Did I just cook my preamp?

This an excerpt from the user guide. May have something to do with it.

Or not.

 

IMPORTANT: A turntable with a functional cartridge MUST be connected to the MOON 110LP prior to connecting the AC power cord, otherwise you may damage your amplifier and/or loudspeakers.

Hey OP,

I just ran upstairs to answer you. I’m not usually an alarmist but it sounds like you have a potentially dangerous situation here.

It seems like 2 things have occurred:

 

1. Equipment has had a malfunction shorting the power supply to the chassis
2. The equipment’s chassis ground is not functioning either by the deliberate removal of the ground pin or a bad outlet.

I strongly encourage you to take this seriously and resolve this. Potential side effects are electrocution or fire.

What may have happened is that the power supply has become shorted to the chassis, hence the burn you received while attaching interconnects. That should _never_ happen. This happens when a short has developed and the normal path to ground (the ground AC pin) is not working correctly. In addition to potentially lethal shocks a fire can also happen as the current is flowing through your interconnects, which are absolutely not designed to do this.

If you have previously removed a ground pin or used a cheater plug, immediately remove the cheater plug and/or get a properly functioning power cord with the ground pin working on both ends.

Otherwise, find a qualified technician to examine your equipment and/or an electrician to inspect your outlets. You may also want to use a cheap AC outlet tester like this one.

Be extremely cautious and use the breakers to disconnect power at the slightest hint of a shock. Also, of course, keep liquids and wet hands away from your equipment and wear insulated shoes while touching it while plugged in.

Thanks for this advice. I agree with what you wrote. I bought the amplifier used and it came with a power cord without a ground. I’m going to immediately replace that power cord with a proper three prong power cord. I think that the preamp developed a short and current was definitely flowing through the interconnects into the amplifier. What a mess.

How the preamp became so suddenly hazardous is beyond me. I can’t rule out the possibility that I connected it to the power when the other end of the TT interconnects wasn’t connected. It’s hard to remember assembly details like that one years later when you’re just moving some equipment around. Nevertheless, that should NEVER cause the dangerous situation that ensued. When I connected a ground wire from the TT to the amplifier after it had been roasted by the preamp, it SPARKED. Very upsetting.

I don’t ignore the possibility that the ungrounded amplifier could be the source of the current, but the amplifier continues to function normally and doesn’t become charged unless connected to the preamp.

@obarrett - I'd have the AMP checked out, inside and out before you do anything. I looked at a picture of the Outlaw RR2160 receiver, and the IEC plug on the back does not have a ground prong.  If that is correct on yours, then 3 pronged power cord isn't going to do anything. Something maybe wrong on the inside of the Outlaw.  Loose wire, someone may have made a modification (to add a ground prong???), who knows what.  It is even possible that the amp's chassis is now hot (power wise).  The fact that you got a spark when connecting the TT/Cartridge's ground wire to the ground on the Outlaw is saying there is some significant voltage on the chassis.

 

How the preamp became so suddenly hazardous is beyond me.

This is exactly why I tell people not to ever remove a ground pin. What happens is, as an example, the amp shorts the chassis to a high voltage, anywhere from imperfect to solidly shorted. That voltage is now on the chassis AND on the signal ground, to some degree. In other words the outer ring of the RCA cable. That current and voltage is now flowing from amp, through IC to other equipment, causing (potentially) a fire on the IC if the current is high enough and damage to other connected equipment.

The problem is complicated by the relatively high resistance of the interconnect ground. They both heat up and prevent the ground pin from forcing a breaker fault, as they should.

What should have happened, normally with a ground pin, is that the amp should have shorted the chassis/ground voltage via the thick ground pin to your outlet, and if the short is strong enough force a breaker or fuse to pop letting you know something happened without an electrocution or fire.

While you are at it, I do recommend you get one of those cheapy ($12) outlet testers to make sure your outlet is also in good shape.

After getting things back into place, I listened to some music using coaxial input before reconnecting the interconnects of the phono stage.

