All things LA2a related

[beatnik]

yeah thats the problem. i'm trying to find a replacement 6V lamp that will fit

 

[sr1200]

Got mine going as well. put everything into a hammon case rather than the deep 2u, no further problems.  I left the grid stoppers on, dont know if that was necessary, but would that effect the tonality of the unit at all?

 

[Unit7]

I'm half way thru a LA2 p2p build. I've searched a lot here for info about the orientation of the zener diode replacing the NE2. I found sonicwarrior's pdf over at silenart's LA2 thread. The pdf states that the cathode/mark on the diode should be facing the 470K resistor (R28) and the other side of the diode facing ground. Just wanted see if someone who actually have done this can confirm. Grateful for any advice!

 

[DaTastenrasta]

Hey guys,

I've searched a lot in the GDiy and everywhere I looked people talk about tech details. I'm finding it pretty hard to find the beginning.

I'd like to build a p2p LA2A. Is there a kit or any page which collects files and data ... like Mnats for the 1176?

Thanks for any guidance!

 

[sr1200]

Most of the P2P la2a's ive seen done on here (along with the 3 or 4 that ive done now) have used the cayocosta plans.  Google p2p la2a, look for something from recproaudio.

 

[rainton]

Hey guys,

I've searched a lot in the GDiy and everywhere I looked people talk about tech details. I'm finding it pretty hard to find the beginning.

I'd like to build a p2p LA2A. Is there a kit or any page which collects files and data ... like Mnats for the 1176?

Thanks for any guidance!

You could have asked me when you were here at my studio last time
There is no such thing as a kit for a P2P LA2A - at least not anymore (since the BLOO was offered 10 years back).

There's some info on Cayocosta's recproaudio.com - so I suggest you look there first.
But be aware this is an advanced build and a totally different level compared to a Hairball 1176 kit where you only have to put things
together as advised in the build manual...

...not only because you have to source most of the parts yourself, but also because you're dealing with high voltages. And P2P is of course
more challenging and prone to mistakes than stuffing a pcb.
Anyway if you need any help or info for that matter, give me a call 

 

[Unit7]

I'm half way thru a LA2 p2p build. I've searched a lot here for info about the orientation of the zener diode replacing the NE2. I found sonicwarrior's pdf over at silenart's LA2 thread. The pdf states that the cathode/mark on the diode should be facing the 470K resistor (R28) and the other side of the diode facing ground. Just wanted see if someone who actually have done this can confirm. Grateful for any advice!

Quoting myself here... Find it a bit odd that noone could give a firm reply on this subject.    The little electronics knowledge I've got tell me that the mark on the diode should face in the direction of the current flow, just like the arrow on diodes on schematics. And to me it seems a little odd that in this case (according to Sonicwarrior's pdf over at the Silentart's LA2 thread) the flow would be FROM the ground TO the 470K (R28) resistor and not the opposite... Anyway, I just ordered two more of those zener diodes in case I blow the first one. If I don't get a reply I'll get back with a report within a week or two! 

Edit: Just got a reply via PM from member Orangechili that his successful build had the NE2 replacement zener diode with cathode facing the 470K resistor. Thanks Orangechili!

 

[Sredna]

http://en.wikipedia.org/wiki/Zener_diode

 

[dbonin]

For the zener diode neon replacement - they have impedance and looking at mouser there are a LOT of options.

Would a zener with low impedance (40 ohms) be better than one with 400 ohms impedance?  I assume lower is better in this case?

Also folks have suggested 60-70 volts as fine, but what about some of the other specs, like zener current and power dissipation?

Thanks for any help!
-Don

 

[Biasrocks]

For the zener diode neon replacement - they have impedance and looking at mouser there are a LOT of options.

-Don

http://ca.mouser.com/ProductDetail/Chicago-Miniature/A2B/?qs=sGAEpiMZZMucm%2f%252bFOY0TQvNzfw4NjimH7f2pIq8g3dg%3d

Mark

 

[dbonin]

For the zener diode neon replacement - they have impedance and looking at mouser there are a LOT of options.

-Don

http://ca.mouser.com/ProductDetail/Chicago-Miniature/A2B/?qs=sGAEpiMZZMucm%2f%252bFOY0TQvNzfw4NjimH7f2pIq8g3dg%3d

Mark

Thanks Mark!  I'm looking for a ZENER to replace the neon completely.  There are lots of options  but most only suggest 60V but there are many other specs to consider.

