pacemkr
New Head-Fier
- Joined
- Feb 6, 2006
- Posts
- 19
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I used tangents guide and already put the thing on a pcb and its working on the first try. =)
Here a couple of questions arise.
1) I have some hum even when no source is connected, its pretty audible at full volume, quite audible at half volume, very audible with a source connected. Is that normal. I tried adding R5, didnt make any difference.
2) There is a very low buzz, that seems to be a result of grounding issues. When I move my hand closer to the amp, the buzzing goes away. How do I fix this?
3) Are 18V really needed? I hooked the amp up to one 9V battery (I'm using the OP2227, I also have OP2134, but I havent tried it) and it seems to be working fine. I'm asuming the opamp is more stable at 18V, but I'm already thinking of the next amp I'm going to build =) and I want to make it really portable. This one doesnt qualify since I'm adding a Meier Bass enhanced crossfeed along with all the switches, two batteries, and quite a bulky case. So I was thinking powering the next one off a single 9V battery, are there any sideffects?
4) I'm using low impedance phones (16 ohm Sony MDR-EX71) can this be why I'm hearing the "humming"? I should get some more serious headphones, but I really love the portability and sound quality taking size into account, so these will be my main phones no matter what. You might say that defeats the whole purpose of having an amp. Thats what I thought, thats why I didnt opt for a portable design right away. But for some reason sound going through the amp sounds better to my ears or I simply convinced myself that it does, either way something is working.
On that note, are there any modifications to the cmoy design that are needed for low impedance phones?
Just in case, here are the "modifications" I used that deviate from standard schematic in tangents guide. I used a TLE2426 for the VG. I did not connect the NR pin on the TLE, since I didnt hear any difference and the 1uF cap is bulky. I used 0.47 uF caps at C2.
Thanks.
Here a couple of questions arise.
1) I have some hum even when no source is connected, its pretty audible at full volume, quite audible at half volume, very audible with a source connected. Is that normal. I tried adding R5, didnt make any difference.
2) There is a very low buzz, that seems to be a result of grounding issues. When I move my hand closer to the amp, the buzzing goes away. How do I fix this?
3) Are 18V really needed? I hooked the amp up to one 9V battery (I'm using the OP2227, I also have OP2134, but I havent tried it) and it seems to be working fine. I'm asuming the opamp is more stable at 18V, but I'm already thinking of the next amp I'm going to build =) and I want to make it really portable. This one doesnt qualify since I'm adding a Meier Bass enhanced crossfeed along with all the switches, two batteries, and quite a bulky case. So I was thinking powering the next one off a single 9V battery, are there any sideffects?
4) I'm using low impedance phones (16 ohm Sony MDR-EX71) can this be why I'm hearing the "humming"? I should get some more serious headphones, but I really love the portability and sound quality taking size into account, so these will be my main phones no matter what. You might say that defeats the whole purpose of having an amp. Thats what I thought, thats why I didnt opt for a portable design right away. But for some reason sound going through the amp sounds better to my ears or I simply convinced myself that it does, either way something is working.
Just in case, here are the "modifications" I used that deviate from standard schematic in tangents guide. I used a TLE2426 for the VG. I did not connect the NR pin on the TLE, since I didnt hear any difference and the 1uF cap is bulky. I used 0.47 uF caps at C2.
Thanks.