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

[Clbraddock]

Do you still offer the 5 different speeds: Classic (Medium), Good Slow, Good Fast, Wayyy Slow and Stupid Fast?

How does the T4B you did for the most recent Analog Vibes Silverface compare to your standard 5 speeds (i.e. which one is it closest to?)

Thanks!

 

[joe-electro]

Hello and Happy New Year! Yes, I still build all 5 speeds, although the Classic, Good Fast and Good Slow are the most popular. I also have custom versions built specifically for the KT-2A/2A-KT and LA-3A, as well as a brand new product, the T4C. A pic is attached of the 5 most popular styles. The T4C is so new I don't have any good pics of it yet, lol.

The Kenetek T4B's I built for Analog Vibes are straight-down-the-middle Classics, designed to sound good on the widest range of signal sources, especially vocals because that's where T4B's really shine.

Hope this helps!

Thanks,

Bill Jones
Owner
Kenetek Pro Audio

 

[beatnik]

Hi Bill

Could you share some details about the difference between the kt-2a and la-3a types compared to the standard versions ?

More info about the T4C would also be very welcome, and if it's already available to order a sample.

Thanks

 

[joe-electro]

Both the KT-2A/2A-KT and LA-3A versions are subtly optimized to the hardware in those units. There are differences in how the T4B operates in those units due to the properties of both the input transformers and sidechains. When the KT-2A first came out I bought one, and was immediately underwhelmed by the stock T4B. So, I grabbed a bunch of my reference T4B's and tried them all in my new KT-2A. I found a couple that I especially liked and went about measuring why those T4B's worked particularly well in that unit. After determining the pertinent specs for both the photocells and EL panel I began building T4B's to those specs and thus the KT-2A version was born.

The LA-3A story is similar but also different. I have rebuilt quite a few LA-3A's for customers in the past, and as a part of that I performed extensive measurements and performance tests on their units, both before and after the rebuilds. The front end of the LA-3A presents a different impedance to the T4B and therefore requires a different attenuation curve from the photocells in order to sound best. Also, LA-3A sidechains have a tendency to become unstable when they get some age on them, (which results in oscillations, both audible and ultrasonic) so the components in the LA-3A version are selected to try to mitigate this instability somewhat. Both the KT-2A and LA-3A sound demonstrably better with the bespoke T4B's in them.

Regarding the T4C, the original Urei T4C was installed only in the Urei BL-40 Modulimiter, which is an LA-3A style opto limiter and an FET peak limiter (not very similar to the 1176 though) in one chassis. It was originally designed for broadcast use, as an RMS leveler and peak limiter in one box, for use in front a transmitter. They were sold in the early to mid seventies, and were rendered obsolete overnight when the Orban Optimods came out. While the T4C was supposed to have a slower attack and slower release than the T4B, the T4C's I've had in house were all over the place. Many were actually faster than what we now call the "Classic" T4B response. Since the BL-40 was designed with the Opto section ahead of the FET section, the result is that the Opto section handled more of the peaks than it should have, and the performance of the FET section was compromised. I designed the Kenetek T4C to have a genuinely slower attack and release, as well as a smoother compression curve (e.g. lower ratio during hard compression) than the original T4C's, and different than any of the T4B's I offer. This allows the FET section of the BL-40 to do its job of peak limiting more effectively, the way it was originally envisioned.

That's all fine and good, but how many functional BL-40's are left out in the wild? Not enough to cost justify the development of a new product, that's for sure. But how many people out there use an LA-2A or LA-3A in combination with an 1176 to do parallel or series compression? Quite a few, I'm betting! The T4C is optimized for this kind of use, to give the 1176 a little more breathing room and let the LA-2A do the more subtle opto thing it does so well. So, if you use parallel or series compression you might like to try a T4C. Also, if you use LA-2A's or LA-3A's across your mix buss and just 'kiss' the signal with 2 or 3 dB max of compression, you might like what the T4C does to your mix.

I'm still finalizing the specs of the T4C and figuring out how to manufacture them consisitently, so we're probably a month or two away from them actually shipping, but I would be happy to contact anybody who's interested when they are actually available. Just PM me and I'll be back in touch.

Thanks!!!

