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Rega TT, earthing and channel imbalance

 

New member
Username: Regap7lover

Post Number: 1
Registered: Dec-12
Hi,

Im new here. Im Robin, 39 years old and living in the Netherlands.

I have got a Rega P7 TT with Sumiko Blackbird and dynavector 10x5 cart, Graham slee gram amp2 se and reflex M (loan from dealer). The P7 and carts are in good shape. The carts are aligned as it should be and the P7 is level. The RB700 arm floats freely when balancing.

The strange thing is that with quite a lot of records stereoseperation is too much to the right channel. I mean that it seems that right is louder than left. This is the case with both carts and phonoamps.

Rega have connected the earth chassis and arm to the earth grounding of the left channel. I have read that with some carts this can be a problem.

I was wondering if this kind of earthing can give channel balance problems?

Hope to hear from you.

Gr,

RobinUpload
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 17571
Registered: May-04
.

No, the ground arrangement of the Rega arm cannot cause channel imbalance. There is nothing in the turntable or arm that can cause channel imbalance if they are properly set up. Additionally, it would be very unlikely for both cartridges or both phono pre amps to have identical channel balance issues. My suspicions would run to other aspects of the system and its set up within the room.

Is the Rega the only source you have in the system? If not, what other sources are used? How do they perform when it comes to channel balance?

If the Rega is your only source, then you can check for more specific issues by reversing the channel leads one for the other; right to left and left to right. Begin with the RCA leads into your amplifier, move to the RCA's into your phono pre amp and then to the leads off your cartridge. Change only one location at any one time and then listen. If no change is peceived, return the connectors to their proper location and move to the next link up the chain. After each change, determine whether any channel balance issues have resulted from that specific change before you move on.

If no one component shows as being faulty, then the problem is more likely to exist in your speaker set up relative to your room boundaries and your seating location.




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New member
Username: Regap7lover

Post Number: 2
Registered: Dec-12
hi Jan,

No problems with cd player and tuner. my speakers are perfectly set up. no channel inbalance with test cd or real music, or other amp input. But not with all records i hear this inbalance.

technically it is better to make a seperate earth wire. my former rp6 did have the same problem.
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 17572
Registered: May-04
.

How the tonearm's ground is arranged is nothing more than finding a method which minimizes hum. You're not grounding the cartridge since there is no electrical connection between the cartridge body and the headshell. And the cartridge is what is responsible for channel balance, not the arm itself unless the arm is improperly installed and set up.

People have complained about the Rega grounding technique ever since the original RB300 arm was introduced back in the early '80's. The issue though is with noise pick up in this arrangement and not channel balance. In 99.999% of installations the Rega arm will not be bothered by noise entering through the grounding point. In all but the most extreme uses - typically where a Rega arm wouldn't the the arm of choice anyway - the Rega arm will not suffer in any audible way from where the arm tube's ground is taken or made. It is effective in connecting to a chassis ground on virtually all phono pre amps since the input jacks are typically not insulated from the chassis which provides the grounding point for the arm.

If you look at your pre amps, you'll see the ground lug is also an uninsulated chassis ground. If you were to check with a meter, you'd find continuity between the grounds of the jacks, the lug and the chassis so you could say all of these points are at the same ground potential which is the key to reducing noise. Unless you're using a fairly sophisticated pre amp with an unusual grounding method, the Rega's grounding point is perfectly fine.



So, who set up your arm?



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New member
Username: Regap7lover

Post Number: 3
Registered: Dec-12
i installed and aligned the cart myself.It is simple. Rega/schon protractor, lots of light, digital gauge, antiskating about 1/3 of vtf that's it. VTA is negative with blackbird and almost neutral with Dynavector. TT is level and Ikea Lack as support.

The RB700 flows freely when balancing. I bought the P7 with sumiko swecond hand at my dealer. Dynavector and phonoamps are brand new.

Have you got a Rega TT with Rega tonearm? No such issues with any record? Do you live in the Netherlands?

Site AqVox:
"The REGA Tonearm can be used further with all Phonostages on the market, the Performance is just better, because a separate ground-cable is the right way to go. Now the tonearm is like 100% of all available Tonearms.It is not very helpfull for the soundquality if the complete tonearm and base which are made of metal and working good as antenna, and receiving a lot of high-frequency dirt and all the electrosmog, up to that is is unnecessary amount of metal-mass in the signal.
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 17573
Registered: May-04
.

As my personal information shows, I live in Dallas, TX. I purchased one of the first three Rega Planar 3 tables into the US from the then current importer back in the late '70's. I've had an RB300 on my tables since they were introduced. I have sold Rega for years though I'm no longer selling audio.

