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Vintage Stax (Clone) ?, stop laughing...stumped again

post #1 of 6
Thread Starter 

I'll get to the laughing part soon.

First things first. I bought on ebay a clone; the hp100 that was marketed by everyones favorite Radio Shack. Seriously, they did have some really nice things and at one time could get just about any electronic component you'd ever want. These days it's more of that "you have questions? we have cell phones" routine. Anyway, the cans arrive without the transformer set and as you can probably imagine after checking the plugs; hey! six pins I wonder if.......oh yeah it works, fits anyway. So, Plugged in turned on kinda moment of truth....and......wait......oh no, channel imbalance, left side fine right side weak or nothing. This has happened before to me and after some research discover that failing drivers do this and it's time to retire the headset. Undeterred I immediately open the cups to check the wiring and drivers. Everything looks connected. Three wires on one side, connects and three more across the headband to the other cup. Hummmm, maybe i should listen to them now?  turn on, hold to ears and.......

 

 

OK, volts are not amps and that's a good thing. At this point lesson learned and I contact the seller and explain that they don't work. Two days go by and I decide to try again. This time I notice when I try to balance the channels that the left never losses volume, could it be that the one post I'd read that said that they just plug in and ALL the other posts that say you'd need to rewire them is TRUE, AS READ ON THE INTERNET! I

 

OK, I have a multimeter should be simple to check continuity from speaker leads to the pin and re solder the channels properly; no. srd4 is a no go; no center pin, srd6 is a go except two blue wires, two red and one green.

 

Were you in my place would you rewire the spare adapter or rewire the headphones to match the adapter?

I guessing now, Green wire is bias and red and blue are channels.

I have the Realistic power schematic but it does me no good since outputs don't match pin assignments. 1 through 5 on the diagram  except I need the plug  codes: 12 o'clock, 3, 5, 7, 9 and center. It might be that the headphones really are defective and I don't have to refund the refund.

 

If anyone has the codes for an SRD-6 that would be great. Comments such as "hey D#@&a!@ there electricty in those wires" also welcome.

 


Edited by ri_toast - 3/11/12 at 9:50am
post #2 of 6

6 pin is low bias headphones. And given the age, they could take days to charge up.

So don't worry about the channel imbalance until they have been plugged in and turned

on for a week. Radioshack electrostatics are just relabled stax.

 

Don't rewire for 5 wire, thats high bias and will destroy the headphones.

6 wire is identical to 5 wire except there are 2 bias pins, and the second

one is in the middle.  230 volts MAX on the bias line.

 

look here in the middle for the correct wiring

http://gilmore2.chem.northwestern.edu/projects/showfile.php?file=gilmore_prj.htm

 


Edited by kevin gilmore - 3/10/12 at 2:56pm
post #3 of 6
Thread Starter 

thanks Kevin. I now have a new bookmark for Headwize. I'll just leave them plugged in for a week and see what happens.

After that I'll open up the box and trace back from the headphones to the pins and confirm the diagram. The one Green wire in the SRD-6 doesn't appear to be jumpered to pin 6, possibly internally in the headphone. I can check that as well.

Magnavox and Marantz also had this model except those units (the ones I had seen) had two sets of plugs; dual headphones.

post #4 of 6
Thread Starter 

What I found was that overnight plugged into a powered only (no signal) SRD-6 was that the right cup that was "soft" has come back. cool

However the balance control on my amplifier does not change the headphone balance; it's not the amp. Now that Kevin G has shown me the schematic I thought it would be easy to identify the connections Left, Right, Pos and Neg using a multi meter with continuity. From inside the cups on the driver wires to the pins on the plug. Nothing doing, from the wires inside the cup to the plug only two connections (now three) show anything. They are plug numbered 3: right cup black wire and pin number 2 left cup green. It doesn't show (an audio signal) just some dropping numbers. I assume this is the magnetic charge being discharged....from the right cups white wire to the center pin 6 i get some reading as well

 

the earspeakers sound ok but I don't understand how the headphones are wired. there are three wires to each driver and I know that bias is one of these on each along with positive and negative. The stax adapter has a one bias wire on pin 1 (the center:6 is a dummy pin) None of the wires on the drivers show any continuity to any other wire on the drivers. My guess that this would be bias. On three wires to the plug I get some readings.

 

IMG_20120311_132201.jpg

 

IMG_20120311_132142.jpg

 

its a puzzle, esp when i use the balance control on the amp, somethings not right. <shrugs>

 


Edited by ri_toast - 3/11/12 at 12:15pm
post #5 of 6

Correct me if I'm wrong, but electrostatic speakers are essentially the same as capacitors, so no actual current flows through the wiring, unlike in dynamic headphones.

post #6 of 6

Current absolutely does flow thru a capacitor. Its just out of phase with the voltage.

All capacitor coupled otl tube amps deliver power to dynamic headphones thru

an output cap.

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