Bill

 

[beatnik]

Many thanks for your detailed answer and the work you do

 

[poppaflavor]

Both the KT-2A/2A-KT and LA-3A versions are subtly optimized to the hardware in those units. There are differences in how the T4B operates in those units due to the properties of both the input transformers and sidechains. When the KT-2A first came out I bought one, and was immediately underwhelmed by the stock T4B. So, I grabbed a bunch of my reference T4B's and tried them all in my new KT-2A. I found a couple that I especially liked and went about measuring why those T4B's worked particularly well in that unit. After determining the pertinent specs for both the photocells and EL panel I began building T4B's to those specs and thus the KT-2A version was born.

The LA-3A story is similar but also different. I have rebuilt quite a few LA-3A's for customers in the past, and as a part of that I performed extensive measurements and performance tests on their units, both before and after the rebuilds. The front end of the LA-3A presents a different impedance to the T4B and therefore requires a different attenuation curve from the photocells in order to sound best. Also, LA-3A sidechains have a tendency to become unstable when they get some age on them, (which results in oscillations, both audible and ultrasonic) so the components in the LA-3A version are selected to try to mitigate this instability somewhat. Both the KT-2A and LA-3A sound demonstrably better with the bespoke T4B's in them.

Regarding the T4C, the original Urei T4C was installed only in the Urei BL-40 Modulimiter, which is an LA-3A style opto limiter and an FET peak limiter (not very similar to the 1176 though) in one chassis. It was originally designed for broadcast use, as an RMS leveler and peak limiter in one box, for use in front a transmitter. They were sold in the early to mid seventies, and were rendered obsolete overnight when the Orban Optimods came out. While the T4C was supposed to have a slower attack and slower release than the T4B, the T4C's I've had in house were all over the place. Many were actually faster than what we now call the "Classic" T4B response. Since the BL-40 was designed with the Opto section ahead of the FET section, the result is that the Opto section handled more of the peaks than it should have, and the performance of the FET section was compromised. I designed the Kenetek T4C to have a genuinely slower attack and release, as well as a smoother compression curve (e.g. lower ratio during hard compression) than the original T4C's, and different than any of the T4B's I offer. This allows the FET section of the BL-40 to do its job of peak limiting more effectively, the way it was originally envisioned.

That's all fine and good, but how many functional BL-40's are left out in the wild? Not enough to cost justify the development of a new product, that's for sure. But how many people out there use an LA-2A or LA-3A in combination with an 1176 to do parallel or series compression? Quite a few, I'm betting! The T4C is optimized for this kind of use, to give the 1176 a little more breathing room and let the LA-2A do the more subtle opto thing it does so well. So, if you use parallel or series compression you might like to try a T4C. Also, if you use LA-2A's or LA-3A's across your mix buss and just 'kiss' the signal with 2 or 3 dB max of compression, you might like what the T4C does to your mix.

I'm still finalizing the specs of the T4C and figuring out how to manufacture them consisitently, so we're probably a month or two away from them actually shipping, but I would be happy to contact anybody who's interested when they are actually available. Just PM me and I'll be back in touch.

Thanks!!!

Thank you very much for all the detailed information and context. I've learned quite a bit on this thread.

Warm mentions this about their socket which houses your Kenetek T4B:

"USA made Kenetek opto-cell attenuator T4' style module. Socketed to allow retro-fitting with other opto-cells."

Does this mean I could plug in your other variants and explore them instead of the stock cell?

And, would you know if the WA-2A comes stock with the Classic speed? I'd like to explore your versions which are slow and faster than the WA-2A stock cell.

Provided that I can try your other intriguing variants in the WA-2A, how to order them?

On the website I didn't see how to order the 4 cells Good Slow, Good Fast, Wayyy Slow and Stupid Fast.

Thanks!

 

[joe-electro]

Yes, it is possible and quite easy to replace the stock Kenetek T4B that came in your WA-2A with a different variant. You can simply remove the existing T4B from the socket and put a new one in its place. The WA-2A comes from the factory with a Kenetek Classic T4B. While the Classic sounds good on the widest range of sources, I also really like the Good Fast in the WA-2A, so I would recommend you try that style first. The Good Slow is good on bass and male vocal, but I find its uses are more limited than the Classic or Good Fast. Wayyyy Slow should maybe be called Stupid Slow, and are for the select few engineers who want that speed. Stupid Fast are hard to come by these days, because photocells that have the desired characteristics are quite rare. But I can build you "Nearly Stupid Fast" T4B's that will sound really good. I love those, too.

Yes, it's not obvious how to order the variants on the website. There's a Comments section during checkout and you can specify the type you want in it. If an order comes in with comments the admin portal flags it with a nice little yellow flag, so I know to read the comments for that order. Or, you can just email me and tell me what you want.

