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
Post removed 
jea48
4,651 posts
 

@obarrett ,

Subwoofer? You keep adding equipment... Does the 120Vac IEC inlet connector on the back of the sub have three prongs? Therein an equipment ground prong? My bet is yes. Correct?

*** Does the CDP use a grounded power cord? Therein the IEC inlet on the back of the CDP has a third prong for the equipment from the wall outlet?

I have been looking for an equipment ground that is grounding the chassis and or signal ground of the RR2160 amp through the outer plug shell ground of an RCA interconnect. If the subwoofer uses the wall outlet equipment grounding that may be the ground. I assume the sub was plugged into the 120vac wall outlet.. It doesn’t matter if the sub is powered on or off. If the cord is connected at both ends the sub chassis is grounded...

The equipment ground was/is the fault circuit path back to the source. That is if the subwoofer chassis is connected to the wall outlet safety equipment ground.

That’s a pretty good size bite out of the outer shell of the RCA plug on the interconnect cable. I didn’t see its’ mate on the RR2160 amp. It has to be there somewhere.

Sometime later today, Friday the 28th, I will work up a testing procedure. It would go a lot quicker if we could respond back and forth Friday night.

 

 

jeffbij
116 posts
 

@obarrett -  Thanks for clarifying on the connections.  I'd take @jea48 up on his offer to work with you directly.  And a nice video on showing how everything is hooked up and what happened.  A picture is worth a 1000 words.

One suggestion that I would make, and please don't take it the wrong way....  You need to cleanup your wiring. I'd also replace those plug-in 2to6 outlet adapters with at least a specifically designed AV power strip or even an old Monster Power HTS series unit from eBay if there is a budget constraint.  Those 2to6 adapters always scare me because they typically not well made and can be overloaded and shorted way to easily.

Also, check the wiring/cabling itself.  I see in the video that you have some stuff coiled up on the floor, etc.  And just to rule it out, make sure you don't have something like a cut in a power cable that has shorted to the interconnects or to one of the chassis. 

Hope you can figure out what happened and that nothing got permanently fried.

- Jeff

 

jea48
4,651 posts
 

@obarrett 

When you receive the multimeter you need to read through the how to use Instruction Manual. Pay close attention to WARNINGS.

MM720 INSTRUCTION MANUAL

To ensure safe operation and service of the meter, follow these instructions. Failure to observe these warnings can result in severe injury or death. 

Page 5

.

Warning or Caution

Read Instructions 

To ensure safe operation and service of this meter, follow all warnings and instructions detailed in this manual.


Risk of Electrical Shock 

Improper use of this meter can lead to risk of electrical shock. Follow all warnings and instructions detailed in this manual      

page 6

.

Pay close attention to pages 5 thru 14.

.

For all the testing you will be preforming the test leads are plugged into the, black lead into the Com (Common) jack and the red lead plug into the red "VΩ" jack.   ("VΩ", Volt / Ohm Jack)  Page 7

DO NOT attempt to measure continuity on a live circuit. 

Page 13.

DO NOT attempt to measure resistance on a live circuit.

Page 14

 

NEVER plug the red test probe lead plug into the  "10A" jack or  "mA/μA" jack when measuring voltages. LIVE circuits. See page 12.
That would create a dead short across the LIVE circuit.

.

devinplombier
455 posts
 

@obarrett 

Odds are that your phono stage's outboard power supply has a short to ground.

Linear power supplies run hot and are generally the first component to fail.

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