Voltage Regulation / Battery Backup

Hey guys,

So..I've got a Marantz MM7025 that I've had a for a few months now. I love it. The only problem I'm having is from time to time the amp will shut off and I'll see the protect light come on. A few minutes later I'll turn it back on and all appears to be well. Also..this isn't at reference volume or anything like that. It happened last night just watching TV at a reasonable volume level. I should say that this amp is not rated for 4 ohm speakers, but Martin Logan has told me that it should work no problems. Also..I demoed my bosses McIntosh MC7150 and it actually shut off during operation as well, so IMO that rules out speaker loads as the cause of the problem. My AVR (NR1603) never experienced this, but I'm assuming current draw from the amp is quite a bit higher.

I live in a 2 bedroom condo built in 1983. My thinking is that its a power stability problem, but I'm using a Panamax M8-AV that is advertised to monitor for "brownouts" and act accordingly, but as I said earlier its only the amp that is shutting off. Is my thinking still possibly correct? The current demands of the amp exceed the other devices, so only it is affected? I've considered picking up a battery to help regulate the power a little bit, but I'm told that the same batteries that you'd buy to protect your network (which I also have..Cyber Power) are different from those that you would use in your AV rack. Is this accurate? Do I need an "AV grade" battery? Does such a thing even exist? I've seen some of these meant for expensive racks for over a grand..and that definitely isn't what I'm looking for.

Any ideas?

HOla. ML electrostatic speakers are not easy to drive, and perhaps your Marantz circuit protection shuts off, due to the low impedance. Also, many times, when you use a very small guage speaker cable, makes this to happen too. Use a heavier speaker cable, like number 12 gauge. You do not say how long is the run of the speaker's cables from your Marantz to the speakers. If you are not using a heavy gauge cable, many amplifier's power output is drained by the cable, and your Marantz, due to this low impedance from ML, is getting overheated.

Here at this forum, you will find a lot of experienced members that had that problem too, and they will enlightened us with their thoughts about this. Happy listening!

roberto said:

HOla. ML electrostatic speakers are not easy to drive, and perhaps your Marantz circuit protection shuts off, due to the low impedance. Also, many times, when you use a very small guage speaker cable, makes this to happen too. Use a heavier speaker cable, like number 12 gauge. You do not say how long is the run of the speaker's cables from your Marantz to the speakers. If you are not using a heavy gauge cable, many amplifier's power output is drained by the cable, and your Marantz, due to this low impedance from ML, is getting overheated.

Here at this forum, you will find a lot of experienced members that had that problem too, and they will enlightened us with their thoughts about this. Happy listening!

Click to expand...

Sorry...I should have mentioned. I have Motion 40s. Very easy to drive.


That photo is outdated (there is amp on the bottom shelf now) but you see the speaker runs are really short.

Your Marantz is sensing a DC at the speaker's binding posts, or sometimes the bias is out of adjustment probably in one channel, making this to have a lot of heat at the transistors heat sink. Right there, at the heat sink, there are temperature sensors that goes off when there over heated.

Check the speaker's wire for a possible short between them at both ends, speakers and amplifier. This also activates the protection circuit. If everything is OK you might have a faulty Marantz unit.

roberto said:

Your Marantz is sensing a DC at the speaker's binding posts, or sometimes the bias is out of adjustment probably in one channel, making this to have a lot of heat at the transistors heat sink. Right there, at the heat sink, there are temperature sensors that goes off when there over heated.

Check the speaker's wire for a possible short between them at both ends, speakers and amplifier. This also activates the protection circuit. If everything is OK you might have a faulty Marantz unit.

Click to expand...

I decided to make a few adjustments to how the stand was organized for the sake of cleaning up wire hell. I must have had a loose interconnect or something because I'm a week in and no issues.