Thread: Modding a 5900?
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Old 01-28-2010, 08:24 PM
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Poobah Poobah is offline
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Well I think the 5900 will remain unchanged...

I've decided I'm going to go with a Tube Dac... In fact it will open a bunch of welcomed options.

1. Either Tube or Solid State options to suit listening material or tastes.
2. USB connection.. Not that I know I'll need it.. but the option is there.
3. Ear Phone Jack.. Again not sure, but might come in handy if Wifey is in a perticular bad mood?

Music Hall DAC25.2 (but Modified in a big way). Total cost after mod's about 3000usd. And interestingly enough, Music Hall fully warrenties Underwood Modifications... So no worries on that end.

But I'm can still be talked out of it (or heck tomorrow I might go with something else entirely?)... (Here's all the details.






Underwood Mod's...

The Music Hall DAC25.2 is a very nice tube DAC that has a USB input as well as both RCA & balanced outputs. It also has a good headphone amp.

The stock DAC has a very good design architecture but is a little on the soft side when run thru the tube RCA output stage. This is fine if listening to Internet radio but not what we want for quality high definition music systems. In addition, the DAC also has a fully balanced side that is only run solid state. We have designed a comprehensive set of mods that makes this DAC superb. The mods were designed by Chris Johnson, the founder and former president of Sonic frontiers.

There is a clock mod as well as both Level-1 and Level-2 mods for both the RCA tube output stage as well as the XLR balanced solid state output stage. We also have a basic $250 mod to upgrade the headphone amp.

The following details the mods:
Clock mod [$799 + frt. preinstalled, $350 + frt. retro-fit]: We add an upgraded Burson Audio clock to the basic DAC. This improves the bass performance, imaging and midrange performance of the basic unit.
At $799 for a new DAC with the $350 clock mod, the clock-modified DAC25.2 is a very good sub $1000 DAC and considerably better than the stock DAC in both RCA tube and XLR solid state output versions.

Level-1 RCA tube mod [$1.390 + frt. preinstalled, $990 + frt. retrofit, $200 for clock mod if ordered at the same time]:
• 3 x dual Analog Devices AD8620 SMT op amps mounted on custom DIP adaptors
• 2 x Mundorf M-Cap metalized polypropylene output coupling caps; 2 x MultiCap RTX tin foil, polystyrene film bypass caps
• 1 x Russian mil-spec 6h23p-eb “ultra low noise” 6922-type tube to replace the stock tube
• 1 x Teflon composite silver-plated tube socket
• 2 feet of DH LABS 23 awg pure 99.99% pure silver, solid-core hook-up wire, with foamed teflon, tape wrap dielectric
• 2 x high curren” ultra low impedance, Linear Technology adjustable power supply regulators/ LT1033 & 1085
• 8 x MUR860 ultra fast, soft recover Hexfred style rectifying diodes
• 5 x Black-Gate N-Series non-polar electrolytic power supply caps.
• 18 x Takman & Riken Japanese-made audio-grade carbon film 1% signal resistors to replace the cheap stock resistors.
• 1 6”x12” Soundcoat sheet damps chassis resonances.
• 4 x small EAR compliant sorbothane isolation feet.
• 7.5 hours of installation labor

The Level-2 RCA tube mod is all of the above with the addition of [$1.790 + frt. preinstalled, $1.390 + frt. retrofit, $200 for clock mod if ordered at the same time]:
• 3 x dual Burson Audio discrete op amp modules on custom circuit board assemblies, terminated with DIP spaced flying leads. These parts each contain over 68 parts per module. They are considered the best opamps made and are effectively all discrete parts
• 9 hours total labor

The final modified RCA tube DAC is superb. It has just enough tube liquidity to add warmth to many system. It outperforms the Parts Connexion modified Benchmark by a good bit.

XLR Solid State Level-1 mod [$1.190 + frt. preinstalled, $790 + frt. retrofit, $200 for clock mod if ordered at the same time]:
• 1 x pair of dual Analog Devices AD8620 SMT op amps mounted on custom DIP adaptors
• 2 x high current ultra low impedance Linear Technology adjustable power supply regulators/LT1033 & 1085
• 8 x MUR860 ultra fast, soft recover Hexfred style rectifying diodes
• 16 x Takman Japanese-made audio-grade carbon film 1% resistors
• 1 6”x12” Soundcoat sheet, for damping chassis resonances
• 4 x small EAR compliant sorbothane isolation feet
• 1 x German made HiFi Tuning“Classic pure silver element/end-cap fuse, which uses a ceramic body and is internally damped and cryo-treated
• 6 hours of installation labor

XLR Solid State Level-2 mod [$1.490 + frt. preinstalled, $990 + frt. retrofit, $200 for clock mod if ordered at the same time]:
• One matched pair of “dual” BURSON AUDIO “discrete” op amp modules, on custom circuit board assemblies, terminated with DIP spaced flying leads. Over 68 parts per module.
• Over 7.5 hours labor

Headphone Output Option [$750 + frt. preinstalled, $290 + frt. retrofit]:
• 1 x Analog Devices AD8620 driver/buffer op amp (mounted on DIP adapter)
• 4 x polystyrene filter-network capacitors
• 4 x Takman Japanese-made audio-grade carbon film 1% resistors
• 4 x Black-Gate C-series audio coupling capacitors
• 1.5 feet of Connex BL-Ag pure 99.9% silver, Teflon insulated, shielded interconnect cable
• 2 hours labor
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Cables - Cardas Golden Reference

Round one to Chuck.

Last edited by Poobah; 01-28-2010 at 09:35 PM.
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