Is there a minimum amp needed to drive electrostats?

[ourfpshero]

i just got a teledyne vintage electrostat but cant get any sound out of it. i dont have a real amp yet, just a miniature radio shack amp sa-155. i doubt it puts out a few watts per channel. i also tried hooking up the speaker leads from my z-680 and same result- nothing. should a weak amp give some sound or is there a minimum threshold needed to get these going?

also do electrostatic adapter boxes generally have indicator lamps of some kind?

 

[moonboy403]

Stats' cannot be powered by regular headphone amps if that's what you're asking.

There should be adaptor/energizer of some sort where you connect it to a speaker amp and you power your earspeaker through the adaptor/energizer.

 

[MrOutside]

electrostats vary too much in power requirements for there to be a 'minimum' amp. in the case of stax, the amp provided will generally be the limiting factor and is a decent indicator of what is required.

 

[ourfpshero]

not usng a headphone amp but a cheap regular amp. i hooked up the energizer to the amps and got nothing. should i get a weak sound at least from a cheap amp or is more needed to even start these things?

 

[Uncle Erik]

Electrostats are not like dynamic headphones. You usually have to have an amp that supplies power to the stators as well as the diaphragm. Dynamic headphones just need power to the voice coil. I'm not familiar with those headphones and what they require, but an amp for dynamic headphones won't work.

 

[moonboy403]

Quote:

Originally Posted by ourfpshero /img/forum/go_quote.gif not usng a headphone amp but a cheap regular amp. i hooked up the energizer to the amps and got nothing. should i get a weak sound at least from a cheap amp or is more needed to even start these things?

Any decent speaker amp should be able to drive any stats to an audible level. So maybe your energizer or earspeaker is shot?

 

[Duggeh]

Pictures, especially of the insides, might be helpful in diagnosing your problem.

I'm not familiar with the headphones you have, although theres an evens chance that they're some kind of Stax OEM model, or possibly an electret. Does the transformer have a mains lead? If not then its possible that it's self-biasing of course, in which case the input power will need to reach a certain level in order to bring the phones to life. However 10 good watts should be a sufficiency to get some sound out of them at least.

Also be certain you've not connected up any speaker loop through there may be to the amp rather than the input leads.

 

[ourfpshero]

heres a few pics. just tried these with a panasonic dvd player/5.1 amp. the satellites are small so i'm sure not much power. i got a whisper out of the headphones rt speaker and a slight sound from the lt. need a real amp! craigslist here i come!

 

[HeadphoneAddict]

Quote:

Originally Posted by ourfpshero /img/forum/go_quote.gif not usng a headphone amp but a cheap regular amp. i hooked up the energizer to the amps and got nothing. should i get a weak sound at least from a cheap amp or is more needed to even start these things?

Sometimes when the phones and energizer are old, they don't charge up well and the sound is very quiet. Sometimes if you leave the music playing the phones will slowly charge up over time and start working. But sometimes there is some parasitic capacitance that has developed and they take forever to charge, and once you turn them off they go back to being hard to charge the next time, and the next and next. That's when the drivers must be replaced.

PS: I am not sure I would invest in a costly amp till you know these headphone are not dead.

 

[ourfpshero]

Quote:

Originally Posted by HeadphoneAddict /img/forum/go_quote.gif PS: I am not sure I would invest in a costly amp till you know these headphone are not dead.

i said craigslist!

plenty of amps for 25$

 

[Duggeh]

They're electrets, not electrostatics, so there won't be an issue with any bias supply.

Some old electrets do just go dead though, although the old line about all of them inevitably wearing out should be taken with a very large pinch of salt.

 

[Hirsch]

Electrets are self-biasing, using a magnet to provide the charge on the membrane rather than external current. Principle of operation is similar to an electrostatic headphone, but the source of the charge on the membrane is not. Once the magnet has died, so has the headphone. Some magnets have a very long life. Others don't.

An electret adapter would attenuate the signal from a power amp to levels appropriate for the headphone, but would not supply bias voltage, since it's not needed.

 

[Faust2D]

Quote:

Originally Posted by Hirsch /img/forum/go_quote.gif using a magnet to provide the charge on the membrane rather than external current.

No.

To put it simply, electret headphones are electrostatic headphones. More specifically, they're a type of electrostatic headphone. The only difference is in the method by which a fixed charge is placed on the diaphragm. An electret foil or film is a thin polymer sheet that has been given, and which will retain, an electrostatic charge of a few hundred volts. It would be as if the hard-rubber comb you used to do simple static-electricity experiments at home (picking up tiny bits of paper, making a small stream of water bend) could stay charged indefinitely.

The only mechanical difference between an electrostatic headphone and an electret electrostatic headphone is the material the diaphragm's made of and whether or not there's an electrical connection to it from the outside world, namely from a bias-voltage supply.


OP:

Try running the phone with the amp for at leat 24 hours at moderate volume. I know of a few headphones with the same problem that "woke up" after some time. Might be the parts in the box or some issue with the headphones. 10w is sufficient to drive most electret very loud.

These look very similar to old AT phones:

 

[ourfpshero]

further adventures. i took my electrets to a local thrift store and asked to hook up my headphones with the promise of buying the amp if it worked. i hooked up my cans to a montrous harmon kardon receiver and got nothing but a burning smell from the receiver! apparently it was 'repaired' in house. that ended that
went home and hooked them up to a boombox i have had forever on garage duty. suddenly both headphone speakers make quiet, but balanced , sound! running them overnight still produces only quiet volume levels.

 

[HeadphoneAddict]

So, maybe the more powerful amp did awaken the phones?