The TC-7535 Caiman SEG at a glance.

[StanleyB]

The latest version of the Caiman SEG has just been released, following up on original TC-7520 based Caiman SEG. Like the previous version, the new SEG is a completely new design of the PCB with previous modifications to the Caiman now part of the factory built DAC, plus additional bits that can't be added or won't fit in the standard unit. For those of you not familiar with the original Caiman SEG: it was and still is a rare unit. They hardly ever show up for sale on forums or eBay. Most owners seem to have hung on to their SEG over the years.
The new SEG is following the same principle, which is to take the initial Caiman design plus most or all of the mods, and add several improvements that can't be fitted to the standard Caiman for practical or technical reasons.
The Caiman GFU and SEG are to all intense and purposes nearly the same sound wise when using the fixed output. So if it is mainly the sound from the DAC section that is of importance to potential SEG buyers, then the GFU would be the more economically viable option.
The SEG was designed in order to solve some issues that some customers were having with the Caiman MKII that could not be solved with DIY modifications. Some of them were very minor things, but important enough in the mind of customers for them to hold out against getting a MKII. A quick breakdown of some of them are:
The gold plated buttons are chrome on the SEG.
The filtering of any noise from the external power supply has been improved from 20mV to just 1mV before the regulators.
The SEG will work with any externally regulated DC voltage between 12V to 15V, and provide extra signal headroom on the variable outputs ( = headphone and pre-amp output) with the higher voltage. That's because the brickwall clamping of the 12V regulator of the Caiman MKII has been removed.
The headphone amp section now has an adjustable preset so that the gain can be adjusted to taste for the sensitive ears. The standard output on the Caiman MKII was in many cases a bit to loud for some headphone users. I developed a fixed mod for that for the MKII, but the SEG has an adjustable gain instead.
A lot of people are now using the MKII as a pre-amp. But the MKII variable output section is a simple design that can't really compete sonically with a well designed pre-amp. The SEG pre-amp section was the main reason for designing a new PCB. In order for a pre-amp to stand a chance of sounding good to excellent, it has to be thought out properly. The pre-amp in the SEG has separate left and right signal, ground, and power lines, which is what you are likely to find in the better designed pre-amps. The advantages of splitting the left and right signal paths are numerous. Do search with Google for more info on that subject. The active part of the pre-amp section is also fully made up of discrete transistors, instead of using an opamp.
Other minor improvements are in the firmware. You can now store individual sound processing options for each signal input. On the MKII you only have the choice of one selection across all inputs.
The LED dimming function is now exactly as described: it dims. On the MKII it is either ON or OFF. Customers asked for the LED to be dimmed so that they could still see which input was operating.
Another thing that people wanted was the ability to use the DAC with perhaps a vintage amp that does not have the 2Vrms CD input that can be found on later amp designs ( i.e. after 1983). So the pre-amp output on the SEG can be set to about 10AM to 12PM on the volume dial, and the output connected to the LINE of AUX input on an amp that does not have a CD input. You can however use the pre-amp audio buffer into a CD input as well. In that case set the volume control to MAX. The sound will be 3dB down though. So you'll need to turn the volume up a bit on your amp.
The audio output on the SEG now has a discrete buffer stage that is connected to both the headphone amp and pre-amp. It offers better loading of the audio signal before driving the headphone and pre-amp section. Many high-end headphone users asked for an improvement to the headphone output that could come close to the Capella. The audio buffer also gives a better performance with high-end interconnects, compared to the MKII.