[Superpredator]

Quote:

Originally Posted by Fitz Congrats on your purchase! As far as chaining multiple amps together, I can't speak for how it will sound. This isn't a far fetched idea though, because you can already use a tube buffer between the source and an amp (typically SS) to allow you to use tubes to shape the sound, but without applying any gain.

Interesting concept. I use my Aria as a preamp to a crapass Onkyo R1 (mostly for convenience), but had never considered preamping a headphone amp for any reason. I probably won't do it, but it's nice to know I can.

I am hope hope hoping the Darkvoice makes my K340 happy. I have started using the Aria/K340 at home for medical transcription editing (where I need to review doctors' dictation and detail is of the utmost importance) and the K340 is by far the best headphone I've used for this purpose. I may shift the Aria to my desk at work, and it will be a little odd to hear tube glow/goodness of the Darkvoice coloring dictated audio.

I noticed in the e-mail from Jian Liu a mention of a three-day shipping time, but no mention of the ten-day wait to have the amp converted for 110 voltage. Does anyone know if they've eliminated this wait time? That would be swell.

 

[SonicDawg]

Having the K340 and the Darkvoice I can vouch for the great synergy this combo has. The tube amp definitely has the juice to push the beast, while its control of the bass really makes them sing.

 

[Fitz]

Okay, I'm still waiting on one part, and have a few others still to be soldered in, but right now this system with the modded Darkvoice is pure heaven. I just had a major eargasm.

 

[echo1]

I am still reading alot about caps. But one thing I would like to ask is what is the value in range for a high frequency coupling cap? Fitz used 1uf but can other values be used as well or is a 1uf a sweet spot. It is an answer I cant seem to find on searches. A lot about speaker crossovers, but little on this question. Any help would be appreciated.

 

[echo1]

I am still following your upgrade path. I am going to change the sockets. I just got some soviet tubes that because they dont sit in the sockets tightly there scratchiing. I know its the back socket because if I move them around I can find a spot where it will stop.
And I am glad that your upgrade resulted in a "eargasm"
The results are super.

 

[Fitz]

I'll be posting pictures and some more detailed info on the upgrades and resulting sound tonight. So stay tuned.

 

[DDQ]

Has anyone seen this listing on ebay: Darkvoice 336 220V It went for $152.50 ($60 shipping)

 

[Fitz]

Quote:

Originally Posted by DDQ Has anyone seen this listing on ebay: Darkvoice 336 220V It went for $152.50 ($60 shipping)

Interesting, looks like a test sale to me. Maybe we'll see a return of eBay sales.

 

[futuro107]

http://cgi.ebay.de/DarkVoice-THA336i...QQcmdZViewItem
This one looks with more confidence.

 

[echo1]

Ok I am awaiting with anticipation.I am holding off all purchases except the tube sockets.

 

[phergus_25]

Fitz's DV and W5000 combo is some of the best synergy that I haevv heard. Im not going to give away his upgrades and all, but I will tell you taht it is awsome.

 

[Fitz]

Since it may take me a while to get even a couple paragraphs written in-between what I'm doing right now, I'll start off with some pictures:














And here's the box containing all of the leftover parts:

 

[Fitz]

Okay, so the obligatory pictures are out of the way, now let's move on to the mods. I'm not going to go into detail about every little component changed, but I'll cover the main stuff. Also, I am highly critical of many parts of the design here, and may mention extreme differences, so please don't take it as negative traits of the amp itself. I'd rather just state my opinions and the differences in 'normal' descriptors, rather than half the post being "slightly", "somewhat", "a little", etc.

- - -

What started as a simple mod to reduce the 60Hz hum caused by the AC heaters on certain tubes, is the cause of all of this. Because I was using cheap components I had on stock to do the original "Fitz mod", I took it in and out more than once, unsure whether it was negatively affecting the SQ in other ways. To put an end to constantly soldering and desoldering, I drilled and filed a slot in Darkvoice's front panel to accomodate a DPDT switch, which I used to enable/disable the mod. There was a fairly big volume difference between it being on or off, and the changes in hum level on certain tubes made it difficult to compare, so I still didn't get anywhere with determining the effects. I decided I'd eventually replace the mod with high quality components, and repurpose the switch for something else, and left it at that.

Or at least that's what I told myself.

