@cogitech
Recently finished my amplifer. Used all Transcendar iron, the 7 Watt OPT, a choke and a mains. 5670 as driver and el84 as power. 20% UL and just a tad over 8 db NFB.
I build it in the looks I encountered as a kid rather then a "modern" look. Did not like the old Philips colors and choose a brown /copper colour. (I worked for Philips after leaving university where I studied vacuum tube technology in the last class to be taught in that subject - solid state afterwards).
I splashed ut on a TKD potentiometer (leaves an Alps in the dust).
In my 55 years of playing with tube technology I always considered tube rolling as something of "hog wash". However with this little amplifier something happened: I perceive a difference in changing the output tubes - did not like the Electro Harmonix, nor the NOS Tesla but liked the Telam and Polam tubes (came out of Philips subsidary in Poland - the last Philips factory to make EL84).
I've got more than 20 different 2C51 / 5670 / 6N3P / 6N3P-E / 6N3P-EV (last three Russian, not the Chinese brown stuff) and about 30 odd EL84 / 6BQ5 / 6P14P-EV so it will last me the rest of my life.
I had a bit of work to do to improve the square wave response and feel that the transformers I used 7 years ago (the 10 watt versions) were better in that respect. But with this amplifer I hear more detail than I have ever heard before in any of my amplifiers. I prefer it a lot above the Yamaha natural sound RX-E600 that I used previously.
You mentioned the Allergo website - I looked at it and do not give it much credence for their calculation of power required.
I use the little amp during the day and evening and drive it from my Apple Mac Mini (decent signal - noise ratio) and use Foobar 2000 as music player. Foobar 2000 has a volume slider that displays volume in dB. Some calibrated test CD's were used and it seems to work OK.
From this I noticed that I listen mainly between about 50mW and 120mW output on my ProAc Tablette 10 at about 2 feet from both. (lowest distortion vs maximum output happens around 11 Ohm speaker impdance making for approx 6500 - 7K primary impedance)
Regarding transformers: I have had the lot, never took a shine to PP and like the SE. But as @TubeLab remarked: the more iron you have to magnetise the more it seems to loose the finest details. In other words: you have to "right size" in power and matching OPT.
Like yourself: I do not need lots of power - if I need to go loud then I have some SS amps.
Unfortunately health is failing so I am calling it quits making stuff after 55 years playing around with HAM radio and tube gear.
Enjoy the hobby!
Recently finished my amplifer. Used all Transcendar iron, the 7 Watt OPT, a choke and a mains. 5670 as driver and el84 as power. 20% UL and just a tad over 8 db NFB.
I build it in the looks I encountered as a kid rather then a "modern" look. Did not like the old Philips colors and choose a brown /copper colour. (I worked for Philips after leaving university where I studied vacuum tube technology in the last class to be taught in that subject - solid state afterwards).
I splashed ut on a TKD potentiometer (leaves an Alps in the dust).
In my 55 years of playing with tube technology I always considered tube rolling as something of "hog wash". However with this little amplifier something happened: I perceive a difference in changing the output tubes - did not like the Electro Harmonix, nor the NOS Tesla but liked the Telam and Polam tubes (came out of Philips subsidary in Poland - the last Philips factory to make EL84).
I've got more than 20 different 2C51 / 5670 / 6N3P / 6N3P-E / 6N3P-EV (last three Russian, not the Chinese brown stuff) and about 30 odd EL84 / 6BQ5 / 6P14P-EV so it will last me the rest of my life.
I had a bit of work to do to improve the square wave response and feel that the transformers I used 7 years ago (the 10 watt versions) were better in that respect. But with this amplifer I hear more detail than I have ever heard before in any of my amplifiers. I prefer it a lot above the Yamaha natural sound RX-E600 that I used previously.
You mentioned the Allergo website - I looked at it and do not give it much credence for their calculation of power required.
I use the little amp during the day and evening and drive it from my Apple Mac Mini (decent signal - noise ratio) and use Foobar 2000 as music player. Foobar 2000 has a volume slider that displays volume in dB. Some calibrated test CD's were used and it seems to work OK.
From this I noticed that I listen mainly between about 50mW and 120mW output on my ProAc Tablette 10 at about 2 feet from both. (lowest distortion vs maximum output happens around 11 Ohm speaker impdance making for approx 6500 - 7K primary impedance)
Regarding transformers: I have had the lot, never took a shine to PP and like the SE. But as @TubeLab remarked: the more iron you have to magnetise the more it seems to loose the finest details. In other words: you have to "right size" in power and matching OPT.
Like yourself: I do not need lots of power - if I need to go loud then I have some SS amps.
Unfortunately health is failing so I am calling it quits making stuff after 55 years playing around with HAM radio and tube gear.
Enjoy the hobby!
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