I wasn't suggesting getting rid of the preamp, just swapping it out for another identical preamp, both to see if the hum is still present and if not to discuss purchase with Berning. No more suggestions from this quarter
Living with unsolvable hum - Any audio detectives out there?
For over a year I have put up with a hum in my system, coming through the speakers (not chassis hum). I cannot make it go away. It seems to be related to the preamp because it stops when I replace the preamp. But I had my local tech hook up the preamp on his bench and it is quiet as a mouse. I've also corresponded with its designer, David Berning, who has been very responsive and helpful. But no luck solving it. I thought it may be related to the separate power supply's umbilical but David Berning said likely not. Earlier this year I even bought a star grounding component from Granite Audio and connected everything to it. Didn't work. After trying everything the engineer at Granite could think of (he was great), he was stumped too. These people have forgotten more than I'll ever know about the subject, so I gave up at that point and just lived with it. I had also tried everything they and a few knowledgeable friends have suggested (see below). But now I would like to take another swing at solving it. Any ideas? What kills me is that now I can't recall when it started, which would be very helpful to diagnose. The system sounds as good as I've ever had it now, and I LOVE the Berning preamp. So replacing it or other major components is not an attractive proposition for me.
For any intrepid detectives, here are the facts:
- Hum is typical 60 cycle sound- both channels equal volume of hum- loud enough to hear at the listening position, but just barely. Quite noticeable when standing at the rack.
- Hums with any source, not volume dependent, still hums with no source components attached (I even tried unplugged them from the wall too). But the hum stops if preamp is disconnected from amps.
- System plugs into a dedicated 20 amp line with eight plugs. Nothing else is on this circuit except my audio system. I had an electrician verify and tighten all the ground connections. The service is a relatively new 200 amp service. The electrician tested and found no ground issues or noise in the dedicated line.
- Tried shutting down all breakers in the house except my dedicated audio line. No effect, surprisingly. I had high hopes for that one!
- Tried cheater plug on everything including the preamp. No effect.
- Tried different interconnects between pre and power amps... No effect.
- Replaced all linestage tubes. No effect.
- Moved components around, moved the power supply, even used long interconnects to move the preamp three feet in front of the rack. No effect.
- Tried an extension cord to plug the preamp into a different AC circuit. No effect.
-The only thing I know of that could try, but have not tried, is replacing the power supply tubes, but I didn't bother because on the bench it made no noise for my tech.
My system:
- Power: Temporarily I'm using a Shunyata T6000 distributor (the hum existed prior to this, and the Shunyata didn't solve it). All Cardas Golden Ref or Golden power cords, except T6000 is plugged into the wall with Shunyata Sigma HC cord.
Analog: Koetsu Rosewood Signature Platinum, Jelco TK-850, Cardas Golden Cross phono cable
Digital: CEC transport and Audio Logic DAC, Golden Cross interconnect.
Preamp: Custom Berning Octal tube preamp with separate tube rectified switching power supply, built-in Jensen transformer MC stage at 24x gain (on the high side, I know, but it sounds amazing compared to other winding options)
-Power amps: Quicksilver v4 monos with KT150 tubes
-Two REL G2 subs (hum existed before them, and persists when they are disconnected and unplugged)
Somehow the interaction between the preamp and other components seems to be creating the problem. Source components don't seem to matter, but amps are Quicksilver v4 monos. Speakers are Verity Audio Parsifals. Interconnects, speaker cables and power cables are Cardas Golden Cross.
Speakers: Verity Audio Parsifal Encores. No surround sound or home theater.
For any intrepid detectives, here are the facts:
- Hum is typical 60 cycle sound- both channels equal volume of hum- loud enough to hear at the listening position, but just barely. Quite noticeable when standing at the rack.
- Hums with any source, not volume dependent, still hums with no source components attached (I even tried unplugged them from the wall too). But the hum stops if preamp is disconnected from amps.
- System plugs into a dedicated 20 amp line with eight plugs. Nothing else is on this circuit except my audio system. I had an electrician verify and tighten all the ground connections. The service is a relatively new 200 amp service. The electrician tested and found no ground issues or noise in the dedicated line.
- Tried shutting down all breakers in the house except my dedicated audio line. No effect, surprisingly. I had high hopes for that one!
- Tried cheater plug on everything including the preamp. No effect.
- Tried different interconnects between pre and power amps... No effect.
- Replaced all linestage tubes. No effect.
- Moved components around, moved the power supply, even used long interconnects to move the preamp three feet in front of the rack. No effect.
- Tried an extension cord to plug the preamp into a different AC circuit. No effect.
-The only thing I know of that could try, but have not tried, is replacing the power supply tubes, but I didn't bother because on the bench it made no noise for my tech.
