I just signed onto the Darkvoice drop the other day. I bought it as an amp for Sennheiser HD700 headphones primarily. I also own the Massdrop Hifiman 4xx and AudioTechnica ATH M50 headphones.
I'm using both my LGV30 phone or Fiio X5 iii as sources for music, paired with Fiio A5 or Montblanc amps to drive all these headphones. So far, in order of preference , I like the HE4xx the best, followed by the M50, and then the HD700. Im a bit new to headfi. I wouldn't call myself an audiophile, but I do enjoy the differences in performance that higher end audio components offer. BTW, I've got a Massdrop O2 amp on the way as I'm typing this. Anyway, I've read a lot about how the 650's love the DV. Anyone have experience with the Sennheiser HD700 and a DV? What tubes are you using? Why?
Btw, I mostly listen to classic and hard rock/metal. Then, it's a mix of Symphonic Orchestra music, jazz, country, and light opera along the lines of Andrea Bocelli and Sarah Brightman, but definitely not limited to them. So, if you have HD700 cans, let me know what tubes you like best. TIA.
HeinsbeansHi. A few comments suggestions in response to your questions.
Since you find the DV dark with the 650, it's really important that you pick "brighter" or more neutral tubes and avoid "tubey" tubes that are warmer. Also keep in mind that it takes some trial and error to find the right "synergy" between the power and driver tubes (but that's the fun of playing with tubes,)....,ok, some recommendations:
1. If you don't like the 7236, I would skip the 5998 as they are quite similar. The 5998 will likely be too dark for your tastes (it's a "tubey" sounding tube).
2. For a power tube, I'd go with a 6as7g. The rca jan-6as7g is very good and inexpensive. A Tung Sol or Chatham 6as7g is better than the RCA, but is more expensive ($60 +).
3. I would definitely get a new driver tube. The GE is ok, but not great. Of the tubes you mentioned, I would recommend the Sylvania vt231 or Sylvania 6sn7gw (which is an amazing tube but expect to pay minimum of $90. There are several versions..go for black base short bottle). I also recommend the Raytheon vt231 since you are looking for a brighter tube. I think the other tube you meant is the Ken-Rad vt231. Great tube, but probably not what you want (it's another "tubey," tube and will likely be too dark for you. On the less expensive end, you may want to consider a Sylvania 6sn7gta (50's vintage). Very good for the price.
4. I strongly recommend making some basic mods to your 650. It's easy (no soldering) and completely lifts the "veil" you are describing. When I first got the darkvoice, I had unmodded 650's and like you I found it way too dark (in fact I almost returned the DV because of this). After some minor mods, i couldn't believe the difference. I've read descriptions of a properly modded 650 as a cross between a 650 and an 800. I agree with that description. The great thing about the mods is they are reversible and incremental allowing you to tweak the sound to your tastes. I removed the foam behind the drivers, added dynamat, and did the "quarter" mod. This link gives step by step instructions for doing these and other mods : http://www.superbestaudiofriends.org/index.php?threads/sennheiser-hd650-love-appreciation-thread.44/.
Hope this helps.
HeinsbeansI would keep the stock cable..I'm not a big believer in cables (to a point). The rca cable is probably okay but you might see a minor improvement with better interconnects (more of a longevity issue in my opinion). I think you have the right idea to invest in tubes.
All the tubes you ask about seem fine, although all are pricey. If you are willing to be patient, you can get a decent 5998 for about $50 to $60 (US). The 6sn7w's are not the 6sn7w's I was talking about. It gets confusing, but you want a 6sn7w without a "chrome dome". In other words clear glass.
This thread on headfi is indispensable for proper identification of 6sn7 type tubes (it's worth the time reading through it, especially to avoid spending $100 on a $30 tube. https://www.head-fi.org/threads/the-6sn7-identification-guide.209782/
Also, brentjessee.com is one of the best places to get guaranteed great tubes, but you'll pay premium prices. If you are already willing to spend $100, you may want to go with him. He's also very helpful and responsive (and honest) if you have questions.