Where to buy a good vactrol ? - Page 1
Forum section: electronics / projects

author: Jan Audio
author_rank: Frequent Contributor
timestamp: April 01, 2020, 04:20:52 pm
content: Hi, i want a vactrol for a audio-compressor, what normal shop can you buy such a thing ?Or where else ?thanks

author: RandallMcRee
author_rank: Frequent Contributor
timestamp: April 01, 2020, 04:30:11 pm
content: If you simply google you can find specialty shops that sell NOS parts. I purchased several a few years ago...Also Ebargh but then you don't what the heck you are getting.E.g.https://www.amplifiedparts.com/products/optocoupler-vactec-vtl5c1-vactrol-new-old-stockRandall

author: Jan Audio
author_rank: Frequent Contributor
timestamp: April 02, 2020, 11:34:57 am
content: They are a bit to expensive for me.Maybe with a LDR and LED with printed case somehow ?, maybe not.Ebay 5 for 5+ dollar no good then ?, maybe i should try.

author: rvalente
author_rank: Frequent Contributor
timestamp: April 02, 2020, 12:26:29 pm
content: I've seen some guitar pedals using a LED + LDR inside a small black tube, you could use a 8mm black pneumatic (PU tubing) is really cheap...

author: 2N3055
author_rank: Super Contributor
timestamp: April 02, 2020, 12:35:16 pm
content: In a pinch I used drinking straw, and then a black heatshrinking tube over.. Worked well enough..

author: SeanB
author_rank: Super Contributor
timestamp: April 02, 2020, 12:44:19 pm
content: 5mm CdS cell, red 5mm diffused LED, and a 2 part layering of black low temperature heat shrink and you have them. Order 100 of the CdS cells and match yourself a few pairs using a small black project box and a red LED one side and a pair the other side, and you can make a stereo set with this as well.

author: rvalente
author_rank: Frequent Contributor
timestamp: April 02, 2020, 01:01:43 pm
content: Quote from: SeanB on April 02, 2020, 12:44:19 pmJust out of curiosity, why RED led? Does the LDRs have different responses in wavelength?

author: 2N3055
author_rank: Super Contributor
timestamp: April 02, 2020, 01:14:16 pm
content: Quote from: rvalente on April 02, 2020, 01:01:43 pmThey do..Farnell seems ho have some..https://export.farnell.com/advanced-photonix/nsl-32/optocoupler-2kv-resistive-o-p/dp/3168773?st=ldr

author: RandallMcRee
author_rank: Frequent Contributor
timestamp: April 02, 2020, 03:43:17 pm
content: Quote from: 2N3055 on April 02, 2020, 01:14:16 pmGood find. The OP asked for a Vactrol which has a specific Iv/Rx curve, although its pretty loose if I remember correctly. Buying an NSL32 (its the only one actually manufactured these days unless you pop over to an H11F1M) gives slightly different characteristics. But if you are being cheap (e.g. trying to save money) just realize that making one yourself with a well-defined characteristic will be *really* tough.Good luck.

author: Jan Audio
author_rank: Frequent Contributor
timestamp: April 02, 2020, 03:47:14 pm
content: I have 3D printer, only no black filament.Way to expensive, they have LDR at tayda $0.24.

author: SilverSolder
author_rank: Super Contributor
timestamp: April 02, 2020, 09:07:27 pm
content: These of any use? On sale!https://www.goldmine-elec-products.com/prodinfo.asp?number=G15396C

author: Jan Audio
author_rank: Frequent Contributor
timestamp: April 03, 2020, 03:57:31 pm
content: a $50.00 minimum orderCan not buy 20, only 5.

author: SilverSolder
author_rank: Super Contributor
timestamp: April 03, 2020, 04:38:57 pm
content: Quote from: Jan Audio on April 03, 2020, 03:57:31 pmEach pack has 10 each? so you'd get 50 in totalThere is a minimum order total of $10.00 when I look. Maybe it is different for international?Even spending $50 is good, don't forget we have to boost the economy in the crisis!

