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Tube rolling ARC amps & Steelhead

A while back I decided to try tubes. I have had an ARC Ref 2 Mk II preamp for about 2 years, a pair of ARC Ref 300 Mk II monoblocks for about 1 year, and a Manley Steelhead for 3 months. They sounded great, but it never occurred to me until recently that they could sound better - I always assumed that the manufacturers knew best when they put the stock tubes in.

My speakers are Acoustat Spectra 66 full-range electrostats, and, of course, I wanted more bass. After some investigation, I replaced the stock Sovtek 6550's in the monoblocks (8 per channel) with CryoValve 6550C's (from TubeDepot). The improvement in bass was nothing short of dramatic, and I much preferred them to the stock tubes. Nonetheless, the midrange and treble seemed to be lagging behind. After some more investigation into tube replacement options, I replaced the stock 5AR4 rectifier in the Ref 2 Mk II with a Genalex Gold Lion 5AR4, let the amps warm up a couple of hours, and then listened. I was dumbfounded at the change in sound. There was no "good bass" or "good midrange", everything just fell together with remarkable imaging and coherence, and that was with CD's and the tuner! All from changing ONE tube! I then replaced the stock 6922's in the Manly Steelhead with Mullard E88C's (following the advice of another A-gon member), put on an album, and and watched the bar further raised beyond my wildest expectations. All the sound was in beautiful coherence, rock-stable imaging, perfect balance of frequencies, not a touch of harshness, enjoyable at every volume level, like Neil Young was sitting there in the room pouring out his heart to anyone who would listen. I had a friend with me who has heard my system many times before, and he independently remarked "I can't believe it, everything sounds PERFECT!"

My question is - is this a unique experience, or have others found NOS or other tubes to make such an significant difference? I can certainly see why manufacturers don't include scarce tubes with their products, but it still amazes me that the choice of tube can affect the sound so profoundly. I would be interested to hear if others have had similar experiences.

Other equipment:
VPI Scout / Benz Ruby
Levinson 390S
Luxman T12
klinerm

Showing 5 responses by cjfrbw

cjfrbw
148 posts
 
I have tried rolling several different brands of 6dj8 and 6922 variants. The Steelhead can be improved a lot with a good NOS tube. My current favorite is the Amperex orange globe 6dj8 (with splatter shield).
Because the 7044 tubes are cathode follower buffer, I didn't think that they would make much difference. I was disturbed by reports on Audio Asylum that the GE 7044 were extremely microphonic. I tried some D getter 5867 black plate tung sol tubes. Wonder of wonders, it did improve things even more. Better drive, slam and detail, better audibility of lyrics. The steelhead went from being very quiet to dead quiet. I don't like to gush because that gets old, the same old terminology used to death, but it is surprising to hear improvements like this in something that is already so darned good.
Makes me wonder what the Bendix 6900's might sound like, but I don't know if I want to spend $400 or $500 to find out. Some opinions think the tung sol's sound better than the expensive Bendix tubes.
cjfrbw
148 posts
 
Yes, the Steelhead is good stuff. Using the tung sol 5687s is like giving it a steroid boost. If the stock Steelhead with the sovteks and the GE 7044s is like a breath of pure mountain air, then the Steelhead with orange globe 6dj8 and tung sol 5687 d getter is the sonic equivalent of a double fudge sundae. No more solid state pretense, just exotic and refined tube sound like a do-no-wrong SET amp.
The tubes are not that expensive, either.
cjfrbw
148 posts
 
Hi, Rx8man,

I don't know about those tubes, no experience. I have heard that some older sovteks are much better than the current kind used in a lot of componenets. If they are not expensive, it is always worth a roll.
I like the Amperexes best. Orange Globe Amperex 6dj8's (the kind with a splatter shield, some variants don't have splatter shields) have a very nice earthy midrange that I really like combined with sweet highs. Orange Globes are excellent in that transition zone from the lower midrange to bass in dynamic material. Amperex white labels (bugle boy types) have very spacious imaging and nice highs, but they tend to have less overall body than the orange globes. White Label A getters and orange label A getter Amperexes are about half way between the standard orange label and the white labels in sound, a nice mix.. Mullards that I have heard have nice midrange, but not as sweet on the highs as the Amperex tubes.
Ediswan tubes are very clear and balanced, but are rare and expensive, they are more like Siemens and Telefunken types.
cjfrbw
148 posts
 
Some more try-outs.

I tried some raytheon triple mica 7044 and rca triple mica 7044. These are also excellent, great drive, body and clarity. I would call these "siemens-like", and seem to show off the Steelhead best as a "sound microscope" but with reasonable warmth. They seem to have the biggest soundstage and the most immediate imaging.

GE five star 5687 are the smoothest and warmest sounding. A little less drive and punch, but possibly ideal for solid state amps. I did not prefer them to the Tung Sol 5687 or the Raytheon/RCA triple mica 7044 in my system.

I still prefer the Tung Sol 5687 overall in my system. They don't deliver the extreme clarity of the raytheons/RCAs, but they have a response characteristic that I crave in tubed sound. They are punchy and sumptuous. Silky highs cascading down into a limpid pool of midrange and bass transitions.

The only other tubes that might be useful to try in the 7044 slots would probably be the Bendix 6900 (expensive and overkill?) or the Amperex 7119 ( too much mu compared to transconductance?) but I am satisfied with the great improved sound from these other inexpensive tubes, so somebody else can try those.

Just as a caveat, I have the Steelhead hooked up as a line stage now feeding a tubed vintage Luxman crossover feeding VTL 450 sig's in triode to the MRT of Apogee speakers and Bel Canto 2002's to the Low Panel of the Apogees. The crossover uses the somewhat cool sounding telefunken 12au7's, which might be the final arbiter of sound before the amplification stage.
However, when I hook up the Yamaha RX-Z9 with it's solid state amplification and using passive crossovers to the Apogee's, the sound dries out a little but the general impressions remain quite similar.
I also tried putting Ediswan CV2492's back into the 6922 slot in place of the orange globe amperex 6dj8. I would just call that a different variation of wonderful sound, the Ediswan having the edge in body and balance, the amperex the edge in warmth and sweetness.
cjfrbw
148 posts
 
I currently use the tung sol 5687's and like them for their warmth and punch. I think tube rolling is going to depend on your system. I have tried the raytheon triple mica 7044's, and they are also better than the stock GE 7044, which can sound soft and bland. You should try some of these, they don't cost that much, and for the 6922
I don't think there are any bad or best choices, but most decent NOS tubes will sound better than the stock soviet 6922's and some improvement is also possible by changing the 7044's. I would like to try the bendix tubes, but have generally heard that they do better in circuits that bring them closer to their higher 600v rating than in circuits that keep them at 250v or 300v, and they are very expensive. Amperex, Mullard and Ediswan tubes are all good choices for the 6922 slot.
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