eXStata DIY Electrostatic Amp for Intermediate DIYers

[Beefy]

I know that a lot of people in this thread bought Stax jacks from luvdunhill......

I'm measuring the diameter of the jack as 22.32-22.34mm. Can anybody confirm this measurement of jacks in the wild?

 

[pabbi1]

Quote:

Originally Posted by Beefy /img/forum/go_quote.gif I know that a lot of people in this thread bought Stax jacks from luvdunhill...... I'm measuring the diameter of the jack as 22.32-22.34mm. Can anybody confirm this measurement of jacks in the wild?

Yes mine fit snugly in the hole drilled with my 7/8" forstner, so that sounds dead on - 22.25 + wobble...

 

[BoilermakerFan]

Quote:

Originally Posted by pabbi1 /img/forum/go_quote.gif Yes mine fit snugly in the hole drilled with my 7/8" forstner, so that sounds dead on - 22.25 + wobble...

Nice I have a 7/8" stepper Uni-Bit and a 7/8" knock-out punch. I'll see which one works best.

 

[Lou Erickson]

I believe I have all the parts ordered for the solid state, and almost all the parts for the hybrid. My NABUs arrived today, and pots are on the way. Hopefully I'll be able to do a little assembly on Monday!

 

[Michgelsen]

Quote:

Originally Posted by tomytank /img/forum/go_quote.gif I've had mine running for a few weeks, but it's still in the basement, until I can finally finish the case. Having never built an amp case before, I didn't realise how long it takes.....plus I had some bad luck and will have to pick up some more supplies to complete it. The base is done though.

Looks great! I like it that the layout is similar to a Stax amp.

 

[macm75]

It's running - finished initial amplifier offset and balancing. I'm on the first half hour waiting step - so far so good!!!

 

[pabbi1]

Welcome to the club - hope you enjoy the stay.

 

[tomytank]

More bad luck. Second perspex top has broken. I think bending it at the sides introduces too much stress, and any additional working causes it to crack.

Or I need more experience, or more skill. (Or more Perspex!

)

Maybe I should go all wood? (Wood is good. I've got lots of it, and it's easier to work with.)

 

[BoilermakerFan]

Quote:

Originally Posted by tomytank /img/forum/go_quote.gif More bad luck. Second perspex top has broken. I think bending it at the sides introduces too much stress, and any additional working causes it to crack. Or I need more experience, or more skill. (Or more Perspex! ) Maybe I should go all wood? (Wood is good. I've got lots of it, and it's easier to work with.)

How are you trying to bend it? The best way is to heat it evenly in a oven over a wood shaped form. Or you can use a big space heater that flows enough hot air, but most of them now have safety shut-offs if they tilt beyone 15degrees from upright.

That's a really thick piece too, looks to be 6mm or more, that will take some time to heat, soften and then finally bend.

 

[les_garten]

Quote:

Originally Posted by tomytank /img/forum/go_quote.gif More bad luck. Second perspex top has broken. I think bending it at the sides introduces too much stress, and any additional working causes it to crack. Or I need more experience, or more skill. (Or more Perspex! ) Maybe I should go all wood? (Wood is good. I've got lots of it, and it's easier to work with.)

I think it looks sharp. Fall Back, Regroup!

Don't change horses yet. Wood and Plexi, nice combo!

 

[Lou Erickson]

Time for me to ask a dumb question.

I'm trying to match the jfets (Q1 and Q2). I've got a pile of J271s, a DMM, and a 12v wall wart.

I'm trying to follow the directions at The eXStatA Electrostatic Amplifier which looked simple enough.

I never get a reading on the DMM, though. I've got to be doing something wrong.

Here's my understanding:

According to the package, the J271 is a P Channel transistor. So, I need to use the diagram on the right. G and S, which are the two outside pins, go to +12. D, the middle pin, goes to + on the meter. - on the meter goes to ground.

My idea of which pin is which came from a document at Fairchild. Have I read that right?

Can someone confirm I'm doing this right, or what I might be doing wrong?

 

[tomytank]

@BoilermakerFan

It's 3mm perspex. I'm using only what I've got, unfortunately, a hot gun with the perspex clamped upright into a wood bench. Measure, mark, secure.
Being very careful with the distribution of the heat from the nozzle. I heat and wait for the perspex to sag, then bend and clamp with an additional wood brace, until cool.

@les_garten

So far, I have a bunch of offcuts and scraps, and a final sheet of perspex to try once more.

I may give it another go!

@Lou Erickson

If you get no meter reading at all: check your DMM fuse. This happened to me, and it was baffling.
Made me go out and buy a 'proper' DMM with a reset-able fuse.

 

[runeight]

Quote:

Originally Posted by Lou Erickson /img/forum/go_quote.gif Time for me to ask a dumb question. I'm trying to match the jfets (Q1 and Q2). I've got a pile of J271s, a DMM, and a 12v wall wart. I'm trying to follow the directions at The eXStatA Electrostatic Amplifier which looked simple enough. I never get a reading on the DMM, though. I've got to be doing something wrong. Here's my understanding: According to the package, the J271 is a P Channel transistor. So, I need to use the diagram on the right. G and S, which are the two outside pins, go to +12. D, the middle pin, goes to + on the meter. - on the meter goes to ground. My idea of which pin is which came from a document at Fairchild. Have I read that right? Can someone confirm I'm doing this right, or what I might be doing wrong?

If you meant what you said about the pins, please check the data sheet for the pinouts. If not, make sure that your meter is not in diode mode when trying to read the current.

Yes, I know, a voice from the darkness......

 

[paxeaxe23]

OK, another Dumb question. On Alex's site the instructions say to mount all vertical diodes with cathodes up and anodes down. The diagram shows the painted ring which marks the cathode as the upper end. However as far as I read it on the boards (Power supply is what I'm doing right now) the thick white line (which I assume is the cathode), appears to be on the white circle (which I assume is the hole for the diode) so I would have ordinarily mounted the diodes with the cathode (Black or grey ring) down.

Can someone clarify this for me. Maybe I'm just reading the board wrong. I certainly don't want to make a mistake at this stage of my first big (for me anyway) project.

Thanks

 

[Beefy]

The round marking on the board is where the 'body' of the diode goes. The thick line points to the adjacent hole where the bent leg goes. Ring on the diode/cathode goes up.