This one based on the 33 Pentode running up into Class AB2 in PPUL or PP Triode. At lower levels it runs Class A. Built about 20 yrs ago, it sits here on the shelf like many other projects. And as usual, how it sounds depends mostly on what reproduction system it drives. And the source material.
Two years ago I ran some THD & IMD tests, all shewn here. For the tests that used to be done at 60 Hz & 7 KHz, I used instead 80 Hz & 7 KHz. That way it is possible to see any problems associated with the PS at 60 Hz & 120 Hz.
The 2-Tone Tests will look very busy to those who have never seen spectra caused by multiple tones. Adding more looks even worse no matter whose amplifier!!
Two years ago I ran some THD & IMD tests, all shewn here. For the tests that used to be done at 60 Hz & 7 KHz, I used instead 80 Hz & 7 KHz. That way it is possible to see any problems associated with the PS at 60 Hz & 120 Hz.
The 2-Tone Tests will look very busy to those who have never seen spectra caused by multiple tones. Adding more looks even worse no matter whose amplifier!!
Attachments
This is a list of the 2V directly heated tubes used in 1930s home radios powered by storage batteries:
19 – Dual power triode. Also available with octal base: 1J6G
20 / UX120 – Power triode
22 / UX222 / CX322 - Sharp-cutoff tetrode
1B5 / 25S – Dual detector diode, medium-mu triode
30 / CX330 – Medium-mu triode, similar to type 01A. Also available with octal base: 1H4G
31 / CX331 – Power triode
32 / CX332 – Sharp-cutoff tetrode
33 / CX333 – Power pentode
34 / CX334 – Remote-cutoff tetrode
49 – Dual-grid power triode, similar to type 46
The JHstewart design is interesting, I was not aware that 4.5W are possible with this kind of tubes.
Some time ago I made a quick test with directly heated tubes designed for battery radios. I had limited supply of the above mentioned 2V tubes, so I mostly tried 1.4V tubes. 1D8GT is a good candidate for a compact single ended headphone amplifier. It would be easy to power it from cheap standard 18650 lithium batteries; 90V b+ would require a switched mode power supply. A basic charge pump could be enough, due to the low anode currents. DAF96 (gain stage) and DL96 (power stage) are another option. To reach enough gain for a effective global feedback loop, I believe that two gain stages are required.
19 – Dual power triode. Also available with octal base: 1J6G
20 / UX120 – Power triode
22 / UX222 / CX322 - Sharp-cutoff tetrode
1B5 / 25S – Dual detector diode, medium-mu triode
30 / CX330 – Medium-mu triode, similar to type 01A. Also available with octal base: 1H4G
31 / CX331 – Power triode
32 / CX332 – Sharp-cutoff tetrode
33 / CX333 – Power pentode
34 / CX334 – Remote-cutoff tetrode
49 – Dual-grid power triode, similar to type 46
The JHstewart design is interesting, I was not aware that 4.5W are possible with this kind of tubes.
Some time ago I made a quick test with directly heated tubes designed for battery radios. I had limited supply of the above mentioned 2V tubes, so I mostly tried 1.4V tubes. 1D8GT is a good candidate for a compact single ended headphone amplifier. It would be easy to power it from cheap standard 18650 lithium batteries; 90V b+ would require a switched mode power supply. A basic charge pump could be enough, due to the low anode currents. DAF96 (gain stage) and DL96 (power stage) are another option. To reach enough gain for a effective global feedback loop, I believe that two gain stages are required.
Excuse my lack of knowledge on abbreviations Pcan --don't laugh but I thought 2V meant a tube not a heater voltage .
Yes early portable radios of both the USA and the UK had 2V heaters till 1.4 ones were introduced in B7G base form .
I have an old USA radio repair book=Radio troubleshooters Handbook by Alfred A. Ghirardi--Murray Hill Books Inc. NY ( no longer in business ).
Yes early portable radios of both the USA and the UK had 2V heaters till 1.4 ones were introduced in B7G base form .
I have an old USA radio repair book=Radio troubleshooters Handbook by Alfred A. Ghirardi--Murray Hill Books Inc. NY ( no longer in business ).
The Highland Clearances to put sheep in their place is still remembered in Scotland , you don't need 100 % Scottish blood to be Scottish .
The East coast of Scotland has a lot of Scots with Viking blood and the west coast has many with Irish blood , large number of Scots with red hair /pale skin .
The East coast of Scotland has a lot of Scots with Viking blood and the west coast has many with Irish blood , large number of Scots with red hair /pale skin .
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