 @obarrett 

??? please explain ??? coaxial input? Source?

To get a spark as well as an electrical shock there had to be a difference of potential, voltage, of a least around 40V to 50V measured between the two points you received the electrical shock. I assume all the equipment is plugged into a single duplex outlet fed from a single circuit breaker in the electrical panel.

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Simaudio Moon 110LP phono preamp. Factory plug in power supply is two blade, no safety ground pin. I assume the power supply is the original.

Outlaw Audio RR2160 amp has only a two prong power inlet connector. No safety ground prong. Unit has the Double D symbol logo on the unit indicating the 120Vac power wiring is double insulated. Chances of a hot bared conductor to chassis fault? Slim to to none.

VPI Classic. Has a 3 prong inlet connector. Safety equipment ground is used.

I wouldn’t think the tone arm would be connected to the AC mains safety equipment ground.

Do you have a multimeter you can use to check for continuity/resistance, as well for voltages? If not buy a descent one. You can pick a descent one for around $50.00.

If you have one or buy one, post back.

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@obarrett Said:

Incredibly, when I was unplugging the phono preamp, I actually got some current from simply touching the exterior of the box.

To receive the electrical shock your body had to have a point of entry and a point of exist. Can you recall what two metal objects you were contacting at the same time? One was the metal case of the 24Vdc fed phono preamp. I assume the plug in power supply (output 24Vdc) for the the phono preamp is plastic. Is the wall duplex outlet cover plate plastic?

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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.

That doesn't sound right. The phono preamp should be grounded to the tone arm, not to the wall AC mains safety equipment ground...

Using a multimeter, this could easily be verified. 

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Safety advice: do not turn on the questionable electronics until repaired, and get a socket tester for your house. They’re not expensive and are worth getting.

The OP should first locate the problem. Was it the phono preamp power supply that caused the problem?

Or was it x or y or z that caused the problem that damaged the phono preamp?

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FYI, in older homes with old two wire branch circuit wiring, a plug-in circuit tester works good for finding reversed AC polarity. They will tell you if there is an OPEN GROUND. What they don’t tell you if the tester says OK is the EGC (Equipment Grounding Conductor) really an EGC that runs back to the electrical panel or is it a Boot Leg EGC created by installing a jumper from the neutral terminal on a duplex receptacle to the EGC terminal screw on the outlet. It will also not tell you if the neutral conductor and EGC conductor are reversed on the outlet.

.

EDIT:

works good for finding reversed AC polarity.

works good for finding reversed Hot/neutral AC polarity.

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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:

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.

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

 

 

 

 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?

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:

RR2160 amp has built in DAC and has two coax inputs. One to CD player one to bluesound node.

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)

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(CDP digital out used as a transport)

Does the CDP use a grounded power cord?

yes you’re right the preamp was grounded to the tone arm.

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.

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Incredibly, when I was unplugging the phono preamp, I actually got some current from simply touching the exterior of the box.

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.

you asked what two metal objects I was connecting. I was connecting the interconnects from preamp OUTPUT to the analog INPUT of the TT.

analog INPUT of the TT. ??? You mean analog input of the RR2160 amp?

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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.

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.

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From original OP:

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.

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.

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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.

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

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@obarrett

Two examples of good multimeters.

 

This is a good multimeter that will last... The extra cost feature of LoZ setting eliminates false phantom AC voltage readings.

Klein Digital Multi-Meter, TRMS Auto-Ranging, Temp, Low Impedance

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This is also a good multimeter. It doesn’t have LoZ though.

Klein 600 Volt Digital Multimeter, TRMS Auto-Ranging, Temp

 

@jea48 , when my old Radio Shack meter failed the drop test and I needed a new one (like immediately to bias my amp) I went to Lowes (because they are super close) and I bought a South Wire.  How do those stack up?  I saw that they had Fluke meters, but for what I thought at the time was an ungodly amount of money.  I could always upgrade to a Klein; I am pretty sure that now Lowes sells them as well.

