Electrostatic Headphone Scrapbook
From: Jason Grossman
Subject: Re: USED STAX SR-A LAMBDA W/ SRD-7 ADAPTER ELECTROSTATIC HEADPHONES EARSPEAKERS | eBay Date: 20 October 2011 9:38:46 am AEDT To: David Braddon-Mitchell
On 19/10/2011, at 9:58 pm, David Braddon-Mitchell wrote:
Summat like this? http://www.ebay.com.au/itm/USED-STAX-SR-A-LAMBDA-W-SRD-7-ADAPTER-ELECTROSTATIC-HEADPHONES-EARSPEAKERS-/250907101055?pt=LH_DefaultDomain_0&hash=item3a6b3a877f#ht_2552wt_1413
The phones in that ad look fine. They're missing some foam, but so are mine and I don't find it a problem at all. The problem is with the adapter.
As I'm sure you know, electrostatics need a very high voltage. In the old days they used to come with step-up transformers which you plugged into the output of your amplifier. That's what's in the ad. These days, instead of step-up transformers they come with dedicated amplifiers which are tuned to work at high voltage.
By reputation, the old step-up transformers were not very good. Quite likely this is not true; but the problem is that it's very hard to tell, because how they sound depends on both the quality of the transformer and the ability of your particular amplifier to drive it. If you can be bothered to do a test, they have one of these old energisers in stock at Classic Hi-Fi at the south end of King Street. (They actually had 3 last time I looked: Stax, Audio Technica and Koss. Maybe that's what made you ask about Kosses. I tried the Koss in there recently, and didn't like it. When I looked they didn't have any dedicated amplifiers, and they don't sell the headphones separately.)
Proper, dedicated amplifiers are also called "energizers". So, "amplifier" and "energizer" are good; "adaptor" and "adapter" are probably bad.
I have one of the cheapest of the dedicated amps (SRM-Xh). I use it with a decent external transformer. I've never compared it to a better one.
The most expensive amps have tubes. Normally I think tube amps are ridiculous for hi-fi, but I'm told tubes can more easily run at high voltage than transistors, so it's not so completely stupid in this case. Still probably overpriced though. There are transistor options in between my cheapo and the expensive tube ones.
By the way, 30 years ago Stax decided to change the "bias" (which I think means the standing electrostatic charge) that their headphones run at. Almost any headphone you can get these days runs at the newer "Pro" bias, and every amp made since 1981 has at least one Pro bias output, so this is not a big deal. Also, the pins are different, so you can't accidentally run a headphone on an incompatible amp and blow it up. But if you get the headphones and the amp separately, you can double-check on the list at http://en.wikipedia.org/wiki/List_of_Stax_products. I can't remember why they made the change. I'm pretty sure it didn't make a big difference in sound quality.
OK, now let me refine the categories I drew on the whiteboard.

Some info about the current range, written earlier this year: http://www.head-fi.org/a/stax-lambda-primer-for-electrostat-newbies