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Old 7th February 2012, 01:37 PM   #1
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Default STAX Anyone?

Hey Soundfreaks!

My question regards STAX electrostatic headphones:

Being that these are electrostatic, they need a LOT of power to run. In fact, as most of you know the 'phones actually run off the SPEAKER outputs on my Adcom through a switchbox.

What I need to know is this...STAX owners, what type of amplification (brand, type, wattage) has worked the best for you? I am using my Adcom GFA-555II and they seem to work extremely well with that amp but sound nowhere near as good as they do on my old Sansui 2000. What's up with that? Open-ended transistor topology on the Sansui?

Anyhow, I love them so...

Also, if anyone knows if/where replacement headbands are available? I could use one.

Thanks friends!

DoctorRon
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Old 7th February 2012, 07:45 PM   #2
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Strictly speaking, it's not that they require a lot of power. Only their impedance is awfully high (typically about a megohm @ 1 kHz), requiring voltage levels in excess of 100 Vrms for maximum output. Hence the transformer box connecting to the power amp output.

You neglected to mention the model that you have. It has to be an older one, seeing that it uses a transformer-based "energizer" (which, likewise, has yet to be mentioned). Note that two different bias voltages were in use for 'stats, "Normal" and "Pro" bias, with different plugs and energizer units. Some models were available in both versions (e.g. Lambda / Lambda Pro).
They're only selling Staxes with dedicated amplifiers with a line-level input nowadays.

Re: the headband, I'm not sure how many 'stat-heads are infrequenting this forum. You'll probably be much better off asking on Hype-, err, Head-Fi, or maybe even a search for <your model> + headband will already turn up something - I can't imagine a topic like this wouldn't have been discussed before.
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Old 7th February 2012, 09:31 PM   #3
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the Stax are rather low distortion, so you will hear the amplifier's sonic character clearly.

...as the other poster said they do NOT need any real power, they need voltage swing. So, consider making your own "direct drive" amp for them?? There are a number of nice designs online and I think a few discussed here as well...

It is also possible to run them with transformer coupling, but you'd need more like 1:1 transformers, and probably would do well with some tubes to drive that, although Mosfets are also possible, maybe even nice...

Line level input eliminates the need for a largish power amplifier to generate the voltage swing. Most power amps that have the required voltage swing on the output are designed to back that up with current to drive the usual speaker load.

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Old 7th February 2012, 11:45 PM   #4
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Holy crap, is this THE Bear? The Symphony 1 Bear? Amazing! We have a common RW friend.

I appreciate both of your comments. My Stax are 404s.

What is the benefit to running with transformer coupling? Excuse me as I am a network engineer with only a basic understanding of amplifier design, though I know terminology!

If I understand correctly voltage delta is what is needed and a conventional amp, thru necessity, is amping both voltage AND current (to drive big old coils). Estats don't need this current, just the voltage swing. So they act like big caps I guess...is it the "dielectric" that swings along with the voltage, thereby making audible sound? If so I assume that's why my Audiostats clipped most amps--too much voltage swing? Or the disparity between voltage and current? Both? Neither?

On the Audiostats at least there were PSUs to energize them...is this to "charge" the big capacitor (speaker)?

My lack of knowledge embarasses me but thanks for schooling me!!!

I'll leave you with a funny story:

Early in my audiophile days I really wanted a pair of DCM TimeFrame 2000s. I could not afford them though. BUT, I found a pair of Audiosonic e'stats for a steal. When I went to pick them up I meet my first "real" audiophile!! Dedicated pro listening room, four Mac tube amps on the floor with wires as thick as hotdogs neatly routed...you get the point. Anyhow, he fires it all up and puts on a Rush r2r tape at 15ips and...my God, the openness! The headroom! It changed my life. Parting words--"Thanks for buying 'em..just remember they need a LOT of power!"

So I take them home and hook 'em to my badass ; ') new Carver TFM-25. I slowly turn up the volume. You know what's next...as soon as the music passed about 55db I hear "CLICK" and the amp shuts down to save its own skin! So began a long cycle of buy amp, hear click, buy another amp, click, buy the same amp all over IN ADDITION to the one I just bought so I can bridge the two together, click, ARRRGH!! Even with bridged amplification a window fan would drown the Audiosonics out.

