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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
klinerm OP
80 posts
 
Has anyone tried replacing the 6922's in the Steelhead with NOS (1960's) Siemens CCa's?
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.
klinerm OP
80 posts
 
What ever happened to the days when you could just walk into a store and buy a stereo?

I've purchased 2 1962 S/H CCa's and 4 Bendix 6900's for the Steelhead. I'll post my impressions when they get here. I'm also going to try the TungSol's - it'll be neat if they actually sound as good or better than the Bendix's, for way less money.
rx8man's avatar
rx8man
1,481 posts
 
My friend would be very interested to hear your results, he's trying a quad of TungSols and a pair of Orange Globes soon after his Steelhead breaks in.
klinerm OP
80 posts
 
Well, I believe I'm finally nearing the end of the road in tube rolling everything I own.

ARC Ref 2 Mk II:
1 Gold Lion 5AR4
1 RCA black plate 6L6GC

ARC Ref 300 monoblocks:
8 Gold Lion KT-88's per side
original 3 Sovtek 6AS7G's per side (actually sound much better than NOS RCA's which I tried)

Manley Steelhead:
2 Siemens old version CCa's
4 Bendix 6900's

I tried Tung-Sol 5687's first in the Manley - the Bendix seem less "punchy" than the Tung Sols, but a little more accurate and extended. I'm still not sure if I prefer the CCa's over Mullard E88CC in the 6922 position - CCa's seem more accurate, but I think the Mullard is "sweeter." It's going to take some dedicated listening to get this sorted out.

I'm also playing with subbing power tubes (one per side at a time)in the monoblocks. Have just replaced one Gold Lion with a GE 6550A - noticeably brighter and more forward, which is kind of nice, but I already miss that MOV "ultimate smoothness." I'm ready to try subbing a Tung Sol 6550, a Svetlana Cryo-Valve, and maybe some others, to see what kind of effects they produce.
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