A little hum and buzz ...

[Laudanum]

Maybe I should have posted this in general.  I have a little bit of hum and buzz at high volume with FPIII in system but it isnt the FPIII.
I need to give some background.  This is with TT set-up.  TT - Seduction - FPIII - Crack.   I was initially running the TT (Rotel RP900 Rega 2 clone with Rega RB250 arm).  through a Hagerman Cornet phono stage directly into Crack.  There was a bit of hum at mid volume and higher.  I re-wired the RB250 and probaly dropped the hum 10db or more.  It could only be heard with Crack volume turned up past 3 o'clock and was pretty low level, not heard over music.  I built Seduction and the hum was still there but lower level still at same volume knob setting on Crack (Cornet had 4 db more gain than Seduction).
With FPIII added to the signal chain and the attenuators set mid-way (about unity gain), the hum level is the same with volume on Crack turned up to the same level but there is a little bit of buzz as well.  Again, low level, cant be heard over music.  Of course, with gain added by cranking up FPIII a little bit, the level increases accordingly for the same volume setting on Crack.  I shorted the inputs of FPIII and it is quiet.  I shorted inputs of Seduction and it is quiet.  So, the turntable is the culprit (and not unusual I would think as there is a little bit in the main system as well at high volume with a different tabe and componenets).  

If youve been patient enough to bear with me, here is the question ... where does that little bit of buzz come from if Seduction, FPIII and Crack are all quiet?  Again, there is that low level hum from the turntable. But im wondering where the buzz comes into the equation.  Knowing the little that I do know, it's usually indicitive of a ground "issue".  But again, components are quiet with inputs shorted which seems to point the TT as the source, but still, no buzz without FPIII in the chain.  So Im thinking probably a ground potential (if potential is the right word) between the TT, Seduction and FPIII and maybe Crack as well.  Not a "fault" of/in any one component, Rather the combination of all of them, with the TT seemingly the ultimate source of the issue.  Also, I can really induce the buzz by touching the cartridge clips.   I can live with this as it's low level and cant be heard over the music at all and is also really only present at volume levels I would only occassionally listen at.  But if I could get rid of it without too much hassle I'd try it.  And ideas to try, where to start?   I havent tried anything yet because Im not sure where is best to start.

Thanks

 

[Grainger49]

Buzz is often a power supply rectification problem.  Try this, put shorting plugs into the input of the Seduction.  You should have a pair of shorting plugs for troubleshooting, cheapest RCA plugs you can find with the hot and shield shorted together, soldered.

Is there noise?  If not then the table is the source.

If the noise persists listen at a high volume and turn off the Seduction.  If it is a power supply problem in Seduction then it will go away immediately when you hit the switch.  Either way, turn it back on so you don't get the turn off thump through the system.  One half a second should tell you if the buzz is gone.

Then if the buzz persists get a barrel connector, female RCA to female RCA, and unplug the cables from the Seduction insert the barrel connectors and plug the shorting plugs into the cables/barrel connector.  This tests the cables between Seduction and FP III.  If the buzz persists continue...

The FP III should get the shorting plugs next, power down for a half a second, if it persists check the cables between the FP III and Crack.  Then short the inputs to Crack.

This is just chasing down the source of the buzz if it is power supply (or cable) related.  Happily if you have the shorting plugs and barrel connectors it will take you all of 4 minutes.  It took longer to type this out.  If you don't have these parts, and you should always have some of these since you are a hobbyist now, it takes a trip to Radio Shack, some soldering and 4 minutes.

If you find something from this post back and we can go from there.

P.S. touching the cartridge clips always injects some noise.  I usually get hum but it may have something to do with dielectric strength of our skin.  (that is just a joke)

 

[Laudanum]

Hi Grainger.

Yes, I have some shorting plugs.

Ok, I had tried it last night and didnt hear any noise but I didnt have the volume high enough.
Here is the deal-

-Seduction has a little bit of hum, no buzz.  But you have to turn the volume up on Crack to almost max to hear it.
-Foreplay has some buzz, no hum.  It is independant of the "volume" settings of the FPIII attenuators.  But again, near max volume on Crack to hear it.
-Crack is dead quiet.
-Shorting the cables at any point makes no difference.

With the turntable in the system, both the buzz and hum is louder.

