Really Cheap Compressor

nonost · Post by **nonost** » 21 Mar 2019, 10:55

BTW, at higher comp settings I get unity at around 10:00. At 12:00 I get an obvious boost.

nonost · Post by **nonost** » 23 Mar 2019, 12:25

I've removed de Sustain 2-3 wire from the board and there's no distortion. And of course no compression at all.

phatt · Post by **phatt** » 28 Mar 2019, 00:17

nonost wrote:Amazing effect. I built it almost stock. Changed the input cap for a lower value, 4.7nf or 6.8nf are perfect. With that cap the frequency response is really flat. I've also added a 100pf in parallel with the 220k resistor.

The only thing that bothers me is that it adds some gain on top. In a clean amp you can't notice it but in a amp set about to break up you can definitely hear that the gain is increased. I've removed the LDR and found that the distortion is still here. It is ok? I've tried a couple op amps without luck...I guess this is how it behaves

Yes it is the point of the unit,, unlike those sterile comps this thing works brilliantly for guitar as it adds a little hair when it compresses harder.
If that is not to your liking then you may have to try another unit. I've used a few brands and most add lotsa nasty Hiss and most compress way too hard.
Be aware that if the input signal is too big it will overload. but as *mictester* has noted you can raise the value of the 220k input resistor.
If you bypass that series input 220k with a cap it will likely make that problem worse.

Some complain of slight treble loss,, after 50 years of guitar playing I see that as a good thing as most gear today has way too much bandwidth and it's no wonder players keep chasing their tail trying to get a good sound. too much bandwidth just kills any chance of dialing in a great tone.
Phil.

mictester · Post by **mictester** » 29 Dec 2019, 05:29

BIG NEWS!!![/color]

I've finally found a Vactrol that's cheap and works well in this compressor! the part is the LCR0202. I built two compressors using this part, and they sound really good. These boxed Vactrols don't let light in, so testing the board outside the case is easy!

I got mine from Ebay (for another project altogether). I had some left over so thought that I'd try them out, and they work well!

Ben N · Post by **Ben N** » 29 Dec 2019, 09:20

Thanks, mictester. Did you get them from a Chinese seller? I just looked for them on Aliexpress, and they are pretty cheap there, too ($3-5 for lots of 10), but I'd just like to make sure of what I am getting. Did you spec them out, and, if so, are they a one-to-one replacement for any of the better known vactrols (NSL32, VTL5Cx)?

Cub · Post by **Cub** » 25 Jan 2020, 11:26

mictester wrote:I've finally found a Vactrol that's cheap and works well in this compressor! the part is the LCR0202.

Thanks, Chris. That's great news, indeed!
Do any component values have to be tweaked at all, or is it just a straight up swap?

mictester · Post by **mictester** » 30 Jan 2020, 12:08

I just dropped the LCR0202 straight in and it worked right away. I've even etched a PCB to accommodate this part (it's just a minor tweak of my old PCB). Sounds fine!

ppluis0 · Post by **ppluis0** » 30 Jan 2020, 22:13

Hi Mictester,

The datasheet indicates 2.5 mSec of response time.
How we can measure this data ?

I'm trying to implement a clone of an Zvex wah probe for a friend of mine and the usual approach of a green led and 5mm photocell encased into a piece of shrinking tube result extremely slow.
Can this new optocoupler be similar in this regard to VTL5C9 ?

Cheers,
Jose

nonost · Post by **nonost** » 26 May 2020, 14:39

For those who feel a little lack of treble response I have to say that it changes among pot settings.

I've used a 180pf across the 220k resistor because I use the sustain pot at around 70% and I don't hear that tiny lack of treble anymore. With that cap at 100% sustain, you will notice a bit more treble than the bypass signal. So have that into account. For low settings (below 50%) a bigger cap would be needed. That's been my experience.

I wanted to ask you about the performance of this circuit regarding distortion/gain(I don't know what term is better here). At 70% sustain and unity, mine only adds a little bit of grain to the signal. Like going from 9 of volume pot of the guitar to 10 (with log pot, of course). Is it okay? Or should it be totally clean? When my unit distorts is when I set the volume above unity, it starts to raise the volume and grain pretty noticeable.

Really nice circuit

nonost · Post by **nonost** » 26 May 2020, 17:45

I've tried increasing the input resistor but I only reduces the overall volume of the circuit, the grain remains. And I would swear it reduces compression as well. So I wiill stick to the original value.