Thanks!!!

Bill

 

[poppaflavor]

Yes, it is possible and quite easy to replace the stock Kenetek T4B that came in your WA-2A with a different variant. You can simply remove the existing T4B from the socket and put a new one in its place. The WA-2A comes from the factory with a Kenetek Classic T4B. While the Classic sounds good on the widest range of sources, I also really like the Good Fast in the WA-2A, so I would recommend you try that style first. The Good Slow is good on bass and male vocal, but I find its uses are more limited than the Classic or Good Fast. Wayyyy Slow should maybe be called Stupid Slow, and are for the select few engineers who want that speed. Stupid Fast are hard to come by these days, because photocells that have the desired characteristics are quite rare. But I can build you "Nearly Stupid Fast" T4B's that will sound really good. I love those, too.

Yes, it's not obvious how to order the variants on the website. There's a Comments section during checkout and you can specify the type you want in it. If an order comes in with comments the admin portal flags it with a nice little yellow flag, so I know to read the comments for that order. Or, you can just email me and tell me what you want.

Thanks!!!

Bill

Thanks very much for your reply Bill, I reached out to you through your website after I realized I could contact you through there and received your reply by email. I apologize for the redundant communication... hopefully this info here will be of use to other folks as well!

I replied to your email, very much looking forward to experimenting with these T4B variants (and get on the T4C when it becomes available). I've tube rolled my WA2A a couple times with some tasty NOS tubes, but Opto Cell rolling will be uncharted territory. Going to be a fun exploration!

Matt

 

[frejo89]

One question after seeing this picture of the Kenetronik "Opto-Switcher":

Does a T4B really fit into a 1u case, when fitted horizontally ?
I never hat one of those in front of me

 

[joe-electro]

Yes, a Kenetek T4B is 1.375 inches square, so it fits with a little room to spare in a 1U enclosure. You have to choose the right socket and orient it just right, but it will fit.

Thanks!!!

Bill

 

[poppaflavor]

Yes, a Kenetek T4B is 1.375 inches square, so it fits with a little room to spare in a 1U enclosure. You have to choose the right socket and orient it just right, but it will fit.

Thanks!!!

Bill

Hi Bill, Would you be able to provide an update on the progress to case out the switcher? I don't mean to keep bugging you but I'm positively ACHING to get on and put in the selection of your T4Bs that I have and start exploring. Currently I'm just leaving the top of the comp off and manually dropping them in an out, but doing it with a flick of the finger would be magical!

 

[joe-electro]

Hi Poppa,

Thanks for the nudge. Right now, I'm tied up with fulfilling some fairly large T4B orders for my OEM clients, but after those ship I can get back on the T4B switcher thingy. The only thing remaining to do is the sheet metal, which is always the most PITA part for me. If anybody can share good, reliable sheet metal vendors I would be most grateful.

As soon as I know when those will be available I will update this thread.

You mentioned that you keep the top off of your comp, and this brings up another issue you need to be aware of. If the T4 socket is inside the unit you will need a way for the cable to go from outside the case to inside the case. This would probably involve some simple modding such as making in notch in either the top or rear panel for the cable to feed through. The cable is about 3/8" in diameter. Just so you can be thinking about that. I am planning to sell replacement top panels for the Warm and K-T units with the notch already punched. As far as other units go... well this *is* GroupDIY.

Thanks!!!

Bill

 

[poppaflavor]

Hi Poppa,

Thanks for the nudge. Right now, I'm tied up with fulfilling some fairly large T4B orders for my OEM clients, but after those ship I can get back on the T4B switcher thingy. The only thing remaining to do is the sheet metal, which is always the most PITA part for me. If anybody can share good, reliable sheet metal vendors I would be most grateful.

As soon as I know when those will be available I will update this thread.

You mentioned that you keep the top off of your comp, and this brings up another issue you need to be aware of. If the T4 socket is inside the unit you will need a way for the cable to go from outside the case to inside the case. This would probably involve some simple modding such as making in notch in either the top or rear panel for the cable to feed through. The cable is about 3/8" in diameter. Just so you can be thinking about that. I am planning to sell replacement top panels for the Warm and K-T units with the notch already punched. As far as other units go... well this *is* GroupDIY.

Thanks!!!

Bill

Wonderful, thanks Bill! I'm not sure why I didn't get a notice that you'd replied here. But I've re- bookmarked it and I'll be checking in to make sure I don't miss when you announce the availability here.