When I added the W5000s to my system, some of the Darkvoice's limitations with low-impedance extremely-sensitive headphones became apparent. The W5000s were actually a really good set of headphones to use during the modding process, because of how many noise artifacts (hiss, hum, RFI, etc) they can easily reveal in your signal chain, that nothing else shows. The biggest problem was the fact that I had only a few degrees of the volume control I could use before it went from too quiet to too loud. I could live with it at the time, but I knew I would need to do something to get more control over the volume.

Another problem I discovered was the lowest registers of bass were rolled off and lacking in impact, even with tubes that should give plenty of kick. Unfortunately, the original Darkvoice models had less output capacitance than the current production models, and it proved to be just too small for the 40 ohm W5000s. I'm still of the opinion that the Darkvoice should be using more output capacitance, but there's no way they can add anymore film caps inside and at the price-point (in China, our price is much higher than MSRP), it wouldn't be economical for them to use audio-grade electrolytics. I actually didn't even notice this for a while, going to show just how much of a basshead I am. I don't remember why, but I had the W5000s hooked up to my M3, and noticed a lot more bass than I was hearing before, and comparing back and forth confirmed that there was some rolloff on the Darkvoice.

And the final major promptor for me to do the modding was the tube sockets. The sockets they use are regular cheap run-of-the-mill tube sockets, which just don't grip tightly and evenly enough for the large output tube. With some tubes, especially used ones with groves already worn into the pins, getting them to sit correctly in the socket without periodically cutting out can be tricky. It wasn't a problem for the stock tubes, or the majority of tubes I own, but it was enough to warrant them being changed since I had other modding plans.

I was originally going to just do these three mods (volume pot, output caps, and tube sockets), and change the wiring to using stranded teflon SPC so I could easily relocate components and wiring without having to creatively bend and cut the existing solid core wiring every time. I don't know who I was talking to at the time, but at some point I randomly came up with the idea to just replace all the main components in it "for the hell of it". I was only half-serious at the time, but the idea grew on me, and then I started making notes of part values, and where to source good components for it...

 

[SLCanhead]

All I can say is WOW!

Oustanding looking...it sounds the inside went through quite a transformation, too (pics!?!)

I can't wait to hear your thoughts on the sound!

Great job!!!

 

[Fitz]

It took me a while to decide on specific parts and suppliers for all of the 1st stage mods, which at the time were supposed to be the only mods I was going to do. While the parts were filtering in, I went ahead and stripped out all of the components inside the Darkvoice, so I could start planning how to put the new ones in and make it all fit. It took a little while to get far with this, between finding time to work on it, and waiting for the parts to arrive so I could do it in the proper order. Multiple times along the way, and even up to just a week ago, I was coming up with new changes, revisions, and additions. I probably spent a bit too much on shipping making so many orders, but every time I didn't anticipate any more changes, and I didn't want to make everybody wait in limbo while I did the "neverending mod". I actually spent countless hours working in the evenings this week just to make sure I would have it ready for you guys. I think I put the last parts in late Friday evening.

So I guess you want to know what the hell I did to my poor Darkvoice, don't you? Well here's the gist of it:


Volume Potentiometer:

I found that the Darkvoice is using a 100K linear pot by default, which is the reason why it seems to reach it's usable limit at just 9'o'clock. With replaygained FLAC files (e.g. quieter), and the W5000s, I had a usable range of 1 "hour" on the volume knob. They could've added a couple resistors to make it behave more like an audio pot, but for some reason didn't. I replaced the stock volume pot and mounting PCB with an Alps RK27, the so-called "Blue Velvet", which was harder to find in 100K. There simply isn't room to put a good stepped potentiometer in there, and I prefer the minute control of a continous volume control anyways, so I stuck with the Alps. When all is said and done with this and the other mods (that reduce volume to some extent), I have a primary range of about 9'o'clock to 3'o'clock, with most of the time spend around 12'o'clock. The much more gradual volume change is an extreme improvement in usability,


Cathode Bypass (AKA the original "Fitz mod"):

This stayed exactly the same as my original mod, save for using some Nichicon KZ "Muse" caps instead of the cheap Nichicons I had on there before. It makes tuberolling painless without having to worry about any super-microphonic tubes picking up hum from the AC heater supply.


Resistors:

I replaced all of the large resistors with Ohmite wirewound power resistors, and the smaller ones with Vishay/Dale RN series mil-spec resistors. Why? Well it would've been difficult to recycle all of the stock resistors. The stock power resistors had a really cheap coating that flaked off if you looked at it. And the Vishay/Dales are just simply the "cool" DIY resistors.