I've also reduced the input cap but it doesn't seem to affect the grain. It helps to the little treble loss but in my experience the 180pf cap across the 220k resistors works much better.

nonost · Post by **nonost** » 26 May 2020, 21:26

Wow! I've tried another LDR and it's solved!!!

I tried lots of them (tayda, musikding.de, from ebay, etc...) and these was the right one.

I have to say that all of them give compression and a lot of volume but this one gives more compression and no distortion/gain/added to the signal at unity. That's what I was looking for. I wanted it clean and now I finally got it. And it comes with more compression that the other units, so it's great

BTW, I've used 3mm green leds. I will upload a picture of the LDR just in case. I can't remember who is this though :S

I built it stock but a 180pf cap across 220k resistor that I have to check if it's still ok with the new LDR.

mictester · Post by **mictester** » 11 Jun 2020, 16:48

Where did you find the perfect LDR? Do you have a part number for it? I used to use the RPY58A, which worked perfectly (without Jimi's "fuzzy goodness"!).

parrottsquawk · Post by **parrottsquawk** » 26 Oct 2020, 18:03

Anyone built this with an LM358? <thanks in advance>

bow_and_error · Post by **bow_and_error** » 27 Oct 2020, 01:53

I'm in the same boat with LDRs; they're getting harder to find and the specs are all over the place. I've had OK luck with the GL5549, but I've had to test & sort them as the light & dark resistances are not consistent. Sadly, they aren't fast enough to really replace a VTL5C1 in some circuits.

I recently went on an eBay binge and picked up the whole "unbranded" VTL5Cx line, which are embossed with either "SR VTL" or "SL VTL". They'll be here in a few weeks, so I'll post how they sound in a few opto compressors.

Good see some positive reviews of the LCR-0202! It came up in a muffwiggler thread, but not many folks had first-hand experience with them. The datasheet looks promising, and they are even cheaper than the knockoff VTLs! I'll have to pick a few up, but I don't think they will fit my current vactrol hot-swap layout...

stojanos · Post by **stojanos** » 31 Jan 2021, 01:42

Just installed LCR02020 purchased from Aliexpresss (5 for £2.67 - LuLuMi Phone Store). Now it is a very good comp. Almost as my Strymon OB.1. Just very small distortion on attack at unity. Will investigate further.

H3R3T1K · Post by **H3R3T1K** » 09 Dec 2021, 18:11

Hello everyone. I registered here to ask about this comp. I'm having three built with integrated HPF circuit as my always-on secret weapon for bass with 2 backups. I was looking for a simple compressor that won't destroy all my dynamics going into the dirt box. Goal is to just even out string output and account for uneven playing. I want a more even signal going into the dirt box without losing all dynamics. I'm getting my kits from Musikding.de as I'm in Germany. Before laying down the cash I just wanted to ask if the recommended changes for bass mentioned here https://www.musikding.de/docs/musikding ... BOM_de.pdf are up to date. Schematics here: https://www.musikding.de/docs/musikding ... schalt.pdf

Is everyone enjoying this comp for bass?

lykwydchykyn · Post by **lykwydchykyn** » 09 Jan 2022, 19:39

hi all; I've built this circuit using an LCR0202 on the breadboard but it's pretty dirty. There's a subtle fuzz tone leaking in, I'm guessing from the second op-amp, and I seem to be driving the op-amp a bit too. Those who've built this with the vactrol, did you replace both LEDs or did you keep one? Did you make any other adjustments?

EDIT: Nm, had the LCR0202 pinout wrong. Dang useless datasheet.

Ben N · Post by **Ben N** » 12 Jan 2022, 12:48

So share your hard-earned wisdom, lykwydchykyn. What's the right way?

lykwydchykyn · Post by **lykwydchykyn** » 14 Feb 2022, 22:55

Ben N wrote: ↑12 Jan 2022, 12:48 So share your hard-earned wisdom, lykwydchykyn. What's the right way?

Basically, the pin with the dot on it is the ground side of the LED. The datasheet doesn't spell this out, it just tells you which side is the LED and which side is the LDR (actually, it doesn't even give those terms IIRC. It just calls the dotted side "input" and the other side "output").

Domin · Post by **Domin** » 30 Mar 2022, 06:06

I made it yesterday and tried it today with my bass, is there any way to make it more compressed? Ehat about increasing pot resistance? Will it drive leds harder ?

Really Cheap Compressor [documentation]