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The Headcase Stax thread


thrice
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1) Install 5 megohm safety resistor in the bias supply following the last bias cap if there isn't one or it is a different value.

2) Toss the output chokes and install good constant current loads with appropriate heatsinks.

3) Install 5 kilohm safety resistors in the output if there aren't any.

If you are in the mood, put in a somewhat higher voltage transformer that will allow you to install a regulated power supply.

 

That should fix the major issues, don't know if there are others.

Edited by JimL
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One can always hope... springs eternal and all that. 

The WES is a particular clusterfuck though as it didn't work on so many levels.  It's a collection of 4 mono phase amps really so you need the super noisy phase splitter to the circuit for it to work with RCA inputs and then we have the inductor output loads which simply don't work.  Add to that a really, really crappy power supply and all the usual Woo audio safety concerns. 

So back in the day, for those that are unfamiliar, there was some discussion that they were just doing the best they can or some such BS so I said...can I do better?  I set some rules, same power supply voltages, same tubes naturally (though not the rectifiers as they are just stupid) and as similar a parts count and general topology as possible.  So output caps like in the original, inter stage caps etc.  Throw it all in a spare box and here it is:

_2132049.thumb.jpg.9eaf928fc5bffb668585c9e0dc95d98a.jpg

The massive tower was just something I had and as you can see... it is pretty much empty:

_2132044.thumb.jpg.93c7fcf2af3d4d5ecb769df0594994e5.jpg

The chassis was reused from a dac project our resident "circular hole cutter tech" did so extra holes galore and then it was powder coated to look nice.  _2132048.thumb.jpg.9698e31e911120d2731c235a485ece2a.jpg

That's why it has only XLR loop outputs on the back.  So here is the money shot... 

_2132041.thumb.jpg.ff2216247154f2caad77516c51ea462b.jpg

Sooooo...this is a small DC supply to run the heaters of the tubes and my SSPS (simple stacked PS) feeding +300/+600 plus bias to the amp.  The amp it self is a combination of a modified SRX front end with a new grounded cathode output stage.  That pic is from the first testing so there were some changes done later on but it worked well enough and about 1/4th the size of a WES... 

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23 hours ago, SeaWolf said:

If you're attached to an all tube design, well almost all, just build a Megatron?

 

Edit:: speaking of woo has anyone seen what's going on inside their new stat amp?

Or, if you're cheap like me, build the SRX Plus. Based on an original Stax circuit, with constant current loads and sources to set the operating conditions.

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2K? ummm. It depends. Do you do it or do you order someone?

I think mine, adding everything (cases, custom made trafos and bla, bla, bla...) remained around 1K€ (1.2K$) . I´m sure that if you are conservative and you reuse things like the case or use generic material like trafos, the cost can be quite minor. For this reason IMHO for a small budget, the SRX-P is a great project.

 

 

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yup bargain compared to this.

https://www.ebay.com.au/itm/STAX-SR-Omega-1-Electrostatic-Headphones-One-of-a-kind/192736088566?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160908105057%26meid%3Ddca0e907a47e440a86b6d1d4d4db1198%26pid%3D100675%26rk%3D3%26rkt%3D15%26sd%3D302948944629%26itm%3D192736088566&_trksid=p2481888.c100675.m4236&_trkparms=pageci%3Aae159fd7-f30c-11e8-81c2-74dbd18059df%7Cparentrq%3A5a622a211670a99b5d686a2cfffe35cc%7Ciid%3A1

Guess I can kiss goodbye to ever owning one.

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