rhooper
Head-Fier
- Joined
- May 25, 2005
- Posts
- 76
- Likes
- 0
I just finished working on my first amp: a CMoy with a modified Linkwitz crossfeed filter. It works and sounds great!
During construction of each component, I had only one major stumbling block. For the CMoy, I forgot one pair of jumpers on the amp portion. For the crossfeed, I spent a good 3 hours trying to make it work -- whenever I had the switch hooked up, it didn't seem to work -- I never got crossfeed or I always got crossfeed at the same level. It turns out I'd miswired the rotary switch late last night. Yay to alligator clips and screw caps.
I must say the amp really makes my Grado SR-80s sound much much better running from either my Audigy 2 or my iPod photo (30gb). The only thing I noticed is that the Audigy 2 really isn't that clean a signal, at least not after the speakers. There's a noticeable hiss that gets amplified if the volume isn't high enough on the PC.... unlike the iPod that has zero hiss at any volume level.
So here's the pics. Click the thumbs for larger versions:
Casework
Power/dc plug at back on side. Input is bottom, output is top. Volume then crossfeed 3-way rotary.
Bottom view (inside)
Yep, I mounted the audio jacks on a small piece of breadboard -- and boy am I glad I did. It made working with them much much easier, especially during mounting them.
Top view (inside)
Should give you a good idea how tight it is in there and why the switch ended up on the side. Remember that there are two screw "posts" inside preventing most components from being really near the side. This includes the on/off switch.
CMoy board (with most of the wires out of the way)
I originally built it with 6x gain. After adding the crossfeed, I found that max volume wasn't quite enough. I could have calculated 8x gain and dug around for the right resistors. I chose to go to 11x gain instead as I knew I had the right 1% resistors to do that. This sticks pretty closely to the tight layout by Tangent. It current has an OPA3132 in it, with an OPA2227 standing by to try later.
Modified Linkwitz Crossfeed Filter board
Not much to say about this. Did the design on paper beforehand. I created an excel spreadsheet to the layout process.
Time to go update my info to incude my amp!
I must say the amp really makes my Grado SR-80s sound much much better running from either my Audigy 2 or my iPod photo (30gb). The only thing I noticed is that the Audigy 2 really isn't that clean a signal, at least not after the speakers. There's a noticeable hiss that gets amplified if the volume isn't high enough on the PC.... unlike the iPod that has zero hiss at any volume level.
So here's the pics. Click the thumbs for larger versions:
Casework
Power/dc plug at back on side. Input is bottom, output is top. Volume then crossfeed 3-way rotary.
Bottom view (inside)
Yep, I mounted the audio jacks on a small piece of breadboard -- and boy am I glad I did. It made working with them much much easier, especially during mounting them.
Top view (inside)
Should give you a good idea how tight it is in there and why the switch ended up on the side. Remember that there are two screw "posts" inside preventing most components from being really near the side. This includes the on/off switch.
CMoy board (with most of the wires out of the way)
I originally built it with 6x gain. After adding the crossfeed, I found that max volume wasn't quite enough. I could have calculated 8x gain and dug around for the right resistors. I chose to go to 11x gain instead as I knew I had the right 1% resistors to do that. This sticks pretty closely to the tight layout by Tangent. It current has an OPA3132 in it, with an OPA2227 standing by to try later.
Modified Linkwitz Crossfeed Filter board
Not much to say about this. Did the design on paper beforehand. I created an excel spreadsheet to the layout process.
Time to go update my info to incude my amp!
