Noob Stax research - Page 4

There are two kinds of units, Keith: Amps and transformers. Amps generate their own power, and hook up via RCA jacks. You can use the "line out" or "tape out" of a receiver, or just plug in a cd player/ music server / phono preamp directly. All amps need to be plugged into the wall, and in America you want to find one for 110 or 117 volt usage.

Transformers convert power from a speaker amp. That includes receivers, so long as you can use those receivers to drive traditional speakers. Transformers sometimes plug into the wall, and sometimes don't. Either way, every transformer needs a speaker amp or receiver to drive headphones.

Living in the States, you want either a 110 or 117 volt unit. Stay away from the 220s, unless you want to pay someone to modify it for you, which is sometimes difficult.

Except for the SRM-X, SRM-Xh, SRM-001, SRD-X, and SRD-X Pro, which can be run off batteries. And the other version of the SRM-X that doesn't have a bias supply - there is one of those, isn't there? for electrets.

Point of clarification, btw. Transformer boxes are always SRD-something. Amps are almost always SRM-something. The SRD-X is the oddball, because it's a normal-voltage amp with built in transformers.

Yeah, 7 volts isn't that much of a difference.

The voltage at your wall socket isn't going to be 110 on the nose anyway.

I second waiting for a meet before you purchase. Especially if you can hear vintage gear at the meet. I've been to 2 meets, one had all kinds of vintage stats, the other didn't. Personally, I like the cost of the vintage gear over the cost of the new stuff. I haven't heard a lot of the new Stax, but for what I've heard, and with my ears, my vintage gear is anywhere from 80-95% of what new stuff sounds like and 10% to 50% the cost.

Absolutely right, and well stated. Also, do be sure you buy a transformer/amp with the right bias supply to power whatever phones you're interested in. The safe way is to buy a matched set. Generally, though, anything newer that 20 years old uses pro bias, and many things older than that use normal bias. Some amps and transformers can supply both.

Eric, what's the bias supply for electret phones? are they compatible with any drive unit other than the SRD-4?

Electrets have semi-perminant bias, and work with any amp or transformer box.

They have the same plug as a pro-bias stax, but the bias pins aren't connected at all. They'll work from any socket.

As i understand it, they make the electret film by melting down and forming the plastic in a strong electric field which causes the plastic molecules to align themselves with the field.

In theory, the film itself cannot lose it's "charge" except by being exposed to the same sort of forces that formed it.

In practice, a lot of old electrets don't work so good anymore. There are plenty of theories why - Sony thinks it's because capacitive charge builds up in the transducer and in most designs it cannot be drained off.

I have a fully working pair of SR-30's in real good condition, and a fully working pair of SR-80's in goodish condition that need new pads - and SR-80 pads cost more than an SR-80 is usually worth. I also have one kinda good SR-30 driver and one kinda dead SR-30 driver.

Audio-Technica electret drivers look a LOT like stax electret drivers, and they probably all came off the same production line. The AT electrets have different plugs, but should work with any stax box if reterminated or adapted.

Other electrets - who knows? The Sony Uni-Electrets may need a higher step-up ratio than most boxes can provide, and the Toshiba back-electrets don't need so much voltage. And then there's weird stuff like the Philips electrets i saw on french ebay recently, and the elusive maruni es-801.

In short there are two ways to drive a Stax (or other electrostatic headphones).
1. Direct driven amplifier. Like the Stax SRM-007t, SRM-717, SRM-1/MK2, SRM-T1, ... and lots of aftermarket amplifiers like the KGBH, KGSS, GES; Aristaeus, ...
They are complete amplifiers, which take line in level (RCA or XLR). Then output signal to drive the headphone, including bias voltage (to charge the diaphragm).

2. Energizer / Transformer. Like the Stax SRD-7, SRD-7 Pro, SRD-7 MK2, ... and aftermarket energizers like the Illusion ESC-1001.
They are just a transformer box, not a complete amplifier. They accept speaker level input, feed from a regular speaker amplifier. Then output signal to drive the headphone, including bias voltage. The bias voltage can be powered by the mains (most common), or drawn from the input signal (SB unit, which are less common).

Some related info:
* The Stax amplifiers (at least the newer one) are limited to the mains voltage in the country it Were originally sold in. Japan = 100v, US = 110v, Europe = 230v, ...
They also cut away unused cables on the trafos, making it hard to alter the voltage. All this to protect their international distributors.
* The Stax energizers accept any mains voltage, regardless if its 100, 110 or 230v.

Stax headphones operate using two (or actually three) different bias voltages.
- Pro bias (5 pin connector) -> 580 volts. All phones since ~1990 have Pro bias.
- Normal bias (6 pin connector) -> 230 (or 200) volts. Most phones prior to 1990 had Normal bias (230v), while the "really" old ones had 200v.
Pro bias headphones can run on Normal bias amplifiers/energizers, but not the other way around.

Hope that answered some questions.

Oh, I've plugged my normals into the pro socket before (a perfect storm of my wife plugging them in and eric's swiss army extension cord). They certainly "ran", though the constant thumping sound in the right driver can hardly be considered running well.

Not recommended, though luckily it was turned all the way down. I may have done some damage, but at least I didn't arc them.

It's not that I'm surprised that this happened, it's that I'm surprised this happened so soon after i sold you the cable.

be careful with that thing! With great flexibility comes great potential for mishap!

(for those who are just joining us - it's not a custom cable i made - it's a Stax(tm) extension cord that has a 5 pin plug on one end and a 6-pin socket on the other. This allows you to use one extension cord for all your stax 'phones, which is good, and allows you to plug your normal-bias staxen into pro-bias sockets, which is bad. Sherwood wanted one, by pure happenstance i owned two, so i sold him one)

You have two solutions available to your the red pill and the blue pill. If you take the blue dynamic pill you will live a long and fruitfull life obvlious to the other side and with a healthy wallet. If however your take the red stax pill you will know the truth the whole truth and may not want to go back.

What I did was pick up a set of sr40 electrets with an srd4 transformer (no power needed as this is self biasing) and realised the dynamics were a screen to keep us from the reality.

Pretty cheap investment - you will get your money back if you resell sans postage and things only get better. I've now got a set of normal bias original lambdas (have yet to compare with the pro's but my understanding is that they are slightly better) and am saving for the £1000 o2's.

I've downloaded the plans for the blue hawaii done a lot of reading and learned a lot even down to designing a bias and power supply from the ground up but I have a long long way to go before i'm building one.

In the meantime i have a couple of srd7 mk2 Self bias adaptors one of which i'm playing with hoping to replicate or improve on and the other in daily use.

I imagine the next time it happens will be when my kids accidentally plug it in wrong. Since I don't have kids yet, I expect few mishaps in the immediate future.

My poor wife had no idea where this ridiculous plug fit into all those ridiculous sockets.

The one time I'm happy that my wife doesn't care to listen to my headphone stuff.