@immatthewj

Is this the meter you bought?

Compact 3-In-1 CAT IV Digital Multi-Meter

Is this the amp?

Cary V-12; it features a dozen EL34s and each pair has a switch in between them that configures that pair to either triode or ultralinear.

If you are only using the multi-meter to measure DC ma it's probably ok.

https://www.caryaudio.com/wp-content/uploads/2013/06/CAD-280SA-V12.pdf

Just curious what are you setting the DC ma bias at?

 

 

No, @jea48 , it is actually the Southwire "10041N autoranging multimeter."  I use it mostly for DC mA but occasionally I use it for checking continuity and less often for checking AC voltages.  It is not like I am a tech person, but I would like to think that the readings I am taking are close to being accurate.

As far as the bias on my amp, it is currently set at a few hairs (on both sides) under 260 mA.  Without going back and checking, I am about sure the manual says 270 to 300; back at the end of '17 when Cary tech support would still take telephone calls, in some context the subject came up and the tech guy said to shoot for 40 to 50 mA a tube.  (I think the context of that conversation was how to bias it if running less than six tubes per side.)  @decooney told me that when he had his V-12 he liked it set way lower, but when I tried that I didn't think I liked it as well.  Who knows, maybe it was psychological.  on my end.

 

Just curious what are you setting the DC ma bias at?

@jeffbij Yes I’m sorry I misspoke. I was connecting to the RCA input of the amp, not the TT.

 

@jea48 yes wired coax to router, then Ethernet from router to bluesound node. Ethernet is not shielded. Both cables pass close to the interconnects going to/from the preamp through the back of my cabinet. I made a video: https://youtu.be/dPq8B54utCw?si=o6S-uJqUXYGxfJiT.

yes, I meant analog input of my RR2160. Apologies.

spark from outer shell of RCA cable. In video I show exactly where as it left a crater in the metal casing. NOT the center pin of the interconnect.

 

i ordered the Klein tools MM720 you recommend. It should arrive tomorrow. Please tell me what tests I should start with and how to execute them. I’m not going to get a separate outlet tester if it can be achieved using the multimeter. Thanks for all your help.

@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.

 

 

@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

 

@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

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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.

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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.

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@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.

@obarrett

Curiosity killed the cat.

Assuming the subwoofer uses the EGC, (Equipment Grounding Conductor) from the 120V wall outlet,

and assuming the sub amplifier’s circuit ground is connected to the chassis, (high probability),

and therefore the return signal ground in the RCA interconnect cable is connected to the signal ground of the RR2160 amp,

And therefore the circuit signal ground of the RR2160 amp is, (high probability), connected to the chassis, either directly or indirectly, the RR2160 amp is grounded to the 120Vac wall outlet EGC.

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Therefore, the first thing I want you to check is the output voltage of the plug-in SMPS Wall Wart) for the phono preamp.

Here is a photo, I believe, is the same as yours.

plug-in SMPS. 18Vdc output.

The test:

You might want do the test on a kitchen counter top or a table.

mm meter.

Install the two test leads. Black lead in COM jack. Red lead in VΩ jack.

This test will, should, tell if the SMPS power supply has some kind of an internal fault that somehow is passing a high AC mains line voltage to the output of the power supply.

For the test you might want to use a factory OEM three wire grounding type power cord. The center offset ground IEC EGC ground contact will be used to hold the black lead probe tightly in the EGC ground contact. That will free up a hand...

Set the mm to V (volts). V is to the right side of OFF. mm will default to AC volts.

First check the wall receptacle outlet, you will be using, for the correct Hot / neutral AC polarity. At the same time you will be checking checking for an EGC ground.

Insert a test lead probe into each of the two straight slots contacts. You should measure 120Vac nominal.

FYI (If the duplex outlet is a 20A the neutral will have a "T" slot. If a 15A duplex receptacle the neutral contact will be the longer slot of the two parallel slots. Therein the Hot is the shorter of the two.

