Projects

Analog output stage for CD-players
Take a CD player with a well designed power supply for the digital section and a multibit DAC with current output. Then connect the current outputs and the DEEM signal to the separate board which holds a dead silent analog power supply and a discrete Class A analog section with selected top grade audio transistors from Toshiba and Rohm.  In pure HIFI terms the combination levels players at SEK25.000 (USD3000).  In musical terms it levels any price range with its superb timing, dynamics and its very natural sonic signature.  
I use the Arcam Alpha 5 as the base (after modifying the DAC grounding scheme which is not too good in the original design).  The DAC is the well known TDA1541.

20W Power Amplifier
My first project started more than 10 years ago, and has now reached a standard that I still have problems to beat with the newer designs.  The amp has a huge power supply with 180.000 uF of capacitance and a 350VA transformer. A softstart delay is incorporated in the design.  This little amp is best suited for either driving the mid/high in a bi- or triamp system, or driving a full range speaker (e.g. B&W Nautilus 801).  

The bass is very clean and tight but slender than on the bigger designs.  A full range speaker works fine because the amp has full control over the sub bass range, which makes the amp sound very BIG (one blind test victim on the Nautilus 801´s rated it around 100 Watts!).  But a smaller speaker which falls off below say 40 Hz sounds smaller than normal because the amp totally lacks any bass booming that makes the bass sound bigger on a small speaker, something I call the distortion loudness effect. An amplifier without the distortion loudness effect does not show its true bass potential until matched with a top notch full range speaker, which is why these amplifers are so rare on the market.

The mids and highs are this amps best asset, and I wonder if I will ever make an amp that beats it. If you like the very natural mid/high of a reference tube amp you know what I mean.  This 20W design is a (solid) proof that tube quality can be reached using solid state devices.

Musical timing and dynamics are in line with the rest of the power amplifiers so mixing them in bi- or triamp combinations can be done without problems with frequency dependent sonic signature. I also kept the gain equal for all models (23 dB) so there are no problems with level matching.

50W Power Amplifier
This is the first of the power amplifiers build as two separate mono power modules with everything except the cooling device fitted to the PCB.  Just connect transformer, on/off LED, softstart relay, input RCA and output speaker cables to the board and you are ready to rock. The power supply has 132.000 uF of capacitance and uses two 500VA transformers.  A softstart delay is incorporated in the design.  

Sonically this is an improvement over the 20W design but not in all respects.  This amp does sound bigger and more powerful, but falls short of the 20W´s stunning mids & highs. The 50W design also sounds a bit less open.

Capable of 450 Watts peak in 1,5 ohms it controls all normal speakers with ease, but as with the 20W design the bass is still slender than e.g. a KRELL.  But note: only slender, not less controlled.

100W Power Amplifier
This amplifier was made primarily to make furniture jump around, i.e. deep, tight BASS. The power supply has 180.000 uF of capacitance and two 500VA transformers.  Eight 15A Sanken devices per channel takes care of just about any load presented to the amp. I would have preferred using two 1000VA transformers but I made a shortcut here due to lack of space, I did not want to build two mono blocks.  A softstart delay and now for the first time also protective circuitry are incorporated in the design, and all is collected on two mono power modules.

Even though designed with only bass in mind this amp actually blows away my 50W design, it is better in every respect. As I guessed beforehand the 20W amp has a slightly better mid range but that is all. Listening to the 100W amp gives a true high-end experience with its clean, powerful and yet very relaxed way of playing music.

Line Amplifier
This line amplifier is a spin-off from the 20W design.  Basically it is the front end of the 20W power amp modified to a lower voltage and with a few replacements of the active devices.  Do I need to say that the mids and highs are OK ?  In musical terms this line amplifier matches the rest of the electronics.

RIAA Equalizer
In the old days before my ARCAM CD Player I only had LP´s to play, so of course I had to make a RIAA equalizer good enough for my needs.  A discrete two stage design with passive correction in the treble (75us) and active correction for the rest (318 us and 3,18ms). A friend with a LINN Sondek / EKOS / EMT-pickup has used this stage for years now without indicating any need to upgrade.

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