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Phono cable/grounding/loading questions

Hi, I am finally settling with my analog set up which I run in balanced(RCA @ TT end with ground wire and balanced at phono pre-amp, balanced from phono to preamp..)configuration. I do have some questions that I need answered to convince me what is right. I have looked in to archives but have not found clear cut answers. So here goes:

1. Is the purpose fully designed phono cable always better than the regular ics used as phono cables?
2. If there is no hum present without ground wire connected at TT end, technically is it correct to do so? (When I connect the gorund wire, the presentation a little more articulate but on brighter side)
3. Could I use phono cable with RCA/RCA and use RCA/balanced adapter at phono preamp end? Would I be getting full benefit of balanced configuration this way?
4. My helikon cartridge loading with all new burn-in cables sits at 40 ohms currently and there is still peak (4-5 db) at 10 K hz. Rest of the spectrum very good but this peak is annoying at times. Why is this happening?
5. Bi-wire question: Is it okay to use biwire speaker cables with Jumpers or is it defeating the purpose? More importantly is this dangerous?

Sorry to load you with too many questions but I wanted have only one thread to put my mind to rest.

Thanks in advance!!
nilthepill

Showing 4 responses by dgarretson

dgarretson
2,593 posts
 
1. A dedicated phono cable is usually lighter guage than a std. IC to carry that minute signal. It generally uses two identical conductors for signal-- which might not necessarily be true of a general-purpose IC, where shield could be functioning as a return or be connected to the return at both ends of the cable. But I don't think there is any rule about this.

2. The ground wire to the TT is not an electrical ground. It is a chassis ground. So in connecting it you may have some small relief from RFI and potential problems with static electricity.

3. A phono cartridge is not strictly a balanced source; it is sometimes called a floating balanced source. Just two conductors per channel in opposite phase from each other (representing the ends of a coil), and no electrical ground. Neither end of the cartridge coil has an inherent ground orientation, just an inverted phase relationship in AC with respect to the other conductor (like a loudspeaker). By converting it to an XLR plug you are not really getting the benefits of a balanced source, but may be losing up to 6db to noise(as per prior Audio Asylum post by Victor Khomenko of BAT).

Rather than use an RCA/RCA-to-RCA or RCA/XLR converter, I suggest eliminating excess metal and metal-to-metal contact with a cable terminated DIN-to-RCA or DIN-to-XLR (Assuming your arm has a DIN plug.)

4. I too have a Helikon, which I prefer loaded down with 100R in a BAT P10 phono stage. Subjectively I'm not hearing your 10kHz peak, but I have not taken measurements. Possibly room effect??

5. Please clarify your speaker binding post arrangement. The purpose of biwiring is generally to separate the treble & bass arrays via separate cables back to the amp. Leaving jumpers between the w & t binding posts would defeat the purpose but would not be harmful.

Dave
dgarretson
2,593 posts
 
Raul,

The BAT phono stage has both RCA & XLR inputs but ONLY balanced outputs. The RCA input is inverted within the phono stage and passed through differentially balanced amplifiers for true balanced output to the preamp. As I mentioned above, a cartridge is not a true balanced source. There is no third ground pin, no inversion of +/- with reference to a ground, no common mode noise rejection. So the matter comes down to whether to use the XLR connector or the RCA connector into the balanced phono stage. The XLR input will divide the output current of the coil between the differential amps and produce a lower SNR than an RCA. A low-mass RCA plug (Nextgen, Eichmann, etc.) may also sound better than XLR due to the XLR's heavy metal barrel.

This issue has been covered in several threads elsewhere. Here is a good one for background:

http://db.audioasylum.com/cgi/m.mpl?forum=vinyl&n=111640&highlight=phono+balanced+connection&r=&session=

Regards,

Dave
dgarretson
2,593 posts
 
Nilthepill,

I bought my Hovland phono cable a long time ago and had it terminated DIN to XLR for the BAT P10 prior to reading Victor K's remarks about the preferability of an RCA connection into a phono stage-- a balanced phono stage. I may reterminate the cable RCA. The Hovland people also told me that their cable would sound better with RCA than with XLR, particularly when a low-mass plug such as Tiffany is used.

Inside the balanced phono stage a fully differentially balanced circuit can be derived from a single-ended source and passed to downstream components.

Not sure how your custom cable handles ground. You might just try running a separate chassis ground wire from the TT to the ground post on the phono stage. It probably won't affect the sound.

Not sure what you mean about the speaker jumpers. Are you saying you've biwired the speakers but you prefer the sound with the jumpers in? If so, you've defeated the biwiring and you are not hearing the biwire speaker cables as they were designed to work. But it's also possible that the speakers sound better when not biwired.

Dave

dgarretson
2,593 posts
 
Larryi,

I agree about the Helikon's lighter bass (with my Graham 1.5tc, which is also a little shy in the low bass.) I find it's possible to contour up the bass with a good sub like the Vel DD-15 and am surprised how articulate and linear the bass region now sounds in my system. Sub has one preset EQ for CDP and another for TT. Wouldn't refuse a Titan, tho.

Dave
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