Telenordia (now named "Tortenmann") TK-23 Kompressor: This is a boutique optical comp pedal from Germany. All of Tortenmann's pedals are based around a germanium transistor gain stage. Germ transistors are often used for the "vintage" wooly coloration they can add to a signal, and that is the case here. To my ears, this pedal does what the Menatone JAC was supposed to do; they both use a similar gain stage concept and a very similar (maybe the same) optical element, but while the Menatone ended up sounding kind of scooped and modern, the Telenordia has thick mids and a warm old-school tone with a sort of "raw" edgy character.
The highest frequencies are gently rolled off, giving the overall tone a dark quality; the lows are quite strong, with maybe a little bit of the lowest frequencies reduced--but not enough to actually bother me, even with a low B on the bass. The make-up gain stage can be pretty noisy at higher levels; I found that if I fed it a nice clean strong input signal, kept the threshold high, and kept the output gain below 12:30, the noise level was not bad, quite tolerable. But if you want to lower the threshold much for heavier squashing compression, that will mean turning the output gain up into the very-noisy range. That's to be expected from most germ gain stages, unfortunately. Another quirk of the germanium is that if this pedal is exposed to heat or direct sunlight for a few hours, it will stop working until it cools down.
The compression action is very smooth and natural, even if you set the threshold low. The threshold knob goes clockwise from high to low. Aside from the threshold, the only control over the compression is a unique push-pull knob labeled "Dry Feed/Attack". This is not a traditional attack control, just speeding or slowing the attack; instead it adjusts an amount of the signal that bypasses the gain reduction element, which can act like the blend function of the Barber or Guyatone pedals, and the "pull" position also adjusts the attack and the shape of the gain reduction a bit. This control is very subtle, but it allows some unique refined qualities to be dialed in to the response and tone of the compression. The fixed ratio is moderately high, and will handle some big peaks, but not like a hard limiter.
The construction is typical of good-quality small-run handbuilt pedals. The housing is plain unpainted aluminum with only minimal engraved markings. There is an internal dip switch that sets the LED light to indicate either on/off status or the amount of compression (but not both). It runs on normal Boss-type 9VDC, although they strongly recommend only using an isolated power supply or battery, not a daisy chain supply. The footswitch is true bypass.
Compared against some of the other "warm/fat"-sounding comps I have, the TK-23 has more complex texture and more of a rough edge to the tone. While the quirks and subtleties of this pedal mean it won't be right for everyone, the action is super smooth and the tone is bold, fat, and "musical", and I like it.
Small update: The company has changed hands in early/mid 2010. The old owner had some serious customer-service problems, but the new owner is taking care of business. The Tortenmann website is not up yet, but you should be able to get service by emailing them.