All things LA2a related

[college101]

SO my cd output is low, and thats why it is showing -20, and then bumping up on the louder parts of the songs!?  That sounds right!


I know I am monitoring the output

 

[Sredna]

+4 is supposed to be -20 ?  HUH...im lost

+4 will read +4 when there's that much signal passing through . . . . when there is no signal passing, it should read something else . . . 

From the LA2A manual:

"The meter is calibrated to read 0 VU (or 100%) when the amplifier output is +10 DBM or +4 DBM,
depending upon the swith position"

 

[Sredna]

SO my cd output is low, and thats why it is showing -20, and then bumping up on the louder parts of the songs!?  That sounds right!

I know I am monitoring the output

That's right, and -20 is the lowest level to be shown. Lower signals or no signal still shows as -20.

 

[Biasrocks]

Every vintage design tube vari-mu limiter I've ever worked with requires anywhere from 2-5 hours before one can align the meters and walk away, expecting zero to be at the same point upon return.   That's about the amount of time required for temperature to stabilize.  

There's nothing audiophoolery about it.   Likewise, none of this should prevent you from working immediately either.  

Agreed, tube gear needs time to come up to operating temp, settle and sound optimal.

I generally power up everything in the studio at least an hour or two before session start.

Calibration, as you pointed out is another matter.

This is the type of phoolery I was referring too.

http://www.haglabs.com/frydaddy.html

Regards,
Mark

 

[Sredna]

Wow!


The Frydaddy schematic is on the page, lets do some cloning!  ;D

 

[college101]

So I dont need to test the meter then, I need to figure out why I am getting no signal when in Gr mode then...

 

[college101]

OH..I need to burn all my cables in!! This is the problem...Joking  Joking

 

[emrr]

This is the type of phoolery I was referring too.

http://www.haglabs.com/frydaddy.html

Yeah, that's a good one. 

 

[Biasrocks]

So I dont need to test the meter then, I need to figure out why I am getting no signal when in Gr mode then...

Don't panic!

Are you getting signal on the output of the LA2A, or no GR showing on the meter?

If it's the latter, your input signal isn't hot enough to trigger gain reduction.

Can you run your CD player into a mixer to boost the signal before going into
the LA2A?

Mark

 

[college101]

AHHG...just thought of that...I will try and get my hand on a little mixer to try and boost it...

In GR mode, the needle floats to zero, and then does not move, but this must be because the signal is not hot enough...


OK..so overall..If I get a little mixer....run the cd player into it, then take a out of mixer into the la2a--and boost the output of the mixer..I will be able to get it to +4...

 

[college101]

ONE MORE THING...So with the signal being so low, that is why the controls have made no impact on the signal....cause its not at +4...

Adjusting the gain control will do nothing at -20...Right?

 

[Biasrocks]

Adjusting the gain control will do nothing at -20...Right?

You should get more signal on the output if you increase the gain and you should see this on your +4 VU setting.

This control is post GR, so it will make no difference to the threshold to get compression happening.

Mark

 

[college101]

OK..yes Biasrocks...but if my cd player level is so low, I wont really be able to tell if it is working? (in reference to adjusting the controls while only using the low cd level) Right?

right now, if I have my cd player set to the max output level(cranked) adjusting the controls doesn't really change anything Im hearing...Im geussing that is because the level is so low...so low I cant hear the adjustments occuring...

The needle does bounce around..but its very little compared to what I was expecting...

 

[thestudio]

Is anyone making a chassis for La2a ???

 

[Sredna]

right now, if I have my cd player set to the max output level(cranked) adjusting the controls doesn't really change anything Im hearing...Im geussing that is because the level is so low...so low I cant hear the adjustments occuring...

The needle does bounce around..but its very little compared to what I was expecting...

That's strange because the gain control should give remarkable change in output, did you wire the
gain pot correctly? Did you test with and without TB4?

Actually the LA2A (with original transformers) got quite lot of gain, so much that you could use it
like a mic preamp so a CD player should have no problem to drive it into compression...

 

[college101]

I went by the schematic, but its set up just like cayacosta's gain pot from recproaudio.com

 

[college101]

Im gonna by a small cheap o mixer soon, and then try and boost it

Last time I checked...The signal coming out of the la2a to my guitar amp on zero was loud...so it seems like that is true, but if the signal is low, I may not be able to hear that change...

 

[college101]

I made a huge error--I dont want to talk about it...about to fix it...and then re-test

 

[originalscottyg]

I just completed my LA2a using Cayocosta's layout.  It turned out great and sounds virtually identical to a vintage unit at the studio where I work. I just wanted to say thanks for all of the amazing resources and the people who are so generous with their time and knowledge!

 

[originalscottyg]

Here's a view of the front panel: