We’re often asked if we recommend putting the “XYZ-brand” T4B into our Opto Comp and DA-3A.

The answer is emphatically, NO! I’ll explain:

In 2017, during the development of the Opto Comp, I dug in hard repairing and deconstructing vintage T4A and T4B optical cells from vintage LA-2A’s (btw, some of these units even used 3 photocells instead of 2; shows how much they cared about matching metering to the actual compression back then!). Every one of them, literally, was built in a way I hadn’t seen from any other manufacturer before. This research informed our decision to start making our own optical cells, in the same tradition as the originals.

What are the differences between modern T4B’s and the vintage ones?

The short answer is that the original T4B had a 2.2 megohm resistor sitting across both legs of the EL panel. Every modern T4B I’ve seen, even today, uses this same design scheme, but adds a 4n7 capacitor coming off one side of the EL panel terminating on a tube pin. It’s a very simple difference that has a giant impact on the behavior of the T4B (aside from photocell matching, which is supercritical if you are aiming for true 60’s vintage authenticity). Because of the way most modern T4Bs are being made, we call them “JBL Era” T4Bs. From what I can surmise, these are likely the last revision T4B that were made, and what JBL was selling in the late 90’s and early 2000’s. Everyone except us makes them THIS way!

So. swap out your Audioscape T4B? I think NOT!

Will putting an AudioScape T4B in a budget LA-2A-clone make it sound as good as our Opto Comp?

Again, NO! A great device is the sum of its parts. The 1:1 vintage-accurate transformers, NOS tubes, carbon composition resistors and the premium Cornell dubilier capacitors that we use do heavy-lifting of their own and work together in concert to make the Opto Comp what it is. Not to mention the countless hours we spend tube rolling every Opto Comp to make every single unit the best it can be when it comes off the line. All of this, plus the experience of building thousands of these now. We are the pros.

The same rings true for our DA-3A, whose T4B’s are matched perfectly to LA-3A specs. The LA-3A is very different from the LA-2A in its attack/release characteristics. The same expertise and meticulous quality control goes into everything we build at AudioScape.

I know that a lot of people who build/mod equipment like to buy our gear, it’s a big source of pride for us here. I just want to make clear the lengths we go to, so you can just turn on a unit and be satisfied that it’s the best it can be. The idea is that you’re making music with this gear, and that’s what we want your mind free and clear to do :)

Cheers,

Chris