Chinese fake vactrols

[hayun]

I bought some FAKE VTLs from Aliexpress.

Not surprisingly, there are problems with them.

Relatively well known issue; the package is not sealed properly. It leaks, so additional work is needed to seal it.. with black heatshrink tube or tapes, paints etc.

The dark resistance is high(over 40M), on resistance is very low (200~300ohm with 5mA). It ‘looks’ ideal for switching circuit..

However

The response time is problematic.
the decay speed (off resistance rising) is noticeably slow.
I didn’t measured it, but I can hear the delayed volume difference.

For example, I tried them on SLO circuit;
The resistance of the muting LDR rises not fast enough when it’s off, so I can hear the volume difference in the moment of switching.
Although it’s a brief moment(say..0.5sec?), clearly audible. (it’s not with proper LDR)

Maybe.. it could be used for VTL5C4 replacement, like some of VTLs used in Mesa Mk series.. it’s used intentionally for slower switching.

I have some GL5549 with high dark resistance(over 40M), low on resistance (4~500ohm with 5~7mA) and very fast response time. It works perfectly with switching circuits, but not all GL5549 are guaranteed to work like that.

p.s. Regardless of part numbers, they are all similar with resistance range.

again, the response character is definitely wrong to replace original VTLs, so it’s hard to expect working properly on sensitive circuits.. like compressors or modulations etc.


** UPDATE **
After more test, I have noticed that these VTLs can’t pass high level signals properly. There is significant volume loss, compared to normal ldrs. What a junk. It’s not usable on tube amps.

[jabguit]

you had me at Aliexpress.......

[R.G.]

As a general note, new-manufactured LDRs have become problematic worldwide. Environmental restrictions In the manufacturing countries - first world and China, for instance - have make the use of cadmium sulphide and cadmium selenide compounds illegal. Even where they can be manufactured, they're illegal to import in many cases.

I ran into this that a through a friend who makes univibe clones. He found the ear-perfect LDR at a Chinese supplier, saved up his pennies and ordered several thousand. The big batch did not match the sound of the samples. He eventually found that between his samples and quantity order, the supplier changed to a no-cadmium formula because of new laws.

CdS and CdSe LDRs are probably now in the same situation as old-school germanium transistors - pockets of old ones in dusty shelves.

[hayun]

As a general note, new-manufactured LDRs have become problematic worldwide. Environmental restrictions In the manufacturing countries - first world and China, for instance - have make the use of cadmium sulphide and cadmium selenide compounds illegal. Even where they can be manufactured, they're illegal to import in many cases.

I ran into this that a through a friend who makes univibe clones. He found the ear-perfect LDR at a Chinese supplier, saved up his pennies and ordered several thousand. The big batch did not match the sound of the samples. He eventually found that between his samples and quantity order, the supplier changed to a no-cadmium formula because of new laws.

CdS and CdSe LDRs are probably now in the same situation as old-school germanium transistors - pockets of old ones in dusty shelves.

Yeah the RoHS.. I didn’t know there is non-cadmium ldr

I remember I barely finished the Univibe build before, with extremely limited source of cds. it was literally ‘lucky’ that I found acceptable ones, just only 4 left..(old Silonex cds) it was like a trasure hunt.

As a hobbist it’s just sad that DIY is getting more difficult with discontinued components due to the ristrictions or the changes of industrial system etc.

I’m planning to build Mesa Mk4 preamp now, it requires so many ldrs.. I’ll almost run out my stash after finish it. I replaced some of them with relays though..
I should study about mute circuits for switching freedom.

[maxkracht]

Tayda still sells LDRs, i've used them for tremolo and switching. Might require a bit of sorting to get the specs you want, but they aren't too expensive.