• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Pre-Amp / Pwr-Amp Jumpers

pustelniakr

pustelniakr

Silver Miner at Large
Subscriber
This one might be one for EchoWars...I have 2 SA-9500-IIs that need the pre-pwr amp jumpers. One has some but they are corroded and not pretty. The other probably had an equalizer connected between the amp stages. I saw the restoration work you did on one fellow's amp, that used brass jumpers and thought you or someone else could help.

Where do I need to look to get a couple sets, or how would I go about fashioning them?

Suggestions please?

Rich P
 
Register to hide this ad
If you don´t have any jumpers for the moment, take just a normal stereo chinch audio cable for connection.

302929_BB_00_FB.EPS.jpg
 
My local True-Value hardware sells 12" lengths of 1/8" brass rod. I bend it around a wooden dowel wrapped with duct tape to the proper bend, cut and chamfer the ends with a Dremel grinding stone, and sand smooth. Polish with Brasso, and yer done!

The tricky part is the proper bend on the dowel. Work this out carefully or you will be wasting a few brass rods before you figure it out.
 
Echo how about some step by step pics and some of the rods themselves. I am having a hard time finding them (might be me too :stupid: ).....

Yank
 
Go to your local welding supply house and get 1/8th brass brazing rod. It comes in 3' lengths and is relatively cheap. I buy 5 pounds at a time because I find thousands of uses for it.
 
the ingenuity of folks to keep this vintage stuff up n running...i'm taking notes....;)
 
Bigyank said:
Echo how about some step by step pics and some of the rods themselves. I am having a hard time finding them (might be me too :stupid: ).....

Yank
Click to expand...
My local True-Value hardware carries 1' lengths of the stuff. I used a 1/2" ratchet extension and wrapped it with duct tape to the desired diameter (see pic). Wrap the brass around the duct tape so that the ends are more or less parallel. Then it's just a matter of cutting the ends off to a proper length (I have some spare jumpers that I use for a guesstimate of length), and I carefully grind the ends to a slight chamfer and smooth the rough spots with Scothbrite. Lastly, you may have to adjust the width slightly so that it fits properly in the jacks.

Very simple.
 

Attachments

  • Homemade_Jumpers.jpg
    Homemade_Jumpers.jpg
    28.4 KB · Views: 630
There's no safety risk...the voltage on the jumpers is less than a volt. Plus, there's millions of receivers and integrated amps out there with metal jumpers, with the only related problem being misplacing them after pulling them out for some reason.
 
I've made quite a few also. I have used 1/8" copper grounding rod and two pair of vice grips to do the bending. I then taper the end with a grinding wheel and then sand them lightly.
 
Your local model airplane or train hobby shop will most likely carry K&S hobby metal a normal display also includes 1/8th inch copper rod. If you want to make an audiophile grade version of the jumpers.
 
Another way is go to Home Depot, and in the electrical dept you'll find 10 GA bare Copper wire sold by the running foot, something like 40 cents per foot. Get a couple feet, plenty to mess around with. Much better metal at passing a cleaner musical signal than Brass, and the Copper is much friendlier to bend, it's more malleable than the brass rods.

A good quality, inexpensive alternative approach.



cheers
 
10ga wire is too small (spec is 0.1019"). 8ga is about right (0.1285", but might be tight), but it's hard to find in solid-core...most 8ga wire is stranded.
 
This is not a critical thing...if an old coathanger would fit, I would have said it would be fine. You're getting into the realm of tweaks, and as far as I'm concerned the original steel jumpers are the preferred tool here.

Any interconnect will be many times longer than the original jumpers, and I'd propose that that is a bad thing.
 
The original "steel" jumpers on my SX-939 actually have what I assume is a copper core with some kind of chrome or stainless steel plating.

I was sanding with sandpaper to get some corrosion off and underneath the plating I can see copper colored metal. So my guess that even the OEM jumpers are just plated copper. I should have just stuck with using one of those green Scotchbrite pads and Brasso.

Good to know it's not going to be a hazard.
 
EchoWars said:
10ga wire is too small (spec is 0.1019"). 8ga is about right (0.1285", but might be tight), but it's hard to find in solid-core...most 8ga wire is stranded.
Click to expand...

MY error there.

I was just at Home Depot, and there's spools of solid core Copper wire of various gauges. Yeah, the 8ga was around 40 cents a running foot. Not stranded. Round out the leading edges of the jumpers and they should slide in if the center to center alignments of the new jumpers are close. Often enough, there's slop in the old jacks.

hth

cheers
 
Danger Boy said:
what if you used silver wire or silver interconnects as jumpers? would that be good or bad?
Click to expand...

Pure Silver, per se, is the best conducting metal on the planet. It's really excellent for audio purposes. I make up my own, because I know how to make it happen, and have the metals backround.

However, you would be hard pressed to find this gauge wire in pure silver anywhere. One *might* be able to find the gauge in *Sterling*, which has Copper added and is the usual alloy found around being used(it makes the final blend harder for function durability). Copper is the next best conducting metal. However, the Copper added to Silver makes the final blend prone to tarnish. Copper is inherently a very dirty metal, and very difficult to refine clean. It's why great efforts are usually taken to *electroplate* the Copper parts, simply trying to prevent oxygen from reaching the Copper. If no oxygen reaches the Copper, it doesn't corrode. Gold is usually used as one plating choice, it never tarnishes. Gold passes a signal better than Rhodium, which is getting expensive. Less noble metals get used as cost cutting happens, Nickel, chrome, etc... But those impact the high frequencies which travel on the surface(s)

Easy way to clean Copper or Sterling is to get a cheap bottle of a Tarnex-type product. It smells like rotten eggs<g>, but it's easy to just dip the parts in the stuff, they clean in seconds, rinse well, dry well, and just slide them back in the stereo.

