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Anyone have any information on modding the Music Hall dac25.2/3?

post #1 of 4
9/21/11 at 12:39pm
Thread Starter 

I just bought the Music Hall dac25.3 and first replace the stock tube with a 1968 Miniwatt Dario French Mazda 7308/E188CC tube.  The difference is phenomenal!  Thanks to Brent Jessee over at audiotubes.com.  I want to continue to improve this unit and would like to do the work myself.  I am considering the Burson op amp upgrade next.  It is a simple plug and play op amp replacement.  Does anyone have information beyond this?  I would like to replace the clock, capacitors, resistors, and diodes that will benefit tube output as well as xlr output.  Any suggestions or information would be greatly appreciated!  

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post #2 of 4
9/21/11 at 1:03pm
Just some food for thought, but I'm in the camp that finds a good circuit more important than the parts in it. A great circuit with modest parts will sound good. A poor circuit stuffed with boutique parts is still a poor circuit. (No, I am not suggesting your DAC is bad. I haven't heard one.)

I just don't think going boutique helps much if you already enjoy the sound. You'll spend a lot, might not get much performance gain, and people will be reluctant to buy it if you decide to sell. You might dump hundreds into it and take that as a loss.

There are some practical considerations, too. This is likely built on a PCB. You might find some boutique capacitors you want, but the lead spacing won't match up with the PCB. You'd have to fabricate some kind of bracket or mounting to use them. Things can get complicated, fast. Also, unless you've done some DIY, you might damage it. It's easy to lift a pad or cut a trace accidentally. You'll also have to disassemble the whole thing to get at the bottom of the PCB. Are you ready to do that?

If you really want a customized DAC, why not build one from scratch? There are boards available for a number of good designs. You could order the boutique parts you want and build it as you like. You'd probably find a new build easier to deal with than disassembly and desoldering.
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post #3 of 4
9/21/11 at 1:41pm
Thread Starter 

Thanks for the input!  I am comfortable with desoldering and pcb boards.  I build computers as a hobby and love to tinker.  The reason I am looking into this is there are several places that mod this dac to what some claim to be phenomenal results. I have seen claims that this dac will rival those in the 3-5K range once upgraded.  True?  I can't say, never did an A/B.   At $1700+ for the upgrade it is something I could do for around $400 provided I can get the information on proper replacement parts.   Here is a site that does the job: http://www.underwoodhifi.com/mod_musichall.html

Here is an example of someone who has done some mods:

http://bursonaudioblog.blogspot.com/2010/08/burson-opamp-upgrade-to-music-hall-dac.html

http://www.computeraudiophile.com/content/Music-Hall-DAC253-Modifications-Upgrades-Clock-OpAmp-Capacitor

This is where parts can be obtained:

http://www.partsconnexion.com/

I have tried getting information on other forums and am still awaiting a reply.  I contacted Underwood to inquire about buying information for diy, but they kindly declined.  I have enough info to get started should I decide to move forward, but would like to find out as much as possible.  If I could get a schematic or prints I would be golden!  The burson op amps are an easy replacement and some have claimed after that and a new tube other add-ons provide minimal change so that may be the end of it.  Just want to see what information is out there among our fellow headfiers.

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post #4 of 4
9/23/11 at 6:19am

FYI, the tube is only in the single-ended output circuit, not the balanced.  one dual triode cannot do 2 balanced outputs unless it time-shares!

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