Torm
Head-Fier
- Joined
- Jun 4, 2006
- Posts
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A friend recently visited Bejing on a business trip and he brought back a DIYEDEN Great March DAC for me!
Im pretty sure somebody on Headfi have already modified this DAC and i know pacific valve sells a unit modified by them.
I am asking if anybody knows what (if any) components that could be replaced to improve the unit. I have identified three Burr Brown op-amps on sockets, eight larger caps (25v 2200uf) etc. See linked image. Overall it seems to me that there are a number of components in the unit that could fairly easily be replaced by higher quality components. But which ones, and to what?
http://home.online.no/~jaschjer/greatmarch.jpg
This is what the pacific valve modified GM looks like: http://pacificvalve.us/images/Circuit3.JPG
According to Pacific Valve they have done the following mods:
*Input resistance changed to 75 ohms
*Output resistance (RA) is changed to closely match preamps input impedance
*Main Capacitors changed to Roederstein, WIMA and Black Box
*Changed RCA sockets to gold plated sockets
*Replaced OPA627 OP AMP with Analogue Devices AD827
When comparing their pic to mine i can see that they have switched three of the large green caps (i cannot see the specs of the caps as they are zipped down) - why not all four? and why have they used different caps where they have switched?
It seems they also have only swithced out one of the OPA2604s..the middle one. (also they say they have switched from OPA627 - however my unit have OPA2604s)
Im pretty sure somebody on Headfi have already modified this DAC and i know pacific valve sells a unit modified by them.
I am asking if anybody knows what (if any) components that could be replaced to improve the unit. I have identified three Burr Brown op-amps on sockets, eight larger caps (25v 2200uf) etc. See linked image. Overall it seems to me that there are a number of components in the unit that could fairly easily be replaced by higher quality components. But which ones, and to what?
http://home.online.no/~jaschjer/greatmarch.jpg
This is what the pacific valve modified GM looks like: http://pacificvalve.us/images/Circuit3.JPG
According to Pacific Valve they have done the following mods:
*Input resistance changed to 75 ohms
*Output resistance (RA) is changed to closely match preamps input impedance
*Main Capacitors changed to Roederstein, WIMA and Black Box
*Changed RCA sockets to gold plated sockets
*Replaced OPA627 OP AMP with Analogue Devices AD827
When comparing their pic to mine i can see that they have switched three of the large green caps (i cannot see the specs of the caps as they are zipped down) - why not all four? and why have they used different caps where they have switched?
It seems they also have only swithced out one of the OPA2604s..the middle one. (also they say they have switched from OPA627 - however my unit have OPA2604s)
