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My DIY electrostatic headphones
May 7, 2017 at 2:11 PM Post #2,657 of 4,061
You're welcome, Jaab.
yes, the voltage is modified. as the TPD needs 540 v, there are plugged on 540v. originally, they were plugged at the norm output, then around 380 if I am not mistaking.
Thank you for the link. But as you probably know, the srx is not an electrect, it is a an electrostatic, in both pro and norm versions.
 
May 7, 2017 at 2:56 PM Post #2,658 of 4,061
The link was just for general purpose (not linked with the srx normal -> pro ), there is people interested by experimentation of new kind of stator, looks like one stone two target!

I'm a little bit lost with your response (lol)
srx normal bias + extra spacer ~ pro feed with pro voltage (it's why I asked first if the original connector of the normal srx was modified from 6 pins to 5 pins, to feed it as a pro headphone) because you said no modification of the connector I assumed it was feeded with a normal bias voltage!
 
May 7, 2017 at 4:16 PM Post #2,659 of 4,061
Ok, I understand for the link but I don't know much about what is on ths link.
for the srx I explained : I turned them to pros. so pros always use 540v. the rest is only norm.
I didn't say no modification to the connector. I said I removed the original cable and took a stax lambda cable, a pro one, then it has 5 pins only.
 
May 11, 2017 at 1:34 AM Post #2,660 of 4,061
What I am interested in is what type of amplifier does the HE-1 use inside the headphone. They claim that they use a "high voltage class A mosfet amplifier" inside the headphones to negate the cable reactance but that doesn't make sense to me since the HE-1 amplifier has like 4 of what looks like high mu tubes per channel for amplification and offloading the cable capacitance to the tubes instead of an output buffer would be a non ideal situation, not to mention why would you need a solid state amplifier after a bunch of tube amplifiers. I can see putting a power buffer inside the headphones because it would have vanishingly low capacitance in itself when designed properly but I just don't see the point in the internal "amplifier"

The reason I wonder is because if we are using FR4 as stators then it should be simple to apply such a buffer or "amplifier" using smt components on a pre-etched copper section of the FR4.
 
May 11, 2017 at 10:43 PM Post #2,661 of 4,061
I believe the tubes are telefunken 12au7 AKA 208S. mu=20. In electrostatic headphones, the cable's capacitance is a very real problem. By sticking the output stage inside the cups, you no longer have to drive that load. It may just be a buffer in the headphones.
The 8 tubes is a little odd, though. Assuming they are 12au7's, there are 16 total triodes. That's a lot.
 
May 12, 2017 at 2:34 AM Post #2,662 of 4,061
Well, the amp if the is balanced it would be 8 effective triodes and depending on what kind of differential amplification topology they are using you can knock that down to 4 or less per channel, assuming they are in fact dual triode tubes.
I actually have a question pertaining to cable capacitance in electrostatic amps. Why is cable capacitance a bigger deal in electrostatic amps compared to conventional ones? An output power buffer should be able to handle it pretty easily. I suppose an internal buffer in the headphones would make sense because of the lack of power required to drive it through the cable but still, why the general premise of cable capacitance being an issue on normal ES amps?
 
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May 12, 2017 at 12:05 PM Post #2,663 of 4,061
Hi Coinmaster,

Electrostatic panels are capacitive loads. A panel in an average electrostatic headphone can have a capacitance of about 50pF or more and the cable connecting the panel to the energiser can more than double the capacitance. It is the panel capacitance combined with the cable capacitance that acts as a load on the electrostatic energiser. Keeping the capacitance as low as possible is important.

David.
 
May 12, 2017 at 12:12 PM Post #2,664 of 4,061
Hi, I read through the thread and built a pair of headphones, i got a SRM 007t to use with them but i would like to rewire it for 220V.

As you can see i have reconnected the purple and blue from the transformer, to rewire it for 220v I should connect the white wire from the switch to brown, then connect purple to grey. or have i gotten it wrong?

IMG20170513000100.jpg
 
May 12, 2017 at 3:47 PM Post #2,667 of 4,061
VictorLow,

I agree with Wachara, more photos and build info please.
The power supply looks like a linear PSU, which makes sense for that energiser. The Japanese mains supply is 100v AC. From the photo, it is not possible to say whether the purple and blue wires are for 220v or not.... Really need a circuit diagram, or least info on the transformer. But you do need to be carefull, there may not necessarily be tappings on the transformer for 220v input?

Wachara,

I don't think the transistors in the head-set make it any less safe,..... whether the amplification is done at the amplifier or ear-cup, you still have the same high voltage present on the panel. The Sennheiser idea of reducing the capacitance in this manner does seem a bit odd.... As 100VoltTube mentioned earlier, the valves seem to possibly be just pre-amp and the HV by FETs in the ear cup. I am not convinced it will make that much difference, but then, I have not had a chance to listen to the new Orpheus.

It would be good if there were reviews showing the Frequency response of the Orpheus, does anyone know of any that have been published?

David.
 
May 12, 2017 at 4:28 PM Post #2,668 of 4,061
Muamp said:
Hi Coinmaster,

Electrostatic panels are capacitive loads. A panel in an average electrostatic headphone can have a capacitance of about 50pF or more and the cable connecting the panel to the energiser can more than double the capacitance. It is the panel capacitance combined with the cable capacitance that acts as a load on the electrostatic energiser. Keeping the capacitance as low as possible is important.

David.
Click to expand...
This is what confuses me. If the cable capacitance is double the stator capacitance then that also applies to conventional headphones as well, and in both cases such capacitance can easily be overidden with an output buffer. I don't see why its a bigger deal with ES headphones if there is only an extra 50pf or so compared to conventional headphones.
 
May 12, 2017 at 5:07 PM Post #2,669 of 4,061
Hi Coinmaster,

Electrostatic panels are purely capacitive loads. Electro-dynamic speakers have an impedance which is resistive and inductive. Electrostatic panels with capacitive loads, at high frequencies will have very low impedance, possibly less than one Ohm. Reducing the capacitance will have a higher impedance, especially at high frequency. If a cable feeding an electro-dynamic speaker has any capacitance, the overall effect on the load is insignificant, the resistive and inductive parts will be predominant.

David.
 
May 12, 2017 at 5:33 PM Post #2,670 of 4,061
I see, I wasn't sure how it was any different with a purely capacitive load. Can you just increase the stator spacing and up the voltage to reduce capacitance? What is the average p-p voltage required to drive these DIY headphones? Is there some sort of standard ratio between stator voltage differential, spacing, and AC amplitude required to get X amount of decibels?
 
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