Tube Sockets:

I've already expressed my dislike of the stock tube sockets used, on a purely mechanical basis. Rather than replace them with similar cheap sockets, I decided to go fancy and get a pair of teflon sockets with 6-pronged gold-plated pin grips, that're bolted down to the socket without any wiggling at all. Way more expensive than normal tube sockets, but they do exactly what I wanted, and tubes slide in and out smoothly without any repeated adjusting after insertion.


Power Supply:

There wasn't a significant reason for me to replace the power supply capacitors other than they went along for the ride while I was doing all the other mods. I left the transformer and bridge rectifier alone, just to avoid having to mess with the mains supply anywhere. Me and 120VAC have a bad history and don't always get along, so I stuck to dealing with it after it was DC. The new Nichicon caps do look nice though, showing a mostly black surface with most of the labeling hidden.


Output Capacitors:

Ahh, part of the original plan. After running the numbers several times, doing some simulations, and reading up on other tube amps, I came to the audiophile-dreading conclusion: I needed to put electrolytics in the signal path. There was no way to get enough film caps in the Darkvoice chassis to achieve what I wanted. I settled on using some Nichicon KZ "Muse" capacitors with a Solen tin foil bypass across them. Since I take audiophiles seriously more often than I should, part of me was dreading how it would sound when I had it all hooked up. Let's just say... there wasn't a damn thing wrong with it.


Crossfeed:

Some love it, some hate it. I happen to be of the former category. I decided to use the switch I cut into the panel as a control for crossfeed, and add one of my favourite tweaks to the system. I used Solen tin foil capacitors and Vishay/Dale RN series resistors for the crossfeed, all epoxied and folded up in a nice little point-to-point bundle between the switch and the volume control. Probably the hardest thing I had to do in the entire Darkvoice, due to me underestimating the size of the caps and how much space I would have (I based most of my measurements off the stock Darkvoice, neglecting that many replacements and additions would take up more space and thus affect the other mods). I settled on the switch to toggle between off and high crossfeed, using the modified Linkwitz design by Chu Moy. I never got a huge improvement with the wide-open K501s in the past, but with the W5000s, the difference is phenominal. With many (not just older) recordings, it makes the sound much more transparent, and takes away the feeling of pressure on your ear if an instrument is playing mostly or entirely in one channel.


Headphone Jack:

This is one of the parts that quite literally arrived at the last minute. I decided to incorporate a groundloop breaker into my Darkvoice, using a resistor and capacitor. The only problem is I had to use a headphone jack with a long nylon bushing to not directly connect the two grounds at the front panel. I completely missed the page in my Mouser catalog for the Neutrik jacks that would work, so ordered a Switchcraft jack from avcable.com. Tuesday I got a call that it was out of stock, and even the one that was the normal length was out of stock too, so I figured this mod would simply have to wait to be completed. But I talked with Mike at avcable.com some, and the next day they got the shorter one in stock so he went ahead and shipped that out to me with the promise that he'd ship me the longer one if it didn't work. It showed up Friday afternoon, and with some creative work with a dremel and razor knife, managed to make it sit further forward on the chassis so that it would stick out enough so the W5000's metal plug wouldn't short the signal ground to the chassis. I got it to fit with quite literally about a third of a millimeter clearance all around between the plug and chassis, and couldn't get it to wiggle close enough to short. Whew!

Headphone Jack continued:

I was still a little concerned about the electrolytics being hooked up to the output, so I added fuses in line with the headphone jack, to protect my W5000s if one of those caps ever goes bad and shorts out. I bought various values, but am using just 63mA ones right now, which are big enough because they didn't even flinch when I turned the volume knob way past "too loud to bear" (with the headphones off of course). And I compared them to just bare metal jumpers in the fuse holders, with no audible difference. I also added a pair of 75 ohm resistors in series with the output, similar to the idea behind the various adapter cables that add impedance to headphones. It gives me more range on the volume control, but otherwise I don't notice any major sonic differences. I think the other mods already took the Darkvoice to the point that this "trick" doesn't have much effect anymore.


Front Panel:

The main secret that I had to keep from you guys to leave a little bit of suspense. I went back and forth on whether I wanted to do this or just, and just said screw it and ordered it one day. It turned out, really, really nice. Way better than I had expected by all means. Any marks you see on the front of it in the pictures are shadows from the light bouncing off debris on my desk, because the panel is immaculate. They've also improved the edges drastically from the pictures I've seen before.