author: schmitt trigger
author_rank: Super Contributor
timestamp: April 03, 2020, 04:58:08 pm
content: I was under the impression that CdS photocells had a wavelength response which peaked around 550nm, green.See attached datasheet.

author: 2N3055
author_rank: Super Contributor
timestamp: April 03, 2020, 05:23:34 pm
content: Quote from: schmitt trigger on April 03, 2020, 04:58:08 pmThat's curious. All those that I used, used to be around 650-660 nm..Nice to know.

author: floobydust
author_rank: Super Contributor
timestamp: April 03, 2020, 06:20:27 pm
content: I recall CdS photocells are most sensitive to green, like the human eye. CdSe are red-sensitive. But there is doping involved I think for higher gain but getting slower response.I'm not sure why Vactrol is using red LED's - perhaps they were brighter/cheaper back in the day? Some even used neon lamps. 40mA LED drive for a 5mm part seems oddly high, so they need brightness.I would try a CdS photocell with a high efficacy pure green LED in some heatshrink tubing and do some pulse experiments. The response time made the sound of a compressor what it is, so important to try keep that if cloning vintage gear. It seems faster CdS parts have shallower slope.The parts are still relevant. Stumbled ontoJim Williams (July 1990), "Bridge Circuits Marrying Gain and Balance", Linear Technology Application Note 43He uses Vactec VTL5C10 or Clarex CLM410 in an ultralow (better than a JFET) distortion sine oscillator 0.0003% or 3ppm fig.48 wow. Bless his soul.

author: schmitt trigger
author_rank: Super Contributor
timestamp: April 03, 2020, 06:26:18 pm
content: Your comment made me research further.I found the following datasheet. It is indeed a CdSe photocell and the sensitivity peaks at 690 nm. Definitively blood red.See attached.

author: Jan Audio
author_rank: Frequent Contributor
timestamp: April 04, 2020, 01:14:24 pm
content: Why are those amerikan shops so racist ?

author: 2N3055
author_rank: Super Contributor
timestamp: April 04, 2020, 01:42:54 pm
content: Quote from: Jan Audio on April 04, 2020, 01:14:24 pm

author: schmitt trigger
author_rank: Super Contributor
timestamp: April 04, 2020, 03:23:53 pm
content: Quote from: Jan Audio on April 04, 2020, 01:14:24 pm?

author: Jan Audio
author_rank: Frequent Contributor
timestamp: April 04, 2020, 04:29:46 pm
content: Americans minimum order : 10Others : 50

author: schmitt trigger
author_rank: Super Contributor
timestamp: April 04, 2020, 08:19:59 pm
content: Well I am in Mexico, as as you can see in the attached images, it will allow me to order in multiples of 1, 5 10 or 50. You have to change the part number's last prefix.Could it be related to EU customs?

author: Moshly
author_rank: Regular Contributor
timestamp: April 04, 2020, 11:09:08 pm
content: I did some test using different colours a while back, (see attached).Looks like the modern high brightness red give the most liner response.HB Red: 90's translucent red high brightnessR,G,B: modern water clear Chinese high brightness RGBUV: modern water clear ChineseGreen O: 80's opaque greenNotes: Graph is LOG/LOGHB Red:red line touches top of graph.

author: Jan Audio
author_rank: Frequent Contributor
timestamp: April 05, 2020, 12:37:01 pm
content: Quote from: schmitt trigger on April 04, 2020, 08:19:59 pmNo the minimum order,customs here are from €22,- + €13,- handling fee.I like to order the maximum of 5 packages for 12,50 nothing more.Its ok, at least they dont geo-block like other shops.I am going for 100 piece optoresistor from china ( 5 types ) for almost 5 dollar.

author: floobydust
author_rank: Super Contributor
timestamp: April 05, 2020, 11:43:48 pm
content: Found a bit more Vactrol data. The spectral mismatch (red vs green drive) is intentional it seems.I'm not sure what CdS cell size has to do with anything, beyond power dissipation. Those chinese CdS cells are tiny.I have some huge old GE CdS cells hermetically sealed glass lens and their gamma γ (which is like a thermistor Beta) spec is high. I think that's from the number of squiggles the cell has between electrodes.