Naim Prefix Earthing
Posted by: Laurie Saunders on 10 January 2002
I would welcome any comments from anyone with experience of using a Naim Prefix. I have a Lyra Helikon/"K" Prefix/Hi-Cap/52/SCap/135s. Installing the Prefix gave a big boost to sound quality, as did adding the Hi-Cap, and removing the "K" boards from the 52. I initially left the earth wire from the Prefix unconnected from the 52, and was delighted to find that RF interference had been banished, and that noise & hum levels were vanishingly low. However,using my CD player as a "reference" the sound from my record player had aquired a slightly "thin" sound,which , though not unpleasant was also less dynamic than I had expected.Connecting the earth wire to the 52 suddenly brought back the RFI, though paradoxically, the sound now also seemed to have more oomph. I then used a ferrite ring on the earth wire, and this has killed the RF, but I can`t be sure if it has also degraded the sound. I am always suspicious of devices that are used to kill susceptibilty to RFI, I believe that they are treating the symptom rather than the cause. For example the Naim "S" phono boards use a filter to kill RF but in doing so they make the sound quality far less good than the RFI-susceptible "K" boards. Any helpful comments/advice on this topic would be welcome
Posted on: 10 January 2002 by Ron Toolsie
If you have not already done so, try moving the earth wire into different positions in space. In some positions it acts as a perfect antenna. Since FM stations are polarized, it may make technical sense to have it vertically (or is that horizontally?). I ended up tying a thread to the wire, lifting it around and when I found the right spot, fixing the thread to a wall allowing the earth wire to occupy the position of least RF pickup. I've not tried the ferrite core yet- I do have one around which will go in place TONIGHT!
Ron
Dum spiro audio
Dum audio vivo
Posted on: 10 January 2002 by Ron The Mon
Ron T,
You said;
quote:
Since FM stations are polarized, it may make technical sense to have it vertically (or is that horizontally?)
It used to be the case that a few years ago FM stations used to broadcast either horizontally OR vertically. It was one or the other. Now, since about two years ago, most stations have changed over (in the U.S. at least) to multiple polarization. Virtually all stations now do this. However, this doesn't mean moving wiring won't affect RF interference. In fact, since I have had RFI from the same radio station for over 20 years(at 5 different locations), I decided to contact the station. The guy who maintains the antenna corresponded to me through e-mails for several days until I solved it! These guys are tech-heads who want to help. If you have RFI, send the station an e-mail.
FWIW, what worked for me was lengthening (soldering an extension) the ground wire and routing it away from all other wires and metal. I started with a really long wire and kept cutting it until RFI was gone. Do this at night when RFI is higher.
Ron The Mon
Posted on: 11 January 2002 by Bosh
I could tell no sonic difference with the earth connected or not (but may be Im cloth-eared as although I can detect display off differences I cannot consistently detect other differences such as direct track access, etc.)
I do however notice a buzz/hum when I touch the cue arm with the prefix earth connected, due to I presume an earth loop
Posted on: 11 January 2002 by Steve Crouch
Laurie
Although off topic, I note you use a Helikon. Is this low output and did you audition anything else? Also, what did it replace?
Cheers
Steve
Posted on: 11 January 2002 by Laurie Saunders
Steve Crouch:
The Helikon I use is not the low output version.
The output is about 0.5 mV (under "standard conditions")
It replaced a Rohmann, which was great but a little too "polite". I auditioned the Helikon against the Lyra Clavis DC (discontinued) The Helikon was the same type of sound only better. I guess I did not audition all the possible options since it is pretty difficult to get home dems of run-in catridges at this level. Unfortunately I have reached the point where dealer dems are largely a waste of time since not only is it impossible to simulate my own room/system, but most dealers I have visited in the last few years don`t seem able to set up a system properly.
Posted on: 11 January 2002 by JosephR
I don't have any such problems with my Prefix, my location's fine I guess ...
I was browsing through Stereophile magazines I had bought in my full round-earth days, and came across a review of the Prefix in 1996, used with non-Naim equipment. Came out as Class A with Supercap, Class B with Hicap. Of course, with Naim equipment, it probably would be Class AA. I just wonder how they connected the Super and Hi Caps to the non-Naim preamps ?
The review did mention they were picking up signals from the FM radio station. If I remember correctly, the dealer then made a slight mod inside the Prefix to cure this. Let me find that darned magazine again and find out who the dealer is ...
Posted on: 11 January 2002 by Steve Crouch
Thanks Laurie
I agree about the difficulty demming cartridges. I am planning to hear the Dynavector Te Katora again now that I'm fully Fraimed but it would be good to hear alternatives given the price!
Steve
Posted on: 12 January 2002 by JosephR
Ok, found the magazine, July 1996, reviewed by Steven Stone and Wes Philips. No mention of any dealer, though. Steven Stone - "... but a small change in the grounding scheme (something about a loop of wire inside the Prefix being eliminated) reduced this to a minimal level." I guess that should jog Naim UK or NANA's memory ?
Wes Philips - "Even out here in New Mexico, I noticed an immediate reduction in the RG-generated "haze" that so frequently overlays music" - he used an "E" for his Transfiguration Supreme (0.25mv) and gave it Class A (unusual review, haha, he must be auditioning very softly)... the guy loved his Prefix so much and found it so good that he claims that he thought he had the Supercap (he didn't know that what he had was a Hicap) - until a guy named Chris Koster asked him to try a Supercap ...