Next insert a test lead probe in the small slot Hot contact of the receptacle. Insert the other test probe in the ground hole. You may have to move the tip of the probe to one side or the other to make contact to the ground contact. You should measure, read, 120Vac nominal. The same voltage as you measured from Hot to neutral. This shows two things. The hot /neutral wiring AC polarity is correct and an EGC ground is present.

(FYI the reading could be slightly higher due to a loaded VD (Voltage Drop) on the hot and neutral circuit.)

One last test. Measure for voltage from the receptacle neutral contact to the ground contact. (Using a wall duplex receptacle I measured 1.4mV ac.

(Note. On a regular grounding type receptacle the center trim screw that holds on the outlet cover plate is also connected to the EGC ground. You can also use the screw head for the ground connection. Insert probe tip tightly against the straight recessed slot for the screwdriver to make a good electrical contact.)

FYI, use the same method above to check the two wall duplex receptacles that feed your audio system equipment, for the correct hot/neutral polarity and and the EGC is present.

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Finally, testing the plug-in SMPS.

Plug the OEM power cord into the wall 120Vac receptacle outlet. (Outlet has been checked, OK.)

Set the mm to V (volts). mm will default to AC volts.

OEM IEC power cord. Insert one test lead probe in one of the outside female contacts. Insert the other probe in the other outside female contact. You should read around 120Vac, nominal.

Insert one test lead lead probe in the center offset ground contact. Insert the other test probe in one of the outside female contacts.... From Ground to Hot contact you will measure 120Vac nominal.

Leave the test lead probe inserted in the ground contact of the IEC power cord.

Plug in the SMPS into the same duplex outlet as the OEM power cord.

Be careful, the outer sleeve contact of the SMPS power cord connector may be Hot voltage ground.

Next, depending on how much time has elapsed the MM may have to be shut off. Then turn mm selector switch back to "V" (Volts).

Next touch the other test lead probe to the outer sleeve contact of the SMPS output cord power connector. Does the mm meter display a AC voltage? How high of a voltage?

If you measure a high voltage you need to check it’s a real power voltage and not a false phantom voltage.

Remove test lead probe from the SMPS output cord connector. Turn mm selector switch to LoZ setting. (Last setting on right side of off.) Never change the selector switch with lead probes connected to a possible live voltage.)

Check for the high voltage again on the connector sleeve contact.

Also measure for a voltage to the center female contact of the power connector.

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If you did not read, measure, high voltage, or any voltage... Question... Is the SMPS 120Vac plug in blades the same width or is one wider than the other? Therein polarized. If both blades are the same reverse the SMPS 180 degrees in the receptacle and preform the test for high voltage again.

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If still there is no voltage readings, you should then check the output DC voltage of the SMPS to make sure it is working properly.

Remove test lead probe from the ground contact of OEM IEC power cord.

Test;

Set MM selector switch to "V" (volts)

Press the SEL button once to switch to DC volts. mm should display V DC.

Voltage test. 18Vdc female connector. Without touching the metal probes with your fingers... Touch, contact, the RED lead probe to the center female contact, of the power connector and touch the BLACK lead probe to the outer metal sleeve of the connector, both at the same time. You should read + 18Vdc nominal. If you do not read +18Vdc make sure you a making a good contact to the connector.

You can Also use the LoZ setting as well. Rotate the selector switch to LoZ. Press SEL button. mm should display V DC. Red lead probe to center contact. Black lead probe to outer sleeve contact on power connector.

FYI the outer sleeve electrical contact is B- negative of the DC power supply. It also should be circuit ground of the power supply and Phono preamp when connected to the preamp.

If it does not read +18Vdc? or the meter reading is + - + - + - + repeatedly 18V? Or maybe the mm is reading a higher voltage??? Note what you are seeing.

Post back the results of the testing.

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I will test now following your instructions and report back. The subwoofer plug into the wall has three prongs but when it plugs into the subwoofer it has only two. So it’s not grounded either. I will be around for the next few hours and will send messages as I proceed through your instructions. Thanks so much.

