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My experience tube rolling ARC LS5/II

I got my LS5/II on monday, and spent about 3 hours listening to it with its ARC Sovtek 6922s. I had already heard an LS5/III/Sovtek in my system when we did a big preamp shootout (which was handily won by my Croft Epoch V), and knew I did not like the Sovteks. I had also heard the difference Seimens E88ccs made in my LS15, and was itching to change the tubes. I find the Sovteks nasal, and the German tubes much more natural.

The 2 brands I've focusing in on are Amperex 6dj8/e88cc and Siemens E188cc/E88cc. Since this takes 10 tubes, I did not have enough of either type on hand as all my ebay purchases from last week had not arrived, so I threw in all I had, mixed, along with the Siemens e88cc from my PH3, and 1 single Amperex PQ. And right away the sound was dramatically improved. Going back to the Sovteks was brutal - the sound was now dull and gray.

The next day, 6 more Siemens arrived in the mail. I now had 10 siemens, plus about 6 Amperex 6dj8s. I was still not sure of the tube layout, and which the cathode follower was, so I kept moving tubes around.

I them tried an all Siemens layout. It was totally superb - very detailed, great bass, very detailed, lots of air, very tight.

The next day, I got hold of Leanard. So, the tube layout is as follows: top row - 2 cathode followers. middle row - 2nd gain stage; bottom row: 1st gain stage. 5 tubes in left are 1 channel, other 5 on right are 2nd channel. Within each half, left column is positive, right col is negative.

I then tried saving 2 siemens from use by changing out the cathode follower tubes, since they are supposed to be 'not that critical'. First tried the ARC 6922 EH, then tried 1986 6H23EV..no good - sound got flat. Tried 2 Amperex as CF. Bass went away..So, best tubes in the CF are going to be Siemems.

If anyone tells you the cathode followers don't matter, don't believe it. They had as much impact as tube changing in the first gain stage.

By now I had over 10 Amperex as well. I then tried an all Amperex layout. Nice midrange, but much less bass. This would be great in a limited LF system. Was surprised since a lot of people like Amperex.

Next, back to finetuning an all Siemens layout.

1st shot: Row 1 - Siemens E188cc (as an aside - left channel pair - thin rod getter holder; right ch pair - thicker getter holder. Need to figure out the difference between these e188ccs); 2nd row E88cc, CF E88cc.

As described above - very detailed, very tight sound. Amazing on drum skins, and things like cymbals and triangles. If anything, a bit too detailed. Live concerts don't have such precise imaging, soundstaging and treble.

It was 2am, and I called it a night, wondering if the CF impact was due to my being tired.

This evening:

Verify the CF has the impact I remembered. Its amazing how good the Siemens in the CF sound.

Swap row 1 and row 2 - ie Siemens e88cc first, then Siemes e188cc. CF were Siemens E88cc. The sound lost its magic and livliness. Duller, more recessed. Less bass too. Did not really work. I was surprised with this, since the archives suggest that the E188cc is supposed to be the darker tube.

Moved the E188cc back to row 1. Next decided to try Amperex 6dj8 A frames in row 2, with Siemens e88cc as the CF. Now, the midrange got pronounced, with a lot of detail from voices, but with a loss in image depth and treble clarity. Surprisingly, the bass held up. So the Amperex tubes were not a loss after all. But after a while, I could not get used to loss in treble quality.

Next up for row 2: Amperex Ecc88 with 1 thick bar and 0 getter (2 with grey pins, 2 with gold). These were much better than the A frame Amperex. Bass was good, midrange was amazing - I could hear detail in singers' inhalations. Treble and detail was less than the Siemens in row 2. But after spending time listening, I decided that the treble was pretty accurate, and the overall presentation was more involving and natural ie musical, vs the all Siemens being a bit distracting with its wow factor.

So, the final layout: Row 1: Siemens e188cc; Row 2: Amperex ecc88 (but not A getter); Row 3 cathode followers: Siemens E88cc.

Next step will be the make all the tubes in each row be of identical construction, especially the e188cc in the first row, since I have pairs of everything.

Samir.


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Topic - My experience tube rolling ARC LS5/II - Gofast 19:11:11 04/12/07 (6)


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