[TheChairGuy]

I get hum when I have the TT ground wire attached to the ground post on my Dynaco PAS-4.

It's there if I just attach it to any chassis screw on the Dynaco.  No other equipment can be reached with the relatively short ground wire - so I haven't tried it on anythign else.

Allowing the ground wire to dangle happily downward, attached to absolutely nothing but air, eliminates and audible hum.

wtf is goin' on here?

All my AC powered equipment (including the TT) is plugged into an excellent BPT balanced power unit. Did the BPT reduce ground loop hum to absolute zero?

The hum is absolutely not there with the ground wire dangling.

The follow-up to this is...is there any harm in having it un-connected?  it does indeed sound better now as I can ratchet up the volume to CD listening levels - it's simply outstanding to listen to now.

Okay, knowledgeable vinyl-files (or others lurking in these parts) - what da' hell is goin' on here?  

[Russell Dawkins]

Have you tried this with the power cable to the turntable or the preamp reversed in the socket? The older style plugs have the same size blades on both sides and do not prevent this, as newer plugs/sockets do. Is the turntable plugged into the same house circuit?
Russell

[John Casler]

My "wild stab" would be that the cartridge "ground" pin is either defective, or the pins are not connected properly, so when you "connect" the ground wire, you actually are not.

Does that make sense?

[Scott F.]

Here's my 'guess'. If you are using an unrestored PAS, I think they connected the ground to the chassis. In turn, you may be getting some voltage through your building ground. That voltage transfers through the case into the phono ground. As you charge your turntable grounding wire with that nominal voltage, the insulation is so thin that the EMF bleeds over to the signal wires causing the audible hum.

As for leaving the ground wire off, no problem at all. It won't hurt a thing.

[TheChairGuy]

Hey guys, thanks for your inputs!

Russell
One of the first things tried was to reverse the two prong plug to the 10 outlet BPT unit.....no difference.  The entire system is hooked up thru the BPT unit -  and that's plugged into the a single outlet.


John
I'll fiddle around with the cartridge leads - haven't tried that one yet.

All 8 point of attachments (on cartridge and headshell) seem quite commendably tight, and the leads are new - the very nice PCOCC leads that come with the Audio-Technica cartridge.  That's a helluva' nice bonus to get with a $84.95 cartridge.  

I had a post from a couple weeks ago where I was asking for help in color coding the headshell leads...the  JVC was devoid of any indication of it.  'andyr' gave me the pattern that his headshell followed, we both figured that it's probably universal, and I followed it to a 'T'.

http://www.audiocircle.com/index.php?topic=22530


Scott F.
The PAS-4 is fairly new - about 10 years old.  It's not the old Dynaco PAS tube pre's (last one ending in the 3 or 3x)...it's a new design made by Panor Corporation (the folks that bought, and tried to revive Dynaco a decade ago).

I don't know if their grounding scheme is faulty in designing the unit, but in most other ways it's pretty amazing for the money.

http://www.audioreview.com/cat/amplification/preamplifiers/Dynaco/PRD_118264_1591crx.aspx

So, if I can't figure the source of the hum when, seemingly, properly grounded...nice to know nothing adverse happening to the system as the gound wire dangles freely.


When ground is connected, the hum is intolerable at 60% of the dial...and 'bad' starts to begin at about 30%.  The TT needs more volume to get to CD levels so it needs about 45% of the volume control to get the right rockin' volumes. So, there is much hum listening this way.

Without connecting the ground, it's absolutely silent (free of hum) 100% of the way out.  Just a little tube hiss...but, amazingly, no more background noise than I have heard with my solid state Superphon Revelation pe-amp phono section at 100% out.

I keep coming back to the same thought/question; is the BPT responsible for wiping out all elements of hum? Is this one of it's more remarkable virtues?  Everything I have ever plugged into it has improved in marked ways.

[JoshK]

I'd just leave it unattached.  You absolutely don't have to attach it, it is an option that needs to be experimented with and you found out which works for you.  But if you want to persue further for curiousity sake, beyond what others already mentioned, try to trace down the bearing grounding and/or the motor grounding and reference this to your phono lead ground.  This is usually what one does when they get static build up that leads to pops when starting a record.  

Basically grounding can be a real pain in consumer audio, its best to right out a list of where everything is grounded (both power & signal ground), what is three prong and two and then try a bunch of experiments and see if you can't figure out what is going on.

[BobM]

It's obviously setting up a ground loop in the Dynaco. I would definitely try grounding it to something else that is not a piece of equipment - like a grounded outlet screw or a cold water pipe.

Josh is right though, you don't really need a ground on the TT, so if its fine hanging loose I might just go with that. I need a ground in my system due to static electricity problems in the wintertime. If you experience this with the ground wire hanging loose than you may want to try a Zerostat to help alleviate it.

Enjoy,
Bob

[TheChairGuy]

Thanks guys....I think I'll just let it 'hang loose' then.

So long as my system ain't gonna' fry from it, or the house burn down - I've got no issues just letting it dangle away.