Stax Adapters/Energizers for Electrets?
Aug 2, 2002 at 6:44 AM Thread Starter Post #1 of 7


100+ Head-Fier
Jun 3, 2002
I own 2 pairs of Stax electret earspeakers (SR-30 & SR-80) which are currently powered by a Stax SRD-4 adapter and 2 pairs of electrostatic earspeakers (Lambda Signature Pro & Lambda Nova Signature) powered by a Stax SRM-T1.

I've been thinking about upgrading to a better apapter for the electrets but have been confused with the range of adapters and energizers produced by Stax, and was wondering whether anyone could help me out here.

According to the list of apapters and energizers posted on the Electrostatic Headphone Circuit (, Stax apparently produced 2 different lines of adapeters/energizers, namely, a line of adapters beginning with the prefex "SRD" and a line of energizers beginning with the prefix "SRM".

Based on my current equipment used, I believe that the "SRD" adpaters are normally used to drive the electrets, whilst the "SRM" energizers are normally used to drive the electrostatics. However, upon conducting a search on the internet, I've been getting confused, since I've seen some users using the "SRD" adapters, namely, the SRD-7, SRD-7SB and the SRD-X to drive the older electrostatics.

My question is, if I want to upgrade from my SRD-4, can I consider all of "SRD" adapters?

Aug 2, 2002 at 10:59 AM Post #2 of 7
After posting my above post I sent out a similar enquiry to Stax Japan, and received the following reply.

Judging from their reply, it seems that all Stax electret phones can be powered by both their "SRD" adapters and "SRM" energizers.

Problem solved.

Dear Sir,

We thank you very much for using our products.

About your inquiry:
SR-80 can use with all the adapters and driver units of our company, because bias voltage is unnecessary.

Best regards,

electrostatic audio products
K. Suzuki
Web manager

> I have a SR-80 electret earspeaker powered by a SRD-4 >adapter. I would like to upgrade to a better adapter.
> Is it correct that all of the adapters beginning with the prefix
>"SRD" (e.g. SRD-7, SRD-7SB AND SRD-X) will work with the SR->80?
> Thank you.
Apr 2, 2003 at 9:32 AM Post #3 of 7

As I recall, the SRD4 adaptor was *only* used with the electret headphones SR30, SR40 and SR80.

These were sold, in UK, as SR34, SR44 and SR84 (meaning headphones + adaptor) as they could not be used with any other adaptor....!

The other headphones such as Lambda, Sigma, SR5, etc were all electrostatic types and these needed specific energisers, such as SRD7.

The SRM was originally made just for the electrostatic types and when the PRO versions of the electrostatics came out, the SRM had two sockets - one for "PRO" types (which needed a much higher bias voltage) and one for normal types. These were marked on the front panel as PRO.

So, I don't think, despite what Stax say, that the electret headphones can be used with electrostatic type energisers.
Apr 2, 2003 at 5:23 PM Post #4 of 7
The literature for the SRM-313 states that it can drive all Stax headphones, Pro, Normal, and Electret. The electrets need no bias voltage, they just need the driving signal which all of the Stax energizers and adapters provide. They use the same connector as the Pro headphones, the 5 pin, which can be plugged into either the Pro or Normal jacks. The bias voltage pin on the electret's plug is connected to nothing, i.e. they have the 5 pin plug but only have 4 wires going to the elements.

You are right about the SRD4 because it has no bias voltage so it can only power electrets. The SR34-84 were low end models that were smaller and not circumaural like their bigger brothers.
Apr 2, 2003 at 8:24 PM Post #5 of 7
Hi Scott,

Thanks for the update - like all things, a little of everything rings true - it's just down to the specific details and the confusion that can arise.

Would've thought Stax could have put up a "compatibility list" showing which adaptors/energisers work with which earspeakers..!


Jun 5, 2017 at 7:13 PM Post #6 of 7
It would really be nice to find out how OP, ze-ant, made out. I know it's along time ago; but I'm in the same situation now. I'll let you know in 5 minutes if my SR-30s blow up.
Jun 5, 2017 at 8:07 PM Post #7 of 7
It is safe. I have a pair of SR-40s and a pair of SR-X mk3s plugged into an SRD-7 and all is well. I also tried the SR-30s with no ill effect. Now all I need is new earpads.

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