Steve really does outfit everyone with a terrific set of stock tubes. I have become a big fan of the stock 6N1P's in the CSP2+. The Genelax 6922 is a great tube for the input position. I have enjoyed the USAF-596's a lot. So far the Philips are showing really well. I have had them playing for about 12 hours now. I got them from Upscale Audio as new tubes. So far so good for sound. I suspect they are going to be a bit airier on the top end. I am using a small Def Tech Supercube 3 for a sub with the Decware DM945's. For speaker listening, I have plenty of bottom end...
I'll put the HD800's on tonight and see if the Philips can keep up on the bottom with the 596's.
I thought the Philips 5R4GYS was detailed but gutless. Almost no bass. It was my least favorite rectifier in the Decware amps.
Let me cut-and-paste my personal notes from this year...
Now presenting my personal "Rectifier Rolling Roundup" (using CSP2+ with HD800):
Note: All tubes ranked WORST to BEST. All opinions are my own 2c so no refunds or guarantees final sale only yada yada. I broke them up into tiers which represented notable jumps in sound quality.
And now... the RRR:
Tier one: Not ready for prime time
Philips 5R4GYS - Very detailed but too sterile/cerebral. Weak bass. Blech.
Shuguang (stock tube) 5U4G - Unremarkable by any measure. Truly generic tube.
RCA brown base 5R4GY - Lush midrange but bass is too strong, sloppy, and bloated.
Tier two: The steely trio
Sylvania 5Y3GT red lettering - Excellent sparkly detail up top, but suffers from that Philips-esque steely/lack of lushness/soft bass thing.
Tung Sol 5Y3GT - Similar to the Sylvania with slightly better bass but again too flat and sterile. Voices lack the magic. Sort of "hi fi" sounding.
Bendix 6106 - Similar to the above, but a bit brighter up top. Pass.
Tier three: Competent, but unremarkable
RCA 5U4G black base - Decently lush and top-to-bottom tubey-ness, but... meh.
Sylvania 5U4G - Similar to the RCA 5U4G above. A bit darker.
Tung Sol 5U4G - The best of the cheap 5U4G's. Better balanced than the Sylvania, but still unmemorable. Keep looking.
***you are now crossing the DMZ Line of Recommendation***
Tier four: I could live with that... if I had to
Valve Art 274B cryo - Lively soundstage and finally some tubey magic. Bass is a bit light, but not sterile. A good & cheap starter tube, but why stop here?
Mazda 5Y3GB mini coke bottle - Neat-o heater & bottle design. A bit better definition than the Valve Art.
Sylvania 5Y3G mini coke bottle - Similar to the Mazda, although more delicate and distant. Resembles a "polite USAF-596".
Brimar 5R4GY - A little soft on top, but the midrange is truly gorgeous. Bass really pumps. This one is a bit of a midrange specialist, but it certainly creates magic there.
USAF-596 - Very detailed, top to bottom. Also looks cool. Overall excellent. However... there is a subtle lifelessness to it that I do not like. It's slight... but it's there. Enough to make me keep looking. But I think most folks would be happy to stop here and enjoy the ride.
Tier five: The ones I kept
RCA 5Y3GT - Amazingly cheap yet it ROCKS w/solid bass presence and tone. It lacks that final n'th of detail compared to some of the others, but it's hardly a dealbreaker. Lots of personality here. This tube was featured at the Austin 2013 meet & it was very well received.
EML 5U4G meshplate - My favorite. Yeah, it's the most expensive by far, but it beats all the rest in this lineup. Maximum detail and gobs of lush evocative tube magic. The only ding would be that the bass doesn't quite slam with as much authority as the RCA... but it isn't deficient by any means. Especially when paired with a good visceral signal tube up front like the Mullard old shield 1960's/70's E88CC. Ultimately, the EML's finesse is what carries the day. It just gives me the most of what I dig about tube amps. Just be sure to let it warm up for about 30 minutes for maximum effect.