Stax earspeakers sound better when left on
Jun 20, 2004 at 12:27 AM Post #31 of 43
A while back someone sent me some marantz electrostatic headphones
that had not been turned on ever. (more than 20 years) Took 4 days
for the charge to build up. (low bias)

It should be noted that all stax transformer boxes did continuously
charge the headphones when plugged in. They did so with a voltage
doubler directly off the AC line. All of these were low bias to my
knowledge. I do not think there ever was a high bias transformer
box.

Here is a quickie single sided board layout.
http://gilmore.chem.northwestern.edu/biasboard.zip
 
Jun 20, 2004 at 2:49 PM Post #32 of 43
On a related note: does any one know how long the tubes in a Stax amp will last, if the amp is left on almost constantly? I know they last very long, but how long? And is it easy to replace them by yourself?

As for the heat problem, I use the most primitive approach -- to fan the amp manually! it is surprising that vigorous faning br the hand for just one minute can cool it down quite a bit.
 
Jun 30, 2004 at 11:36 PM Post #34 of 43
Quote:

Originally Posted by kevin gilmore
It should be noted that all stax transformer boxes did continuously
charge the headphones when plugged in. They did so with a voltage
doubler directly off the AC line. All of these were low bias to my
knowledge. I do not think there ever was a high bias transformer
box.


I modified my SRD-7 transformer box by adding another stage to the voltage doubler; with the result that it drives high-bias headphones. So it can definitely be done.
 
Aug 17, 2005 at 3:21 AM Post #37 of 43
I just wanted to resurrect this thread to see if anyone had developed a box that could keep the stators in electrostatic headphones charged, thereby negating the need to keep the tube amp on all the time.

Simon
 
Aug 17, 2005 at 3:56 AM Post #38 of 43
the circuit kevin gilmore posted will do it simple enough. If you can't find a proper transformer, you can always connect two radioshack 120-24v transformers back to back w/ a fuse. Quad the voltage for ~500V bias. I'm using that right now and notice the charge up time even more w/ my leaky electrostats.

http://hyperphysics.phy-astr.gsu.edu...oldoub.html#c3

DSCN2677.JPG
 
Aug 17, 2005 at 3:56 AM Post #39 of 43
You could use an inexpensive Stax amp like the SRM-212 to keep the stators charged; the 212 would also double as a transportable amp should you get the mad urge to take your cans on the road. I don't know how much charge, if any, the headphones would lose from getting unplugged and plugged back in, though.
 
Aug 17, 2005 at 5:37 AM Post #41 of 43
"just wanted to resurrect this thread to see if anyone had developed a box that could keep the stators in electrostatic headphones charged, thereby negating the need to keep the tube amp on all the time."

As I mentioned in an earlier post, you can look for a used Stax SRD7 pro adapter. This adapter will supply the bias voltage needed to keep the diaphragms charged. I have seen them used on eBay or Audiogon for about $35 - $65.00.

"Does this apply to the senn electrostats? What about when using stax amps to drive them?"

Yes, Except of course the Senn's need a plug adapter to work with the Stax.

I personally do not worry to much about the charge time. I use the phones daily and they will maintain a charge as long as I do not discharge them by touching the pins. I usually power up the amp (717) about an hour before using.

Ken
 
Aug 17, 2005 at 8:52 AM Post #42 of 43
Quote:

Originally Posted by Ken B
As I mentioned in an earlier post, you can look for a used Stax SRD7 pro adapter. This adapter will supply the bias voltage needed to keep the diaphragms charged. I have seen them used on eBay or Audiogon for about $35 - $65.00.Ken


Ken

Thanks for reiterating your suggestion. I will keep a look out for one of these.

Simon
 
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