Hi all, I recently picked up a 72 and as it’s an early one, it has two BNC inputs. Now I know that this has been touched on before, but my question is slightly different. I want to use a Yamaha cd player on the second BNC and I do have the pass through boards. The problem are the connectors. Is the BNC connector suitable to use with a CD player? I’m pretty handy with a soldering iron, but making up interconnects with an RCA on one end and a BNC on the other is not something I’ve done before and BNC’s seem to be designed for co-axial cable. I have some naim BNC’s but they probably won’t fit Mogami 2549 as the hole in the back end of the plug is 5mm and the 2549 is 6mm thick. I could use a spare lavender interconnect I have or get some suitable cable but it would be twin core with a braid. I’m trying to avoid using an adaptor as it’s something else in the signal path.
People say to just use the DIN tuner input but I have a NAT03 on that and I like to select aux for CD replay and phono for the LP12. The cd player has twin rca’s out so logically a left and right socket is suitable.
So is the BNC OK for cd use and can the BNC connector be used with twin core cable (signal and return) instead of coax when making a specific interconnect? The 72 has 50 ohm BNC’s and the 75 ohm sockets are slightly different.
Richard I feel this one may be for you. Ultimately, I could replace the 2nd BNC sockets on the 72 to RCA, those WBT nextgens are nice, but I really don’t want to drill the holes out on the 72. Hope all this makes sense.
All my 72s, when serviced had the bncs changed for rca. It’s what the real world uses despite naims insistence bnc sounds better. I dont think there is any need to drill holes.
And yes, the early 72s with ( potentially) 2 rca inputs were a favourite of mine. I still have one in reserve.
The holes are “D” shaped so that the BNC does not rotate when turning the BNC collar. I don’t think the rca socket would fit into the “D” shaped hole. Does anyone know what brand RCA plugs naim replace the BNC’s with?
Adaptors are best avoided except as a temp measure. If you are unable to fit the correct 50 ohm BNC connectors to your interconnect then you may be best replacing the BNC sockets with good quality RCA Phonos, such as from WBT (keep the BNCs in the box just in case you ever sell on or wish to revert to standard). Your Naim dealer may be able to do this for you.
IIRC BNC was introduced with late 32/early 32.5 when components were more advanced in mid-80s. Naim heard an audible difference between BNC and RCA when using phono input and that’s why the change. (they didn’t hear a difference in 70s so the even-older preamps were with RCA)
They are mean for phono input so better change to RCA, or RCA-DIN using tape input if you don’t plan to change yet (tho buffered – not as clean sounding as Tuner input)
Thanks Richard, so fitting 50 ohm BNC’s to an interconnect is viable for CD replay? Is the ARO arm cable similar in construction to an interconnect cable as plenty of BNC’s have been soldered to them.
Also, the aux input has the variable boards, does some wire have to be cut if these are removed and replaced with the straight through boards? Bit confused about that, Sorry for all the questions, my 552 was much easier to install!
If you replace the 328s with 326 its a straight replacement. If you dont have any 326 boards then you can either use jumpers or remake the wire that was cut initially.
The Aro cable is just an interconnect. BNCs were used to provide an impedance match between plug and socket and minimise losses (more pronounced with the very low level signal from an MC). No harm though using them for line level sources.
If boards are already fitted then there should be no need to cut any links.
Perfect explanation, think I’ll make up the required interconnect as I dont want to butcher such a nice pre. I like the nextgen WBT’s as the newer naim stuff uses them, but they do seem big and I think the holes from the outgoing BNC’s would be too small, so not really a reversable mod. Thank you Richard.
It is more than three decades ago since I had a 72, but I seem to recall that before I got a CDI I think I had input boards with a level adjustment on the CD input, which sounded better than the the straight through boards and ameliorated a lot of the harshness and glare from early CD players. When we got a CDI the straight through boards were better. It was so long ago I may be getting confused though.
The 72 was a lovely preamp and probably my favourite having owned 42-5, 72, 92, 82 and 252. My least favourite was the 252. Beautifully refined but no PRaT. Sadly I never owned a 32-5, which for my money was the nicest looking of the lot.
I would use BNC to phono adapters. That they have an effect upon sound quality in not a given. You can of course find quotes from engineers/sources in both camps.
MS: Let me change the subject briefly and ask you to clear up one or two misunderstandings about Naim equipment – or rather get authoritative answers to questions in response to which I’m sure many people, will have received conflicting opinions. Firstly, why use BNC connectors on the phono inputs of your pre-amps?
JV: If you look at the characteristic impedance of the majority of arm cables it’s somewhere around 60 – 80 ohms. By using a BNC plug/ socket which has an impedance of 50 or 75 ohms, depending on which one you pick, you bridge the interface to the cable with the correct impedance. An RCA (phono) connector has an impedance around 220 ohms so from the signal’s viewpoint it sees a ‘step’ in its path. This step causes reflections (at electron level) and its effects are very audible.
This is apart from the electromechanical aspects – particularly with the large, heavy RCAs which hang on the back of the preamp sockets, waving in the breeze. These are amazingly sensitive to mechanical feedback: they vibrate all over the place and because the signal is so delicate at that stage, the colorations they impose on the signal are very marked. The difference between the low mass, cheapie, RCAs (which tend to sound better assuming they’re made properly) and the huge ‘audiophile’ types is clearly audible in terms of mechanical feedback, ignoring the quality of the electrical connection.
In the systems of ten years ago (1979) you wouldn’t have heard the difference between BNC and RCA. In fact, in those days we did lots of things that I knew would affect the sound quality but you couldn’t hear the effects at the time. The early preamps used DIN phono inputs, which, in theory, should have sounded better but they didn’t And whatever connectors one used the ground connection should be isolated where it entered the amplifier – again I couldn’t hear or measure a difference. So back in the early 1970′s we used the cheapest RCA sockets: there’s no point in using something more elegant if it doesn’t bring any benefit. As systems got better we changed to insulated RCAs. And as they got better still you could hear the problems RCAs caused and so we went over to BNCs.