EDIT:

Be careful, the outer sleeve contact of the SMPS power cord connector may be Hot voltage ground.

Should read:

Be careful, the outer sleeve contact of the SMPS power cord connector may be a Hot voltage to ground.

EDIT:

Next, depending on how much time has elapsed the MM may have to be shut off. 

Then turn mm selector switch back to "V" (Volts).

Should read:

Next, depending on how much time has elapsed the MM may have turned itself off.  Reset .  Turn the selector switch to off, then turn to "V".

 

The CDP appears to be grounded with three pins and the power cord has three prongs. The amp is placed on top of the cdp so they are touching.

The CDP appears to be grounded with three pins and the power cord has three prongs. The amp is placed on top of the cdp so they are touching.

OK ...

@obarrett

Hopefully you can understand my long above post. Looks like I should have proof read it a couple of times after posting it. I spotted a few double words here and there.

I corrected a couple of poorly worded sentences in my post above. Read through the Long post... I will check your thread occasionally tonight for any posted questions you may have.

I watched your video a couple of times again today. I can’t explain why the SMPS could pass an AC mains voltage to the phono preamp, You wouldn’t think it could... But, you said in the video you received an electrical shock touching the metal enclosure of the preamp. The power supply DC B-, and circuit signal ground, is connected to the preamp metal enclosure, directly or indirectly. If not the enclosure would act as an antenna.

 

I did your test from your long post.

wall:

hot neutral 121.7V

hot ground: 122.0V

Neutral ground: 0.285V

 

OEM ITC:

Two females: 121.3V

female ground: 121.7V

 

SMPS (one lead in ground of OEM ITC, the other on the sleeve contact of the SMPS):

48V on V

0.13V on LoZ

thoughts?

 

SMPS (red lead center, black on sleeve):

18.5V on B

0L and it beeps on LoZ

 

Note: this wasn’t using the outlet where everything is currently plugged in. I used a spare outlet. I can test the outlets where things are plugged in too.

 

and to elaborate: yes I felt current on the enclosure of the preamp. I also felt current, I believe, on the enclosure of the amp at some point. And when I connected the tone arm ground cable to the amp ground (the amp has a built in phono stage), there was also a spark. I believe current was flowing through the interconnects between phono preamp and amp, but i don’t know the source. But since all this I’ve listened to about 3 hours of music using the amp with no issues whatsoever (phono disconnected of course).

I just tried an additional test.

I plugged in the preamp to the wall using its SMPS.the blue light went on, off, on, off four times getting fainter then went off.

I plugged the black lead into the ground of the OEM IEC power cable. I put the MM on V. Red lead on any one of the four RCA inputs/outputs of phono stage. Same reading as in the SMPS: 48V, but when I switch to LoZ, drops to 0.128V.

 

i then unplugged the phono, connected it to TT via RCA Input on phono, plugged in again. Measured 49V with red lead on the shield of the interconnect plugged into the R input of the phono, which dropped to 0.14V on LoZ 

i then unplugged the phono, connected it to TT via RCA Input on phono, plugged in again. Measured 49V with red lead on the shield of the interconnect plugged into the R input of the phono, which dropped to 0.14V on LoZ

I would NOT connect the input or output jacks of phono preamp to anything .

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SMPS (one lead in ground of OEM ITC, the other on the sleeve contact of the SMPS):

48V on V

0.13V on LoZ

thoughts?

48V AC on V Might not be real power.

0.13V on LoZ real power .... ???

Thinking on this one.

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SMPS (red lead center, black on sleeve):

18.5V on B

0L and it beeps on LoZ

18.5Vdc on V correct?

0L and it beeps on LoZ. I may have read the instruction manual wrong. LoZ may only be for AC voltage.

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I can test the outlets where things are plugged in too.

Yes, check them.

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and to elaborate: yes I felt current on the enclosure of the preamp. I also felt current, I believe, on the enclosure of the amp at some point. And when I connected the tone arm ground cable to the amp ground (the amp has a built in phono stage), there was also a spark.

