Carrie Amp v3
May 6, 2014 at 4:12 AM Post #16 of 24

00940

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  I thought the regulators would be necessary because of variation in voltage vs. load. Why wouldn't that apply here?

 
Recent DC-DC converters have pretty good load regulation. And since you're using opamps with extremely good rail rejection at audio frequencies (where the PS will be modulated, higher frequencies will be dealt with by bypass caps), you should be fine.  I wouldn't do it for a discrete design of course.
 
But one should take note of the switching frequency of the chosen converter and design an LC accordingly.
 
May 24, 2014 at 3:44 PM Post #17 of 24

joneeboi

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How's it look now?
 
  1. Joined both ground planes into one big happy family
  2. Symmetry for everyone!
  3. Removed all the bits related to rail splitting and regulation
  4. Switched from 12 V DC-DC converter to +/- 15 V version
  5. Isolated grounds again
  6. LC filter on power rails
  7. Added SO8 on bottom
  8. More through hole components
  9. Increased to 8 mil separation
 

 

 
Nov 20, 2014 at 11:30 AM Post #18 of 24

TBomb06

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Consider me in for whenever these become available! I love(d) my Carrie Amp, and when something on the board recently gave up the ghost I was really bummed I didn't have a spare board :frowning2:
 
Nov 25, 2014 at 12:57 PM Post #19 of 24

joneeboi

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I've built a couple in the past few months, so now I have some great learnings to apply. Will definitely update this thread when I get there, which should be early in the new year.
 
Jun 27, 2015 at 3:57 PM Post #21 of 24

joneeboi

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There are a couple reasons why I tried this 2 channel design.
 
The Mini^3 was a design by amb and morsel, used with permission. I wanted to break away from borrowing someone's design into standing on my own two feet, so to speak. I know it's more or less a Cmoy circuit, but I still have some curiosity left in me to play around with different designs, even if I re-invent the wheel a little..
 
Also, it's a hypothesis to see if the difference in sound signature feels better to me from a rolled opamp, two channel perspective compared to a fixed, three channel design. After hearing the Senn Orpheus for the first time, I realized that I'm not the type of listener to value accuracy above all. I like my music to get me moving, so I'll do that with equalizers, headphone mods, component swaps, or whatever I can get my hands on in a pinch. I'll stream music on YouTube, Spotify, sing along to CDs in the car, go to concerts and music festivals, and in plug my ears in a small, packed night club. I hated my brother's Etymotics for their uninvolved clarity, and I loved the few minutes I had with a friend's punchy Beyer T1s. I listen to my PortaPros unamped on my walk to work, and I got a powered USB hub just to amplify music with the Carrie Amp directly from my iPhone. That is, I'll go nuts getting the right sound, but I'm too practical to focus purely on reducing THD.
 
I like the splashy, messy Grado front row seat sound, and I like the HD650 minus the veil. I think innovation in hifi audio can mean fancy circuits as well as doing the same thing in a different way. Think of a restaurant doing burgers, hot dogs, and fries. They aren't inventing new food groups or item menus, but they could bring something new to the table by doing it in their own way. JDS Labs found success doing a Cmoy with bass boost, and I'm doing it here with socketed single channel opamps, star ground, and a ground plane. I'm not sure whether it'll measure better or worse, but I'm still in search of that perfect sound signature for me.
 
It may not make total objective sense, but I'm just trying to follow my ears.
 
Jul 14, 2015 at 10:16 PM Post #22 of 24

KimLaroux

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Seems reasonable. At least you know where you're going with the design.
 
I have a bunch of op-amps I got over the years, some sent as free samples and others given by friends to try out. Sadly I never had the chance to try them out as all my gear is using discreet circuitry. I could use one of these new carries. It seems like fun.
 
I was also wondering about powering it from a USB hub and feeding it music from a smartphone. Nice to see the idea confirmed. Maybe I should get one of those doodlebugs instead of a hub. It'll give me a nice bedside setup.
 
Mar 25, 2019 at 9:19 PM Post #24 of 24

KimLaroux

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4 years later...

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Its working. But it has really audible high pitched distortion and noise. That's when powered straight from my desktop, or trough my powered USB hub. Dunno if it's coming from the GrubDAC itself or added later on by the v3 amp. Ah well. At least I can shelf this project in peace now, and sleep better knowing that I completed it and its working.

Anyone else ever assembled one of those and made them work?
 

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