Power Considerations

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L1 Model II This information is applicable to the L1®  Model II
L1 Model 1S This information is applicable to the L1®  Model 1S
L1 Compact
F1 Model 812This information is applicable to the F1 Flexible Array Loudspeaker
L1 Model I This information is applicable to the L1 Model I
Classic This information is applicable to the L1® Classic

Electrical Power

As a general note, we want to remind you that all electrical equipment must deal with poor power conditions and power outages. Hardware and software designs can be sophisticated in this regard and we put enormous effort in this area.

At a certain point, if the voltage drops too low from the wall circuit, or there is a power outage, contemporary digital electronics including ours will start a reset sequence. Assuming the AC power recovers, the reset sequence with digital electronics usually takes a few seconds. If that few seconds is longer than the power outage, it can be a frustrating wait.

There are practical things that musicians can do that will minimize the chance of an interruption in their performances – practices that are valuable to know and use in general for all stage equipment.

  • Use AC extension cords that are as short as possible. Do not use a 100’ cord when a 25’ cord will do.
  • Do not use thin-gauge or flimsy extension cords. Good cords are worth the extra expense.
  • Avoid the practice of stringing AC extension cords together: if you have 20’ to the wall socket, use one 25’ cord rather than 3 x 8’ cords. The reason is that the electrical connectors at the junction between cords can introduce extra resistance, especially if they are bent or corroded.
  • Split power-hungry equipment (amplifiers and lights) over as many different power circuits as you can. Lots of power-hungry equipment loaded onto one circuit will lower the voltage and can cause equipment resets and failures, especially in very loud musical performances.
  • Check for non-performance-related equipment on stage circuits that may contain compressors or large motors: refrigerators, air conditioners, snow cone machines, etc. can cause a large drop in the voltage. If possible, move these appliances to other circuits or have them turned off during the performance.

Source: Bill-at-Bose

Surge Protectors

From Hilmar-at-Bose

Surge protectors are not a bad thing, although the Power Stands for the L1 Classic, Model I, Model 1S, Model II and Compact have built-in surge protection.

"Surge" means a lot of voltage coming through the power over a short period of time. That's pretty rare and the main cause is lightning, some accidents involving power lines (mostly on poles) being cut and touching something they shouldn't (e.g. the wrong side of a power transformer) and some really big compressors (e.g. industrial-sides freezers or fridges) turning on or off.

With the exception of lightning and some very bad power accidents, the Power Stand can handle that all fine by itself. With lightning, anything is possible. No piece of equipment that I know will survive a direct hit into a directly connected power line. But then again lightning might strike a few blocks (and transformers) away in which case a surge protector might be able to take the first hit and die quickly enough to protect the attached equipment.

In this regard, even cheap surge protectors will work fairly well and there is only a really small number of cases where a cheap and very expensive surge protector might make a difference.

On a side note, its a good idea to have all equipment that connects to the Power Stand on the same power strip. That helps with ground loops. On the other hand it's not a good idea to turn things on and off with the switch on the power strip. That may cause your fuse to blow (due to the so-called "in-rush current") and might result in pops and clicks.

The proper way to turn things on is to follow the signal, i.e.

  1. Instruments
  2. Outboard effects processors
  3. Power Stand
  4. External power amps (e.g. third-party power amps)

Turn off in the reverse order.

Source: Hilmar-at-Bose

Power Strips

There is no technical reason why a power strip, a power cord or any sort of power conditioner should make a difference [to the sound or your system]. Our system (and many others too) are designed to deal with all sorts of AC power fluctuation and have high-quality internal regulators. These regulate with much higher precision than any external device could do anyway, so "conditioning" or "cleaning" up the AC power doesn't make any audible difference whatsoever.

Source: Hilmar-at-Bose

Power Conditioning

We do not recommend external voltage regulators[1] because we found that in many cases they cause more harm than help. The amps and power supplies in the L1 use highly efficient switching technology, Many voltage regulators are not a good fit for this technology since they are simply not fast enough.

Source: Hilmar-at-Bose

We Bose designers do not believe that a power conditioner provides more headroom, dynamics, better sound, or more fidelity for our equipment.