My system:
- Power: Temporarily I'm using a Shunyata T6000 distributor (the hum existed prior to this, and the Shunyata didn't solve it). All Cardas Golden Ref or Golden power cords, except T6000 is plugged into the wall with Shunyata Sigma HC cord.
Analog: Koetsu Rosewood Signature Platinum, Jelco TK-850, Cardas Golden Cross phono cable
Digital: CEC transport and Audio Logic DAC, Golden Cross interconnect.
Preamp: Custom Berning Octal tube preamp with separate tube rectified switching power supply, built-in Jensen transformer MC stage at 24x gain (on the high side, I know, but it sounds amazing compared to other winding options)
-Power amps: Quicksilver v4 monos with KT150 tubes
-Two REL G2 subs (hum existed before them, and persists when they are disconnected and unplugged)
Somehow the interaction between the preamp and other components seems to be creating the problem. Source components don't seem to matter, but amps are Quicksilver v4 monos. Speakers are Verity Audio Parsifals. Interconnects, speaker cables and power cables are Cardas Golden Cross.
Speakers: Verity Audio Parsifal Encores. No surround sound or home theater.
82 responses Add your response
Did you try not plugging pre into the Shunyata T6000? Apropos of nothing, with my gear, I found a Fuhrman reference to be a sound diminisher and switched to another power conditioner. If you hold the pre amp and the hum goes away or decreases there’s proof positive of a ground issue as you are acting as a ground. Have you ever given your pre amp a light to medium smack/tap? Seriously. |
Could it be something else interfering with your pre amp like a nearby light? Something metallic? Proximity to another component? Did you blow out/clean pre amp especially all tube connections? Before any more hair pulling could you get a loaner pre amp just like the one you have and try that? Did you pray to St. Jude? |
@montaldo you posted... - Hums with any source, not volume dependent, still hums with no source components attached (I even tried unplugged them from the wall too). But the hum stops if preamp is disconnected from amps.Since the hum appears with the preamp only connected - try this... Take a piece of wire with a small piece of insulation trimmed at each end - touch one end to the neutral collar of any RCA or XLR jack - touch the other end to a ground point IF the hum disappears then the neutral side of the pre-amp is not at ZERO volts. This is common with components that have a two pin mains plug or a wal-wart power supply. A SOLUTION... - build a ground lead by attaching a piece of wire to the GROUND PIN ONLY of a mains plug - attach the other end to the NEUTRAL ONLY of an RCA or XLR plug of the pre-amp - plug the RCA/XLR end into any unused socket - plug the mains plug into any outlet Hope that helps - Steve |
It’s the Preamp as you already know. Both channels is a clue, perhaps a good one. Some more investigation. Is the hum present at both low level inputs and high level inputs? Connect only 1 high level source, one input at a time? Is it present at each input? repeat with low level inputs. Learn anything? Have another system, i.e. office, shop, to move the preamp into? Good? If good, then there is some unholy combination of interconnects/speaker wires/crossover component. If ok on the other system, you can in good faith sell it to someone who lives in Lake Woes Be Gone ........................... My McIntosh SS Preamp C28 had a faint hum on low level inputs only. I bought a box, sent it to McIntosh factory, it came back ’fixed’. Same low level hum, low level inputs only. How the heck can I sell it knowing that? I took it apart, gave the evil eye to the internal ground connection to the chassis. Unsoldered it, stripped end of wire, removed paint from the area, replaced with bolt and lock washer. Gone. ............................... Days gone by, FM antennas were like the plague. |
Most Variacs are not isolated. <<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>. I didn’t mean to imply that, JUST this is an option, a single coil, autoformer.. It is a great trouble shooting device, in lue of isolation.. cheaters, GF isolators, and a few others... It will serve MY purpose.. The more you type, the more I learn..about you.. You related to Donald Trump. by chance? Watch and LEARN... let the mechanic give it a shot. I’m the one doing the bragging, ALL right.. LOL Let’s see if I can HELP... If not pick it apart AFTER that, ay... Just saying. OP... excuse me, I had to make an adjustment, left cheek sneak? Romp.. Time to feed the chickens.. Regards |
Oh buddy, your Spidey Senses are tingling are they?... LOL It’s always what you haven’t done... the way of the mechanic... Worse yet, or done WELL and correct..No reason to doubt your own work. No reason NOT to recheck others. I NEVER trust anyone... Brothers in all, that is the difference between a professional, and (NOT). Don’t assume stuff... Especially trouble shooting.. CRC, Check RE Check!! You’ll get it figured out EVEN if you don’t stop the noise... BUT so you know, I’ve always figured out what caused the noise. EVEN if the person didn’t want to, OR couldn’t afford to fix it.. The issue for me is simple. I WON’T put up with it.. there is a difference... My stuff is BLACK. Almost spooky it’s so quiet.. Valve, SS, Class A, AB, D. Mix and match. Quiet a church mouse. I have a buddy that says he doesn’t like it... YUP... Too quiet.. :-) That’s quiet... Happy Happy |
