DIY interconnects

[mkrzych]

Hello,

I have some spare Mogami 2549 mic cable and thinking to try DIY interconnect with them. Since it is a double conductor shielded wire I have a question for you. What is more common and better for short RCA connection:

1. Should I strand two conductors together, connect them to hot pin of the RCA Neutrik connector and connect the shield on both ends OR

2. connect one conductor to the hot pin of the RCA but second together with the shield being connected on one side of the IC only (afair it's called pseudo balanced).

 

Do you think that type of the solder really matters? I can use Cardan Quad or WBT silver or regular one?

Thanks for your suggestion.

[Audio_ELF]

I would go pseudo-balanced and use a lead free solder.

[mkrzych]

I would go pseudo-balanced and use a lead free solder.

 

Why?

[Audio_ELF]

Why?

Because...

 

That's how I've always made up interconnects and they have always performed well. No more than that.

[Panelhead]

I like 63/37 Kester. I know that lead is bad stuff, but this is good for almost all applications.

Normally I connect the cables at each RCA and the braided shield at the source end only. For balanced cables there are lots of options. 2, 3, and 4 conductor cables.

[mkrzych]

I like 63/37 Kester. I know that lead is bad stuff, but this is good for almost all applications.

Normally I connect the cables at each RCA and the braided shield at the source end only. For balanced cables there are lots of options. 2, 3, and 4 conductor cables.

 

So on the source end I should connect one conductor to hot pin and second one together with the shield to the outer RCA jacket. What about the second end? Od course one connector to hot pin, but the rest?

[pooger]

I've made many interconnects with that cable; and always (for RCA) done it a third way--used both wires at each end, but the shield only on the source end. (This may be same as Panelhead, I'm not sure if he was using all 4wires.) as for solder, I've been on a pound spool of SN62 since building (new!!) dynakits. Like the silver content. But quality of solder is less important than good technique.

[mkrzych]

I've made many interconnects with that cable; and always (for RCA) done it a third way--used both wires at each end, but the shield only on the source end. (This may be same as Panelhead, I'm not sure if he was using all 4wires.) as for solder, I've been on a pound spool of SN62 since building (new!!) dynakits. Like the silver content. But quality of solder is less important than good technique.

 

Regarding shielding connected only on the source end - does it make sense from the electrical point of view, where you need the circuit continuity?

[sandyk]

Regarding shielding connected only on the source end - does it make sense from the electrical point of view, where you need the circuit continuity?

 

For continuity reasons I use cables such as those from BlueJeans cables of a coaxial type construction, as well as DIY cables made from cable like at the link.Jaycar Electronics - Search Results for WB1508

I use quality resin core solder (not the necessarily evil ROHS stuff) for superior connections with decent quality gold plated RCA plugs.

The incoming earths from the DAC etc's cable are then individually switched along with the active conductor in the preamplifier, and the earth reference then comes from the circuit board of the amplifier itself, extending all the way back to the source device.

A lot of care in this area results in improved S/N ratio.

 

P.S.

The soldering technique and preparation matters more than the solder used provided it is from a reputable brand.

[sandyk]

One for Eloise.

 

http://nepp.nasa.gov/whisker/reference/tech_papers/2011-kostic-Pb-free.pdf

 

 

"Lack of Technical Guidance

•DoD

–No position

•Federal Aviation Agency (FAA)

–No official position

•NASA

–Prohibits pure tin as a finish and often requires 3% lead

•European Space Agency (ESA)

–Tin/lead required solder for assembly

[Panelhead]

I may have used an inferior product, but used lead free for years. Went back to eutectic blend lead/tin. I had issues with failed connections using lead free that appeared to deteriorate over a couple years. Have never seen that problem with leaded solder.

The conductivity should not be an issue. The connection should be metal to metal and held together with solder.

[sandyk]

I may have used an inferior product, but used lead free for years. Went back to eutectic blend lead/tin. I had issues with failed connections using lead free that appeared to deteriorate over a couple years. Have never seen that problem with leaded solder.

The conductivity should not be an issue. The connection should be metal to metal and held together with solder.

 

It can be a real P.I.T.A for even an experienced DIY person to remove components on PCBs with several layers that were soldered using lead free solder. Another problem can be the growth of virtually invisible tin whiskers with lead free solder.