There are a number of technical reasons for this that I won't go into online, but a good way to think of it is that we have already put in all the power conditioning required to make the products sound as good as possible.

Source: Bill-at-Bose ST 09:09, 12 August 2008 (EDT)

Reviewed with L1® Support June 16, 2014 ST 11:27, 16 June 2014 (EDT)

Background Information

The following is from a discussion with MikeZ-at-Bose

The power regulator/supply in the L1 takes in the AC wall voltage, whatever it is, and converts it down to much lower DC voltages to run the preamps, DSP's etc. As long as wall voltage is within the range I quoted earlier (90V-135V), the DC voltages that the preamps and DSP's see do not change. As part of the process of converting from AC to DC the power is also filtered. No matter what happens at the wall, the audio portions just see clean DC power. When the voltage goes outside the bounds, the unit just shuts down gracefully.

That's o.k. I like the engineering talk and thanks for your time. : )

I would love to know more about how it works if you have the time, cuz it sounds like you're telling me that in addition to a mixer section and power amps, the L1 base also houses a full voltage regulator and conditioner?

How does it work? Are you using a step-up transformer to regulate voltage? The reason I ask is because the process of simply converting AC to DC is a pretty common practice. : ) There are also many computer power supplies that use the conversion as a cleaning process, but that doesn't mean that the computer doesn't perform better from clean, consistent power.

My toaster is designed to work within a voltage range, since 110v is never guaranteed from your wall. So, I'm curious because I must just not understand. I wish I knew more about the engineering aspect of it. I can only report the facts of what I (and others) hear. Anyway, If you have the time, or the notion....I would be interested in a more in depth description. : ) Thanks

So first, why do we need power regulation or conditioning anyway?...

I just re-read your post and Im glad you mentioned the toaster! The toaster is like most electrical appliances in the world - it isn't very picky about it's power - and we would never notice the difference in performance. All the toaster does is take wall voltage and feed it to the heating element (the portion that glows red). If the wall voltage dips to 100, the power to the element drops proportionally. The toast will toast maybe ~18% slower in this extreme case. Noise on the AC line would have little effect on the element- the element takes a long time to heat up and cool down compared to the speed of the power changes, so it won't care about momentary dips. For example, if a refrigerator kicked in in a poorly wired house, the power may go down to 80V for a tenth of a second. The temperature of the element probably would not change measurably, and the end product (toast) would definitely not suffer.

With audio equipment, we are using our ears to judge the results. We're going to hear and care about sudden dips and changes in wall voltage, unless we regulate the power.

Digital equipment, like a computer, relies on constant voltage levels inside it's microchips to operate. These voltage levels (usually around 3.3 volts DC, or less) dictate the 'ons' and 'offs' at the heart of these devices. If the voltage goes outside a very narrow range, the digital does *not* degrade it's performance - it just ceases to operate.

The L1 has both analog audio portions (preamps, power amps), and digital portions (ToneMatch EQ's, effects in the T1, etc). Both of these portions rely on regulated, constant power to operate well. In the case of the digital portions, it relies on this constant supply of power to operate at all.

The power needed inside the L1 is DC. The amplifiers need around +/- 30V DC, the preamps need around +/- 18V DC, and the DSP's less than 5V.

How's it work?

The L1 uses a low noise switched-mode power supply. These are very light and efficient. Here's an article on how they work: http://en.wikipedia.org/wiki/Switched-mode_power_supply . In a switched mode supply (or switcher), the DC voltage is created from AC by rapidly switching a transistor on and off. The average of these on and off times, after a lot of filtering, becomes the DC voltage (pictures are in the wikipedia article). Regulation is done by varying the amount of the time the transistor is on and off. The switching occurs very fast, always more than 30,000 times per second. Sometimes much more. Switchers are an abstract concept and there isn't really a good analogy that I can think of for how they work.

For our supplies, there is a lot of extra filtering and tighter than usual regulation to make sure none of the artifacts from the wall power are audible. This is a major part of the product's design, and the focus of a lot of testing.

For some more reading on power supplies in general: http://en.wikipedia.org/wiki/Power_supply

Hope this is helpful and answers your questions


Source: MikeZ-at-Bose