You have already tried many things and gotten a lot of good advice so I will offer a few short items. First, did David Berning offer you another pre amp? For starters, it would be interesting to see if the problem continues with an identical model. If it doesn’t, then you could make some sort of deal with him about swapping your current one for the replacement. Second, I don’t know what a cheater plug is, but I have had a few hum problems many years ago. One was solved by a PSAudio device that turned hum into a light (nightlight). It was the size of a match box, attached to the power strip, and the first hum problem that I had disappeared completely. A few years later with changing components a nastier hum wasn’t defeated by this some I bought something called a “Humbuster” from Sweetwater. This required plugging the problem component in to the humbuster and then plugging that into the power strip and was entirely successful. I couldn’t tell if the SQ from the component in question was affected |
I think checking the main a second time is a good idea. Neutral and grounds. Do I think there is a problem in the main? NO. If your confident with you’re electrician. Electricians and mechanics are NOT in short supply in my family, my brother retired as the local BA in Martinez CA. 12-15 last count. 4 HD local 3 mechanics.. No shortage of skilled labor, or muscle :-) ALL of them learned what "tight" is from Uncle Scotty..(ME) ALL were taught how to torque properly.. I use a Variac when I run into things like this.. Most electricians DON’T have them. Most old audiophilers DO.. You have a voltage difference between a "piece" of equipment and usually ALL the rest. or You have an old piece that need to percolate for 10-40 hours to tighten up the old caps.. So they just don’t leak all over.. Tube rectified in a preamp? MATCHED and checked for noise. NO excuse, on that one... You have to make sure it's not noisy at YOUR house... Not the Tec....Your house. audio2design, mentioned an isolation transformer. A variac is, with the added feature of being able to VARY the voltage. I suggest (only for a test) to very the voltage from 110 all the way to 122 VAC, SLOWLEY, and see if the noise goes away. 1. I would recheck MY main. I don’t trust anyone more than me.. NO ONE. Check for 120 (A) 120 (B), 240 between. To ground less than 1% of the total being checked.. 2. I would make sure I had a good PC going to my Pre amp. I’d change the PC no matter what. Just to test... I would pull the fuse clean the pocket with Isopropyl, LET IT DRY and inspect the HECK out of the fuse holder look for carbon trails.. LOOK close.. Reinstall a new fuse, a busman will do. NO fancy fuses for now... 3. The valves for the PS you know where the noise is coming from.. those valves would be changed (just for a test) MATCHED and checked for noise. NO EXCUSE on that one for sure. The pins and pockets on ALL the valves need to be cleaned and reseated, and pin pockets need to be checked for tightness and brushed and cleaned. All this takes about 1-2 hours, from the mains to cleaning everything.. I would test NOW, did you get lucky, no luck go to # 4 4. I’d smoke a little weed about now.. :-) Mind you, after everything you did THINK. Clear your ears and 5. Hook up the Variac a DMM and turn it to 100 volts and go from there up to 122 or so.. You have to have a DMM, (no analog). LISTEN. If it goes away, because of a voltage difference, LOL don’t be surprised. If it doesn’t go away don’t be depressed.. Closer than you think.. Regards.. |
It’s a tough call because that preamp has no problem outside the house and the problem is replicated on other circuits inside your house... and isolating the circuit is of no help. A voltage imbalance can cause dc to offset the ac waveform, as can fast switching loads inside the house — which can be ruled out because you turned everything off except the audio circuit. ...Or the utility power itself may be a problem. That’s why an electrician should analyze the power into the house. It’s possible that preamp is more susceptible to power issues than your other equipment. My guess is that dc is finding it’s way into your electrical system. |
Check the voltages in the main panel. Measure phase A to ground (120 vac) and phase B to ground (120 vac). Then across A and B (240 v). If phase A and B are not the same, call an electrician. There may be a loose neutral in the meter pan and the voltage is not seeing a low impedance back to the panel and the imbalance causes a voltage on the neutrals in the house. This can cause hum in transformers. There’s always a voltage on the neutral, but it’s usually less than 2 volts. Anything more and it’s a problem. Before that, tighten all the breaker lugs and neutral lugs in the panel. They do come loose. This alone may solve the problem. If it was me and the voltages are correct at the panel, I would go to the panel and install a temporary circuit. Install breaker and connect a 10 ft wire (romex or armored) to a receptacle in an enclosed electrical box, plug in the preamp and see if it still hums. If it doesn’t then the problem is the wiring in the house (e.g. the neutral wires have a long run back to the panel, creating a voltage across them). If it still hums, then I’m at a loss. |
Ground zero claims that their system negates the AC ground connection impact. That assumption is based on the assumption that their ground connection is much better than the one via the AC plug. That is not guaranteed, so for test purposes to start let's ensure it is gone I am concerned that perhaps you didn't have strong ground connections to the equipment. Hope you have a meter. Take a measurement between a ground wire and a few screws to make sure. I would be inclined to try the preamp on a small isolation transformer. Perhaps there is a ground path or common mode noise path we are missing. |
