« on: April 02, 2008, 10:01:24 AM »
I’m contemplating the build of an LA-2A. CJ’s simplified LA-2B, as a matter of fact.

In looking over the components and their pricing/availability, it’s obvious that T4B is going to be my main concern. After searching through the information around here, I have contacted ADL and DripElectronics, as they are supposed to offer replacements. ADL wanted $250 and Drip hasn’t replied yet (been a week). ADL’s figure is about what I’d spend on all the other components…

I’ve found the diy vactrol half-assed version, which I’ll probably do as an interim solution. I’ll get everything else built up first, and make any adjustments or work out any bugs. Might even be a cool thing to be able to swap in for certain applications…

The best possible solution that I see would be to build my own T4B. I’m fine with this, but here is my problem: I don’t have the means to test LDRs. On CJ’s site, he explains in detail the work needed to match LDRs and to find examples with the spec’d decay times. So, how can I overcome this?

How bad could it turn out if I just used whatever comes in the mail?

Would someone consider the sale of some tested and matched LDRs?



« Reply #1 on: April 02, 2008, 10:17:48 AM »
Not helping here, but where is that "simplified LA-2B"?
"All PCB traces are curved to emulate the electrical response of point-to-point wiring" -Drip

« Reply #2 on: April 02, 2008, 10:23:35 AM »


« Reply #3 on: April 02, 2008, 11:05:47 AM »
...Do you have an EFL panel yet? -THAT's the difficult / expensive part...

"A waist is a terrible thing to mind"
Quote from: PRR
Ah, but that was 1999; we don't party like that any more.


« Reply #4 on: April 02, 2008, 11:25:43 AM »
I'd say wait for Drip to reply and go that route, unless someone has any good reason not to do so.  He's slow, but does respond.  I just got one the other day.

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounde

« Reply #5 on: April 02, 2008, 11:28:18 AM »
Well, now that you point that out...

I had read a link (http://recording.org/users/kev/T4B.htm) that stated Panasonic EL was available through Digi-Key. It's dated, so I just checked it out, and they do sell it, but it's a non-stocked item. I assume this would entail some hefty minimum order figures. Price isn't listed...

So I suppose that introduces another question now...  

Anyone have a good source for EL panel?

« Reply #6 on: April 02, 2008, 11:50:19 AM »
sounds like its time for another groupbuy : EL panels and LDR cells ?
curiousaudioparts at  gmail  dot  com

« Reply #7 on: April 02, 2008, 11:56:52 AM »
I thought CJ's T4B site was missing all the photos, is there another link?

btw, I talked to Drip and he said that he should have some ready this month.

« Reply #8 on: April 02, 2008, 11:59:31 AM »
It is still missing pics.

I posted a link to a schematic that's elsewhere on his site that does work...

I read through the t4b page anyways and found plenty of good info nonetheless.

« Reply #9 on: April 02, 2008, 12:09:33 PM »
Dave has some JBL reissues for around $200 plus shipping,


gary o

« Reply #10 on: April 02, 2008, 12:54:01 PM »
In the past I got EL panels small ones from RS & Farnel in the UK & wasnt expensive.

I had been wondering if theres any difference between the different EL panels ( so check to make sure RS farnell is right) , I tried different color panels.....sounded the same to my humble lugs....what was interesting was when I first knocked up my La2A there was no info about for me so I experimented with light bulbs diodes & black boxes & my any old LDR I could find, I didnt no any different..I found that simple cheap neon bulbs work really well as light source, then when i got the EL panel thru the post I couldnt decide what I liked best so I have a switch for different charactor ...prob nothin like orig ..I dont no sadly dont havereal LA2, I then added a 10 pos rotary switch to swap 10 different LDRs....all the wrong ones.....what Im leading to is all this be it not the right parts still pissed all over my store bought recording channel, so dont think you can really go wrong just biuld what you can fiddle and add later its fun....good luck.

Gary O.

« Reply #11 on: April 02, 2008, 01:39:50 PM »
The neon lights sound like an interesting alternative.

Do you have any specific color or even part number that worked out for you?

Between the exchange rate and post, I doubt it'd be that cost effective to get EL panel from over there. I would like to find someone in US.

gary o

« Reply #12 on: April 02, 2008, 02:01:53 PM »
The neons were most common cheap as chips 20p over here they cost me theres a neon in the LA2 circuit thats used as a 60V regulater I believe its the same one as that.

Im not as electronically wise as most here....so maybe some clever nice chaps could chime in ..so i dont understand about the technicallities I just no it works and sounds different to the EL panels.....I literally had crock clips hanging out of my LA2 so i could see the light & brightness of the light as I sung thru the LA2, i then stuck it in small box with LDRs where no daylight can get i & recorded the results...I ABed well to Z ed any light i could find.. LEDs I read about vactrols with similar ressponse as T4Bs tried those...I sawed some of.those in half to try just there LDR with my neon & EL panel

Farnell in USA I had to get my vactrol from them cost small fortune for delivery....not so bad if u buy load a bits for future builds tho



« Reply #13 on: April 03, 2008, 02:50:11 PM »
sh*t!  I can't even get the T4B's through JBL parts anymore!  I wonder when that happened?

Zach Griffen Audio


« Reply #14 on: April 03, 2008, 03:18:23 PM »
Quote from: "usekgb"
sh*t! I can't even get the T4B's through JBL parts anymore! I wonder when that happened?


david kulka at studio electronics bought the remaining JBL stock last year and is now selling them.



« Reply #15 on: April 03, 2008, 05:37:14 PM »
I did hear that he bought a bunch, but didn't realize he had cleaned JBL out.  I used to be able to get them for cheaper directly through JBL.  I guess I can't complain though, because Dave just sold me 10 rev audio taper 25k pots for some pre's.  Seems like a pretty good business he's got going out there.

Zach Griffen Audio


« Reply #16 on: April 03, 2008, 11:28:58 PM »
EDIT: edited to make me appear more knowledgable than i am
you'll find drips price very reasonable. the panel is difficult$$$$ to source but i believe matching and or getting the correct, on resistance, off resistance and delay time is the difficult part.   its on the forum somewhere.  drip goes through quite a few   to find two that match,or have matching slope, read in the metas ?? also if you need the t4 info i believe i have it saved on my pc somewhere. have to run right now and wont be a t pc till sat.   email me your email address .i'll send that stuff to you
Everyday is a gift. Thats why it's called the present


« Reply #17 on: April 05, 2008, 12:38:03 AM »
u can not quantify this particulaer sound, but i can..

1 2 3 4 5 6 7

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