Petra Cable for phono interconnects

[Mopic5]

Just wanted to bump this up because of a promise I made a while back about posting photos about re-terminating Petra cables with male RCAs phono connects of your choosing. I see Jeff beat me to the punch on the “denuded” Petra connects authored by the ever helpful, Dave Pogue over on AudiogoN.
http://www.terrypogue.com/Dave/NudeICs.html
It should be remembered that this type of connection is relatively delicate and subject to becoming undone with moderate pressure. So it’s probably not the best method if the environment behind your preamp is “high traffic” with a lot of patching/unpatching going on. It’s possible that the “denuded” interconnect might be reinforced with strategic use of hot glue. But I haven’t tried this.

A more tradition, solid join is achieved with soldering iron. Below are pictures that were provided to me by Gatto Murr (Piero) over at Lenco Lovers. Although they picture a solid core co-ax, the basics apply to the Petras – just plan on pre-tinning both the stranded core and the ground braid.

-Mario

 

[hakaplan]

Mario, I'm a little confused. Is this the finished product--without the screw on caps? Is that what "denuded" means here? Why would anyone want it like this?

 

[Mopic5]

No Howard, the denuded Petras connects are on the Dave Pogue link. Or was that what you were questioning? What is pictured here are the solder joins, unsrewed so that people can see.
- Mario

 

[Blue Shadow]

Do the Petra cables have removable/reusable male RCAs or are they molded on requiring cutting them off and tossing them? Since some are using this cable, is the RCA on it of good quality or is it necessary to get good (not the best but good) results?

 

[Mopic5]

Hi Blue Shadow,

The stock Petra connects are fine in most situations. I've occassionally experienced loose fits on a couple of pieces of older preamp gear.
By and large this is a general purpose post on the how-to if you want.
Some DIY plinths have female interconnects already built in, so unless you want to go with a stock 6 footer, you'll be cutting anyway.
And also if you buy this stuff in quantity lengths (extra cheap) you'll be looking to do this.
(For the life of me, I can't remember the internal construction of the stock Petra male IC. Howard??

 

[hakaplan]

Blue Shadow: No the Petra connectors are molded into the cable and it would be difficult to reuse them.

Mario: Okay I see. Dave Pogue's were unsoldered. What you showed were traditional soldered connectors, and then I assume you screw on the caps which are not shown in the pictures.

 

[Mopic5]

Hi Howard,

Excuses, excuses. Stop looking at the pictures and read the post.

All best,
Mario

 

[hakaplan]

Hi Howard,

Excuses, excuses. Stop looking at the pictures and read the post.

All best,
Mario

Not excuses, early senility. :stupid:

 

[Brett a]

I thought I’d post a report on my experience with the Petra cable upgrade on my Pioneer PL-550 (w/ AT 440 MLa cartridge > Cambridge Audio Azur 640p phone stage > Siltech ST-18 G3 interconnects). It’s been about a month with maybe 80 hours of run time since I installed them. I’ve always been open to the idea of cable burn-in, but never experienced it until this project.

When I first hooked the deck up with these cables, it sounded like crap. The highs were pain-inducing; way too pronounced, with a distorted,” etched” sound. I checked my VTA using a small level with two strings hanging from it so I could check that the tone arm was level while on the record. And sure enough, I found that my VTA, which had been set by eye, was actually high about 3/16”. After setting it level, things calmed down a bit, but that sweet LP sound I’d loved so much was still lost. So I set my cartridge from the Baerwald, back to the Stevenson null points. This helped a bit too (maybe). But it wasn’t until after about 20 hours or so of cable burn-in that things really calmed down to the point where I could hear the improvements without being distracted by shrill, out-of-balance highs.

So, after a full month of use, I find the cables to be quite clear, bringing increased soundstage depth and definition-and a generally more ‘open’ sound. However, they still lean a little toward bright; although this could be caused by something else in the chain that these cables simply reveal.

For the time and price of admission, these cables are a bargain. The fact that they revealed problems with my cartridge alignment is a testament to their accuracy. As for the brightness, I'm hoping just a bit more will settle out.


As for their stiffness, the body of the PL-550 has room in it for the larger arch these cables need to make inside the plinth. For strain relief, I removed the stock plastic cable holder and rigged one by wrapping the Petras twice with strips of rubber from a spent bicycle inner tube, then wrapped that with friction tape, creating a plug that I pulled half-way through the metal bracket.

This is just another in a list of tweaks and upgrades I've done to my PL-550 which just continues to sound better and better. It runs as quiet as an LP is clean, has impressive dynamics, clear 3D soundstage. no inner groove distortion, and spot-on pitch. I continue to be amazed at the sound a few hundred carefully spent dollars can deliver in an analog front-end.

Now on to tonearm wire upgrade!:thmbsp:

 

[perryinva]

Interesting..I've never been a believer of burning in cables at all..how a few mV of signal can even remotely affect a wire of any kind is beyond me..and I'm an engineer. More than likely, the changes you hear are the different loading of the new cables on the motor generator (which is what a cart is, of course), which made you aware of deficiencies in your installation. Since higher impedance cables roll off highs, it is only natural that new low impedance cables will make your input brighter. Not to belittle your opinion at all, but I'd be more inclined to think that you're just getting used to the sound. Hve you tried different carts to see how the sound changes? I found that my Signet was WAY too bright with the new Petras cables on my YP-D8, but my V15-III is delightful. May be just the different stylus angles or loading that make more of a difference, but no matter..the Signet sounds very good on my LT-20 with original cables....though I haven't tried the V15 on it yet, still looking to get another one. I also had a a heckuva time incorporating a good strain relief. Copious use of TY-raps worked for me.