Audio2design: I set up a star grounding system and grounded all the components to the Ground Zero unit, including wires from the amplifier chassis to it. No effect. I did not try a wire from the preamp ground to the power amplifier chassis by itself, But I assume if this would work then the star grounding would have worked right? However I don't think I did that in conjunction with cheater plugs. Why would I do those two things together? I am interested to know! |
To me the simple fact the volume does not change tells me this hum is not coming FROM the pre-amp, because then it should increase when the pre-amp volume is turned up. Only thing I can think of is its an interaction WITH the pre-amp. I would say Bingo! on this explanation and perhaps there is something inherently wrong with either component that only comes up when the two are connected. The issue may be masked with different components. Stick with your cheater plugs that remove the AC ground at first, and then find some nice thick copper wire and run it between the pre-amp and amp chassis as short as you can. You may need to use a screw on each one and make sure you have an electrical connection to the chassis. Do not make the connection to an RCA connector. Of course my next question is whether the RCA on either are electrically connected directly to the chassis. |
Thanks for all the responses! noromance: Wifi routers etc can't affect the system if their AC circuits are turned off, or can they? I tried turning all breakers off except the sound system, and the hum persists. russ693: I think I tried reversing plug polarity when I tested cheater plugs, but will try again to be sure. I have disconnected everything except the preamp and amps and it still hums. I've swapped interconnects. No difference. petg60: Regarding checking with multimeter, would you clarify exactly what should be connected and what I should measure? I'm a bit ignorant of electrical stuff so just want to make sure. millercarbon: Hilarious... and agree with everything you said. At year end I said to myself "Hey why don't I frustrate the cr%p out of myself again and try to solve the hum again?" Yes, it does not seem to be the preamp per se, but the interaction with it. And the only things it can be interacting with are the power supply or my amps... assuming this is not coming from the air in terms of RF or something. slaw: As I noted, unfortunately I can't, at this point, remember when the darned hum began. I realize that would be very helpful. erik_squires: Never thought to check if one amp only relieves the problem! I will check. ozzy: Interconnects are all RCA. I have not run the sources straight to the amps but I have replaced the preamp with a preamp section of a cheap receiver, and the hum goes away. |
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loud enough to hear at the listening position, but just barely. Quite noticeable when standing at the rack. I have about this same amount of noise, at least. Every time I think it might be worth trying to eliminate it I think how much time and effort that can eat up, and for how little, and balance that against how likely it is I am even able to find it, and say naw not worth it. Then I read one of these stories and say to myself, good man miller, pick your battles. The improvements made the day I spent tweaking my turntable are monster, and instead could have had naught but frustration to show had I spent that time tracking down noise instead. Then I drop the needle and whatever the volume even extremely quiet vinyl is more groove noise than the other, so what really would be the point? Just sayin'. Anyway, the one fact that stands out to me is Hums with any source, not volume dependent, still hums with no source components attached (I even tried unplugged them from the wall too). But the hum stops if preamp is disconnected from amps.To me the simple fact the volume does not change tells me this hum is not coming FROM the pre-amp, because then it should increase when the pre-amp volume is turned up. Only thing I can think of is its an interaction WITH the pre-amp. Since you have already tracked down and eliminated everything there then the only thing left seems likely to involve a rather detailed technical knowledge of your amplifier. And with that I can only punt and hope Ralph is there to make the catch and run out the play for a touchdown. |
I’ve fretted over hum a time or two...one was when my 2 subs weren’t grounded the same (how that happened is still a mystery, clearly operator error), and recently when moving some things around I mistakenly swapped power supplies between a Schiit Loki EQ and a Magni 2 headphone amp...the Loki was not happy as it requires 16 VAC and the Magni 14, so the Loki pointed out this issue by adding a nice low end hum...noticed the power supply swap after some hair pulling checking of every damn thing. Man... |
This is a tough one and it would take a book to explore all the possibilities but let me tell you what I do in these cases. I pull the equipment off the rack and set everything on the floor. Then I put the most basic system together. Amp, speakers, source, etc. Then I use my ground breaking RCA interconnects or a ground breaking power cord/device to isolate the problem. My toughest case so far was an ungrounded preamp that would hum. Turned out if I reversed the two prong plug, the hum went away. Drove me nuts but I was totally relieved when I solved the problem. So...good luck and just get down and dirty and work the issues until you can with certainty identify the offending hook-up or component. |