Thanks very much for the heads up about the access for the cable. I do have the WA2A unit, so I'm probably going to take you up on your pre-made replacement top panel. I know this is GDIY though so hopefully I'll still be allowed back in here if I don't cut my own notch out of my stock panel

Side note- I did finally get my first DIYRE preamp kit to build so the journey begins!

 

[Clbraddock]

Awesome, I’m definitely interested in the switcher too.

 

[poppaflavor]

Both the KT-2A/2A-KT and LA-3A versions are subtly optimized to the hardware in those units. There are differences in how the T4B operates in those units due to the properties of both the input transformers and sidechains. When the KT-2A first came out I bought one, and was immediately underwhelmed by the stock T4B. So, I grabbed a bunch of my reference T4B's and tried them all in my new KT-2A. I found a couple that I especially liked and went about measuring why those T4B's worked particularly well in that unit. After determining the pertinent specs for both the photocells and EL panel I began building T4B's to those specs and thus the KT-2A version was born.

The LA-3A story is similar but also different. I have rebuilt quite a few LA-3A's for customers in the past, and as a part of that I performed extensive measurements and performance tests on their units, both before and after the rebuilds. The front end of the LA-3A presents a different impedance to the T4B and therefore requires a different attenuation curve from the photocells in order to sound best. Also, LA-3A sidechains have a tendency to become unstable when they get some age on them, (which results in oscillations, both audible and ultrasonic) so the components in the LA-3A version are selected to try to mitigate this instability somewhat. Both the KT-2A and LA-3A sound demonstrably better with the bespoke T4B's in them.

Regarding the T4C, the original Urei T4C was installed only in the Urei BL-40 Modulimiter, which is an LA-3A style opto limiter and an FET peak limiter (not very similar to the 1176 though) in one chassis. It was originally designed for broadcast use, as an RMS leveler and peak limiter in one box, for use in front a transmitter. They were sold in the early to mid seventies, and were rendered obsolete overnight when the Orban Optimods came out. While the T4C was supposed to have a slower attack and slower release than the T4B, the T4C's I've had in house were all over the place. Many were actually faster than what we now call the "Classic" T4B response. Since the BL-40 was designed with the Opto section ahead of the FET section, the result is that the Opto section handled more of the peaks than it should have, and the performance of the FET section was compromised. I designed the Kenetek T4C to have a genuinely slower attack and release, as well as a smoother compression curve (e.g. lower ratio during hard compression) than the original T4C's, and different than any of the T4B's I offer. This allows the FET section of the BL-40 to do its job of peak limiting more effectively, the way it was originally envisioned.

That's all fine and good, but how many functional BL-40's are left out in the wild? Not enough to cost justify the development of a new product, that's for sure. But how many people out there use an LA-2A or LA-3A in combination with an 1176 to do parallel or series compression? Quite a few, I'm betting! The T4C is optimized for this kind of use, to give the 1176 a little more breathing room and let the LA-2A do the more subtle opto thing it does so well. So, if you use parallel or series compression you might like to try a T4C. Also, if you use LA-2A's or LA-3A's across your mix buss and just 'kiss' the signal with 2 or 3 dB max of compression, you might like what the T4C does to your mix.

I'm still finalizing the specs of the T4C and figuring out how to manufacture them consisitently, so we're probably a month or two away from them actually shipping, but I would be happy to contact anybody who's interested when they are actually available. Just PM me and I'll be back in touch.

Thanks!!!

BillView attachment 119825

Your context and comparisons for the upcoming T4C have gained new prominence for me since I acquired an Orban Optimod 8100A and a FM demodulator to allow me to pipe in that sweet sweet Optimod AGC/Limit sound (esp the HF Limit, dreamy 'not in love' song sound).

Could you please describe the qualitative differences between your Waaay Slow and the T4C in terms of RMS/Peak leveling and attack/release?

Thanks a bunch for pushing the creative ADSR envelope. It's most certain to push forward creative production and apt use in records.

 

[fragletrollet]

Hey

Curious on how the switcher is wired, as I am toying with the idea of having the slow (standard) and fast cells switchable in a dla2a build I'm (very) slowly building.

There are three separate switches on your expander. Are the three cells connected in parallel? Is it only the cathode of the ldr's that are switched, with the other connections always in circuit? Will more than one switch accentuated result in several ldr's outputs (cathodes?) connected together? Is there some summing of the signals involved?

Best regards,
M