Kingston

Dual LA-2A like it should be, pictures
« on: May 09, 2010, 05:29:39 PM »


Some of my best panel work this far. Many important features brought to front panel using on-off-on switches and relays. true 600 ohm output pad for example. The 'preamp' setting takes out all series resistance before the first stage (68k, and the "limit" resistor). Becomes a brilliant medium gain (something like 60dB) preamp with very low noise.

Sidechain high pass filter brought to front panel (0ohm, 500k, 1meg). Indispensable, highly interactive. I initially experimented if the Arco 50-380pF trimmer from sidechain should also become a series of switches on the front but it was too subtle. Couldn't hear any "de-essing".

Mostly PIO caps and carbon comp resistors, more than double the usual filtering capacitance, some russian alternative tubes (rewiring under the PCB) and DC heaters. The DC heater regulator (overkill, but what the heck) also controls B+ safety relays. If regulators die, B+ comes off, tubes will live instead of eating destructive B+ voltages.

Completely noiseless. I actually did not expect this, as I've read that LA2A is generally "noisy", whether it's tube hiss or hum from transformer etc.. Well those can be completely avoided so lets put an end to that myth. The circuit itself, and silent-arts PCB layout are capable of close to theoretical noise floor. With unity gain medium compression usage noise is around -100dBu. Max gain (about 60dB), it's still below -80dBu.

I come from the school of paranoid wire shielding. The transformer is a custom way over specified number, well shielded. Generally lots of attention was put to shields and faraday cages. It pays off.





Don't laugh at the "handbreak" aluminum pipe, the "Kingston-duct". It's a grounded duct to safely take mains VAC to front panel. Mains VAC likes to leak everywhere, and I'd rather brute force it out, than live with hum.

I already noticed the gain reduction VU zero likes to move as the unit heats up. It's those neons, old school regulators. I'll replace with zeners to stabilise metering.

a couple of last nuts to tighten, then this beast starts active service, hopefully will keep at it for the next 30+ years.

Mike
« Last Edit: May 09, 2010, 07:27:27 PM by Kingston »


tv

Re: Dual LA-2A like it should be, pictures
« Reply #1 on: May 09, 2010, 05:35:35 PM »
Yeah. The notorious "Kingston Duct".
If you sprinkle when you tinkle, please be neat and wipe the seat.

mikefatom

Re: Dual LA-2A like it should be, pictures
« Reply #2 on: May 09, 2010, 05:37:27 PM »
Whoa!  :o :o 8) :o :o  Really well done sir!  8)

Silvas

Re: Dual LA-2A like it should be, pictures
« Reply #3 on: May 09, 2010, 06:55:50 PM »
Wow

LA2A taken to the next level!

Amazing
Camilo Silva F.
Camilo Silva F. Mastering
Chia, Colombia

ArnauTS

Re: Dual LA-2A like it should be, pictures
« Reply #4 on: May 09, 2010, 07:30:04 PM »
Awesome work ;D
if you can have it all, stop in the middle

Re: Dual LA-2A like it should be, pictures
« Reply #5 on: May 09, 2010, 08:50:46 PM »
Nice solution to non standard power locations.  Why can't se all just have AC on the right side of our enclosures people?
  :P

Kingston

Re: Dual LA-2A like it should be, pictures
« Reply #6 on: May 09, 2010, 09:35:24 PM »
Nice solution to non standard power locations.  Why can't se all just have AC on the right side of our enclosures people?

There's no such standard. And in this case, it would have looked ugly and broken the symmetry.

Re: Dual LA-2A like it should be, pictures
« Reply #7 on: May 09, 2010, 11:10:44 PM »
Damn dude.... Just magnificent....  (Only loses to your mila cuz that was P2P ) :P

seriously you're doing some really amazing work.

[silent:arts]

Re: Dual LA-2A like it should be, pictures
« Reply #8 on: May 10, 2010, 11:48:15 AM »
UUHHH - I nearly missed this one :o



very nice build with well thought additions / features.
I like the DC heater idea ...

Jonte Knif

Re: Dual LA-2A like it should be, pictures
« Reply #9 on: May 10, 2010, 01:28:06 PM »

Way to go! Onnea!


Ptownkid

Re: Dual LA-2A like it should be, pictures
« Reply #10 on: May 10, 2010, 01:33:37 PM »
Holy sh*t that looks amazing!!!

mrclunk

Re: Dual LA-2A like it should be, pictures
« Reply #11 on: May 10, 2010, 04:58:15 PM »
wow, thats cool.
Inspired me to finish mine.
Love the split panel look.

tv

Re: Dual LA-2A like it should be, pictures
« Reply #12 on: May 10, 2010, 05:38:12 PM »
All those switches on the panel look like "dont f**k with me"..
If you sprinkle when you tinkle, please be neat and wipe the seat.

Flundran

Re: Dual LA-2A like it should be, pictures
« Reply #13 on: May 11, 2010, 07:08:31 AM »
It has the "Teletronix Engineering Co." logo on it, although this is not made by that company. Why?

andre tchmil

Re: Dual LA-2A like it should be, pictures
« Reply #14 on: May 11, 2010, 07:12:27 AM »
It has the "Teletronix Engineering Co." logo on it, although this is not made by that company. Why?

In remembrance of Tat.

sodderboy

Re: Dual LA-2A like it should be, pictures
« Reply #15 on: May 11, 2010, 07:15:00 AM »
Certainly deserves a crown on the panel.  Make sure you anchor that Kingston duct.
Mike

Kingston

Re: Dual LA-2A like it should be, pictures
« Reply #16 on: May 11, 2010, 07:28:17 AM »
There are two steel brackets below the duct serving two functions: anchoring it and grounding it.

The pipe is very lightweight and even one bracket would have been enough.

tv

Re: Dual LA-2A like it should be, pictures
« Reply #17 on: May 11, 2010, 05:06:20 PM »
But hey, I really think you should try to make The Duct look more badass. Like drilling some hole-pattern in it, adding some wire mesh - something.

(in your next build)

shall we christen it "The Duct of Silence" ?
If you sprinkle when you tinkle, please be neat and wipe the seat.

Kingston

Re: Dual LA-2A like it should be, pictures
« Reply #18 on: May 11, 2010, 05:20:35 PM »
drilling some hole-pattern in it, adding some wire mesh

Yes!! I have always pondered what exorbitantly overpriced thingymagadget I will sell to the ever-gullible audiophile community.

The final product will also feature directional installation with NASA grade kevlar-rigid insulation. And no longer your everyday aluminum pipe, we now have gold sputtered steel with silver wire mesh.

Will work wonders with your directional IEC cables and really there's no point listening to music without it because it will otherwise have no 3d.
« Last Edit: May 11, 2010, 05:22:33 PM by Kingston »

Re: Dual LA-2A like it should be, pictures
« Reply #19 on: May 11, 2010, 05:30:12 PM »
Awesome! Upeeta, arvostan!


 

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