yet another stax amp
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zzz

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This is a side-project amp, made because it was simple, designed for the Staxes, and transformers wouldn't be able to handle Weebl. 2x 12AT7 + 6SN7 per channel, fake resistor current sources driven a few octaves beyond their power rating to bias the tubes (will possibly put some hv pnp goodness there), and a few optimistically rated auricaps in the signal path.

Some pictures:

The workspace.



Amp running, something playing, phones on my head. KGSS acts as a high-voltage ac donor, transformers on the left power the filaments. Black things hanging in the air are holcos pretending to be a volume control. Dig the wicked wiring, eh. If tubes were mounted on the opposite side of the board, it all wouldn't have looked like that (blimey, a major pin-matching screw-up). Lancome container carries the flux supply.



Closer look at the boards.



The valves themselves. 12AT7 are new production taken from different batches/manufacturers. 6SN7 were apparently all purchased at Sears (really) about 40-50 years ago. I have about 20 of those.



Amp turned-off, safe to handle mode. Power supply is one of them not blowing up kind.



Not much of the listening impressions as I only had about half an hour of time with this amp in subpar listening conditions, and it barely started getting good when I decided that family matters were more important than messing around deadly explosive electronics. And tube collectors will snicker at my valve picks, but hey, whatever, I can still say something about what I think of it:

1) Bass is not the amp's strongest point in terms of oomph, but what is there is very nicely textured. KGSS goes deeper but there's more blending going on below a certain frequency. Upper bass/lower midrange seems a little sucked in with this amp but I blame it for the most part on the source and to some degree on the cabling. Every damn setup where I used the Outlaws (yeah, my only cables...) exhibits this problem to a certain extent.

2) There's a certain subrange in Hope Sandoval's voice that this little amp recreates so well that I would dare to say that it wipes the floor with KGSS/Cary combo. In that subrange.

Someday when I have the time for that, the board will get a facelift, a decent *single* transformer (5 were used now), a volume control, and an enclosure. Possibly with an external psu, Stax EMP of sorts. I decided to call it Bob. KG's new creation truly deserves a Weebl in my book.

Want to get real broke real fast? Try DIY.
 
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post-227385
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setmenu

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Wow!
love the table top rats nest...must be a few volts floating about
on there yes?
I have not as yet dived into the realms of amp design so cannot
comment on yours..sorry no doubt another more knowledgeable
member will.

But I would dearly love to try/build some different amplification
for my 404s at some point[using a standard 006 amp at the mo]
must remain focused though and not deviate into more areas,[side projects..hehe]
because as you say this Diy lark does cost lots of time and money!

Good luck with the 'side project' though




Setmenu
 
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post-227388
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zzz

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Quote:

Originally posted by setmenu
Wow!
love the table top rats nest...must be a few volts floating about
on there yes?


heh. around 600vdc, not more. this is a rather low-voltage amp
.
Quote:

Good luck with the 'side project' though


luck is for wankers.

danke
.
 
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post-227413
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kevin gilmore

Señor Stax. Señor MAXX.
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I used to use the kitchen table for purposes such as this.
After numerous holes and burn marks i was finally encouraged
not to.


Nice old tek scope. One of the ones with the nuvistor
front ends. Slightly tough to keep working perfectly, but
a great old piece to say the least.

Happy Holidays
 
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post-227586
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zbuddah

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what a creation
I'm assuming the Lancome bottle isn't your beauty secret but rather a container....
 
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post-228351
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eric343

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Nice
Your next step would be to find some good benchtop material, to avoid holes, burn marks, and flaming tablecloths.


Just one question - is this the KG Blue Hawaii output stage (combined with the KGSS input stage to form Bob), or something totally different?

What wires are you using? I've never seen those thick white ones before...

(well, I guess I lied about the one question thing...)
 
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zzz

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no, this is a stax srx design, author unknown (to me).

wires are plain vanilla 500v isolated ones. white isolation makes it easy to mark them. I have some 60ft of stranded 14awg 2500v too, but that's a bitch to solder.

table is pretty safe as a bunch of newspapers protect it from byproducts of soldering while yellow pages and a stack of acm communications do the same for drilling.

eh, work again tomorrow... later. a tardy happy thanksgiving to you all.
 
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post-228899
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NotoriousBIG_PJ

Step 1: Plug power cable into wall. Step 2: Plug other end of power cable into....umm.... Step 0.5: Order something to power with power cable.
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I was hoping you would post about your latest amp adventures hehe. Keep us up to date and get some new uber cables too. And maybe take another 8 months of work to pay for it all.


Sigh, it seems so long since I've had an amp. I hope my Antness KGSS is in the mail.


Hey, do you have any of the stax amps to compare your diy amps with?

Biggie.
 
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post-229160
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eric343

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Antness does KGSS-en? I thought he only did KGCA-en (Kevin Gilmore Class A dynamic)...

What headphones are you going to power off of it? Those RS-1s will be fried if you plug them into an electrostatic amps...

In any case, congratulations on joining the Elite Circle of Electrostatic Headphone Owners.
 
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zzz

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I noticed that a plague of yabas around KG's amps confuse the bloody hell out of the uninitiated. piggy is talking about a dynamic amp he's getting from antness, as indeed even DC offset levels deemed perfectly acceptable for stats would make Grados go *puff*.

It is kinda sad that I don't have any official stax amps to compare my efforts to but oh well. I am not in a position to fork any sort of money on anything audio-related for quite a while. Same goes to cabling.
 
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NotoriousBIG_PJ

Step 1: Plug power cable into wall. Step 2: Plug other end of power cable into....umm.... Step 0.5: Order something to power with power cable.
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Hey, everyone was calling it KGSS before that official naming thread so I kept calling it that since I didn't know one of his electrostatic amps became named that. I guess I'll call it KGCA because I want to be cool... guys am I cool yet or do I actually need to own a soldering iron?!

Biggie, don't call me Piggy.
 
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zzz

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yeah, I'm guilty of unleashing this mess by talking about `building kgss`a few months ago without saying what exactly that is. anyhow.

Quote:

Biggie, don't call me Piggy.


heh
. sorry, couldn't resist. http://sinfest.net/d/20010805.html (no, that's not the one I've been thinking about).
 
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post-230511
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Possum

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Just use the full name. It's a lot clearer that way, and it's sounds more meaningful to call it the "Kevin Gilmore Dynamic Class A" than KGDCA - kind of like a tribute to the designer. Well, if any abbreviation is to be used, don't shorten Kevin's name. I haven't seen anyone on diyaudio.com call any of the Nelson Pass designs NPBLS, NPA, etc. It's always Pass or Nelson Pass and the acronym. Don't let Kevin Gilmore's name get lost in an acronym, like how a lot of people who bought CHA-47 didn't even know what it stood for.
 
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eric343

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*cough* META42 *cough*

Kevin Gilmore CAD it is


(Class A Dynamic)
 
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