EDIT:
works good for finding reversed AC polarity.
works good for finding reversed Hot/neutral AC polarity.
.
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.
- ...
- 84 posts total
Thank you all for your responses. It’s a big help to me as I’m not an expert on electromagnetism.
@jeffbij although the amp is not grounded, it functions fine with no voltage/charge unless connected to the phono preamp. When connected to phono preamp it predictably becomes dangerous.
@erik_squires as it turns out as others have pointed out, no ground pin was removed and the amp is by design ungrounded. I agree it’s dangerous. Could you elaborate on what an outlet tester would tell me?
@jea48 RR2160 amp has built in DAC and has two coax inputs. One to CD player one to bluesound node. Since this episode I’ve been listening to music off the node without problems. Thank you for pointing out the RR2160 doesn’t have a ground pin. At least one of us is paying attention, I guess. The preamp and amp are plugged into the same single duplex outlet; the TT is plugged into a different single duplex outlet but was OFF when this happened. Could you describe what information I could use a multimeter to obtain? I will get one if it will help diagnose. yes you’re right the preamp was grounded to the tone arm. yes the outlet cover is plastic and the plug in power supply for the photo preamp is plastic. you asked what two metal objects I was connecting. I was connecting the interconnects from preamp OUTPUT to the analog INPUT of the TT. those inputs are near the speaker wire plugs for the right speaker. When I touched the interconnect from the preamp to the amp analog input the second time, there was a large SPARK and even some SMOKE. It created a small crater on the housing of the interconnect. Obviously extremely hazardous. @lynn_olson @jea48 do I need a multimeter, socket tester, or both?
I had an idea which may be totally wrong but I noticed the blue light in the 110LP flickering the last couple months, and it’s connected to the circuit inside the preamp by a wire. Maybe something went wrong with that wire and it shorted to the exterior of the preamp box. It would be easy enough to check by disconnecting that wire, but first I need to get the appropriate equipment. I was going to just get a no contact voltmeter, but it seems maybe I should instead get a multimeter? Let me know what you would advise.
thank you. |
@obarrett You said:
Do you mean that you connected the interconnect cables running FROM the turntable and plugged them into the INPUT connections on the Moon 110LP, and the ground cable from the turntable to the ground stud on the Moon 110LP as well? And then plugged interconnects from the OUTPUT connections on the Moon 110LP to one of the AUDIO IN connections on the Outlaw receiver, correct? ... just trying to get it straight in my head... - Jeff
|
A basic one would tell you if you if the wiring to the outlet was correct and reasonably functional. For instance, the ground wire may be missing or broken, in which case a ground pin on your gear would be useless. Now that I think about it, get a more advanced one so you can see the N-E (neutral to earth) voltage. This will help you see also that the neutral wire is near ground (should be 2V or less).
|
@obarrett Said:
bluesound node Internet provider line into your home? Fiber, Coax cable, other? Are you using WiFi or hard wired Ethernet cable to the bluesound node ? IF hard wired is the cable used a shielded ethernet cable? (Looking for a possible ground path) . (CDP digital out used as a transport) Does the CDP use a grounded power cord?
IMO, that is the way it should be done. With multimeter you will verify the tone arm is not connected, grounded, to the TT EGC. .
I thought you meant unplugging the preamp power supply from the wall outlet you were touching the metal "box" of the preamp with the other hand. Thus my questioning about the wall outlet cover plate. If metal it would be grounded. I was looking for a possible difference of potential, voltage, from the phono preamp metal "box", to ground that caused the electrical shock. You clarified with this.
analog INPUT of the TT. ??? You mean analog input of the RR2160 amp? .
Don’t do any more experimenting using the phono preamp. The normal operating input voltage of the phono preamp is 24Vdc. Power wise just a few watts. That normally will not cause sparks. . From original OP:
That would imply a significant difference of potential, voltage, between the two points. Just a guess you had your fingers of one hand holding the outer ground shell of the interconnect and touched the rear metal panel of the RR2160 amp with the same hand. (In and out points were the finger(s) of the hand.) Sparks? From the outer ground shell of the interconnect plug to the rear panel or outer ground shell of the RCA jack on the RR2160 amp, OR center pin of interconnect cable to RR2160 amp? (Hopefully you were not successful in plugging the interconnect into the Line in RCA jack of the RR2160 amp.) Where is the difference of potential, Voltage, power, coming from? That is where the multi meter comes in. I will instruct you where to use the multimeter. If you do not also buy a plug-in circuit checker I will instruct you, using the multimeter, how to preform the same tests as the circuit tester. Using the multimeter we will verify the RR2160 amp does not have an internal Hot 120V to metal chassis fault. We will try to run tests on all the associated equipment until faulted culprit is found. .
Multimeter... As for checking the 120Vac wall outlet. A multimeter can preform the same tests as a plug-in circuit tester. Buy both if you want. If only buying one, buy a multimeter . |
- 84 posts total