STAX Earspeakers - The Audio Transformer Rabbit Hole...

In this video, we continue the STAX journey, searching for how far we can take audio transformers for electrostat's. How far can we go? Down the rabbit hole we go...

[@alnicospeaker]

I did exactly that as a teenager, many old german tube radios had an electrostatic tweeter, some of them sound really fantastic. Hook them up to +200 and -200V and feed an output transformer "backwards" from any amp you like. Use a small-ish bass-blocking capacitor in the primary to reduce distortion.

[@mbanb6775]

Those Edcor transformers have too high of leakage inductance and capacitance. You could try an audio specific toroidal transformer - those should technically have the greatest bandwidth if wound for audio purposes. You don't want to go with a standard toroid as they are often bifilar wound and have high interwinding capacitance. You would need to contact a company such as Toroidy to get custom toroidal transformers wound. You want to specify that you are looking for high inductance (300-500H) and very low leakage inductance and capacitance. Something like a 1+1:12+12 or a 1+1:10+10 turns ratio, etc. (depends on how much voltage drive you have from the amps hooked up to them). You could make sure they use thin enough wire to give sufficient primary resistance as well. If you provide Toroidy with the details on what you are trying to do they should be able to help you out, though it may be a bit costly if they have to do a huge amount of interleaving to get the transformer to the specs you're looking for.

[@whatcouldgowrong7914]

Many thanks for the advice, I shall look into this also! :)

[@nothingelse1520]

I wanted to buy a Lundahl transformer box then I saw a used Blue Hawaii BJT for the same price so I got that instead. I wonder what has better frequency response. A Lundahl box or Blue Hawaii

[@whatcouldgowrong7914]

It depends on the transformer setup specifically, a Lundahl LL1630 is about as linear as it gets (depending on the amplifier also) and only struggles around 20hz where its limited to about 280VRMS) this scales ip very quickly after 30hz where it can run head to head with direct drives. I personally prefer transformers and they’re much cheaper to build compared to a blue hawaii etc and you can use many amps to change the sound profile.

[@phuocnguyen8774]

I can make my own electrostatic headphones. But what I can't do is the amplifier. I am not an electronics person. That hindered my passion.

[@ellerycoffman]

Looks like the top setup would be two LL9202AM's or eight LL1603's (4 per channel)?

[@markuss9229]

Just go straight for an LL9202AM

[@whatcouldgowrong7914]

I'm working with someone else who is testing the LL9202 (non-AM) currently and encountering similar issues to the Edcor unfortunately and cannot run without external resistors due to the low impedance on the primary side... Not sure if there is anything out there that can more closely replicate the LL1630's winding characteristics but just more capable with core saturation?