Supratek was possibly the first audio company to release a Directly Heated Triode preamplifier, the first Cabernet had an option to use either a 300B, PX4 or 45 DHT tube .
Later on I went to a 101D DHT tube in the Dual Cabernet.
The Dual Cabernet was also a revolutionary product as it was the first preamp to provide 2 seperate output stages in the one chassis.
One stereo output was a 6SN7/6H30 line stage with an output impedance of 50 ohms, perfect for driving difficult solid state amps and especially useful for powering active sub-woofers. With its own seperate volume control it was the ideal device for integrating a sub woofer into a stereo system.
The main stereo preamp output used a 101D DHT tube , which is an excellent tube to use in combination with the 6SN7/6H30 , as freed of sub-sonic bass requirements , the 101D is ideal for upper bass to high frequency operation, with the wonderful ease and dynamics of DHT tubes.
There are very few new production DHT tubes suitable for pre-amplification use, the 101D is probably the best all round new production DHT preamplifier tube as it has perhaps the best sound balance of the candidates available.
Which is why other tube audio companies have started using it in the last few years.
Of course there have been many other DHT tubes available since the 1930's and my favorite tube to use in a preamp has for a long time been the 71A tube.
I've been using it for many years in my own preamps, I wish I could have offered it as an option for the Cabernet but unfortunately it hasn't been manufactured for a very long time and it is very hard to get matched pairs in pristine condition, it's taken me years to assemble a collection just for my own use.
During 2011-2013 I started using obscure NOS Russian DHT tubes in my preamps and am excited to have found some tubes that equal the sound quality of the best 1930's DHT tubes.
These are available in limited quantities, are exceptionally well built and sound fantastic!
I've purchased enough stock to build preamps and supply spare tubes, and these tubes have been incorporated into new Supratek designs that replace the circuits in the Cabernet and Cortese preamps.
I'm very pleased to be able to use a DHT tube in the Cortese phono preamp. The high quality Single Ended Class A phono stage, designed for moving coil cartridges, really deserves the best line stage. The fundamental requirements of a line stage are: a suitable gain structure and low output impedance , in order to be able to drive any power amplifier. Input impedance also plays a part.
The 6SN7 line stage used in the Cortese was an innovative and very good sounding design that ticked all the boxes, and although I was very happy with it, I would have loved to use a DHT tube. Unfortunately, there just wasn't a suitable DHT tube available to work within the confines of space and engineering in the Cortese.
Now there is!
The Russian 4P1L DHT tube is ideal as a line stage for the Cortese. Of course it has the usual state-of-the-art design which loads the tube optimally and it incorporates the feature of being able to be used as capacitor or transformer coupled output.
This gives the user a choice of gain and impedance structure, and two different types of "sound" .
Personally I feel both choices are extremely good sounding , and it is just a matter of what is best choice for your system.
DHT Cortese 4P1L tube at back
The Cabernets are designed solely for line stage use and the engineering possibilities for DHT use are quite exciting.
As noted above the obvious choice for present production pre-amplification DHT tubes is the 101D.
In 2012 the design of the Cabernets changed from directly coupling the 6SN7 driver tube to the 101D, in favour of capacitor coupling , in combination with grid chokes , and the use of exotic Lundahl output transformers.
This form of circuit enables a different type of bias which we label LowR , the primary advantage of which is to negate the need for large capacitance decoupling and bypass caps, the source of "veiling" in many tube preamps.
This greatly enhanced what I consider most important in pre-amplification- the ability to throw a realistic soundstage with realistic 3D imaging, (depth and width), with dynamics that show greater expression of micro and macro layers.
Vividness is a term I've been using to describe the Supratek sound for many years, and with the new DHT designs it is again enhanced.
It has been very exciting to me to be able to source DHT tubes with the quality and sound characteristics of the DHT tubes produced in the "golden age" of tube manufacture and design , the period from 1920- 1960.
While the Western electronics industry veered towards low cost, high production solid state technology that promised high profits, the Russian tube manufacturers refined and developed very high quality tube products that matched and exceeded the best tubes available from the West.
Of all the Russian DHT tubes I've tested and experimented with over the last few years my favourites are the 4P1L and 6P21S, which are both multi-grid low power tubes, however, connected as triodes they are superb preamp tubes with low impedance and ideal gain. To find a tube that sounds as good as the best 71A is very satisfying.
The Cabernet Dual is the premier preamp in the Supratek line up. The 6SN7/6H30 output stays the same , but the 101D tube is replaced by the 6P21S for a fuller sound that seems more musical, yet as detailed and of higher resolution than the 101D.
The 6P21S has a greater range then the 101D, the bass of the 6P21S is deep and tight, yet it also has exceptional mid and treble sound.
Only the highest quality parts and components are used- Lundahl and Magnequest transformers and grid chokes. Capacitors are paper-in-oil, chosen to compliment the sonic signature of the preamp.
The tremendous advantage of the Cabernets shunt regulated power supply remains, and the overkill size of power transformers means the Cabernet electronics perform quietly and effortlessly .
The chassis's are still fabricated from 1.2mm solid copper, far more important than it seems, and covered with high quality chrome or powder coat.
All Supratek preamps, and power supplies, are made from 1.2mm copper.
The Cabernet Single is exactly the same without the 6H30 driver output.
(BTW the The 6H30 driver in the Dual Cabernet can also be used as a valve output stage for suitable dacs)
Supratek hasn't been a "conventional" retail audio manufacturer for a long time, I dont depend on it for income and the reason for Supratek's existence is more about a passion for high end tube electronics than a commercial venture.
The (small) profit from preamp sales goes back into R&D- for every 3 or 4 preamps sold there would be at least one prototype built to investigate a new concept or idea.
I have a lifetime's experience of DHT use for preamps, and my passion for DHT preamps is stronger than ever before, even with so called claims for the demise of preamps as they supposedly are not needed with digital devices.
This is rubbish and reflects poor equipment and listening skills, or perhaps the claimants have just never heard a good tube preamp. It is true that good tube preamps are rare, but a good tube preamp will be the heart and soul of a system that takes you to the essence of the music.
Because the Supratek preamps are completely handmade, and it is not a commercial profit making venture , very few are actually built.
I've found it impossible to supply worldwide demand and as a consequence the Chardonnay, Sauvignon, and Grange preamps will no longer be built.
The Chenin will continue for a little while longer and then I will be concentrating on only building Cabernet and Cortese DHT preamps, as I am available.
The reliability and very long life time of the Cabernet and Cortese is something I take very seriously. New models are not regularly introduced and there is a great deal of thought and commitment to longevity. A classic tube product should last 50 years and more.
Directly Heated Triode Preamps are the pinnacle of preamp design and I hope to be able to continue to enrich the musical lives of future owners.
