2. amps-preamps
  3. 193768-203308

Did I just cook my preamp?

I have a Simaudio Moon 110LP phone preamp amplifying a Dynavector 20X2L cartridge on a VPI Classic. It feeds in to an Outlaw Audio RR2160 amp which drives Magnepan LRS speakers.
 

I recently moved and two months in I realized my speaker placement wasn’t quite right, so today I reorganized my listening room. This involved unplugging some power cables but I kept most of the interconnects in place. I did have to disconnect the phone stage from the amplifier.

 

After getting things back into place, I listened to some music using coaxial input before reconnecting the interconnects of the phono stage. When I tried to, I actually got some electric current that burned my hand slightly. This came from the back of the amplifier. I made sure everything was unplugged and tried again - this time a spark and smoke from the interconnect making contact to the back of the amplifier.

 

I’m so confused why this would happen, but eventually I did get everything connected. Now the output from the phono stage is just a bump every 1 second. It doesn’t amplify the signal from the TT.

 

My amplifier has a built in phono stage and using this I was able to verify that the turntable is still producing a signal. The built in phono stage sounds terrible, however, as thin and flat as paper. It is music, however.

 

When I connect the phono stage to the power, the blue light on the front illuminates for a moment and then goes dark.

 

Incredibly, when I was unplugging the phono preamp, I actually got some current from simply touching the exterior of the box. Something is seriously wrong and dangerous with my setup, and this box was grounded to the turntable with a ground cable, which was connected to the outlet with a three prong cable with ground.

 

Has anyone experienced anything like this before? I will email Simaudio and see if they’ll repair it. I’m also taking recommendations for replacements. I liked the 110LP and maybe will just replace with the 110LPV2.

obarrett
jea48
4,709 posts
 

@obarrett 

Here is a photo of an old 3 wire rubber/cloth covered wire, steel armored BX cable.

https://i.sstatic.net/pvjp6.jpg

I assume the outlet box that is now blanked off was the Hot 120Vac ground contact duplex receptacle outlet. I hope the electrician taped off or put wire nuts on the two conductors before he blanked off the outlet box. The outlet was the end of a branch circuit with several other wall outlets, and more than likely ceiling light fixture(s) a head of it.

I would suggest you buy this pair of voltage testers and check all the rest of the wall outlets in your apartment.

https://www.homedepot.com/p/Klein-Tools-Digital-Non-Contact-Voltage-and-GFCI-Receptacle-Test-Kit-NCVT1PKIT/323310181?source=shoppingads&locale=en-US&gStoreCode=2115&gQT=1

Use the non contact voltage tester to check for a Hot 120Vac ground contact. Any of those outlets are a possible electrical shock hazard. Put a piece of tape over the outlet so you will remember not to use it/them.

You might consider something like this to plug a power strip(s) into to feed all of your audio equipment. Feed everything from one duplex receptacle wall outlet. The total combined load amps of all the connected audio equipment is around 3 or 4 amps.

https://www.homedepot.com/b/Electrical-Electrical-Cords-Extension-Cords-GFCI-Plugs/GFCI-Outlets/N-5yc1vZcgerZ1z0p5yb

.

erik_squires
16,708 posts
 

Just a gentle reminder that you are allowed to use  GFCI outlet where there is no real ground.  If you have an old house and want to connect 3 prong outlets this is the only safe way besides actually getting a live ground.

Not ideal but much better than using a 3 prong outlet to fake it.

 

jea48
4,709 posts
 

https://www.homedepot.com/b/Electrical-Electrical-Cords-Extension-Cords-GFCI-Plugs/GFCI-Outlets/N-5yc1vZcgerZ1z0p5yb

FWIW.

The OP can not take the chance of changing the wall outlet to a GFCI duplex outlet.   No way...

The OP could lose the power to the outlet just like the dead one that is now blanked off.

There is a very good chance the outlet is used as a feed through box. Circuit in,  circuit out. Four old rubber cloth covered wires. Chances of moving the old  conductors around, removing the old outlet, and wiring the new GFCI outlet without the old brittle insulation falling off at the steel cable support bracket or breaking falling off the wires at the BX steel armor are slim to none. Or the wires just breaking off at the support bracket from disturbing them.

Not only the outlet the electrician in trying to install the GFCI outlet in, how many other outlets could/will lose power in the process?

Not necessarily a problem, a box extension would need to be installed for the GFCI outlet because of the shallow depth of the switch box.

That’s why I suggested a plug-in type 15 amp GFCI.    

 

obarrett OP
28 posts
 

Thanks for explaining all this to me, Jim, it’s much clearer to me now. I understand what you’re saying about the neutral wire being broken when the outlet was taken out of the wall. I think everything else you say is accurate to what I have observed.

 

The suggestion of using a GFCI cord seems smart to me. for now I have everything plugged into one outlet, which does not have the reverse polarity. I also got ahold of an old APC power conditioner, although that does not solve my grounding problems.

 

The idea of using a non-contact voltmeter to check for other hot ground seems like a good idea. Thank you.

obarrett OP
28 posts
 

P.S. I replaced the 110LP today and everything is sounding great.

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