These minute tin whisker growths can cause short circuits. During my career with Telstra I would have had to replace 100s of relay springsets that developed short circuits from a spring to the metal frame. Towards the end of my career with Telstra I found that a large value electrolytic capacitor charged to the Exchange voltage of 52V could disintegrate the whiskers if connected directly across the fault, thus saving the need to replace expensive relay springsets. More often than not , there was no visual evidence of anything happening, but the s/c disappeared completely.I imagine that the growth of tin whiskers may also be of concern to NASA and the military.

 

Alex

[mkrzych]

[…]

The incoming earths from the DAC etc's cable are then individually switched along with the active conductor in the preamplifier, and the earth reference then comes from the circuit board of the amplifier itself, extending all the way back to the source device.

A lot of care in this area results in improved S/N ratio.

 

P.S.

The soldering technique and preparation matters more than the solder used provided it is from a reputable brand.

 

So, should I solder the shield to the outer jacket of RCA on the receiver side together with one conductor as at the source end or solder there on that conductor which was at the source end stitched together with the shield? There must be some pro audio standard in this case IMHO.

[sandyk]

So, should I solder the shield to the outer jacket of RCA on the receiver side together with one conductor as at the source end or solder there on that conductor which was at the source end stitched together with the shield? There must be some pro audio standard in this case IMHO.

 

I can't answer that one for you, as it would depend on the equipment itself, and would require S/N measurements to see which method is most effective in the specific situation .Personally, I wouldn't be using microphone cable for interconnects, as I want the earth return resistance to be as low as possible, and with the highest possible screen coverage of the cable.

Most consumer type equipment is designed around RCA type plugs and sockets and the use of unbalanced coaxial type cable.

 

In my case, I made a small battery powered low noise preamplifier in order to boost the sensitivity of my C.R.O. so that I could identify and further reduce any low noise residuals.

RF/EMI from nearby SMPS TV's etc. has a way of getting into everything !

[Speedskater]

From a noise point of view, for longer (more than 10 feet) RCA unbalanced analog interconnects, the most important thing is low end to end resistance of the shield/return conductor. The difference between a poor choice and a good choice can be up-to 25 dB. Bill Whitlock, Henry W. Ott & Bruno Putzeys all write about it.

[mkrzych]

From a noise point of view, for longer (more than 10 feet) RCA unbalanced analog interconnects, the most important thing is low end to end resistance of the shield/return conductor. The difference between a poor choice and a good choice can be up-to 25 dB. Bill Whitlock, Henry W. Ott & Bruno Putzeys all write about it.

 

Well, in my case IC will be 0.5-1 meter, so not so long. Capacitance is also important AFAIK. In the double conductor wire and shield like in my case, to make sure that the groung will be carried only via one conductor not shield I may leave it not soldered one one end. Don't now how it is really matter.

[Speedskater]

At 1 meter neither end to end resistance nor capacitance matter. About the only thing that would matter is shielding, but that's no big deal.

[gmgraves]

So on the source end I should connect one conductor to hot pin and second one together with the shield to the outer RCA jacket. What about the second end? Od course one connector to hot pin, but the rest?

 

 

To do quasi-balanced, you need coax with two shielded conductors. One of which is the "hot" side and one is the return. Connect the hot side to the RCA "pin" as usual and connect the return to both RCA's "barrels". The shield, OTOH, should be connected to one of the two barrels ONLY, and trim the shield on the other end far enough back so that it cannot ever touch the second barrel. Also, don't forget to mark the cable in some way as to which end has the floating shield. Cable manufacturers typically use arrows pointing away from the shielded end. This is important if you are interested in using a "star grounding" technique (recommended) which can *lower one's noise floor somewhat. For those who don't know, star grounding means that all of the shield-ends of the quasi-balanced interconnects terminate at one's pre-amp or amp (in the case of an integrated). In practice, this means that all the interconnects have their arrows pointing away from the preamp, even those connecting the preamp to the power amp. One last thing, for star grounding to work effectively, all the interconnects in the system need to be quasi-balanced.

 

* quasi-balanced cables do not provide any dynamic shielding because even though the shield is no longer carrying the return signal, the return signal is still present on the shield, but it does provide for a modicum of static shielding, which simple unbalanced interconnects do not. Most of the time, in most situations, it doesn't matter but if you live in an RF noisy environment, it can be a problem solver.

