Surge Suppression - to use or not to use


I am looking for a particular tech note that was written regarding this but can't put my hand on it at this time. So, this is from memory...

In a word, yes, it will affect the performance of the amplifier or ANY (other manufacturers included) amplifier that uses power factor correction in their amp power topology.

The amplifier pulls current from the wall using a larger "slice" of the sine wave than a normal Class A amplifier for example. The Power conditioner detects this and thinks that it is a problem with the device's AC load and attempts to "Protect" it and limits the current which affects the amplifier.

When PowerMatch first came out, I had several contractors that commented that our amp did not seem to have as much output and drive as they thought it had during our demos or in another installation. When we followed up with them, we discovered that there was a power conditioner in the rack and the amplifier was plugged into it. When they bypassed it, the issue went away.

It is my understanding that a surge suppressor does not affect the amplifier in the same way. I am sure that if I am incorrect, I will be schooled appropriately <smile>

Hope this helps - when I find the document that we issued as a tech note, I will pass it on to you....


Hi Steve,

Bruce and I share a common limitation - a great memory for some of the more practical high points of our technologies, but the occasional inability to find the documentation.  It exists ... somewhere ... in support of Bruce's commentary and mine here.  But after a number of years with Bose, our back-up hard drives get more and more difficult to navigate.

In an email a few years ago responding to this specific issue, one of our product development team engineers wrote the following to one of our colleagues.  Perhaps his explanation will help you as much as it helped me.  I have edited out the name of the power conditioner manufacturer (it is irrelevant to the topic):

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“[The Bose product development team] has done some experimenting in the lab with a PM8500 and [one of the most common] 20A line conditioners.  [The team] couldn’t find any instability or other anomalies related to [this particular line conditioner]. But we still don’t recommend their use with PowerMatch – here’s why:

  1. The one effect that the Furman had was to add a significant amount of impedance to the power source.  During a period of very large peak power demand, this can add an additional 7-9V of drop in the line voltage.  Since a PM8500 uses about 45ARMS (@120V) when it’s delivering its rated 4kW, drop in the supply line can be a significant problem.
  2. The PowerMatch amps are quite well protected against most line conditions, surges, etc.  A line conditioner (as opposed to regulator) can’t provide any help for brown-outs; in fact they exacerbate that problem due to the additional line drop. 

Those are the main reasons we still don’t recommend Line conditioners.  As far as a generator goes, the main issue would probably be similar – How much does the line voltage drop if there’s a large peak in the audio?  We’ve tweaked the amps so they’ll actually deliver a significant amount of power (not full rated power) down to about 75V on the line.  Going below that will cause the amp to shut down.  A PM8500 will run at a continuous power drain of about 1,800W  (15A @ 120V), but it can still draw bursts of ~5kW.  Can the generator deal with that?  I will say that most systems won’t hit those power levels, but a subwoofer amp in a large system might...”

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Best regards,




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