Vactrol or LDRs for LA2A or other compressors.

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gary o

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Hiya been experimenting LDR cells in my home made LA2A, noticed the vactrol units being used in other compressors, was thinking of drilling out the LEDs to use the cell from one of these units, but which one ??
the VTL5C3 I think gets a lot of mentions, attack time of 35us,
but what about the VTL5C attack tme of only 1us would ths be better, was gonna buy a few try em but the del charge is 13 pounds on top if in stock.
Or what about Silonex NSL32 or NSL32SR3 would these be good ?

Heres some info cut n pasted from Farnell site.

1313654
VTL5C1
EG & G VACTEC Newark InOne Opto-electronics; Package/Case: 4 pin, Leaded; Propagation Delay: 35uS; Voltage Rating: 100 V; Number of Channels: 1 43F885

In Stock
£2.018

1313666
VTL5C2
EG & G VACTEC Newark InOne Opto-electronics; Package/Case: 4 pin, Leaded; Propagation Delay: 500uS; Voltage Rating: 200 V; Number of Channels: 1 43F886

Out of Stock
£1.633

1313678
VTL5C3
EG & G VACTEC Newark InOne Opto-electronics; Package/Case: 4 pin, Leaded; Propagation Delay: 35uS; Voltage Rating: 250 V; Number of Channels: 1 43F887

In Stock
£1.714

1313680
VTL5C4
EG & G VACTEC Newark InOne Opto-electronics; Package/Case: 4 pin, Leaded; Propagation Delay: 6uS; Voltage Rating: 50 V; Number of Channels: 1 43F888

In Stock
£1.637

1313691
VTL5C6
EG & G VACTEC Newark InOne Opto-electronics; Package/Case: 4 pin, Leaded; Propagation Delay: 50uS; Voltage Rating: 250 V; Number of Channels: 1 43F889

In Stock
£2.079

1313708
VTL5C7
EG & G VACTEC Newark InOne Opto-electronics; Package/Case: 4 pin, Leaded; Propagation Delay: 1uS; Voltage Rating: 50 V; Number of Channels: 1 43F890
In Stock
£2.213


Many thanks................Gary O.
 

chrissugar

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The VTL5C1 is good for designs where you need control over the time constants, like the Fred Forssell opto comp.
The VTL5C2 is a good option if you want to make something with fixed timeconstants like the LA2A. Moonlee use VTL5c2 in their opto comps and I know that many people consider the EL0P the modern version of LA2A.

chrissugar
 

Bluzzi

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Gary - Let us know your findings on the LDRs. I am building 2 LA2As and I am especially interested in building my own T4B (not on those 2 though).

Jim
 

gary o

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Hiya I read that the rise time of the VTL5C2 s 500us & I thought that might be bit slow, wonder if the ELOP use side chain electronics to speed up {dont no how}
Am right in saying an LA2A has a rise of 5ms & decay of 500ms ??

Anyway I read the Silonex NSL32 opto coupler has 3.5ms rse & 500 decay so I ordered 1 from Farnell plus NSL32SR3, SR2 to try.

cut them in half with stanley knife & the NSL32 sounds best more inaudable, the other 2 punp a little due to faster release time I suppose.

Think I might order a handful of the Vactec ones to play with was thnking of puttng very fast rise cell & slow cell in parallel for an experiment.

for my T4B I just have a black plastc box with a white when lit EL panel n the bottom & I also have a standard neon in there as a another light source too & a switch for EL light source or Neon light source & the cells can see both, I can also take the lid off & check how much light is n there too,thing is get a better sound & more compression from the 20 pence neon than the expensive EL panel, dont no if its because the cells react better to the orange glow of the neon rather than the bright white of EL.

dont have a real LA to compare the sound, im just lookng for a nice sound & have found some but I think theres no harm in lookin for nicer ones or just different ones.

Cheers......................Gary O.
 

chrissugar

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The sidechain in the EL*P is an ordinary LM386 amplifier circuit that feeds two VTL5C2 conected in antiparallel, one LED for the positive alternance and one for the negative. Also the photoresistors in the attenuator circuit are conected parallel.

chrissugar
 

chrissugar

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By the way, the Perkin Elmer optocouplers are considered the best for audio because they can handle higher levels. That means that you don't have to attenuate too much then amplify and loose signal to noise ratio.

chrissugar
 

gary o

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Intrerestng im not sure understand how they are wired up in the elop thing & I cant see how opto that slow 500ms would be much use,not slaggin off just wondering these guys must no what there doing, and people like that unit, like I said im gonna buy a handfull of the vactecs one of each I suppose, the expensive del charge applies for the one order so might as well try em all will be fun.
I did try a vactec in a cheap opto compressor I have, a ART Levelar rise time I read is 6.5ms by the way, this little unit I bought from music shop for only 20 pounds it was returned to the shop coz customer said it didnt work only in limit mode,turned out it does work, but works very well you cant hear it compressing exept in limit mode its a great little unit.
Anyway coz I dont want to wreck the ART to try vactec in the LA2A, I left vactec {that has no numbers on it} in place & split signal from a pre amp fed 1 to ART and other to LA & connected cell side of ARTs vactec to LA.
Result was it sounded great loads of reduction going on but you couldnt hear it & sounded much sweeter going thru the LA make up amp.
Thing is I dont no if I was listening to the bear cell or if the ARTs electronics were messing with the led of the vactec,there 2 settings on the ART, auto which im guessing is the cells natural response & fast, auto sounded best fast started to breathe/pump when doing lots.

Cheers .........Gary O.
 

gary o

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Ive just desoldered the vactec from my ART Levelar and it turns out its the VTL5C2, looked thru some PDF files someone sent me & found one for it turns out the rise time is only 3.5ms & fall time 500ms {same as sil NSL32} after all looks like on the Farnell site they were showing the fall time as the rise time, I thought it was a bit high.
So out comes the stanley knife.

Cheers...................... Gary O.
 

chrissugar

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here you can find info for all the VTL series vactrols:
http://optoelectronics.perkinelmer.com/catalog/Category.aspx?CategoryName=VTL5C+Series
Datasheets for VTL5C1 and VTL5C2 :
http://optoelectronics.perkinelmer.com/content/Datasheets/vtl5c1_c2.pdf
Application notes:
http://optoelectronics.perkinelmer.com/content/ApplicationNotes/analog%20optoisolator%20application%20notes.pdf

chrissugar
 
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