By and by I traded them for a pair of DCM TimeFrame 2000s which, you remember, was what I wanted orginally. They were far less "audiophile-tweaky" speakers--but now I had bridged Adcoms to run them with. Funny how in just a few days of soaking myself in gloriously clear decibels the DCMs started sounding "just as good" as the Audiosonics! Then "better." Shows how subjective and malleable the ear is, and how, despite the unparalled clarity of estats, having real accurate and punchy low end more than makes up for it for me. For me, some coloration isn't bad if its pleasant!

Thanks guys,

DocRon

DR
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Old 8th February 2012, 01:45 PM   #5
oshifis is offline oshifis  Hungary
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Quote:
Originally Posted by doctorron View Post
If I understand correctly voltage delta is what is needed and a conventional amp, thru necessity, is amping both voltage AND current (to drive big old coils). Estats don't need this current, just the voltage swing. So they act like big caps I guess...is it the "dielectric" that swings along with the voltage, thereby making audible sound?
Actually, electrostats need voltage and current. Otherwise they wouldn't produce acoustic output power (P = U x I). Being high impedance devices, high voltage and low current is needed (or a step-up transformer). They are frequenty misinterpreted as capacitors, but they are not. Electric charge follows the change of voltage in a capacitor. Charge and voltage are constant in an electrostatic transducer. Charge is constant because of the principle of operation: the charge on the diaphragm is kept constant through a very large charging resistor. The voltage (voltage difference between the diaphragm voltage and the summary voltage (= zero) of the opposing stators) is also constant. Movement and acoustic output is caused by the geometry change of this capacitor, where a resistive part of the acoustic impedance is involved. Like a poor capacitor also "sings" because of loosy mechanical construction, see also this thread:

How to make an awesome teflon coupling cap for very little.
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Old 9th February 2012, 02:05 AM   #6
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Since this is a DIY forum. May I suggest you to build yourself an amp? I've made 2 amps based on this The Tube CAD Journal, Electrostatic Headphones .

The voltage swing is around +/- 300V, and it should play your SR404 plenty loud.

Wachara C.
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Old 9th February 2012, 05:40 AM   #7
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I have used STAX cans almost exclusively since 1984 or so. Currently I use the SR404.

Quote:
Originally Posted by doctorron View Post
My question regards STAX electrostatic headphones:

Being that these are electrostatic, they need a LOT of power to run. In fact, as most of you know the 'phones actually run off the SPEAKER outputs on my Adcom through a switchbox.
As others have stated, they need little power, but lots of voltage.

Almost no one I know or have spoken with run STAX cans via a transformer. I have not used one since the electret SR44 in maybe 1981. I have used a dedicated electrostatic headphone amplifier.

Quote:
Originally Posted by doctorron View Post
What I need to know is this...STAX owners, what type of amplification (brand, type, wattage) has worked the best for you?
I have used a dedicated electrostatic headphone amplifier since I got the Lambda Pro. First was the SRM1, then some direct drive tube units, then a Gilmore solid state design and am building the latest Gilmore unit.

Quote:
Originally Posted by doctorron View Post
Also, if anyone knows if/where replacement headbands are available? I could use one.
Through the STAX agent in your country.
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Old 13th February 2012, 06:19 PM   #8
studeb is offline studeb  United States
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Quote:
Originally Posted by doctorron View Post
I appreciate both of your comments. My Stax are 404s.

DR
So you have 404s, what amp are you currently using?
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Old 13th February 2012, 08:45 PM   #9
GuidoR is offline GuidoR  Italy
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Quote:
Originally Posted by chinsettawong View Post
Since this is a DIY forum. May I suggest you to build yourself an amp? I've made 2 amps based on this The Tube CAD Journal, Electrostatic Headphones .

The voltage swing is around +/- 300V, and it should play your SR404 plenty loud.

Wachara C.
Hi,
I also have made a headamp based on the schematic by John Broskie.
I'm currently thinking to rebuild it with new passive components (resistors, capacitors) and mainly with a new power supply (Salas SSHV2).
The Stax need a huge voltage swing to be properly driven, without the need for /high) current. So, tubes (OTL) territory.
I'm very pleased to listen to my 303s tube-driven, I consider them as an absolute reference for the whole audio band.
And even if you're not an hard-core DIYer, what suggested by Chinsettawong and me it's not a difficult build, apart for the voltage involved.
Another good example is this: the STAX Amplifier


p.s.: electrostatic headphones require to be biased @ 580v: how can you supply them from a power amplifier?
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