Hello all,
A while back, I wrote about a hum problem that I had trouble with. Since I'm still suffering from it, I thought I'd post back with more information and a video to illustrate my point.
The video is here :
My set-up is as follows :
Pro-ject Carbon Esprit, with Ortofon 2M Red
Rega Fono Mini phono preamp
Atoll In30 integrated amp
Dali Zensor 1 speakers
Nuforce Icon HDP DAC
I use the Pro-ject RCA cables that came with the turntable, which is grounded to the pre-amp.
All this is connected to the same surge protector (Belkin Surgemaster Gold as it's called), as are a PC and a monitor.
The hum shown on video is triggered randomly. Often many times during a single listening session (today, for instance I heard it at 4:08, 4:21, 4:27, 4:38, 4:46, 4:52 and 17:01PM, typically I hear that sound for a few seconds before it stops and eventually starts again), some days not at all. I sometimes get the hum when the turntable is not actually turning (as in teh video). I hear the hum on both channels.
I've used three different turntables : my own Pro-ject Carbon with an Ortofon cartridge, a Rega RP1 with another Ortofon cartridge (an OM5e) and my vintage ERA 444 with a Shure cartridge (not sure what the model, other than it's a p-mount), and get that same hum with both modern-day Ortofon-fitted turntables and not at all with the ERA. I've also used a different pre-amp (a cheap TC-4 pre-amp) and got the hum with it as well.
I've put ferrite chockes on the TT cables, to no avail.
I'd be very grateful for some help with this as the issue's driving me mad.
Grrr
- the "good" old case of some grounding problem - and as I can see you are from France - yes, ERA used to produce decent
platines - at least they were properly grounded, not like Pro-Ject or its older relatives, Tesla or better known in the West, NAD. All built at the same factory, now in Czech Republic, all exhibiting the same grounding problem(s). And , unfortunately, they are by no means the only culprit ...
I have the NAD 5120 (Tesla NC-430 ) - that is more or less the same, only worse, when hum is concerned. NOT much you can do about it save modification and PROPER grounding - the kind of buzz/hum as examplified means that the tonearm aluminium tube is not grounded - and there is nothing more susceptible to picking up hum/buzz than than a "shield" in the "air".
The worse source of hum/buzz in turntables is any metal platter that does not have proper connection to the ground - as the size of the unshielded
metal is governing how much it will be picked up, platter generally being the largest surface in a TT.
Get yourself a Digital Multi Meter ( or ohm meter, regardless if it is analog or digital ) and check for continuity. Arm tube ( you might be forced to scrape off some paint in a remote invisible spot in order to make an electrical contact - naturally it occurs under the head of the cartridge mounting screw ). It should read close to zero ohm
( anything above say 10 ohm means questionable connection, in your case I expect infinite resistance = open circuit ). The easiest way out ( without having to dismantle the arm and introduce the fifth wire for the ground AND having to find a way to make a permanent low resistance contact with the arm tube - (the reason why it is not being made in the first place )) is by soldering a short piece of tonearm wire to either of the ground lugs - coded green for the right, blue for the left channel - and attaching the other free side of that wire to the tonearm tube - again it is the easiest to make contact at the cartridge mounting screw, most elegantly to the metal washer between the arm and screw itself. Not as good as a separate ground wire ( as it introduces cable capacitance difference between the two channels that can and DOES affect MM cartridges - LOTS of arms in the market suffer from this ... ). If done neatly, can even look nice. I use this technique with my Eminent Technology ET2 tonearm in case I experience hum. It is highly sensitive regarding the internal resistance/impedance of the cartridge being used; the lower it is, less the susceptibility. MMs are unfortunately high impedance devices ( couple of hundreds of ohms resistance and couple of hundreds of milihenries of inductance on the average ) - and buzzing as in your case is perfectly normal.
You probably would not be able to hear hum/buzz with a low impedance MC cartridge - some quirky way to "force" the user to opt for a (generally) costlier cartridge in the end ?
Ferrite chokes only "help" in case of radio breaktrough (RFI) into phono input - but can not do anything regarding hum. Best way not to pick RFI is the use of quality ( which does necesillary NOT equate costly ) phono cable with separate ground - my TCC-750 can turn into quite a good radio if I am sloppy with phono connection(s).
The fact that you experience the hum randomly may also mean there is an intermittent contact somewhere - and as a tonearm is subject to mechanical vibration per default, it may be hard to track it down.
Vive la difference - mais SANS le bruit ! Bon chance !