All things LA2a related

[Deepdark]

Another one guys. I have some 22ga wire that is rated 300v. Is it ok? Looking at the shielded wire, is 300v rating ok, too? And lastly, I use the Hammond 269JX wich has not 6.3V center tap. I saw somewhere that I should run 2 100R resistor between heaters and ground? Is it necessary? And where do I make this connection? Thanks 

 

[dbonin]

Another one guys. I have some 22ga wire that is rated 300v. Is it ok? Looking at the shielded wire, is 300v rating ok, too?

Yes, plenty good for the shielded wires.

Cheers,
-Don

 

[Deepdark]

Thanks guy. I've uploaded some compression test of my LA2A on my soundcloud: https://soundcloud.com/#eric-labrie-composer

You'll see the first 4 tracks are all a guitar track with different setting. Let me know how it sounds for you I used Hammond PT and UTC trannys  8)

 

[Deepdark]

quick question. Just to be sure. I'm finishing 2 la2a. I tested one yesterday. Cool signal (sowter trannys) really silent in term of noise. I'm playing with gain and peak red pot and of course GR and +4 mode. When on GR, If the needle move when peaks occur, then it confirm that my T4B is working, otherwise, the needle wont move, isn't it!? Just to be sure Since these unit compress really naturally, it can be hard sometime to hear it working.  ;D

 

[fallout]

Would anyone happen to have Kent Stevenson's LA2A layout? I built one of these years ago and i'm looking to build another but the layout is nowhere to be found.. Thanks!

-jay

 

[Deepdark]

this one??

 

[Biasrocks]

Would anyone happen to have Kent Stevenson's LA2A layout?

-jay

 

[Deepdark]

nice layout. Is it necessary to make the star ground on the transformer screw??? I make mine on all my unit on the IEC screw (learned this from the G9 build). Is it common that the led of the hairball meter (8037) burned?

 

[Harpo]

Is it common that the led of the hairball meter (8037) burned?

Depends on the value of the needed current limiting resistor and if supplied from a DC voltage or an AC voltage (with maybe needed additional circuit to protect against reverse voltage that might exceed parts limits).
The layout pic shows a VU meter, illuminated by an incandescent lightbulb (not by a LED).

 

[Deepdark]

Ok. thank you. The led are rated for 20ma use, I think 6V max. I feed it with the heater (as on the layout). Is it better to make a diode, or a resistor to protec the circuit? If yes, which value???

 

[fallout]

Would anyone happen to have Kent Stevenson's LA2A layout?

-jay

Thanks!!

 

[Deepdark]

If I used Sowter transformer 1009 (input) and 1290 (output) is it necessary to put the grid stoppers???? There is no noise when I tested the unit on my systeme. What do the grid stoppers??? Someone used the sowter 1290 too?

 

[Biasrocks]

Rear panel layout. Not sure if this was part of Kent's layout or not.

 

[Harpo]

Ok. thank you. The led are rated for 20ma use, I think 6V max. I feed it with the heater (as on the layout). Is it better to make a diode, or a resistor to protec the circuit? If yes, which value???

6.3VAC*SQRT(2)=8.9Vpk. Mains voltage isn't a constant and might vary by +/-10% and the transformers secondary voltage will follow by the same variation.
Forward voltage drop (Vf) is depending on colour of LED (or series connected LEDs), maybe typical 1.8V per red LED, maybe 3.2V per blue or white LED. The parts datasheet will tell you.
Current limiting resistor needed would be (Vpk - VfLED*number of series connected LEDs) / amount of current you allow for in A.
I'd try (8.9V - 3.2V*2) / 0.02A = 125R (120R is a standard parts value) as an example value for two white LEDs with a maybe reversed 1N400x in parallel to the LED(s).
This is pulsed operation at mains frequency, so allowed current thru LED is higher than your 20mA number. Increase resistor value for lesser brightness and vice versa.

LEDs are best driven with constant current sources and a rectifier and cap in front for DC operation might be the better solution if your eyes mind this pulsing operation.

 

[Deepdark]

Thanks sir for the explanation. Have a nice day 

 

[Deepdark]

Hehe

 

[Deepdark]

Another one

 

[Deepdark]

Interior 2

 

[Deepdark]

Glowing neon. Spec are: integral to the vintage unit. Trannys: sowter 1009 and 1290, hammond 269jx. NOS tubes. Hairball vu meter, diy racked case.

 

[fallout]

Rear panel layout. Not sure if this was part of Kent's layout or not.

It sure was.. I love the way the jensen transformers on the la2a sounds and wanted to build another. Thanks again!

-jay