Was the SMPS unplugged from the 120Vac wall outlet or the power cable from the SMPS disconnected from the phono preamp? Preamp was dead?

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I believe current was flowing through the interconnects between phono preamp and amp,

Yes agree. But, my understanding is the SMPS was feeding power to the phono preamp at the time. Correct?

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But since all this I’ve listened to about 3 hours of music using the amp with no issues whatsoever (phono disconnected of course).

Did you verify this question of mine on 03-28-2025 at 12:33am ?

@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?

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I think I messed up on the DC measurements, i think they were AC. so let me try again:

SMPS (one lead in ground of OEM ITC, the other on the sleeve contact of the SMPS):
0.6 mV DC on V

0.0 mV DC on LoZ

SMPS (red lead center, black on sleeve):
18.15 V DC on V

18 V DC on LoZ
 

 

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?

Yes I verified your question about subwoofer in earlier comment today. The subwoofer pins are only two even though the power cord has three prongs. So I assume it’s ungrounded. But note the CDP is grounded and the amp is sitting on top of it and connected via coaxial cable.

Was the SMPS unplugged from the 120Vac wall outlet or the power cable from the SMPS disconnected from the phono preamp? Preamp was dead?

I believe it was plugged into but I’m not confident on this. But moreover I was trying to connect the interconnects; at some point they were connected, then they were disconnected. So when I felt current on the enclosure of the amp I do not know what was connected to what.

Yes agree. But, my understanding is the SMPS was feeding power to the phono preamp at the time. Correct?

yes with 90% confidence.

I tested the outlets where things were plugged in. The hot/neutral is reversed. So the hot is the longer left slot, the neutral is the shorter slot on the right. The ground appears to be functioning.

@obarrett Said:

I think I messed up on the DC measurements, i think they were AC. so let me try again:

SMPS (one lead in ground of OEM ITC, the other on the sleeve contact of the SMPS):
0.6 mV DC on V

0.0 mV DC on LoZ

SMPS (red lead center, black on sleeve):
18.15 V DC on V

18 V DC on LoZ

SMPS (one lead in ground of the OEM IEC connector of the power cord , the other on the sleeve contact of the SMPS):
0.6 mV DC on V

0.0 mV DC on LoZ

Multi-meter should have been set to AC voltage not DC. I am looking for AC mains voltage on the SMPS output power cord connector. The measurements would be good if only AC measurements.

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SMPS (red lead center, black on sleeve):
18.15 V DC on V

18 V DC on LoZ

This is correct. Voltage looks good.

That doesn’t mean there is not a problem with the preamp. I believe there is. The Blue power light maybe saying there is.

Again, I would NOT connect the input or output of the preamp to any equipment.

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Ok I did AC again and verified the previous numbers. 

SMPS (one lead in ground of OEM ITC, the other on the sleeve contact of the SMPS):
48.7 V AC on V

0.125 V AC on LoZ

@obarrett Said:

Yes I verified your question about subwoofer in earlier comment today. The subwoofer pins are only two even though the power cord has three prongs. So I assume it’s ungrounded. But note the CDP is grounded and the amp is sitting on top of it and connected via coaxial cable.

Yes the sup amp is ungrounded. AC power wiring in the sub amplifier is double insulated.

So where was the spark fault current path? What is the source.

No doubt there is a difference of potential, voltage, between the output of the phono preamp and the RR2160 amp signal ground, (outer shell) of the analog input jacks.

Saturday, check for voltage from the outer shell of the output RCA jack of the phono preamp to the outer shell of the analog input RCA jack on the RR2160 amp.

Should of done that to begin with...

Both units powered on.

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I think we are back to square one.

When you get a chance check the wall outlets the equipment plugs into for proper Hot / Neutral polarity and for equipment ground. At least you will be able to check them off your list.

I’m calling it a night.

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@obarrett

I don’t remember reading a post where you responded to this.

