New Kenetek T4B Opto-Attenuators for your LA-2A, LA-3A and similar builds

[joe-electro]

Kenetek T4B Opto-Attenuator units for your LA-2A, LA-3A or similar projects. Available in 5 different speeds: Classic (Medium), Good Slow, Good Fast, Wayyy Slow and Stupid Fast. For overall general purpose work the Classic is your best bet. Use a Good Slow for bass and male vocals. Some people prefer a Good Slow unit on female vocals as well. Good Fast units are best for drums, acoustic guitars, electric guitars, and up tempo music in general. Wayyy Slow is more like a leveler of the early to mid sixties. Stupid Fast units are almost as aggressive as an 1176 with all four buttons pushed in.

Kenetek T4B's are the best selling T4B on the planet and are in use every day in studios all over the world making great music. Leading manufacturers including Warm Audio, Stam Audio, Serpent Audio and Skibbe Audio have all chosen Kenetek T4B's to ship with their new products.

Every T4B comes with a 3 year warranty and goes through no less than 5 quality tests before getting approved for shipment. Each unit comes with its own warranty certificate showing the date of purchase and serial number.

Matched pairs for stereo mix buss and mastering use are available, as well as Fast/Slow pairs for specialty builds. The T4B unit is the heart of the sound in an Opto-style compressor. Your build deserves the best T4B you can get - a Kenetek T4B.

Order here:

https://www.gearslut.com/index.php?main_page=index&cPath=84

Thanks!!!

 

[ruffrecords]

I thought labels that say "warranty void if removed" are either illegal or unenforceable.

Cheers

Ian

 

[joe-electro]

The FTC says you can repair your own things and manufacturers cannot force you to use their repair services.  Kenetek has in the past, and will continue to honor the warranty on all Kenetek T4B's unless there is obvious damage from misuse or abuse.

Thank you.

PS - Our return rate is less than 1 unit per thousand sold. That is, <0.1%.

 

[XAXAU]

Kenetek T4B Opto-Attenuator units for your LA-2A, LA-3A or similar projects. Available in 5 different speeds: Classic (Medium), Good Slow, Good Fast, Wayyy Slow and Stupid Fast.

Hi this might be a stupid question but is it possible to have a slower attack and a more popping faster release built into these?
Or modify the resistance going into the cell to get a longer attack and use a faster cell?
Unsure how this circuit works to be honest!

Cheers

 

[joe-electro]

This is very difficult to do because the attack and release times are co-dependent. In other words, photocells with a slower release time also have a slower attack time.  Cells with a faster release also tend to have faster attack.  There is a wide variation in attack/release times between photocells within the same batch, due to the manufacturing process.  The photo-reactive material is mixed into a slurry and then sprayed onto the substrate, and not all photocells get the same density of material.

I can select out photocells that have a slightly slower attack and a slightly faster release, but this would be a laborious process. I would have to charge extra for the extra labor.

It's relatively easy to get photocells that have slower attack and release, or faster attack and release. These are what I call "Good Slow" and "Good Fast" T4B's, which you can specify when you order.  You might try a "Good Fast" and see what you think.

Thanks!!!

 

[XAXAU]

This is very difficult to do because the attack and release times are co-dependent. In other words, photocells with a slower release time also have a slower attack time.  Cells with a faster release also tend to have faster attack.  There is a wide variation in attack/release times between photocells within the same batch, due to the manufacturing process.  The photo-reactive material is mixed into a slurry and then sprayed onto the substrate, and not all photocells get the same density of material.

I can select out photocells that have a slightly slower attack and a slightly faster release, but this would be a laborious process. I would have to charge extra for the extra labor.

It's relatively easy to get photocells that have slower attack and release, or faster attack and release. These are what I call "Good Slow" and "Good Fast" T4B's, which you can specify when you order.  You might try a "Good Fast" and see what you think.

Thanks!!!

Cheers

In most other comps  the attack and release can be altered, I understand that a slow cell is slow on bothe the attack and release side

But is there anything that can be done outside of the cell that will slow down the attack? Then pair that with a really fast cell?

