crk
100+ Head-Fier
- Joined
- Jun 22, 2001
- Posts
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Hi Expertz
I've just finished my Apheared 47 and managed to squeeze it into a Curiously Strong Peppermints tin. The circuit is built on Veroboard and exactly as described in Apheared's Headwize article, except the gain is 2. I also added 100pF in parallel with the gain feedback resistor on each gain stage. In fact, I had a lot of problems with stability. I don't have a scope but it looked as if both channels would start to oscillate and produce a DC offset at the o/p of ~80 mV (measured on a Fluke multimeter) and distort. AC coupling the inputs and the 100pF caps appeared to solve this problem. It is powered from a single 9V battery with 4.7K resistors setting the ground point.
Anyway, it sounds great except for a very slight crackle that is just noticable (from time to time) in certain passages (low volume mid-range). I've compared different amps and headphones so I'm sure it is the amp.
Any words from the wize (or fize) would be appreciated....
crk
90% of the time
I've just finished my Apheared 47 and managed to squeeze it into a Curiously Strong Peppermints tin. The circuit is built on Veroboard and exactly as described in Apheared's Headwize article, except the gain is 2. I also added 100pF in parallel with the gain feedback resistor on each gain stage. In fact, I had a lot of problems with stability. I don't have a scope but it looked as if both channels would start to oscillate and produce a DC offset at the o/p of ~80 mV (measured on a Fluke multimeter) and distort. AC coupling the inputs and the 100pF caps appeared to solve this problem. It is powered from a single 9V battery with 4.7K resistors setting the ground point.
Anyway, it sounds great except for a very slight crackle that is just noticable (from time to time) in certain passages (low volume mid-range). I've compared different amps and headphones so I'm sure it is the amp.
Any words from the wize (or fize) would be appreciated....
crk
90% of the time