 

[Eagle1]

Interesting..I've never been a believer of burning in cables at all..how a few mV of signal can even remotely affect a wire of any kind is beyond me..and I'm an engineer. More than likely, the changes you hear are the different loading of the new cables on the motor generator (which is what a cart is, of course), which made you aware of deficiencies in your installation. Since higher impedance cables roll off highs, it is only natural that new low impedance cables will make your input brighter.

I tend to agree. You're hearing what the stock cables were hiding, good and the bad. If your 440MLa is new maybe what your hearing is it's break in which will get even better. That would make more sense.

 

[Brett a]

Interesting..I've never been a believer of burning in cables at all..how a few mV of signal can even remotely affect a wire of any kind is beyond me.. I'd be more inclined to think that you're just getting used to the sound. Hve you tried different carts to see how the sound changes?

I tend to agree... If your 440MLa is new maybe what your hearing is it's break in which will get even better.

The AT 440MLa is my only cart, so I don’t have anything else to try. It’s not that new; it probably has 200+/- hours on it.
I'm not attached to the concept of cable burn-in and would not argue its existence one way or the other. And until this, I never thought I’d heard it. It’s just that things seem to have calmed down so much since making the corrections; I’m hesitant to think that that much difference could be accounted for as adjustment in perception. Perhaps it can. I wish changing cables were simpler, I could do some A/B-ing with the old ones.

 

[Madman007]

This isn't really TT-related but since this thread is about the cables...are those Petra cables good in general as ICs? Capacitance is important for ICs in general I believe, or is there something special about these that makes them particularly suited to be TT ICs?

 

[hakaplan]

This isn't really TT-related but since this thread is about the cables...are those Petra cables good in general as ICs? Capacitance is important for ICs in general I believe, or is there something special about these that makes them particularly suited to be TT ICs?

I've used them for general ICs and they're fine, but the low capacitance is specifically important for turntables. Line level connections (CD, Tuner, Tape, etc) are largely unaffected by capacitance. Also keep in mind that the same holds for shielding--critical for turntables, not for line level.

 

[Madman007]

Oh really. That's funny because so many cable pimpers say capacitance is key for all interconnects.

 

[hakaplan]

Oh really. That's funny because so many cable pimpers say capacitance is key for all interconnects.

Really? I actually haven't seen that at all. In fact, most of the high end cable mfrs don't even include their capacitance specs. Do you mean dealers or folks on the boards? The only dealer I know of who promotes low capacitance is Blue Jeans, and it's for analog cables, which, although including tape, really implies phono.

 

[Madman007]

Yea I meant manufacturers although I'm sure there are individuals who do as well. Bluejeans is one that specifies it, I feel sure others say it's important but don't give specs, and also generic 'preferable cable properties' type articles. I didn't think analog implies just phono though, isn't any line level signal analog? Maybe you meant the original source is analog but once even a digital source has gone through a DAC it's analog too and should be subject to the same considerations?

 

[Hifirob2]

Howard, maybe you can tell me if these cables are suitable for phono cables. I bought a bunch of these to use as audio cables, and didn't like their sound. They are designed for video use - highly shielded monster cables M series M500v 2meter lengths. Attached is a scan of the back of the package they came in - hope you can read it.

Would these work?

Thanks,
Rob

 

[hakaplan]

Howard, maybe you can tell me if these cables are suitable for phono cables. I bought a bunch of these to use as audio cables, and didn't like their sound. They are designed for video use - highly shielded monster cables M series M500v 2meter lengths. Attached is a scan of the back of the package they came in - hope you can read it.

Would these work?

Thanks,
Rob

Rob, actually they are. I can't read the scan, but I looked up the specs. They don't list the exact capacitance, but they claim it's low, which would make sense if designed for video. They are also double shielded. I don't know how they'll sound, but their design actually makes them perfect for phono. I think they're overpriced so I wouldn't routinely recommend them, but since you already have them, sure, give them a try.

 

[Hifirob2]

Rob, actually they are. I can't read the scan, but I looked up the specs. They don't list the exact capacitance, but they claim it's low, which would make sense if designed for video. They are also double shielded. I don't know how they'll sound, but their design actually makes them perfect for phono. I think they're overpriced so I wouldn't routinely recommend them, but since you already have them, sure, give them a try.

Yes, they are expensive, but I found a guy on eBay a few months back who had over 50 of them for 99 cents a piece. I bought close to 20 IIRC, so I have enough for 10 TT's. I'll practice on the cheap belt drives I have in a closet, as my soldering skills are.....wait, I HAVE no soldering skills.

One of my SL-D5's came with heavy duty Monster cables hard wired (guess the originals gave out).....and I could hear an improvement in the sound. So this will be my next upgrade.

Glad this old thread is still going....

Thanks Howard,
Rob