 

[joe-electro]

Since the electroluminescent panel in a true T4B requires an AC signal, I don't know of any easy way of slowing the attack down without affecting other aspects of the sound that we want to keep intact (such as frequency response).  However, if you use an LED as your light source then you can use a nice sidechain circuit such as the Forrsell opto sidechain, which is very versatile and has a very effective attack control. Schematic can be found here:

http://www.forsselltech.com/media/attachments/SideChain_B.PDF

Thanks,

Bill

 

[XAXAU]

Since the electroluminescent panel in a true T4B requires an AC signal, I don't know of any easy way of slowing the attack down without affecting other aspects of the sound that we want to keep intact (such as frequency response).  However, if you use an LED as your light source then you can use a nice sidechain circuit such as the Forrsell opto sidechain, which is very versatile and has a very effective attack control. Schematic can be found here:

http://www.forsselltech.com/media/attachments/SideChain_B.PDF

Thanks,

Bill

Cheers Bill

Back with another silly question

There´s 2 photocells in the t4b, are they both adding to the attack and release? Read something that said the t4b had 2 release stages, one that hits 50% GR in 60ms and the other 50% takes 1-15 seconds.

It got me thinking it could be modified if that was the case, like removing the ultra slow release stage, permanently or or with a switch. Then using a slower single cell to bring the attack from 10ms to 15ms and the release from 60ms to 90ms (or whatever).

Cheers

 

[Rob Flinn]

There´s 2 photocells in the t4b, are they both adding to the attack and release?

No.  One cell does the compression & the other cell controls the meter.

 

[joe-electro]

That's the way T4A and some very early T4B units were made 50 to 60 years ago, when LA-2A's were being used as levelers ahead of broadcast transmitters. All T4A units (that I've seen) and the very early T4B units (up until 1969 or so, coincidentally coinciding with the advent of the LA-3A) had three photocells in them. The third photocell, a Clairex CL705, had a very fast attack release time, and was placed in parallel with the CL505 cell in the audio path. It did indeed give those units a dual time constant, which might have been useful to broadcast engineers at the time. Over the next two or three decades, more sophisticated devices were designed (such as the CBS Audimax/Volumax combo, the Gates Sta-Level/Solidstatesman combo and Urei BL-40, not to mention all of the fantastic Orban units) which did a much better job of controlling both short peaks and average program level.

I have done quite a bit of experimentation with multiple photocells (with different time constants) and have come to the conclusion that there is not enough benefit to justify the additional cost for my production T4B's. In my experience, the overall response of the T4B is dominated by the response of the slower photocell.

That said, I have found that having the ability to switch between T4B's with different attack/release characteristics is very handy sometimes. A simple and inexpensive DIY solution can be found here:

https://www.gearslut.com/files/2xT4B_Mods.pdf

While I came up with this circuit in response to a question posed by someone building a Drip LA-2A, this circuit would work with any LA-2A work-alike.

I am also manufacturing a more elegant and flexible box that houses up to three Kenetek T4B's, and allows up to seven different attack/release curves, by switching in different combinations of T4B's. It also functions as a soft bypass, allowing you to hear the compressed vs uncompressed sound quickly. The box plugs into the existing T4B circuit and does not require any circuit modifications. However, if your T4B socket is located inside the enclosure you will have to come up with a way for the cable to enter the enclosure. The pics below show the prototype unit with a Kenetek LA-2X.  The production version of the box will not be as deep and the cable will be shorter. Please PM me if interested in one of these.

Hope this helps and thanks for reading!

 

[XAXAU]

That's the way T4A and some very early T4B units were made 50 to 60 years ago, when LA-2A's were being used as levelers ahead of broadcast transmitters. All T4A units (that I've seen) and the very early T4B units (up until 1969 or so, coincidentally coinciding with the advent of the LA-3A) had three photocells in them. The third photocell, a Clairex CL705, had a very fast attack release time, and was placed in parallel with the CL505 cell in the audio path. It did indeed give those units a dual time constant, which might have been useful to broadcast engineers at the time. Over the next two or three decades, more sophisticated devices were designed (such as the CBS Audimax/Volumax combo, the Gates Sta-Level/Solidstatesman combo and Urei BL-40, not to mention all of the fantastic Orban units) which did a much better job of controlling both short peaks and average program level.

