Welcome to the world of the first True Single Ended, True Class A ,output-transformer-less Se amplifier, and forever change the way you listen to your speakers.
All tube OTL amplifiers use SEPP, cyclotron or Mr. Futterman’s variations. All these are push-pull amplification stages. They can claim single ended, but they are push pull topologies. Feedback is mandatory in this designs to cancel out the artifacts generated by the problems of not true complimentary driving of the signal, and of course cross-over distortion. Some clever variations have been presented on the market during recent years, but they are nevertheless push pull topologies with many dbs of negative feedback, some of them use up to 60db of degenerative feedback. Of course, these amplifiers are not Class A devices.
Almost all of these ideas were implemented in our lab, trying to create a State of the Art OTL amplifier, but we would always want more, going the extra mile (or two).
However…..We decided to skip everything and re-invent everything from scratch.
The Collatio OTL Series is a special project, and is our statement on how a true SOTA OTL amplifier should sound .
The Collatio II is our showcase, a statement ,a cost no object approach on OTL tube amplification , pushing the envelope on what is possible on OTL technology.
Our amplifier series uses our own proprietary design, and it is in fact a current amplifier.
Current amplifiers have their own technical and sonic advantages, and if especially matched with highly efficient horn speakers, are simply unmatched.
Our output stage is a unique Single ended stage, a parallel-feed power stage,using 20 power tubes in parallel per channel, loaded by 4 massive chokes, and AC coupled to the output terminals, using an exotic film capacitor.
The capacitor is designed to be able to surge 20.000A peaks, and it’s ESR and ESL specifications, are an order of magnitude lower than any audio capacitor, film or electrolytic, thus the capacitor is virtually a single wire at audio frequencies, at the same time protecting your speakers from any mishap.
This power tubes used is the 6c19p, a small envelope tube, a very low internal resistance tube, capable of large current swings and was much preferred over the usual OTL tube candidates in terms of bass slam and timbre. Also it is very cheap tube to replace. A full 32 tube changeover costs far less than a single high quality 845 tube.
The tube bank is biased at 2.6A per channel(20W )and at 5.2A for the 80W version! For reference, any OTL on the market rated at 25W, is biased at around 200~300mA. The output stage is a true single ended power gain stage and thus can only operate in Class A. No global or local feedback is used.
The power supplies must be stable and robust at such a high idle current demand from the output stage.
Our super sized power supply , provides 2.6A per channel steady state, with lowest noise possible.
The double output stage power supplies ,come with double choke filtration and 6 high current high speed capacitors.
The driving stage, is a Directly Heated triode, the 814 tube, a big bottle tube that can deliver 10W of driving power to the output stage. The 20 tube’s (pc) input capacitance need high current drive, to maintain high slew rate.
Driving 20 output tubes per channel at high frequency needs a lot of current, and the 814 tube has a lot to spare. The driver tube is chple loaded, and is DC coupled to the output stage,for supreme slew rate numbers and transparency. The driver stage power supply I s fed by separate transformers and is double filtered using chokes.
All heater and filament supplies have their own power transformer and are douple filtered using chokes and high speed capacitors.
Most OTL have a bad reputation of blowing expensive speakers,after they present DC potential after a malfunction. The Collatio amplifiers are bullet proof in terms of stability and speaker protection.
Their output stage is AC coupled, so that no DC can be present at any times at the speaker terminal. You can break all tubes while in operation with a hammer, still no damage can occur to the speaker;It is really bullet proof.
The capacitor used is a 5kg cap each, high performance film capacitor, with not so typical specs.
The Collatio 20W stereo amplifiers can be used as monoblocks, delivering 80W of OTL SE power with no modification from the user.