I don't tend to take another manufacturer's opinions as fact when they are trying to sell me their upgraded product. I never take a forum's opinion as fact since there are no filters on forums. You can also take that to mean this forum is no different. People say what they want to say and they often have no basis for why they say those things. Even the highly technical sites will disagree about certain things.

However, what your quote is indicating is what I said, the Rega grounding system can, in some instances, cause noise pick up through the signal lead. We live in a RF rich environment and there will always be some anount of noise riding on any audio signal. RCA connectors and any point where the signal is broken by another connector are fairly susceptible locations to RF pick up due to their basic construction. Whether you make a dedicated ground for the Rega arm or not, there are still multiple locations for RF pick up in a low level phono system. As I said, people have been making an issue if Rega's grounding scheme since the first RB300 was built. The issue is noise, not channel imbalance. Rega arms are now used in some very high end systems and they are well suited to use with very low output mc cartridges which would require very high gain stages behind them. If noise were an issue, it would be heard in these systems.

So, do what you want with the ground, you can't harm the arm if all you do is a good job of separating the arm ground from the signal lead. Grounds either work or they don't. If you have signal, the ground is OK - ignoring the fact you might have made a cold solder joint which will have problems down the road. The potential of a bad solder joint is as good a reason as any for most hobbyists not to bother trying to solder a new ground on the Rega arm IMO.

If, as you say, the system performs without this imbalance when you're using other sources, then I would look at your table set up. Am I correct that you have not bothered to make the suggested changes in connections? Start there. Any diagnostic work is done by starting at the end point of the problem and working backwards. As you eliminate each possible point of a problem, you will narrow down where the actual problem should be located. If you simply take a scatter gun approach to solving a problem, without paying attention to the logic of troubleshooting, then you're more likely to not solve the issue while possibly introducing other problems.

I would say your arm set up might be questionable. 1/3 VTF is not a typical setting for anti-skate on any arm. You mention you don't hear this problem on all discs. That would lead me to think even more about the anti-skating set up. Skating is a dynamic situation which is barely ever correct at any one point on any one disc. The groove dynamics plus the sylus shape make anti-skate a seldom correct average over the entire disc. While there are several theories for how to set anti-skating, even to the point of not using anti-skating, they are all as incorrect as they are correct since they are simply trying to make one setting apply to all conditions. (If you remove all anti-skating, you need to increase VTF to compensate for the lack of skating compensation.)

I would suggest you track your cartridges at the very upper end of their suggested VTF. Without a specific test disc you can only guess at the correct anti-skating setting. But I would then suggest you set your skating set up to be equal to the value of the VTF. Just given what you've posted I am guessing you have tried to track the arm without sufficient VTF which will make it more prone to mistracking as it responds to the groove dynamics. You'll do no harm to the disc by tracking at higher VTF's and the stylus will settle down further into the groove. Then literally play with the skating setting until you hear a more evenly balanced sound from both channels.

If this does not correct your problem, then there's not much more I can do with the information you've provided. If you want to work more on this, I'll need more information. Otherwise, you might want to contact your Rega retailer or Rega themself. Rega certainly should be aware of any issues their arms have with multiple cartridges. But grounding should not be related to channel imbalance.



Until you have solved the imbalance problem, I would not suggest you begin to change anything on the arm related to grounding simply because you might cause other problems in the process. Troubleshooting is a process which changes only one thing at any one time and then takes the time to listen to what might have changed. Changing more than one thing at any one time will typically get you to the point where you can't tell what has affected any audible change you hear. Take your time and work backwards. That's what any tech would do.



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New member
Username: Regap7lover

Post Number: 4
Registered: Dec-12
Jan,

bias 1/3 of VTF is according to the cart manual. 2 gram is optimum. Playing with antiskating does nothing for channel balance. changes in connection results in right channel being less loud with some records than left.

Can it be a recording related problem?
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 17574
Registered: May-04
.

"bias 1/3 of VTF is according to the cart manual."


For both cartridges? Both are a simple elliptical stylus shape. It would be unusual for an elliptical stylus to have such a reduction in anti-skating compensation. A Shibata or a "hyper"-elliptical will have an adjustment outside of the norm (as will a concial stylus tip) but ellipticals are what most arms are guessing you'll use and their skating compensation is set to work best with that type of stylus. I'll take your word for it, but this does seem unusual. For this to be the recommendation for both cartridges definitely seems out of the norm.


"Can it be a recording related problem?"


Not necessarily. If this occurs when you've changed the leads at the back of the cartridge (but not until you've swapped the leads at the cartridge itself), all you've established so far is nothing beyond the cartridge is at fault. This hasn't ruled out faulty arm/table set up yet.


If this problem is disc dependent and the problem moves with channel assignment, then it might very well be a disc/recording issue and not a problem with the arm/cartridge itself. But you'll need to do a bit more troubleshooting to establish this. While the Rega arm has no azimuth adjustment, a cartridge which tilts to one side could still be causing your problem. This could be the result of over-torquing the cartridge bolts which would cause the body of the cartridge to twist unevenly. If you have any sort of aftermarket counterweight on the Rege arm, many of these could cause azimuth problems.

First, I would suggest you take a look at the cantilever as it tracks a disc. It's not easy to make correct assessments using the dynamic conditions of a recorded disc but since you have no test discs, we'll have to make do. Looking straight on at the front of the cartridge you should see the cantilever line up under the center line of the cartridge body when the anti-skating compensation is set correctly for the disc. Try this over several discs and over several locations on the disc as groove pitch, frequency response and groove velocity will all impact skating effects. Therefore, skating compensation is not identical at the inner groove if you've set it for the lead in track since groove velocity is several times higher as disc/groove circumference decreases. By averaging several discs and several points on each disc you should be able to establish a more or less correct settting for each cartridge.

Looking directly into the front of the cartridge body while the arm is tracking a disc you should see the cantilever setting comfortably along the center line of the cartridge. Too much compensation will cause the arm to pull ahead of the stylus and you'll see the cantilever deflect to one side and away from the centerline as if the arm is pulling the stylus along the groove. Too little skating compensation and the cantilever will pull in the opposite direction looking as of it is leading the cartridge and tonerarm along. There will be a fairly wide range of settings where the cantilever seems to be set correctly. This simply reflects the variations in the actual amount of compensation each disc requires across its groove path. Average out your results and settle in on the best overall average amount of compensation for each cartridge. As I suggested earlier, set your VTF on each cartridge to its upper 90-100% range. You'll have less groove wear tracking heavy than light.


I suppose the best way to answer your question about this being a disc dependent issue would be to assess where vocals occur in the staging. While there was a brief period in recording styles where vocals would be pushed to each side of the stereo stage, most recordings made over the last 35 years have tended towards a centered vocal. Therefore, using the same basic settings on your pre amp that would accomplish a centered vocal position for CD, play a "problem" disc and listen for center vocal position. If the vocal tends to pull to one side then you would assume it is not the recording. If the vocal remains centered - or any other centralized image other than deep bass instruments which are typically recorded in mono remains centered - while one side of the stage apears to be playing at a higher level, then you would assume the issue is with the disc and how the recording was mixed. Of course, any mono vocal recording should present a very tightly focussed central image when the arm is properly set up. A good reference for how vocals should sound in stereo would be a stereo FM broadcast with a centralized vocal such as an announcer's voice. The voice should occupy a tight central image which remains fairly well centered as you move your head slightly to either side. If this is not the type of image your system presents with all sources, then there might be other problems in the system set up.


Do you know how to check for proper azimuth?

Do you use any sort of record clamp?





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New member
Username: Regap7lover

Post Number: 5
Registered: Dec-12
Thanx again Jan for your advice.

Antiskating:
I was mistaken it is about 2/3 of VTF for both carts.

Testrecord:
I have a Hifinews testrecord. With track one on side one the voice seems to be equal loud on both channels as is for pink noise on track 3 side one. The noise signal for azimuth on side 2, seems to be weak in the centre and when i move my head to left or right it appears loud. So that looks te be good.

Cantilever:
When tracking cantilever is centred with both carts.

Record clam:
No clam because i think sound is worse with it (midrange) and because of its extra weight this can not be good for the bearing. Rega does not have any clams or pucks, that should say enough.

Phonoamps:
Have you ever tried the Grahams or the Dynavector P75?

Greetings,

Robin
 

New member
Username: Regap7lover

Post Number: 6
Registered: Dec-12
Hi Jan,

I have tried to make a seperate eart wire, but those wires are so tiny that im afraid im gonna make it kaput. So lets stick with the original earthing
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 17575
Registered: May-04
.

I'm not familiar with the Graham at all other than by reputation. If I were looking in that price range, I might consider it as an option. I use a Grado Sonata cartridge and the Dynavector house sound is, IMO, a bit too cool to mate well with the Grado's musical personality. I've used a tube based (NOS Siemens E183CC) Audible Illusions pre amp for my analog side for many years now.

Your tests seem to be indicating the problem does not exist in the cartridge or arm set up.



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