I have done quite a bit of experimentation with multiple photocells (with different time constants) and have come to the conclusion that there is not enough benefit to justify the additional cost for my production T4B's. In my experience, the overall response of the T4B is dominated by the response of the slower photocell.

That said, I have found that having the ability to switch between T4B's with different attack/release characteristics is very handy sometimes. A simple and inexpensive DIY solution can be found here:

https://www.gearslut.com/files/2xT4B_Mods.pdf

While I came up with this circuit in response to a question posed by someone building a Drip LA-2A, this circuit would work with any LA-2A work-alike.

I am also manufacturing a more elegant and flexible box that houses up to three Kenetek T4B's, and allows up to seven different attack/release curves, by switching in different combinations of T4B's. It also functions as a soft bypass, allowing you to hear the compressed vs uncompressed sound quickly. The box plugs into the existing T4B circuit and does not require any circuit modifications. However, if your T4B socket is located inside the enclosure you will have to come up with a way for the cable to enter the enclosure. The pics below show the prototype unit with a Kenetek LA-2X.  The production version of the box will not be as deep and the cable will be shorter. Please PM me if interested in one of these.

Hope this helps and thanks for reading!

Thank you for the answers and your builds look amazing, truly

My problem is thatI love the LA2A color and boxtone as well as the compression behaviour but it´s a bit limited for my uses
Sure I have synths to colour and drive, love smashing drumbusses in parallel and using it without compression on the 2 bus
But I can´t justify the price tag(s) of having 2 LA2A´s for those uses

I´ve looked at the 1176 schematic (and others) and it seems the attack and release circuits are separate yet still interacting with eachother
I have no idea how the LA2A is operating but isn´t there a way affect one and not the other?
Like having a stupid fast matched pair but messing with the attack portion to make it slower

I realize that messing with a gem of a circuit like this is silly but as I said I can´t afford a rack full of "one trick ponies"

Would like it to have a popping release but still let thru transients, I could have it needles barely moving but still, it would be nice to have a little bite if possible

Cheers

 

[FarisElek]

Thank you for the answers and your builds look amazing, truly

My problem is thatI love the LA2A color and boxtone as well as the compression behaviour but it´s a bit limited for my uses
Sure I have synths to colour and drive, love smashing drumbusses in parallel and using it without compression on the 2 bus
But I can´t justify the price tag(s) of having 2 LA2A´s for those uses

I´ve looked at the 1176 schematic (and others) and it seems the attack and release circuits are separate yet still interacting with eachother
I have no idea how the LA2A is operating but isn´t there a way affect one and not the other?
Like having a stupid fast matched pair but messing with the attack portion to make it slower

I realize that messing with a gem of a circuit like this is silly but as I said I can´t afford a rack full of "one trick ponies"

Would like it to have a popping release but still let thru transients, I could have it needles barely moving but still, it would be nice to have a little bite if possible

Cheers

This is exactly why people put 1176 in front of or after LA2A's all the time. It's not a one trick pony and there is nothing you can do to alter the circuit.

 

[paulcheeba]

Does anyone know which flat lamps are in an ADL 1500? I’d like to get Kenetek.

 

[joe-electro]

Hello and thanks for your inquiry. The opto-attenuator units in the ADL-1500 are soldered into the main PC board, so Kenetek opto-attenuators won't work in a stock 1500. I've had several clients successfully modify ADL-1000 units without too much hassle, adding an octal socket so that a Kenetek T4B can be used. I managed to find a pic of the inside of the ADL-1500 on the web, and it looks like this unit could be similarly modified as well, if someone was duly motivated.