If you did not read, measure, high voltage, or any voltage... Question... Is the SMPS 120Vac plug in blades the same width or is one wider than the other? Therein polarized. If both blades are the same reverse the SMPS 180 degrees in the receptacle and perform the test for high voltage again.

That is from the long winding thread I posted yesterday. 03-28-2025 at 06:22pm

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One other thing I didn’t think about yesterday. The tests for the SMPS I had you do for checking for AC mains high voltage on the output side of SMPS were unloaded.

I don’t know what I was thinking yesterday... I should of had you do the tests with the phono preamp connected to the SMPS. Therein the connected load. Likely a defective connected load that might be overloading the SMPS. A real world test...

Probably also should have had you use the wall outlet that the SMPS is normally plugged into. IF, one of the blades is not polarized, therein it could be plugged in either way, it would be plugged in the direction that caused the electrical spark fault event.

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IF you want to try the test again.

Test procedure is a little different than yesterday.

You will still use the OEM 3 wire power cord to connect one of the mm test lead probes to the wall EGC. ( an extension of the probe lead)

1) Set up for the test.

Before the SMPS output power cord connector is plugged into the phono preamp.

Connect an IC (interconnect cable) into one of the RCA output jacks on the preamp. Extend the other end of the IC so it will be easy for you to touch the other test lead probe of the mm to the outer ground shell of the IC RCA plug.

2) insert the mm black test lead probe into the female EGC ground contact of the plugged in OEM power cord.

3) Set mm to "V". (mm will default to V AC.)

4) Plug SMPS output power cord connector into phono preamp. (Blue light starts doing its’ thing. Preamp has DC power. SMPS has a load on its’ output)

5) Touch mm test lead probe to the outer ground shell of the IC RCA plug.

What voltage is measured, displayed, on the mm? No need to check for LoZ voltage. The connected load of the preamp is more than enough load. LoZ would only add a small additional load.

6) Check again for a voltage reading after the blue light on the front of the preamp is no longer lit for any difference of voltage measured.

7) Just to cover all the bases... Repeat the test measuring for DC voltage. You probably should let the phono preamp do a reset by disconnecting the SMPS power cord plug from the preamp. Just trying to cover all the bases.

 

Post back your results.

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At some point i was going to buy an outlaw amp but I read a thread that a few people said it caught on fire I would not plug that back in .I don't rember it being an audiogon thread.this could be destructive to all your equipment.be careful.

In looking at the forums alot of the outlaw amps had a ground loop hum and people were going from 3 to 2 prong bypassing the ground.as stated above this is frowned on.hope you get this fixed.there are alot of smart people on here some are electric engineers.  Good luck and make sure you have an observer that can throw the breaker off or some surge protector that can trip.when we built our hospital the young apprentice electrician got fried on the roof .we could not save him be careful.

@mark200mph

I could be wrong, ( the amp hasn’t been checked out yet) but I think the phono preamp is the problem.

I base that on this resent post from the OP. 03-28-2025 at 08:52pm

But since all this I’ve listened to about 3 hours of music using the amp with no issues whatsoever (phono disconnected of course).

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He also posted the same thing earlier in the thread. 03-26-2025 at 10:29pm

@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.

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Hope you get it fixed and can get back to music therapy

Saturday, check for voltage from the outer shell of the output RCA jack of the phono preamp to the outer shell of the analog input RCA jack on the RR2160 amp.

Should of done that to begin with...

Both units powered on.

5.5Vac on V

0.02Vac on LoZ

When you get a chance check the wall outlets the equipment plugs into for proper Hot / Neutral polarity and for equipment ground. At least you will be able to check them off your list.

I sent a lot of messages last night so perhaps you missed:

I tested the outlets where things were plugged in. The hot/neutral is reversed. So the hot is the longer left slot, the neutral is the shorter slot on the right. The ground appears to be functioning.

Explicitly, this means when I’m on V or LoZ and I go into hot/neutral I get 120Vac. When I go neutral/ground I get close to zero, and when I go neutral/hot I get ~120Vac. However, hot/neutral is reversed.

i don’t think it matters but when I plug one lead of MM into ECG and the other isn’t connected to anything I get 5V on V but it disappears of course on LoZ.