I dont know if this makes any difference but Seduction and FPIII are next to each other and the TT sits pretty close to Seduction.

Again, this is pretty low level even with the turntable connected.

Thanks Grainger

 

[Doc B]

My suggestions are as follows -

While we don't condone it, there have been cases of ground loop buzz related to Foreplay being solved by systematically trying a cheater plug on the power cord of various on parts of the system.

It sounds like maybe the tonearm itself needs to be grounded to the Seduction ground post.

Not sure if you are doing this but I would be disinclined to put FPIII between the Seduction and the Crack - too many unnecessary stages. Just run the Sed straight into the Crack.

 

[Grainger49]

Desmond,

There have been a few incidents here of noise from the Rega arm and a Seduction.  It has something to do with the "integral ground" in the Rega arm.  That is, the ground for the table is tied to one of the audio channel's grounds.  Or maybe not.  Anyway, try grounding the arm (as Doc suggests) and/or table to the Seduction.  

Also, do a search for 'Seduction and Rega" on the forum.  You should find some pointers.  

 

[Laudanum]

FPIII gives me the option to run 3 sources into Crack without swapping cables as well as add one of my tube amps and speakers to this second system which I planned on doing in the future.  It also gives me some additional gain/drive for the phono and so far, I think it has been a benefit in that regard.  I dont hear any negatives sonically from adding FP and Vinyl does seem a bit more dynamic with it in the path.  

The Tonearm is grounded to the Seduction ground lug.  When I re-wired the Rega arm I wired a seperate external ground.

Again, the noise is low level ... it's only audible with the volume beyond where I would normally listen.  I dont hear it over the music or between tracks.  I just noticed that it was there and wondered if it could be completely eliminated.  If not, it's fine.  No need to bother with cheater plugs.

For the record, two things.  I had a little bit of low level hum with the Haggerman Cornet that I was borrowing from the main system to run vinyl into Crack.  There is some low level hum in the main system as well when using a different table with the Cornet and a hybrid integrated.  It's been par for the course, atleast with my systems.  And I know it isnt universal but it certainly isnt uncommon.  So I want to be clear that Im not singling out Seduction or FPIII here.  It's nitpicking what amounts to a non-issue.  If I never cranked it up with nothing playing I never would have discovered it.

Second, FPIII and Seduction both sound fantastic which is the bottom line.  

Thanks Doc.

 

[Laudanum]

Desmond,

There have been a few incidents here of noise from the Rega arm and a Seduction.  It has something to do with the "integral ground" in the Rega arm.  That is, the ground for the table is tied to one of the audio channel's grounds.  Or maybe not.  Anyway, try grounding the arm (as Doc suggests) and/or table to the Seduction.  

Also, do a search for 'Seduction and Rega" on the forum.  You should find some pointers.  

Yep, it's tied to the left channel shield in the stock wiring scheme.  As mentioned, I rewired the arm and ran a seperate, external ground.
I may look into grounding the motor later on.  I think I've read something about however I need to do some more research.  But it's really a non-issue.  Everything is sounding great. 

Thanks

 

[Grainger49]

Desmond,

You can experiment with a random length of wire.  Ground it to the Seduction and then to the motor and or the TT chassis.  Grounding for hum elimination is a black magic.  Something that works in my system will probably not work in yours, and vice versa.  I don't even think PJ can predict what will work in a given system.  We all have to ferret it out ourselves.

You are right, there is no sense in spending too much time eliminating a noise you can't hear between tracks.  It bugs us that it is there but the answer is to relax, listen to music and smile.

 

[Paul Joppa]

For what it's worth ... "buzz" has two common sources. One is RF pickup, television signals with a 30Hz frame rate. Anything that is not well shielded can pick it up and it's a b$^#% to sort out. The other is capacitive coupling of power line hum - the capacitive coupling makes a high-pass filter, leaving the higher frequency components. For example, the turntable power line and/or motor may couple to the turntable chassis, inducing a ground current that flows through the ground wire (no problem if the ground is not shared with the interconnect) and then through the Sed to FP interconnect grounds, and the FP to Crack interconnect grounds. Each component will drain some of this current to safety ground as it moves along, but any current in the (small) ground wire resistance will masquerade as a signal.