 

[duantro]

Hello Joe, Do you happen to sell the cells and led panel separately? I stumbled upon a LAZ-3a pcb and need one mono set.

 

[metalockpick]

If you are making your own opto circuit, I find that using fast photocells with high(er) voltage light bulbs will give you a slow attack and a fast(ish) release, the goal being to not squash the attack of the signal, but to hold the peaks below clipping. The idea is to not fully illuminate the bulb, using the time constant of the filament warming to delay the clamping. A low current bulb will dim faster than a higher current one, which aids in speeding the release.

 

[joe-electro]

Hi Duantro,

I'm sorry, we only sell complete T4B's right now, and that's keeping us really busy.

 

[Bobby Baird]

Hi Joe,

I bought some second hand separate fast and slow Kenetek T4B's hoping they would be closely matched to use in my OPTO 6, but they have about a 3 to 4 db difference on the gain reduction meter while switching between the two T4B's. This is actually pretty impressive considering these weren't bought as a pair being only a few db apart in there gain reduction characteristics. The meter was calibrated for the slow T4B. So, in other words after switching to fast I have to increase the peak reduction to get the same level of compression on the meter. Obviously, I don't base my levels of compression on meters alone. I'm just curious if your Fast/Slow pairs would be better suited to have similar or closer levels of gain reduction on the meter while switching between the two T4B's? Is this a common behavior for switching between fast and slow even for a pair you sale to see discrepancy in meter readings? Thanks in advance for your advice.

 

[joe-electro]

Hi Bobby,

Thanks for investing in Kenetek T4B's, even if they were second hand, lol. It's difficult to know exactly what's going on here without having the T4B's in hand so I can test them, but I think there are at least two things happening. First, slower photocells are inherently more sensitive (i.e. have a lower threshold and longer memory effect) than faster ones because they have a higher density of photosensitive material exposed to the light source. Because of this, it would be very difficult to find a set of slow photocells and a set of fast ones that have the same onset of attenuation (i.e. threshold). This was never meant to be a requirement for a fast/slow pair because of inherent differences in the physics of the devices.

Second, I suspect there might be a difference in the sensitivities of the two pairs based on differences in their ages and how they have been used. EL panels are like tires - the amount of wear on them depends on how hard they are used. EL panels that have been used for heavy compression their entire lives will naturally wear more quickly than those that are treated more gently.

As I mentioned earlier, it is impossible to know exactly what's going on without putting the T4B's on the tester and measuring their performance. I would be happy to do this for you if you want to ship them to me. If they are 3 years old or less they are still under warranty, and if there is anything I can do to tighten these up I would do it free of charge, under warranty. You would only be out the shipping cost to me. DM me if you're interested in this option.

Regarding the meter calibration, the meter would have to be calibrated individually to the actual T4B's in use. This is not only because of the differences in T4B's but also differences in the meter circuits in use. And, all VU meters do not have the same voltage and resistance characteristics and therefore calibration must be done for the actual circuit in use as a whole. Most multiple T4B setups are actually hacks, switching the only the EL panels on and off and leaving the photocells in the circuit all the time. In practice this is probably fine, but if you want really accurate performance and meter readings, the photocells need to be switched in and out, and there really needs to be separate pots to calibrate the meter circuit for each T4B as well. I did this using multiple relays in the LA-2A I built named "Frank", which is shown on my Kenetek website. It was a real pain, and I concluded it was overkill for most applications.

Thanks!!!

Bill Jones
Owner
Kenetek Pro Audio

 

[Bobby Baird]

Thank you for taking the time to respond to my questions. You have enlightened my understanding of the complex variables at play. It totally makes since that "it would be very difficult to find a set of slow photocells and a set of fast ones that have the same onset of attenuation (i.e. threshold);" Therefore, making it a fools errand to try and match cells for that. Like I said, they are rather close already not making it hard to adjust on the fly switching between the two. You have a very generous warranty. I don't believe my cells are in need of an inspection as they do their job well. In the future I will be contacting you for a pair of matched classics for my SA-3A build.