What about BNC connectors ... phono ?

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IslandPink
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#1 What about BNC connectors ... phono ?

Post by IslandPink »

Just wondering, after a recent spell of fiddling with RCA phono plugs ( again ) battling grotty sound quality that sounded like the stylus was covered in crud ....
What do people think about using BNCs or something similar for input to a phono amplifier ?
The disadvantage I've always had in my mind is of it being difficult to use at meetings and/or doing comparisons with other people's kit - but maybe you can buy or make adaptors for these occasions ?

Any thoughts ?
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#2 Re: What about BNC connectors ... phono ?

Post by pre65 »

I thought BNC were "better" for the digital connection on CD players and DACs, impedance match perhaps ?

I do have some BNC - phono adaptors. :)
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#3 Re: What about BNC connectors ... phono ?

Post by Mike H »

If phonos work OK for other stuff, must be something else causing it.

Personally I've found gold plated phonos and instrument cable works quite well. Better than ready-made leads from Maplin et al anyway.

I've made scope leads with BNC, quite fiddly.
 
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#4 Re: What about BNC connectors ... phono ?

Post by andrew Ivimey »

BNC... sorry you're going to remind me... (ummm 'balanced neutral connectors' ?)

I have the usual inconclusive tale to tell about 'interconnects' but I have heard differences... big differences!
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#5 Re: What about BNC connectors ... phono ?

Post by jack »

Bayonet Neill–Concelman (the inventors)

Comes in 50 and 75 ohm forms. Normally used with low-loss coax and good to a couple of GHz when used correctly. Not sure why the connectors would make a difference but the use of high quality low-loss coax may.

RCA connectors are a nominal 75 ohm but that is moot unless the entire signal chain is matched and at audio frequencies reflection etc. will be inconsequential.

If you're really keen you could use SMA connectors with RG316/U coax :)
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#6 Re: What about BNC connectors ... phono ?

Post by andrew Ivimey »

Ta.
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#7 Re: What about BNC connectors ... phono ?

Post by IslandPink »

Thanks !
Well, the issue is cleanliness of connection for the small signals . Phono centre pins and the corresponding internal sleeve thing on the socket tend to get dirty fairly easily, even with gold plating. The surface area for the contact is also much greater than is really needed for the small current signals.
What works for line-level signals of a few volts doesn't necessarily work for 0.4mV level on phono input. The 'diode-ing' effects of dirt on the connector are a much bigger effect ( ie. more distortion ) on a 0.4mV AC signal compared to a 2V AC signal.
pre65 wrote:I do have some BNC - phono adaptors. :)
That's good news, thanks !

So anyway, I'd heard ( possibly first from Allen Wright ) that BNCs are a cheap and effective solution to poor contacts on small signal areas, instead of spending big bucks on fancy RCA's . I was hoping maybe Andrew would comment as I know he & Nick used BNC's in input/output to the LCR choke boxes on thier phono amps.

How does an RCA connector give 75R, Jack ? Wouldn't it need some amount of calibrated coaxial attached, to have an impedance ... or it just the 'capacitor' formed between the inner and outer connector when mesured at GHz frequency levels ?

BTW, as an example, last night I took out the Neutrik phono ( from the tonearm ) on the right ( to horn ) channel and re-inserted it ( twice ) . When I put the stylus back down again, there was a significant increase in low-level info and spatial feeling from that channel. Something has to be done :confused3:
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#8 Re: What about BNC connectors ... phono ?

Post by Nick »

Maybe try silver RCA's at least then the oxide is conductive.
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#9 Re: What about BNC connectors ... phono ?

Post by Nick »

The biggest problem I have found with BNC's is fitting to the wire. Most assume crimp connections, so unless you have the right tools and use the specified coax, the problem moves from the contact to contact connection to the wire to plug connection.
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#10 Re: What about BNC connectors ... phono ?

Post by IslandPink »

Ah, thanks.
Silver Eichmann's could be the best bet if still available , smaller contact areas too.
I'll check HiFi Coll. website.

Good luck with your trip btw . Fingers crossed on the tapped horn measurements !
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#11 Re: What about BNC connectors ... phono ?

Post by jack »

Agreed. For BNC/SMA etc. you certainly need a crimp tool. You can buy reasonably priced crimp tools from Rapid (e.g. 91-2440 £16.49 ex VAT) and its certainly worth paying the money. SMA & SMB are not so bad once you get the hang of it - when working with any coax its also well worth getting a little plastic insulation stripper for that really neat finish...
Last edited by jack on Sat Dec 19, 2015 2:22 pm, edited 1 time in total.
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#12 Re: What about BNC connectors ... phono ?

Post by Andrew »

http://www.keysight.com/main/dhtmlviewe ... 2457296-IS

Hi Mark, I know the chap who designed this box, not name dropping, just he knows his onions, as they say, please note the lack of RCA, proper balanced XLR or BNC is what you get.

When I turned up at his desk with some fancy leads to test something one lunchtime he took one look at my leads, then politely put them in the "bucket" as they call it here, took up his BNC leads put some some nice looking adapters on the device end and gave me a gentle lecture on how generally rubbish RCA most are. He then demonstrated a 12db difference in the noise floor due caused by a poor RCA connectors - to be honest mine were OK, but his point was well made.

I still use RCA's but I think he has a point, personally speaking if you want to stick to RCA as a standard, I would invest in some twist locking RCA like AO uses on his arm rewires, I think that's probably a reasonable way forward.

Hope that helps,

Andrew
Last edited by Andrew on Sat Dec 19, 2015 7:53 pm, edited 1 time in total.
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#13 Re: What about BNC connectors ... phono ?

Post by Greg »

IslandPink wrote:Silver Eichmann's could be the best bet if still available , smaller contact areas too.
I'll check HiFi Coll. website.
Have a look at these.

http://www.ebay.co.uk/itm/MS-Audio-Star ... SwiCRUazYG

Although these are rodium, the seller usually offers them in silver. Much cheaper than Eichmann's but uses the same small contact principle. Downside is they take about a fortnight to arrive from Taiwan.
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#14 Re: What about BNC connectors ... phono ?

Post by Paul Barker »

Trouble with silver is it tarnishes and sound vanishes altogether in surface contact conduction.
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#15 Re: What about BNC connectors ... phono ?

Post by IslandPink »

Thanks for the advice. I'm thinking BNC connectors are more suited to coaxial then - maybe not ideal . The Eichman RCA's are making more and more sense ( see blurb on those ) and looking around I realise I have several pairs knocking around the house on other wires.
I also got some advice from Colin Wonfor on outer wire , so will be trying to make up a new set of phono leads after Christmas .

Opps, missed Greg's post . Will have a look at those too , tomorrow . Must dash !
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