[mkrzych]

To do quasi-balanced, you need coax with two shielded conductors. One of which is the "hot" side and one is the return. Connect the hot side to the RCA "pin" as usual and connect the return to both RCA's "barrels". The shield, OTOH, should be connected to one of the two barrels ONLY, and trim the shield on the other end far enough back so that it cannot ever touch the second barrel. Also, don't forget to mark the cable in some way as to which end has the floating shield. Cable manufacturers typically use arrows pointing away from the shielded end. This is important if you are interested in using a "star grounding" technique (recommended) which can *lower one's noise floor somewhat. For those who don't know, star grounding means that all of the shield-ends of the quasi-balanced interconnects terminate at one's pre-amp or amp (in the case of an integrated). In practice, this means that all the interconnects have their arrows pointing away from the preamp, even those connecting the preamp to the power amp. One last thing, for star grounding to work effectively, all the interconnects in the system need to be quasi-balanced.

 

* quasi-balanced cables do not provide any dynamic shielding because even though the shield is no longer carrying the return signal, the return signal is still present on the shield, but it does provide for a modicum of static shielding, which simple unbalanced interconnects do not. Most of the time, in most situations, it doesn't matter but if you live in an RF noisy environment, it can be a problem solver.

 

Thanks, so in case of DAC. CD connected to my integrated amp the shields have to connected to the outrer barrels only on DAC and CD side, but not on the integrated amp side, am I correct?

[monteverdi]

Lead containing solder has a lower melting temperature and will work easier with older solder irons. But I find that connections made with lead-free solder sound better provided one uses the right solder iron. I am using Cardas Ultra pure tri eutectic (Sn/Ag/Cu identical to Johnson Mfg. IA-423) and has a melting temp of 217ºC. Solder is cheap if can buy it small quantities!

[mkrzych]

Lead containing solder has a lower melting temperature and will work easier with older solder irons. But I find that connections made with lead-free solder sound better provided one uses the right solder iron. I am using Cardas Ultra pure tri eutectic (Sn/Ag/Cu identical to Johnson Mfg. IA-423) and has a melting temp of 217ºC. Solder is cheap if can buy it small quantities!

 

Over 200^oC may be too hot for small RCA conductors and inner plug plastic if exposed too long. I am going to use Cardas Quad Eutectic solder - much lower melting temperature - 171^oC.

[Timothy Hoang]

Over 200^oC may be too hot for small RCA conductors and inner plug plastic if exposed too long. I am going to use Cardas Quad Eutectic solder - much lower melting temperature - 171^oC.

 

That is a good solder to use.

 

Usually lead-ed solders will flow much easier even when using a poor soldering iron, thus the reason why 63/37 is so widely used on PCB's because of flow. If you're using higher end soldering irons like MET-CAL then silver content solders (lead-free) can work fine for cable work as it'll melt just as fast, but you'll have to be careful not to keep the heat on there for too long.

 

Like SandyK says, It really depends how your device works with the shield. For starters, i would recommend each end of the interconnect to be made like the other. This means the shield should be connected the same way for each end as well as the signal wire. If you experience noise of any kind, you can simply reopen your RCA connector and cut off the shield that is going into the device to prevent loops.

[mkrzych]

 

Like SandyK says, It really depends how your device works with the shield. For starters, i would recommend each end of the interconnect to be made like the other. This means the shield should be connected the same way for each end as well as the signal wire. If you experience noise of any kind, you can simply reopen your RCA connector and cut off the shield that is going into the device to prevent loops.

 

Not so easy, since one conductor of the two from my Mogami 2549 needs to be soldered on both sides, but the shield only on one side together with that conductor - you need return path being continous.

[sandyk]

Alternative DIY Interconnects.

 

 

DIY Shielded RCA Interconnect Cables

[gmgraves]

Thanks, so in case of DAC. CD connected to my integrated amp the shields have to connected to the outrer barrels only on DAC and CD side, but not on the integrated amp side, am I correct?

 

That's the way Star Grounding works, yes. You don't have to do it that way, but if you want to receive any benefit that there might be from quasi-balanced interconnects, that's how they are supposed to be arranged.