at both 50Hz and 60Hz.  That is why we do NOT support 240V operation at this time.  We have no particular reason to expect problems, but it is not properly tested.
  • Quiet power.  DC power is produced by a high quality toroidal transformer.
  • High capacity output.  It produces 2 channels of 2000mA each.  That should be enough to power many more modules than you are likely to have in your rig.
  • Uses only (1) 120VAC power connection.  You may need several 120VAC power connections if you need multiple third party power supplies.  You won't need to figure out how to keep those power supplies from coming unplugged during transportation, or fitting bulking transformers into power strip outlets that are too close together.

WARNING - There is an issue you should be aware of when considering our 18V Power module.  Our power module is not inspected or certified by any third party for safety.  While we certainly wouldn't knowingly sell something that would in any way harm or endanger our customers or anyone else, it would be irresponsible of us to lead you to believe that we have any kind of safety certification.  We are not listed by Underwriter Laboratories (UL) or any other third party.  If you do use our 18V Power module, you do so at your own risk knowing that a malfunction could injure or kill you or others.  We believe that is always possible with electric products, but with reputable third party certifications you can expect the chance of that to be very low.  We have not had any such reviews or certifications, so we cannot make any factual claim about how dangerous or deadly this module could be.  In the years we've been building and using them regularly we have never had any malfunction of any kind, but that may not be a reliable indication that the module is safe to use.  We want to be very clear about our lack of a safety certification so you can make an informed decision about using that particular module.

DC Power Cables

Use normal DC power daisy chain cables to connect from the 18V Power module to your other modules.  You can chain multiple daisy chains together to power a large number of modules.  If one of your volt/amp meters turns off, you have probably shorted a jack somewhere.  This is pretty unlikely since the module produces center positive (outside ground), but you know how those 1 in a million odds seem to happen at bad moments!

Also be sure to use both power channels, and cable your modules in such a way that the milliamps used are balanced between the two channels (bottom number on each meter).  You won't be able to balance them exactly and you don't need to.  But get them reasonably close, within the bounds of the various amounts of power used by your modules.  Keeping them more closely balanced is better for the transformer in the 18V Power module and will prolong its life.

Use Power Conditioners!

Regardless whether you use our power module or a third party power solution, we very highly recommend you power them through a quality power conditioner that filters out noise and provides surge protection.  We refuse to plug anything directly into wall power when we power up.  There are excellent units available that are not very expensive - about the cost of a single boutique pedal or one of our modules.  Not only do they protect you from circuit-killing surges, but they can remove a lot of hum, whine, and other noise coming in through your power.  We have experienced major improvements in sound quality by using conditioners that cost only $200 or less.  It is one of the best uses of your hard-earned cash. 

If you can afford it, this is a good candidate for spending a little extra to get a better unit.  The specs matter, so read and compare them - don't go by cost alone.  Good units will display the incoming power voltage so you can see problems before they cause damage to your gear.  Better units will fix (regulate) voltage that is too high or too low or shutdown safely if there are extreme problems.  Better units will also provide more outlets which are isolated from each other.  Pull-out lighting is nice and commonly available - mount those units in the top of your rack.  You can also get uninterrupted power supply (UPS, or "battery backup") functionality.  That is probably of limited use for keeping you playing during a power outage, but it can give you time to gracefully shut everything down during a power outage instead of taking an unexpected power down.  Hopefully you won't encounter switching transformers in any power conditioner designed for audio use.  But check just in case, particularly if it seems like a pretty good deal.  A good power conditioner should be heavy!  Good entry-level units like we normally use only take 1U of rack space, but some of the nicer ones may take some more rack space - plan accordingly.

Sometimes "voltage regulation" can be a little unclear.  Units that provide voltage regulation generally pick a specific voltage, such as 120VAC, as the target voltage.  They will accept some range of input voltages, maybe 100VAC - 140VAC, and try to give you a steady 120VAC, plus or minus a couple volts.  They attempt to keep the power at that steady voltage, even if there are slight fluctuations in your input voltage.  They also usually shutdown if the input voltage is outside the range expected.  Most also provide surge protection.  Some also provide some power conditioning, which is usually some form of noise reduction.  That's all great and provides a lot of good benefit.  However, in the USA power used to more commonly run around 110VAC.  These days, it seems you're more likely to see around 120-125VAC.  If you have vintage equipment, such as tube amps, they were probably designed with the lower voltage in mind, and may sound better and tubes might last longer, at the intended 110VAC.  You may find a voltage regulator that provides that target voltage, but more likely you'll see a higher target voltage.  If you want to run at the lower voltage, you'll need something that allows you to reduce the voltage.  One device that does that is called a "variac".  A typical variac unit has a display that shows the incoming voltage and a big dial that lets you set the output voltage to a very wide range of values, with 110VAC being among them.  That's one way to get to a reduced voltage level.  But there's a catch.  Most variacs do not regulate the voltage.  You can set it to produce 110V, but if you have fluctuation in your input, you'll have fluctuation in the output.  The variac "expects" a particular input voltage, so if your input voltage is different, the 110V output setting might produce something higher or lower.  So you have to dial to whatever setting produces 110V, and live with the (hopefully small) fluctuations you'll get from it.  If you really want the bee's knees, you might want to plug your wall power into a power regulator to get a stable voltage (whatever that voltage is, probably around 120V), then run that output into a variac to reduce it to 110V.  With a steady input from the regulator, you should see a steady output from the variac.  We don't have any recommendations about this, so think through what you need and plan accordingly.  It should be pointed out that if you use a variac with that big dial, those dials seem susceptible to unintended bumps and resets and may go to a pretty bad voltage by accident.  To guard against that, you might want to run your variac output through a power conditioner that would protect you from over/under voltage conditions.  In that case your power chain might be:  wall power -> voltage regulator -> variac -> power conditioner.  That can start getting a bit pricey, but you may want to consider it if you play somewhere that has dodgey power or you have vintage equipment that might run better with specific input voltages. 


Back to Modules

Continue to Switching