Is it safe to assume that you have everything grounded properly? One ground lead from the turntable bearing hub and one from the tonearm follow the signal path. So both ground leads should be tied to the SUT, which in turn should be tied to the Io. Are turntable/SUT and Io all plugged into the same circuit? If not, they should be. |
I only have ground from tone arm to Sut. I played around a bit with ground wire from motor unit and plinth to isolated transformer ground that did not do anything. I use tw black Knight Battery power/speed controller on my Raven AC 1 turntable. I tried both with ground lead connected and disconnected between Sut and Io. Tw and Io is plugged into the same conditioner that went to the same isolated transformer. I am not sure it this is a ground loop problem as groundloopmproblem that I saw in the past tend to be there all the time even when music is not playing. In this case, I only get the hum if the needle is playing. |
This is weird but will work-
Get a ferrite core and wrap it around your power core. All your radio interference wil be gone.
Here's an article:
Ferrite cores are small semi-magnetic iron pieces encased in a plastic snap enclosure. Designed to fit around power cords and interconnects, they block electromagnetic interference and unwanted high frequency information. Since ferrite shields can often affect these frequencies in the analog domain, it is usually used for digital and power cables where frequency manipulation is not audible. Ferrite cores have been used for years in the engineering, computing, and electronics industries |
Sorry-just saw you tried the ferrite core...did you try one on every power cord? wrap it twice? good luck. |
You don't have a ground wire tied to your turntable? I have a Basis and VPI tables and both of them have a ground wire attached to the steel hub that seats the platter bearing under the turntable, as well as a ground for the tonearm. |
Tbromgard, I tried it only with phono cable as I use Stealth Dream AC cord on my phono unit, not sure where I would find ferrite ring that big!.
Jmcgrogan2, hmmm... thanks about ground between phono adn bearing hub. I never tried that before and will talk with TW as I am not sure how to connect that. My VPI table does have that but I never had to use it before. |
Just food for thought, isolation transformers work on the idea of induced voltage. First core is powered from your home the second core has its voltage induced keeping everything you plug into it seperate from the "dirty" power supplied to your home. They are fantastic for sensitive equipment. However if this is a plug in unit (three prong) the ground is not isolated from your home and that can act like a big antenna( all grounds in a home ideally are all connected in a panel together) every switch and outlet has a ground. Also dc voltage cannot be transferred from the isolated coil back out to the street and it is not regulated into ac sine wave (also a reason for a iso transformer to prevent all but correct voltage getting to your equipment). So while it likely wouldn't matter even slightly in your case , trace dc voltage can get back onto these coils sometimes and cause harmonic issues, usually this would happen in office buildings with a decent amount of computers. The radio station pick up though could be due to the grounds in your home. To find out if it is the case try taking the outlet you are plugging into out of the wall and remove the ground wire, then put a new wire from that outlet directly to the dirt outside of the home. Of course shut the breaker off first. You could also just remove the ground and see if it goes away before you run the wire. It is not safe to leave it that way though. There is a correct method if this is the problem to fix this by code standards. What I mentioned would just be to test.
Regards,
Bill |
I was dealing with a similar situation not long ago. I'm not sure if your phono pre-amp is similar to mine but, My phono stage has selectable dip switches that allow you to change your grounding. I had to to change my grounding where only the right channel is grounded. This eliminated all but a bit of the hum. Now it is only heard when I have the volume turned up really high. I cannot detect a hum/buzz at my listening position at normal or even higher volume. I have to turn my pre-amp up to max volume to hear a hum at my listening position. I can live with this. At this point I think it is noise from the tubes and not the ground. If your pre-amp has selectable grounding take a look at it. |
Thanks for all the advise. I live in an apartment building so creating separate ground for my audio outlet is not possible although several of my friends who live in a house has separate ground rods placed specifically for their audio system. There is no ground switch on my preamp/phono unfortunately but there is a ground/float switch on my T100 SUT. Sometimes floating ground on SUT seems to help but sometimes not.