Thanks for the link.
-Don

 

[Biasrocks]

Looks like the only specs to worry about are voltage 65AC/90VDC and current 0.7ma.

I'm fairly certain that it's used in the meter circuit for a voltage ref. Mines been rock solid for the 3 years plus since I've built it, no meter adjustment required.

With a 25,000 hour projected life, I'm not sure why you wouldn't just go with the NE2.

Mark

Thanks Mark!  I'm looking for a ZENER to replace the neon completely.  There are lots of options  but most only suggest 60V but there are many other specs to consider.
-Don

 

[rainton]

With a 25,000 hour projected life, I'm not sure why you wouldn't just go with the NE2.

Mark

Because the NE2 is not being made anymore - at least not the one used in the original design - even the NE3 which has essentially the same specs is out of production.

Both neons are rated 115V and 0.5mA

I was just recently looking for a NE2 and even though I'm aware of the zener replacement, with the P2P I'm finishing at the moment I wanted to stick to the original as close as possible in every aspect.
Since I also have another LA2A based on the Drip Opto4 I build 4 years ago when the NE2 was still in production, I took the neon out of that unit and replaced it with a zener and used that NE2 for my new P2P build.

The zener I put in the Opto4 was this one and it works like a charm:
http://www2.mouser.com/Search/ProductDetail.aspx?R=BZX85B62-TRvirtualkey61370000virtualkey78-BZX85B62

But I also found other neons similar to the original NE2 at mouser - with slightly different specs though:
http://www2.mouser.com/Search/ProductDetail.aspx?R=A2Bvirtualkey60600000virtualkey606-A2B

It is rated 65VAC (95VDC) 0.7mA - should work too, or am I mistaken here?

 

[sr1200]

Mouser still sells them, i picked up about 40 last order.
*********************************************************
I stand corrected... I just checked my last order, and they has 1000's in stock... now, none.  If you want a couple let me know, I wound up getting the NE03's (they were just shorter than the ne2, same spec) I have it in one of my P2P's and works just fine.

 

[rainton]

Yeah I just finished my P2P LA2A today and it worked from the spot! 

I've built several different versions of LA2A's before - some highly modified with Hi-End caps, switchable frequency responses and what not - all pcb based though.

With  this particular build I wanted to stick as close to the original as possible.

That's why I used vintage UTC HA100-X and A-24, NOS RCA & Telefunken tubes and a vintage Beede meter (thank you so much for the meter Bernbrue!!)

I know many here have built P2P LA2As already and for those of you it might be nothing special - but right now I'm still proud of how it came out and wanted to share some pics with you guys!
And who knows - it might help those of you who want to build one as well in the future

two tube shields are still missing...

 

[Deepdark]

Awesome build. Where do you get de case???

 

[bernbrue]

Holy Moly,
I see, my meter has got a good home!! Excellent built, Martin! Congratulations!!!!
regards
Bernd

 

[rainton]

Thank you so much guys! 

Awesome build. Where do you get de case???

The enclosure is from fellow forum member androidtube. You can find him in the Whitemarket.
This enclosure is really high quality! I had to slightly modify it though. I needed to add the cutouts for the UTC transformers and the terminal strips,
drill some additional holes on the front panel and back panel and make some tedious changes to the VU-Meter cutout since this case was designed to hold a Sifam AL39.
The Beede meter needs a higher cutout but not as wide as the Sifam,(the cutout of the enclosure is even wider than the Beede's bezel) so that was really tricky!

P.S. Yes Bernd it has a good home 

 

[Deepdark]

Hey guys, quick question. I'm making 2 LA2A and I'm planing using teh Hairball audio 8037 vumeter. I'm searching a way to incorporate the logo found on the original meter on it. I know I can make a decalc with some lazertan sheet, but is there any other tricks? Most important, someone has a file of this logo?

Thanks a lot

 

[rainton]

Hey guys, quick question. I'm making 2 LA2A and I'm planing using teh Hairball audio 8037 vumeter. I'm searching a way to incorporate the logo found on the original meter on it. I know I can make a decalc with some lazertan sheet, but is there any other tricks? Most important, someone has a file of this logo?

Thanks a lot

Yes and yes  ;D

I built one LA2A in the past with a HB8037 meter
I designed myself an inlay with Teletronix logo, printed it on photo paper and swapped it with the 8037's original inlay - very simple

You mean something like this: