All things LA2a related

[Bluzzi]

what do you think I put into my T4B? Makes for a nice slow attack!

jim

 

[CJ]

You probably used Indica.
Switch to Stativa.
Same sound as an NSL 5211-B.
Man, am starting to get dizzy, and it ain't the chronic...

 

[Bluzzi]

[quote author="CJ"]...snip
and change the 220k on v1 to 100 k.[/quote]

CJ - Do you mean both of them? there are 220K going to V1.

jim

 

[CJ]

yes, not much difference, but any gain you can kill is welcome.

now you can put the pot up to #2 instead of #1, big wow, but little tweaks add up.

do not forget to mess with line out termination resistors depoending on iron, nyd can help you here.

 

[Bluzzi]

OK, I already have the 100Ks. Yes any little lowering of gain for now is OK. I mean my stock one is usable its just I wanted to try something different for the second one.

I'm going to use A-24 on input as you suggested and see what happens. My output remains an A-24.

What termination? I don't think I need that on A-24 since i'm driving line level, right?

jim

 

[Bluzzi]

Second question in a row (hey CJ I'm past my 1.7).

I bought axial caps for the filter caps and had a hell of a time making them fit on my first build. Now I'd like to get some Radial types for an easier install.

Schematic calls for 40uf and 30uf. I'm thinking 47uf for all 4 would be even better and easier to find.

I'm thinking of this part and being a damn insecure fellow I seek approval from all you mentors out there.

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=P13677-ND

jim

 

[Bluzzi]

Shameless bump.

jim

 

[AnalogPackrat]

Read the thread, Jim... I posted something about 70 pages back about the radial caps I used to build my Bloo. I don't recall the particulars now, but its in there somewhere. I'm pretty sure I got them at Digikey or Mouser.

A P

 

[Bluzzi]

OK, I'll check. Its not like I haven't scanned it several time. Its getting quite large now. But I hear you.

thanks

jim

 

[Bluzzi]

OK, on page 30 you mention Digikey P5950-ND and P5951-ND for 33uf and 47uf 450V.

One last question though. Why not just use 47uf for all 4?

jim

 

[CJ]

thatsa 1.8

47 is what i use, who needs hum?
Hummer=Good
Hum=Bad

 

[Bluzzi]

[quote author="CJ"]thatsa 1.8

47 is what i use, who needs hum?
Hummer=Good
Hum=Bad[/quote]

"thatsa what I tot" - Groucho

jim (way over 1.9 now) oh wait answers don't count!

 

[hodad]

Here's something I was thinking about. I'm planning to use an old trimax input on my next la2a, & I can either wire it 600:25K or 600:100K. So I was considering wiring a 4PDT switch with the appropriate connections & resistor on either side, so that I could switch between. I know the best way to see how it works is just to do it, but I was wondering if this was doomed to failure to begin with, or if I needed to watch out for anything.

 

[matta]

Hi Guys,

I'm having a slight issue with a VERY low level hum/buzz on my LA-2A and rather than repost it all those that have tackled this might have some suggestions, ideas and thoughts and if you can/could spare a moment please check out this thread: http://www.groupdiy.com/index.php?topic=299204

Thanks in advance

Matt

 

[dave P]

thought some of you guys might be interested in some tests I did in the lab at work. (we make luminescent materials) I found some EL panels lying around, so out of curiosity, I rigged up an LA-2A side chain circuit to test their characteristics. The frequency response of the panels is flat from say 10Hz to about 2kHz then it just falls away to nothing. This means that the LA-2A would not respond to pure high frequency peaks very well, if at all, but would reduce any associated high harmonics if the fundamental notes were below 2kHz and they triggered the panel illumination. By contrast, a green LED has a nanosecond response up to 200kHz and would make a much better light source than the EL panels. I'm sure Bill Putnam would have used green LEDs if they had been around in 1966.
I'd be interested in your comments

 

[CJ]

Green LED is what I use to calibrate, but as a dynamic source, well, how many lasa panels have you ever tested?

Do you know the part number?

Why re invent the wheel. we all like it , just the way it is.

If you were smart, you would buy an LA2, plug in certain cells, and listen to the differential.
Thats what I like to do.
You know what?

Every LA2 could be used for a specific event in the recording chain, it is up to you to determine which event you want tyo shape,, and how.

 

[dave P]

I wasn't trying to be a smart ass, I was just offering an explanation as to why the LA2 seems to be better on vocals.

The other point I was making was that EL panels and the TA modules are hard to come by and can be very expensive. With so many people making LA2 clones it might be useful to have an alternative fast light source thats all.

I guess there's an issue about making exact copies of old vintage gear because its about feeling safe with it as close to the original as possible, but I think its going too far when guys use old carbon resistors when metal film are so much better, for example. If something with a better spec comes along, why not use it? I,m sure the old guys would have.

Its been ages since my last post and I screwed up the address and put CJ in because you were the last one I posted, I guess you thought I was having a go at you! Peace brother!

 

[CJ]

oh relax.

you are ok, be ok with that.
OK?

 

[dave P]

I think English guys sound stuffy and uptight to Americans, we just don't have your way with words! Especially you CJ, you are very entertaining.

But I'm relaxed and very ok and have been experimenting with the LA2 circuit and I think there are mistakes in the feedback resistor values, when you do the math the voltage values are all wrong. In fact the 33k R22 is not necessary and only unbalances the lower 12BH7 by robbing its current. I got better results from a 240k straight to the R10 1.5k to supply 17dB dc feedback and 575k (560+15) from the other side of the C5 cap to R10 to give 3dB of ac feedback. Now your going to tell me to leave well enough alone, but some of us have a curious gene!

 

[khstudio]

Everyone has opinions & ideas.
I see no problem with what you're saying.
This is why we're here in the first place... to share & try ideas.

CJ means no harm, he's just been around the block a 1000 times with the LA2A's.

We all know about the odd response of the EL Panels & the (not optimally designed) output stage. But CJ is right, the LA2A rocks as is but there's always room for improvement, which CJ has done himself.

I actually use the Jensen MODs on the output stage, which I gather helps but doesn't totally fix the problem. I assume it helps the output stage run less "Cold".???