An ideal turntable wiring scheme would put all four signal wires inside a shield, which can double as the ground wire. A good approximation is to keep them close together, with cable ties for instance. It's good practice to bundle the power cords together to minimize loop areas, but this gets sticky. You want the power cord ground to be close to the signal interconnect ground to minimize loop area, but you want to keep them apart to minimize capacitive coupling between them. This is an example of why complex studio installations use balanced and separately shielded lines, and of why killing hum and buzz is a black art!

 

[Grainger49]

I thought of this earlier but forgot to post, try inverting the plug for the TT.  It could help, might not.

 

[Laudanum]

Paul, if I understand what you are saying ... the TT shield doubling as the ground wire is actually do-able, although I didnt do it.  I used about 3 feet of shielded quad cable for the external turntable interconnect (about 150pf / meter).  At the split for left and right channels I individually shielded the pairs and soldered the main shield to the shields run for the pairs, but obviously I didnt connect the shield at the plugs.  Internally, the arm wand ground and the ground for the tonearm base are tied to the shield and an external ground wire.  Technically, the individual, external ground wire running from inside the arm base for connection to the phonostage ground lug could have been deleted and instead a ground wire could have been soldered to the shield at the break-out for the left and right pairs.  That would essentially make the shield with all 4 signal wires the ground that gets connected at the ground post as you suggest.  Well, it actually is now, electrically. But it would become the ground more directly I guess, with a shorter run to the ground post.  That is, except for the 5 inches or so where the individual pairs break out of course. 
I've never seen this done, so of course I didnt do it.  If I get ambitious, I could try this later on.  In fact, I could do so without having to completely re-wire the arm.  I would just have to re-do the plugs so I could neaten up the cable again with some new heat-shrink, whether it "worked" or not.  At present, the ground wire isnt heat shrunk or cable tied along with the signal wire, so I will do that.  But again, this is "search for perfection" stuff.  Still, very interesting suggestion regarding the ground.

Also ... I think that the TV and HT system may be on the same circuit as the audio, but Im not sure.  Dont know if that makes a difference or not.  Both systems are plugged into their own Surge Suppressors with voltage regulation.    Anyway, I may be imagining it but I think that the "noise" is a little lower when the TV is off.  The TV sits only 2 or 3 feet from the TT.  Again, I cant say for sure, I would have to do an A/B.  But again, this is low-level stuff either way.  If there is a difference, it isnt much.

Thanks

 

[Laudanum]

I thought of this earlier but forgot to post, try inverting the plug for the TT.  It could help, might not.

Tried it, I dont think it mattered.  But I should have thought of it.  I remember a couple of my old Guitar amps back in the 70's used to buzz from the Flourescent lights.  Flipping the plug definitely made a difference.

Thanks Grainger.

 

[Paul Joppa]

One thing about video systems is that the cable has a different ground from the power wiring. This makes for ground loops running through the wiring system. You can try disconnecting the cable from the rest of the system, as a test.

Just a thought, we are as you say well past dealing with the obvious!

 

[Laudanum]

Im going to add some weirdness here.

I finally build the cables for my other two sources, CDP and a Digital Player. 

-The FPIII is dead quiet on the CDP input.  So I swapped the CDP to a different input pair on FP and FP is still dead quiet with CDP input. 
Shorted the CDP cables, and that low level buzz is there.  But hooked up to the CDP, it's quiet.  Doesnt matter if the CDP is turned off, or if it's on and stopped or paused.  FP is quiet regardless.
The CDP has a 2 prong plug by the way and I think it's a polarized plug.

- With the digital player selected as source, FP still has the low level buzz.  But the digital player has a self contained battery, it wasnt even plugged into the wall.

Cables from seduction to FPIII and CDP to FPIII are all built the same way.  Canare STP with braid attached at one end only (source).
Cable from digital player is different because of the mini plug connection, it's Canare quad with shield attached at digital players end and cable broken out into left and right pairs at FP input.

Dont rack your brains over this, anyone.  Again, the "buzz" is very low level near highest "volume" settings.  But do chime in if this additional info rings any bells.

Thanks

 

[Laudanum]

Got even more of it ... The CDP has a 2 prong, non-polarized plug.  Flipped it around and voila.  That "buzz" is even lower level now than it was before.  And, I think that little bit of hum is gone or all but gone on the TT/Seduction input.  Really strange how some of this stuff works.