I like to explain something about my audio hobby. It started many years ago when I started my study in electronics at the Antony Fokker school. This study was a combination of electronics and airplane technology. In those two years at the Antony Fokker school I developed my interest in airplanes witch is still there. After those two years I went to an other institute to study at a higher level at Rens & Rens in the city of Hilversum. My first audio project, building an AM radio receiver with an 12AT7 double triode was many years before I went to Rens & Rens. One triode was used as detector while the other was used as audio amplifier to drive a small loudspeaker. The design did not come from a book but was my own design.
The loudspeaker I used was a PHILIPS type AD5060M8 in a small cabinet. Some time later more projects came along. One of those projects was a mono amplifier build around a ECL82 (6BM8) and the followup of this amp was a push pull around two ECL82 tubes. A few years later stereo cam in my life and both ECL82 were used in a single ended stereo amplifier. A record player was used as the music source, the tonearm was fitted with a cheap Ronnete cartridge. During my audio DIY activities witch was not always as safe as it should be I had noticed that high voltage was not pleasant to touch. High voltages are a serious danger and you should always be aware of this. At that time transistor came available and I stopped using tube because of the high voltages they needed.
My first solid state project was a phono preamp with RIAA correction. I needed this preamp because the Ronnette cardridge was exchanged by an Audio Technica AT66 Magneto Dynamic cardridge. This pre amp was used to drive my ECL28 stereo amplifier. I admit that even at that time is was not really high end. The improofment in sound quality was less then expected. This is why I my speakers became suspected as the main problem. New 2 way speakers are build containing an AD8065W8 (8" woofer) and an Isophone dome tweeter. This was really what I was looking for, a huge improofment. But an other problem arrises, short in amplifier power. An new amplifier had to be build. This time I used transistors because of the lower supply voltages and I did not need to invest in expensive output transformers. The design was called 'poor mans QUAD' originating in a magazine called ELEKTUUR. This amplifier was in improofment in sound quality and output power. It was this year (1971) that I went to study electronics at Rens &Rens in Hilversum. In the years thereafter I did build a lot of amplifiers ranging from modified QUAD 405 to full symmetric MOSFET amplifiers. Even my speaker system had several upgrades to keep the quality at the same level compared to the amplifiers I used. The bailys transmissonline speaker end the Rogers monitor was build. The Rogers monitor speaker, also a transmissionline speaker, was a four way speaker that i have been using for at least 10 years. I still think it is a very fine speaker if you own the latest version.
Tubes came back to life.
I could not understand why a lot of people love tube amplifiers because I was able to build very good sounding MOSFET amplifiers. I have heart a lot of story's about tube amps and the gain in sound quality you get compared to semiconductor amplifiers. After almost a year of thinking about the reason what caused the so called gain in sound quality I decided to design my own tube amp. I had to refresh my knowlage about tubes, I had not used them for over 20 years. If I had to proof that a tube amp is not superior to solidstate I had to make a 'perfect' tube amp. If didn't make it perfect there would be room for improofment and I still did not know if a good tube based design outperformed a solidstate amplifier. Because I needed more then a few watts of power I decided to build a push pull amplifier with the famous KT88 output beam tetrode tube and the new designed ECC99 acting as phase inverter and driver. After many months of thinking, building and tweaking I was very satisfied about this amplifier. It really outperformed my latest solidstate amplifier in terms of sound quality. Specialy for this amplifier I did build a set of speakers based on the famous ARIEL designed by Linn Olson. I did redesign the transmissonline using a software package called AJHorn. Minor modifications on the line where made end an improofed tweeter, Scan speak 9700, is used. A change in the crossover was needed and optimized during listening and measurement sessions.
Best regards
Dalojan