[roger_s]

I use a modified 336i (Alps audio taper pot replacing the stock linear taper, Mogami cable from the inputs to the pot, DC heaters, and bypassed PS caps) with HD650s. They're a great combination. I can listen to them for hours.

 

[canbus]

Quote:

Originally Posted by roger_s /img/forum/go_quote.gif I use a modified 336i (Alps audio taper pot replacing the stock linear taper, Mogami cable from the inputs to the pot, DC heaters, and bypassed PS caps) with HD650s. They're a great combination. I can listen to them for hours.

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!

 

[roger_s]

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

Quote:

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!

 

[canbus]

Quote:

Originally Posted by roger_s /img/forum/go_quote.gif 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

Hello Roger & my sincere and immense thanks. Im at the very bottom of the learning curve and your experience and knowledge is helping me to progress.

I know very little about solid state electrics, but im hoping to remedy that situation by attending a few night classes. If its ok I have a few questions.

1) Would life be easier if I shielded the heater wires as opposed to replacing them with a twisted set? In other words could I apply some high quality rf/EM insulating tape and insulate the wires? Or does it not work like that

2) Is there a 'straight swap' higher quality pot that will bolt straight in? Your pot is motorised. Respect

Would it be possible to strip the phono plugs off an rca lead and hardwire the cable to the pot or does the rca 'wire' need to connect to the pcb first. (strange question but I was not sure on this)

Thanks very much roger. Night classes or not, I suspect I will wind up greasing the palm (£) of my local electronics repair man.

 

[FloydCouncil]

Guys, is the EMU 0202 a good DAC for the DV 336SE + HD650 combo?

 

[roger_s]

Canbus,

First things first: The DV is a vacuum tube (valve to you in the UK) amp, not solid state. It packs lethal voltages even when it's unplugged from the mains. If you're new to this stuff proceed with great caution. Amps like the DV 336 are dead simple to work on given their point-to-point wiring compared to a SS amp but treat it with great respect or it will kill you. Really.

You should be able to use shielded wire as long as it's a heavy enough gauge. You'll be pulling about 3 amps through them. I don't know how much benefit over twisted wires there would be, though. Perhaps someone's who's done it can chime in here.

No, my pot's not motorized. It's just a slightly larger version of the supplied pot and it's audio taper instead of linear taper. With the stock pot you're getting blasted with the pot turned to about 10 o'clock. With the audio taper pot you've got turn it to about 12 o'clock before things get really loud.

I don't quiet understand your RCA lead question. But the input RCA jacks on the DV are soldered to the PCB at the back of the amp. So, they're on the side of the PCB that's opposite of where the stock cables attach and thus not reachable without major surgery. On my amp a lot of solder was used to connect the cables to the PCB. At first I was going to clean it off--there's way too much there. But after figuring out what I needed to do to attach the cables I was glad there was a lot of solder to "recycle". By the way, the stock cables are a very small gauge coax with the shield acting as the ground leads for the inputs. In other words, the shields aren't used as shields. And I suspect the major source of all of that hum. Having proper ground leads and a proper shield really turns down the hum.

Roger

 

[roger_s]

I don't know the EMU DAC. I'm using one of these Chinese DAC's. It's working well with the optical output from my Apple AirPort Express. I bought it as a "proof of concept". I'll likely upgrade it with something from Pacific Valve down the road.

Quote:

Originally Posted by FloydCouncil /img/forum/go_quote.gif Guys, is the EMU 0202 a good DAC for the DV 336SE + HD650 combo?