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amt 26th May 2004 08:22 PM

Stax headphone questions
I just picked up a pair of Stax sr-30 with a srd-4 adaptor and no manuel. My question is how does the adapter function. It has speaker terminals and a cable with raw wires (4) on the back. On the front is a switch that selects either "loudspeaker" or "earspeaker". Is the cable missing a headphone jack for plugging into an amp/receiver? And are the speaker terminals for connection directly to an amps speaker outputs? Are these still considered good headphones and worth the time/cost of repairing if need?

Thanks for any help on this.


peranders 26th May 2004 08:40 PM

If I'm not mistaken, your headphones are "electrets" meaning the charge is permanent. You don't need any additional power but you do need high voltage to drive them. The box is transformer and a headphpone jack will not do here. You must have an power amp to drive the transformer.

I have downloaded Stax manuals, not exactly this one, but I'm sure you can find it for your model.

The comfort (for my ears) aren't the best but the sound is :up:

amt 26th May 2004 09:10 PM

Thanks peranders,

I finally got to the Stax history page at their site and found the downloads. Im just about to check them out.


QuarloG 30th October 2013 12:01 AM

I have a question: does anyone know what value the Murata disk cap inside the SRD-4 has?
It is marked P T H and BD4R7M. I'm thinking it's just a ceramic cap, and what with the 5W 27ohm wirewound resistor it begs for an upgrade. The wiring treatment inside mine could be improved as well.

owenhamburg 9th March 2014 06:09 PM

Hope this helps.
According to the SRD5 schematic here it is a 100pf device.

I had issues with ground loops with mine. I replicated the circuit on breadboard and had the same issue. I am not sure this would be a problem with valve amplifiers with floating output transformers, but I could not cure the Hum using the SRD5 circuit without change

In the end I made a newer SRD4 (Possibly a 1980's electret driver with no power bias supply common and cheap on ebay) with a pro bias (some more ladder stages) for my Lambda pros using almost the same circuit. It suffered from ground loops just the same. I cured this with a 240 -> 6V transformer followed by a second in 240V -> 12V in reverse as the supply AC supply, the ladder is then driven with a 120V supply.

If you want to do this soldering the SRD4 transformers center tap is hard as STAX cut off the center tap very close to the transformer in both of my SRD4's. I used a separate box for the power supply. I would suggest the SRD4 in later amps

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