Question... Is the SMPS 120Vac plug in blades the same width or is one wider than the other? Therein polarized. If both blades are the same reverse the SMPS 180 degrees in the receptacle and perform the test for high voltage again.

the blades are the same width. For the following test I plugged the SMPS into the wall in the same configuration as it was in when the incident occurred.

I don’t know what I was thinking yesterday... I should of had you do the tests with the phono preamp connected to the SMPS. Therein the connected load. Likely a defective connected load that might be overloading the SMPS. A real world test...

ok I did this test following your 7 instructions and got the following readings:

52.5Vac on V

0.16Vac on LoZ

i know you said LoZ not necessary but I did it and again the voltage disappeared.

0 on DC on V and LoZ (I looked into ghost voltage and it seems like a purely AC phenomenon).

i was watching the blue light on the 110lp as i was doing this test and it was blinking continually. I made a video: https://youtu.be/Dcaxu_ZM6VQ?si=sj70-NxTUOHN3noQ. The blinking did NOT fade away but kept going like this faintly.

I remember last weekend when I had the preamp connected to the amp’s analog 1 input and I listened, I heard a ‘bump’ paced exactly the same as this blue light’s blink. This was as a record was playing and the preamp was connected to the TT. I heard no music just this gentle regular bump.

 

I’m starting to think neither component (amp or preamp) is behaving evilly on its own (although the preamp seems clearly broken), but only together there is a toxic combination. Note, I used these components together fruitfully for the last 3 or 4 years. It was only when I moved them last weekend that disaster struck. It’s also conceivable to me that the preamp was dangerous but now some circuit is shot and it’s not dangerous anymore. I’d also like to test connecting something else to the RCA input on the amp but I’m not sure I have anything I can test. Maybe my TV. As mentioned I did connect the TT directly to the phono stage of the amp last weekend and it did function normally, just was unlistenable (because of how bad the integrated phono stage is).

 

I’m obviously leery of connecting them again but if there’s some way to do so safely I might be willing to try. Thanks for all your help.

 

and yes, I’ve been listening to music off the amp using the node (am doing so right now) and it sounds great. (Hariprasad Chaurasia today.)

 

one more remark: when I was trying to connect the IC from the preamp out to the amp analog 1 input last weekend, the whole general area of the rear of the amp felt dangerous. It wasn’t just the rca plug. It might have also included the speaker wire which is securely seated in the amp. On this point, you saw the crater on the IC exterior in my video but I’ve been unable to see any corresponding damage to the amp. I just looked closely. It almost seemed like the spark jumped from the air and landed on the IC. I don’t know if this is possible.

 

@mark200mph thank you. Fortunately I can still listen to music over digital and that is what’s keeping me sane.

@obarrett Said:

I will answer this first.

I’m obviously leery of connecting them again but if there’s some way to do so safely I might be willing to try. Thanks for all your help.

NO, I wouldn't if it was my equipment.

I haven't mentioned it yet. You may have damaged the analog L & R  input circuitry in the RR2160 amp. The pair of RCA jacks you plugged the ICs into from the phono preamp.

I haven't mentioned trying to connect a different source to any analog inputs on the amp as yet. You don't know yet what what is causing the problem.

I will go back to you previous post I was reading and respond to it.

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I haven’t mentioned it yet. You may have damaged the analog L & R input circuitry in the RR2160 amp. The pair of RCA jacks you plugged the ICs into from the phono preamp.

This wouldn’t be a big deal if the three other RCA inputs still worked. Last weekend I connected the preamp to analog input 4 on the amp and it made the same soft bump sound. I just remembered the blue sound node also has an integrated DAC and RCA out. So if I don’t mind risking frying it I could try connecting it. Ideally I should find something cheaper, maybe my TV (which is old and I don’t use). I’ll check if it has RCA out when I get home.