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stax mafia electrostatic portable


kevin gilmore

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I have one more, maybe a stupid question - how are these four amplifiers connected - there is no phase inverter there and looking at the pcb I can see that the inputs in the channels are connected (?) - I'm tired of this matter and I can't sleep because of it - can you explain it to me ?

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I have a certain idea - you could add a direct input for a balanced signal - my qudelix gives 4V rms in this mode - bypassing the potentiometer, which is not of high quality - anyway, it is unnecessary in this configuration because the gain control is taken over by the phone or the qudelix itself (of course it writes about my case)

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On 2/8/2022 at 8:26 PM, kevin gilmore said:

well there are 2 ways to do this.  instrumentation amp and inverting/non inverting.

pick one, they are roughly equivalent.

Nice joke :)

I simulated your schematic in topology from pcb and it does not work in any way  - only in single mode, not bridge. And I know it works to you - some "king of magic" :)

I always liked to check the circuit in the simulation before I did something - we have something in common :)

 

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  • 4 months later...
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  • 3 weeks later...

Made with double sided bread board.  HVPS (LT8365) are on the way from JPN.  

I planning to divide it into four and stack these in 2 or 4 layers, but I don't think it will be a size that can be called "portable" but I will try...   top.jpg.7b170df22f48106e7b98d96c8010b6eb.jpgbottom.jpg.b55bfa9ef7d9526bb9878c08410dcccd.jpg

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14 hours ago, Inu said:

Made with double sided bread board.  HVPS (LT8365) are on the way from JPN.  

I planning to divide it into four and stack these in 2 or 4 layers, but I don't think it will be a size that can be called "portable" but I will try...   top.jpg.7b170df22f48106e7b98d96c8010b6eb.jpgbottom.jpg.b55bfa9ef7d9526bb9878c08410dcccd.jpg

As for your pcb board: You have  big cohones, dude :) !!

BTW:

Can you share the source of lt8365 chips in japan ? - I can order them there because only this is what I still need to finish the project.

 

 
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I also searched for the LT8365 but couldn't find a way to buy it as a part.

I can't wait until next year, so It's expensive, but I bought modules (boards). This is up to + or -280V, so I need to make few changes.

https://strawberry-linux.com/catalog/items?code=18365

This shop doesn't have an option to ship to the US, so I got help from a friend in JPN.

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54 minutes ago, Inu said:

I also searched for the LT8365 but couldn't find a way to buy it as a part.

I can't wait until next year, so It's expensive, but I bought modules (boards). This is up to + or -280V, so I need to make few changes.

https://strawberry-linux.com/catalog/items?code=18365

This shop doesn't have an option to ship to the US, so I got help from a friend in JPN.


Can you have contact with him? I am also happy to buy these modules. I found them myself a few months ago ( find my post on diyaudio forum) but I have no friends in Japan.

Without these chips I will not finish this amplifier.

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On 8/6/2022 at 2:32 AM, yabba235 said:


Can you have contact with him? I am also happy to buy these modules. I found them myself a few months ago ( find my post on diyaudio forum) but I have no friends in Japan.

Without these chips I will not finish this amplifier.

Maybe you can try to use parcel forwarding service.

I am not living in US so I don't know which provider is better.

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  • 3 months later...
On 11/10/2022 at 10:30 PM, selfreserv said:

hi @yabba235

i want to build the same one for my kse

except bias 200 v - did you make any other modifications?

Only a few: bias voltage selection, input selection ( bal/unbal) and power on/off.

The first two are implemented based on bistable relays - connecting them requires only momentary power consumption - important when powered by batteries.

Last is simple monotstabile switch.

Because of the relays, the housing is large, but maybe someday I will find smaller relays or think about another solution.

image.thumb.jpeg.0e4456929878a34c5d3dd9c5e81a5fe3.jpeg

(Instead of a discrete stage, I would see a high-voltage OA here :))

Edited by yabba235
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  • 4 months later...
45 minutes ago, usa_love said:

all the high voltage op amps I've seen have extremely low slew rates, which makes the sound sluggish and bad. I firmly believe that it is much better to use small transformers with a large transformation ratio. No matter how much I listened to different transistor solutions - the sound through transformers is perceived much better, it is faster, good transformers are able to transmit sound impulses to the drivers much faster.

It's not that bad, apex's integrated amps are good enough. As for the transformers on the outputs, I say no to them!

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full range low distortion transformers for electrostats are very hard to make. physically big and heavy. Here is one of the 2 transformers inside a quad esl63. interwinding capacitance and other issues are critical. So sure you can build a portable with 4 of these. Not really portable is it.

 klh9 and esl56 are much bigger.

all the stax made transformer units perform very poorly.

kgsshv carbon does 100 volts per microsecond. please show me a full range transformer that do this.

if you really think you can build a suitable transformer the size of a 1 inch cube that does the full frequency range and does not ring like a doorbell, you clearly have not tried to make such a thing.

DSC_0987.JPG

Edited by kevin gilmore
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Hmm, from the translator:

"..Portable (Class A) electrostatic headphone amplifier supports DAC decoding
 Completed the development of the latest portable electrostatic amp, surpassing Stax D10, Sennheiser kse series and domestic products of the same series, push-pull structure, the latest design, the first in China, adaptable to stax or other stax-5pin standard interfaces, and a full range of bias 580 products
     Speaking of why it surpasses most portable electrostatic amps on the market, the reason is that this structure is a COMS current mirror push-pull design. Class A portable electrostatic amplifiers on the market are all class D. Fans should understand the difference between class A and class D power amplifiers..."

Sounds familiar.....and quite avant-garde housing design :)

 
 
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On 4/14/2023 at 9:37 PM, kevin gilmore said:

full range transformer that do this

it would be interesting for me (and I think a lot of people) to find someone's calculations of some (just for understanding) transformers in terms of the slew rate parameters, it seems to me that everything should be fine in transformers with this

I'll try to find someone's research

maybe anyone know or have seen something similar

Edited by usa_love
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