I talked to TW acustic and there is no provision to connect ground wire to bearing hub and they think that my problem is unlikely to be solved by doing that anyhow! |
I spoke to peter lederman from soundsmith this afternoon. I learned a new trick from him. New to me atleast. He said to only earth ground one piece of your audio equipment. If your equipment has a 3-prong power cord, get a 3-prong to 2-prong adapter. He said this helps to get rid of more ground hum. This makes sense to me as there is less chance of creating a ground loop. I have not had a chance to try this method yet but, I plan to. I am going to earth ground my phono stage and then connect the rest of my components to the grounding lug on my phono, bypassing the grounds on the powercords. I will post results on this method after I give it a try |
Hmmm... as soon as I posted the message, the hum went away. May be I should complain more often :)
Some equipments do like grounding, even more so than just with 3 prongs AC cord. My Lamm pre/power/phono has extra ground posts on the chassis and I found that background noise is reduced quite a bit more by connecting those ground post to my isolation transformer as well. |
He said to only earth ground one piece of your audio equipment. If your equipment has a 3-prong power cord, get a 3-prong to 2-prong adapter. He said this helps to get rid of more ground hum. If any of this ever makes a difference there is either a bug in the design or a defect in the equipment; in either case it should be returned to the manufacturer for repair! You should never use a 3-to-2 prong adapter except for testing, as they can cause shock or fire hazard with certain types of failure in the equipment! Suteetat, without an LP on the platter. you should see if lowering the arm will induce the hum. Having the hum only show up when you lower the arm sounds like an intermittent wiring problem in the arm itself. |
08-07-12: Suteetat
Tbromgard, I tried it only with phono cable as I use Stealth Dream AC cord on my phono unit, not sure where I would find ferrite ring that big!.
I hope that you are using a "Preamp" version of the Dream power cord. The Dream was designed so that it provided "star grounding" for a system. Therefore, the "Preamp" version has a clearer path to ground than the "Digital" or "Amp" versions. |
Huh? Not buying that one. |
I did end up trying the method peter lederman suggested. I used some 3-prong to 2-prong adapters from ace hardware. The only component I left earth grounded with the 3-prong power cord was my phono stage. Then my processor,amp, and turntable are connected to the ground lug on the phono stage chassis. This has totally eliminated all hum at my listening chair. The only way I hear a hum is when I turn the volume up to max and I put my ear next to the tweeter or midrange driver. This is more than satisfactory for me. I never listen to music at max volume or sit right next to the speaker anyway. I do listen to music at 85% of max volume sometimes. I can hear no hum at all at these levels. I am going to leave the adapters in place until I can come up with a better solution.
As a precaution, I added some extra shielding to my phono cable and to my tonearm lead wire. I had some scrap monster speaker cable junk laying around. I cut a 12" length off and stripped the shielding from the wire. I then removed a single strand of copper wire about the same diameter of a hair and wrapped this around my tonearm lead wire in a spiral fashion. I left this wire about 3" long and connected the end to the ground lug on my turntable. Once I had this wire installed I wrapped it in PTFE tape. I also wrapped my phono cable in PTFE (teflon) tape. This has also helped to cut down on EFI/RFI interference. It was a tedious process to hand wrap these cables but, the end result was worth it.
Andy
PS
I am using a VPI classic 1 with the exposed wire coming out of the tonearm head. This wire is un-shielded and was picking up interference. That is why I grounded it and added shielding. |
Yes I use pre amp version of dream AC power cord on my phono and pre amp. Also the proper version for power, digital and conditioner so I have a variety of multi color garden hose everywhere :)
I don't know if it is the star ground or whatever but when I auditioned Stealth power cord in my system, I tried only one initially and was not overly impressed. It was not bad but not really better than what I had. Only when my local dealer gave me two more AC cords to tried in my system then it really was a different story. So, the more the better it seems with Stealth AC cords. |
Hi Andy, now that you know a way to fix it, the next step is to find a way to correct the grounding problems that cause the need to lift AC grounds from the wall.
For example what happens if the DAC is unplugged from the wall? Ca you ground everything else normally? If not, then the DAC may be off the hook.
FWIW, in the old days grounding the preamp as the heart of the system was considered normal practice. In this day of liabilities, that is no longer considered a good idea.
If you continue to operate things with the grounds lifted, there is a shock and fire hazard if a piece is damaged or has certain types of failures. |
Atmasphere,
I agree with you. I need to go through my components and determine which piece was causing the problem. Then I will find a way to properly ground it. I have been using the setup for a week or so everyday like this. Still no fires or shocks. That doesn't mean that the possibility isn't there so, I don't recommend that anyone leave their system in this configuration. I do have my components plugged into an APS purepower 1050. I feel this makes it a bit safer by preventing overvoltages. |
