Some LA-Light Questions, Plus Related Level Meter Question

[rockgardenlove]

Hey guys!  I got a Tascam 424mkIII 4 track recorder recently to do some recordings with.  I was recording on my Presonus Firebox straight into my computer.  Both techniques offer different sounds...the tape of the Tascam is a much warmer and smoother sounding setup...anyways, with the new Tascam I notice that it senses volume spikes very easily on things like drums and bass, etc.  I'm looking for a good compressor to get it so that I can keep a pretty regular volume level.  I did search on Johan's LA-Light and found lots of good info, but I'm kind of confused.  I can't tell which threads are citing which version of the schematic, and it seems there are several.  So, here's what I'm wondering in relation to the latest version, here:  http://aronnelson.com/gallery/johan/LA_Light_last_one_001

Is the level of the input supposed to be standard instrument level or line level?  I was reading that somebody stuck a 20 decibel preamp in front of it and it really came alive, but then some other posts suggested that it was being tweaked for bass/guitar use, and now I'm not sure.

What is the power source supposed to be?  Johan in one post said he used 18v (http://www.diystompboxes.com/smfforum/index.php?topic=31647.0), somebody else said they were tweaking for 9v use.  What should I be using for this schem?  Moosopotamus said +/- 15v worked nicely, but I'm pretty sure this was a different version.  Johan then said +/- 12v...this thread: http://www.diystompboxes.com/smfforum/index.php?topic=11590  Fairly sure that last bit is a way older version.

Some posts suggested a Vactec VTL5C2.  (http://www.smallbearelec.com/Detail.bok?no=346)  Does this sound suitable?  If I used the 5C2, I would hook the LED end of the photocoupler up to the place on the schematic with the pair of LEDs, right?

What's the "VU" in the circle towards the bottom of the schem?  I think I recall it being a voltage meter or so, but I'm not sure.

And finally:
If I wanted to put a level meter on the end of the circuit for a visual display of the compression (if that the "VU" isn't one already), how would this work?
http://www.zen22142.zen.co.uk/Circuits/Audio/vumeter.htm

Thanks very much!

EDIT:
http://aronnelson.com/gallery/johan/La_light_studio
This answer some of my questions...mainly the power supply issue, and the meter deal. Cool.  Where can I get those really cool indicators?  They look awesome.

[Nasse]

http://sound.westhost.com/project55.htm
http://sound.westhost.com/project60.htm

http://www.velleman.be/ot/en/product/view/?id=9130

Nice info about VU meters on those Australian links, perhaps they are useful. That LM324 circuit may be good, but looks like it may need some circuitry in front, like rectifier/peak detector but honestly I did not look it so much... opamp comparator vu is good anyway. Check those led driver chip datasheets too, some info about what to put in front of display driver.

That Velleman kit might be nice for stereo compressor/limiter, has displays for in put and output. Dunno if it is available where you live. I just bought cheepo IKEY mp3/wav recorder, and I think I need a portable battery powered comp/lim for it.

[rockgardenlove]

Thanks for the extra links!  The thing that really appeals to me here though is the fact that I have all the materials needed.  I'd rather not have to buy more stuff, but it's not that big of a deal.  I really like those analog gauges on Johan's pic...I'd really like to know where to find them.

Other questions still apply if anybody could help...
Thanks!

[rockgardenlove]

Bump?

[Johan]

Hi Christian
cool you want to try it...
about voltages..just feed it with whatever you're comfortable with..it will vork from a single 9volt battery if that is what you want, all the way up to 30 volt( +/-15volt) wich is the limit for using tl0x2 opamps). connect the virtual ground to signal ground and let the voltages float..that way you dont need any cap's on input and output ( or look at the stompbox version for a more convetial way of doing it)
it is supposed to se a line level signal, but there should be enough gain in the side chain to take an instrument level without problems
the VTL5c2 works well, but I really prefere to use separate LDRs and LEDs..you can use both LED to iluminate the LDR and it is MUCH cleaner sounding with no typical artifacts assosiated with most simplistic compressors/limiters..Marty Mart wrote a build-report on this a few months back, and seemed happy
the two LEDs, two LDRs also allow you to easily use the same lightsourse for both LDRs ( so that the vu traks corectly..)
the VU symbol ways just a way of drawing it...connect any analogue needle type VU-meter you find and adjust the trimmer so it reads "0" db, then it will track the gain reduction as closely as the two different LDRs allow..simple but effective
on the output in the rack-unit I built, I connected a LED through a 2k resistor straigt on the output. the LED obviously clippes the signal, but there is the 2k resistor between LED and output and the opamp can easyly drive that load without geting affected..this way the LED will light up when the output signal is stronger than 1.5 volts...wich just happens to be close enough to +4db pro studios work at

hope this clear things up...
johan

[rockgardenlove]

Thanks very much for the reply!
Good to know about the supply voltage, that makes it easy.  I'll probably go with 30v then.  What LDR would you suggest?  Preferably something from Smallbear.  I haven't worked with LDRs before and so I'm not sure what to get.

I'm not quite sure what you mean about the 2k resistor and the LED.  Do you mean you put the 2k and LED in series with the 100 ohm resistor on the output?  Or do you mean that you put the LED and 2k in series to ground?

[rockgardenlove]

Oh!  One more thing, has anybody tried this compressor on drums?

Thanks!

[Bagge]

I remember Sverige_cruz did some sound samples of drums through LA light. Look here:
http://www.diystompboxes.com/smfforum/index.php?topic=51101.20

http://aronnelson.com/gallery/album72

[sverige_cruz]

I thought I heard my ears ringing... or was that the tinnitus  Yeah - I ran some drums through this guy at one time. I think this is the link (there's also some bass clips on there - look for Kerry's (call1800ksmyazz) last 2 posts - he has them in his album, cause I didn't have one at the time):

http://www.diystompboxes.com/smfforum/index.php?topic=51800.0

I made myself a little pcb and stuck it inside a Raco box. Ugly as hell, but did the job. I got a Radio Shack assortment of LDR's and some Radio Shack LEDs and used some broken off IC sockets to mount them, in case I chose the wrong match. Didn't bother about the meter. I figured it's got to sound good in the mix anyways, so why bother with looks. Meters.... we don't need no stinking meters (http://en.wikipedia.org/wiki/Stinking_badges) That, and the fact I didn't have any meters hanging around to use. I was planning on trying out the higher bi-polar voltage version, and see how that helped headroom or the sound, otherwise. Hey, maybe if you want to use it for recording, try out some input/output transformers. Edcor has some cheap but good sounding stuff http://www.edcorusa.com/home.html. Anyways, I encourage you to build it. It's a nice and easy build.
-- Jesus