Canbus:
I'd start with replacing the pot and the cable from the inputs to the pot. Those were the last mods I made but they had the most profound improvement. There is no hum until I crank the volume all the way up (ear and phone damaging level!) and then there's mostly tube rush.
Bear in mind that this is not an easy mod: The supplied Alps post is smaller than the Alps 100KAX2 that I replaced it with. I had to drill out the index hole (not easy since I couldn't remove the face plate with field stripping the amp and work it past the tube socket and the various wires and resistors there. The input jacks are on a PCB again with no room to work without a major field strip. I ended up tinning the leads of the Mogami cable and soldering them onto the PCB rather than the preferred into the holes in the PCB. The good news is that there's a ground wire right there so attaching the Mogami's shield to ground was dead easy. The shield also provides good support for the input leads since they're relying on the solder to stay put. Remember, the shield is only grounded on one end or it's no longer a shield.
Oh yeah. The stock volume control knob won't fit the new pot. I had a nice brass knob that's a bit larger diameter than the stock knob. The brass looks rather nice against the black chassis.
I found the best way to solder the leads was to use a pair of forceps to hold them in place and steady the iron on the amps chassis while the solder that remained on the PCB and the solder on the tinned leads melted together. Slow and steady is the way to go here!
The next mod I'd do would be to remove the heater wires and replace them with twisted wires. In the stock amp they run parallel to each other--nice hum engines.... They're pretty stiff solid wires so don't plan on twisting them. Their power source is at the end of the PCB that holds the coupling caps so this really a pretty easy mod. I suspect that I would not have needed to go the DC heater route had I replaced the pot and the input cable first. Regardless, those heater leads need to be twisted.
I'd leave the power cap bypass for last and only if you're looking for a small improvement. I used Radio Shack 1uf 400v poly caps. Cheap and "good enough" for that mod. And they're nice and flat so they don't get in the way of the bottom cover.
So, does all of this work? I've got a 6SN7 of Chinese or Russian origin (no markings, but it's clearly not a NOS US or European tube). On the stock amp it hummed to point of being useless. On the modded amp it's as quiet as the RCA that's in there now--nowhere as good a tube but it demonstrates that all that hum was not a tube issue.
The sound is quality is wonderful. Tight, punchy bass, terrific imaging, and solid highs. I think I'll keep it.
Hope this helps.
Roger
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Originally Posted by canbus /img/forum/go_quote.gif
Hi Roger S.
Im awaiting delivery of a DV336i and will probably wind up modding it. Which mod yielded the biggest gain (so to speak)
Thanks!
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