Fwiw, pure Silver oxidizes a white frosty color... These oxides do not impede an electrical signal, completely contrary to Copper oxides

fwiw again, I just picked up a Pioneer SA-9800 integrated amp. It's a wonderful piece. It came with the stock jumpers. I listened for a while that way. Then I redid the music after taking out the stock jumpers, and put in some pure silver ones. I could certainly tell the differences!... It's just one more thing that can be done to help the music pass by cleanly.

It's just the way it is using pure silver for audio purposes.

Problem is, manufacturers(ooh la la *designers*) who make up the stuff for retail market, usually charge obscene prices for their products, giving Silver a bad rap.
 
EchoWars said:
10ga wire is too small (spec is 0.1019"). 8ga is about right (0.1285", but might be tight), but it's hard to find in solid-core...most 8ga wire is stranded.
Click to expand...

EW is right about a possible too tight a fit....and:

Reason for this happens when we DIY'rs have to cut the wire. If we can cleanly saw the wire ends off, the wire shape at the end remains round. Otoh, if we use double-bevelled side cutters to snip, the ends of the round wire get compressed out of round(mildly oval), causing a too-tight fit into the RCA. Using flat-sidewalled flush cutters tend to chop a cleaner edge, however if the metal beign cut is soft like Copper, there will still likely be some small out-of-round artifact. It is up to the DIY'r to dress down whatever small bulges happen on the wire ends, then reshape the wire ends round so there's no sharp edges of any kind.

fwiw, pure Silver is one of the most malleable metals on the planet. Cutting Silver round wire with side cutters deforms the round wire shape everytime. It's very soft. Especially if the body of metal is in an annealed dead-soft state.

hth

cheers
 
Thanks to EchoWars for linking me to this thread.

To eliminate corrosion issues for some materials, it may be possible to take the finished jumpers to a local jeweler (with an in-house shop, of course) for rhodium plating. The cost on this should be minimal (if you have a good relationship with a local jeweler, maybe free). I believe rhodium plating will not tarnish at all, but it will not be very durable. But if you just leave the jumpers in place, it should work fine.

Also, gold-filled wire would also work, and would not tarnish very easily, but I am not sure if it's possible to find gold-filled wire this size.
 
Will V. said:
Thanks to EchoWars for linking me to this thread.

To eliminate corrosion issues for some materials, it may be possible to take the finished jumpers to a local jeweler (with an in-house shop, of course) for rhodium plating. The cost on this should be minimal (if you have a good relationship with a local jeweler, maybe free). I believe rhodium plating will not tarnish at all, but it will not be very durable. But if you just leave the jumpers in place, it should work fine.

Also, gold-filled wire would also work, and would not tarnish very easily, but I am not sure if it's possible to find gold-filled wire this size.
Click to expand...


Jewelers don't usually work for free, especially when Rhodium has a Market value of around $9000 per ounce at present.

Yes, Rhodium is a member of the Platinum family, so it will not oxidize. And yes, it's pretty much impossible to find gold-filled wire anywhere in this thickness. Actually, gold-filled per se went out of market fashion many many years ago, and those USA mfg'rs died and vanished.

Pure Silver plating is more cost effective, and because it is pure, it doesn't turn black, but maybe a frosty white, which conducts electricity. Sterling, otoh, has Copper added to the mix so folks can produce a stiffer end product. However, the small amount of Copper in Sterling is the culprit which causes Sterling to turn violently black.

I just made up a pair of Copper wire jumpers(wire from Home Depot), dressed them down, and pure Silver plated them. Before playing, I annealed them into a dead-soft state. The metal is now pretty limp, even though it is thick wire. It is super easy to bend them with mild finger pressure. Copper is the next best metal conductor, second only to Silver.
 
Marko said:
Jewelers don't usually work for free, especially when Rhodium has a Market value of around $9000 per ounce at present.

Yes, Rhodium is a member of the Platinum family, so it will not oxidize. And yes, it's pretty much impossible to find gold-filled wire anywhere in this thickness. Actually, gold-filled per se went out of market fashion many many years ago, and those USA mfg'rs died and vanished.

Pure Silver plating is more cost effective, and because it is pure, it doesn't turn black, but maybe a frosty white, which conducts electricity. Sterling, otoh, has Copper added to the mix so folks can produce a stiffer end product. However, the small amount of Copper in Sterling is the culprit which causes Sterling to turn violently black.

I just made up a pair of Copper wire jumpers(wire from Home Depot), dressed them down, and pure Silver plated them. Before playing, I annealed them into a dead-soft state. The metal is now pretty limp, even though it is thick wire. It is super easy to bend them with mild finger pressure. Copper is the next best metal conductor, second only to Silver.
Click to expand...

Silver plating would be more cost-effective, but I used to work in a jewelry store, and we weren't set up to plate in silver, but we were definitely set up to plate in rhodium. I think most jewelers are the same way.

And jewelers do favors for free, depending on how well they know you.

Edit: I just looked at the five year price chart on rhodium, and it has increased about 24x. Unbelievable. I worked as a bench jeweler about fifteen years ago, and the price of rhodium was nothing like it is now, obviously. We would sometimes plate a return customer's ring in rhodium for free. We also used to do some other minor work for free, that's the way small town jewelers survive.

Solid silver plating would be more cost-effective, but I don't know who does it. Sounds like you are set up for it,though.
 
You must log in or register to reply here.
Back
Top Bottom