xmokshax
100+ Head-Fier
- Joined
- Jun 13, 2007
- Posts
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- 10
hi all-
first off, let me say that i'm a complete electronics and DIY newbie, so if i ask anything laughably simple or obvious, try to avoid openly making fun of me. chuckling behind my back is fine, just as long as it's not overt.
in any case, i just built my first CMoy, following Tangent's specifications and instructions (which were excellent, by the way). i stuck with pretty much all "default" parts. the amp worked right off the bat, but i'm curious about how i can improve it.
that leads to my questions - i have a bunch. don't feel the need to answer all of them at once (or at all) - responses to any of them will be appreciated. some of these are specific to the CMoy design, and some are general amp-related questions.
1. (this has been asked in another recent thread, but i thought i'd add it to this set of questions as well), how important is matching feedback loop resistors? an important corollary to this is, what is a feedback loop, especially in the context of an op-amp? what function does it serve, and why is it necessary in this case but not in others? i should note that i'm picking my way through Horowitz and Hill, but i haven't made it very far yet.
2. while Tangent's basic specs show a single 9V power supply, all of his examples in supporting text deal with 2x 9V, and his finished amp appears to run on 2x 9V. what's the advantage to doubling the power supply, i.e., what physical difference does it make within the circuit? how will i know if my amp is under-powered (short of adding a second battery in series and seeing if it improves the sound)? what's the best way to add a second battery in series, if i already have the amp built with a single 9V clip?
3. in relation to (2), does increasing the size of the supply and input capacitors produce a need for greater input voltage? i'm thinking of swapping in 330 or 470uF supply caps and 0.22uF input caps, but i might just build a second one if it will require power supply changes as well.
4. i think i've read (perhaps even on one of Tangent's pages) that some amp designs use output capacitors as well - what's the advantage to this?
5. in his section on the CMoy virtual ground circuit, Tangent diagrams a TLE2426-based buffered virtual ground circuit, but then goes on to mention the weaknesses of this implementation and describes more complex buffered virtual ground circuits. is the TLE2426 implementation sufficient for a basic headphone amp? is it better than the basic CMoy's unbuffered virtual ground in most/all respects, and will implementing it improve sound quality? last, does the quality/tolerance of the 1uF capacitor between the TLE2426 and V- make a big difference, or will a basic +/-20% electrolytic do the job just fine?
thanks in advance for any answers you can give.
first off, let me say that i'm a complete electronics and DIY newbie, so if i ask anything laughably simple or obvious, try to avoid openly making fun of me. chuckling behind my back is fine, just as long as it's not overt.
![tongue.gif](http://www.head-fi.org/forums/images/smilies/http://hfimage.head-fi.org/smilies/tongue.gif)
in any case, i just built my first CMoy, following Tangent's specifications and instructions (which were excellent, by the way). i stuck with pretty much all "default" parts. the amp worked right off the bat, but i'm curious about how i can improve it.
that leads to my questions - i have a bunch. don't feel the need to answer all of them at once (or at all) - responses to any of them will be appreciated. some of these are specific to the CMoy design, and some are general amp-related questions.
1. (this has been asked in another recent thread, but i thought i'd add it to this set of questions as well), how important is matching feedback loop resistors? an important corollary to this is, what is a feedback loop, especially in the context of an op-amp? what function does it serve, and why is it necessary in this case but not in others? i should note that i'm picking my way through Horowitz and Hill, but i haven't made it very far yet.
2. while Tangent's basic specs show a single 9V power supply, all of his examples in supporting text deal with 2x 9V, and his finished amp appears to run on 2x 9V. what's the advantage to doubling the power supply, i.e., what physical difference does it make within the circuit? how will i know if my amp is under-powered (short of adding a second battery in series and seeing if it improves the sound)? what's the best way to add a second battery in series, if i already have the amp built with a single 9V clip?
3. in relation to (2), does increasing the size of the supply and input capacitors produce a need for greater input voltage? i'm thinking of swapping in 330 or 470uF supply caps and 0.22uF input caps, but i might just build a second one if it will require power supply changes as well.
4. i think i've read (perhaps even on one of Tangent's pages) that some amp designs use output capacitors as well - what's the advantage to this?
5. in his section on the CMoy virtual ground circuit, Tangent diagrams a TLE2426-based buffered virtual ground circuit, but then goes on to mention the weaknesses of this implementation and describes more complex buffered virtual ground circuits. is the TLE2426 implementation sufficient for a basic headphone amp? is it better than the basic CMoy's unbuffered virtual ground in most/all respects, and will implementing it improve sound quality? last, does the quality/tolerance of the 1uF capacitor between the TLE2426 and V- make a big difference, or will a basic +/-20% electrolytic do the job just fine?
thanks in advance for any answers you can give.
![smily_headphones1.gif](http://www.head-fi.org/forums/images/smilies/smily_headphones1.gif)