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High Performance Audio

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Your Perception About HiEnd is About to Change!

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Diana Forte / Mezzo

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We proudly announce the completion of the Diana Series of amplification with the introduction of two new models.  Along our Diana integrated amplifier, the Diana Forte, arguably the most powerful SET stereo amplifier in the World and the Diana Mezzo, its accompanying Class A pre-amplifier.

The two models share the majority of circuits with the Diana integrated and technically, is a two chassis improved version of the integrated. Customers have the benefit of purchasing the Diana Mezzo Pre-amplifier and later getting Diana Forte for a perfect match.




Diana Forte Stereo Power Amplifier


The Diana Forte’s circuits are based on the Diana Integrated amplifier output and driver stages. The Output stage is scaled up to deliver over twice the power achieving a true 60W (70W peak) of SET magic per channel. The parallel SET output stage is built around the 813 DHT big bottle tube.  This in turn drives an oversized core OPT constructed using special winding techniques to deliver wide bandwidth at full power.


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The amplifier driver stage is the one of the most  linear tubes, the 814 DHT tube, loaded with a special quality double-C core bifilar winded inter-stage transformer. The Diana Forte’s amplifier is connected to its accompanying Diana Mezzo pre-amplifier via our proprietary AC link. As with the Diana Integrated and the Concero amplifiers, all stages are coupled with our special AC link method of coupling, delivering superior performance in the frequency extremes, transient response, and overload conditions.

The output stage PSU is a dual completely separate set of choke-filtered capacitor banks using our unique Super-capacitors.  The SuperCaps come from a selection of special purpose film capacitors with ESL and ESR parameters 100 times lower than any film or electrolytic capacitor.


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The high energy-high speed capacitor banks deliver a superbly robust power rail for the parallel SET output stage.

The driver stage also uses choke filtered capacitor banks, with their own separate power transformer to avoid PSU cross-talking.

All tubes can be biased and monitored on the fly as well as can be matched using the Diana Forte as a stripped-down tube tester. 

All six filament PSUs are triple filtered, so that the all DHT power amplifier delivers the lowest noise floor of any SET power amplifier.


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Max Power: 60W SE Class A (70W peak)

Max Power bandwidth: 15Hz- 110Khz

Noise floor: 100db

Combined gain: X 20 (26db)

Dimensions: 570mmW X 590mmD X 350mmH

Weight: 110Kg unpacked

Tubes: 2X814, 4 X 813




Diana Mezzo Pre-Amplifier

The Diana Mezzo is an improved version of the Diana Integrated’s pre amplifier stage. At its heart, the Diana Mezzo is a Single Ended Triode amplifier boasting an 814 Direct Heated thoriated tungsten DHT.  This 814 Pentode tube, which in triode mode, is more linear than a 300B tube.


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The output transformer is a double-C amorphous core, bifilar winded OPT.

Signal attenuation is performed by a relay-switched array of resistors, in a shunt/ladder hybrid mode.

A pair of Xenon gas rectifiers are used as rectifiers of the High Voltage PSU.

These rectifiers were developed as drop in replacements for some well known mercury rectifiers when mercury was labeled unsafe. So while they present the technical characteristics of a mercury rectifier, they are safe to operate. The high speed capacitor banks are double choke filtered.

Filament PSUs are quadruple filtered using a cascade of choke/resistor-cap pi filters providing very low noise floor for the sensitive filaments of the DHTs.

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Gain: X7 (16db)

Attenuation level: 61 X 1db steps

Maximum signal input overload: 25V

Signal bandwidth @ 20Vrms: 10Hz-120Khz (-3db)

Dimensions: 500mmW X 350mmD X 340mmH

Weight:  55Kg

Tubes: 2 X 814, 2X 3b28

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Collatio Single Ended OTL Tube Amplifier Series

Collatio II

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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.



Full power bandwidth: 6Hz-110KHz

Small signal bandwidth: 4Hz-110KHz

SNR: 110db

Gain: X6 ( 15db)

Full power:  20W @8ohm

                 80W @8ohm mono configuration


Current idle per channel: 2.6A

Idle power consumption: 1190W(depending on bias level)

Dimenisons:    455mmW  X 590mmD X 480mmH (excluding tubes+cage)

                      455mmW  X 590mmD X 630mmH including tube cage

Weight: 120kg

Tube compliment: 2 X 814 , 40 X 6c19p-v 

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