It's been far too long since I've done some tube rolling, so I was delighted to hear from Sue & Richard at Sophia Electric that they wanted me to give their new Sophia Electric EL34-ST vacuum tubes a review for Positive Feedback.

I'm a real pushover for the ST bottle shape, I just love the way it looks, so the new Sophia Electric EL34-ST vacuum tubes really pushed my visual buttons!

I thought it would be fun to try the new Sophia Electric EL34-ST vacuum tubes in my Leben CS-600 integrated amplifier, which has been with me longer than any other amplifier I own.

The Leben CS-600 is just a silly good amplifier, and is definately an old friend at this point!

I decided I wanted to try my Leben CS-600 with my Altec A5 Voice of the Theatre loudspeakers that I just hot-rodded with Lefson resistors in the crossovers, in my audio-visual system.

I have been using my A5's with my vintage McIntosh MC225 stereo amplifier and Leben RS100U line stage (above), which is a really nicely matching combination of electronics with the A5's.

So I got busy and and unhooked the McIntosh MC225 stereo amplifier and Leben RS100U line stage,  set them aside, and then installed the Leben CS-600 integrated amplifier in my vintage Altec A5 Voice of the Theatre based AV system in their place (above).

I set the Leben CS-600 to its 16 Ohms setting for driving my 16 Ohm Altec A5's.

I'm using the Acoustic Revive Power Reference TripleC NCF AC power cord that's in for review to provide AC to the Leben CS-600 (far left in the photo above).

The interconnects from my Philips TV to the Leben CS-600 are Belden 8402 microphone cable interconnects with the shield connected at both ends, Yazaki-san style (far right in the photo above).

Speaker cables are Duelund DCA16GA tinned-copper cables with no terminations, and are connected nude to the CS-600.

For a source I'm using the new Oppo UDP-203 Ultra HD Blu-ray Disc Player that I got a while back.

For interconnects from the Oppo to the Leben CS-600 I'm using Duelund DCA16GA tinned-copper cables terminated with Gold Duelund RCA's that Chris at Parts ConneXion made for me to try.

By the way, the more I use the Duelund RCA's the more I'm liking everything about them, they're very nicely done and still work well with the narrow spacing on vintage gear, which is a requirement with my vintage tastes!

For connecting the Oppo to AC I'm using the superb Sablon Audio Quantum Gran Corona, which really is a sweet match to the Oppo!

Now a little more about the Leben CS-600. I fell in love with the Leben CS-600 integrated amplifier over ten years ago now when I wrote an article about it for 6Moons.

I ended up buying the review unit (the ultimate recommendation) and have been using it nearly every day in my AV system, where it has been reliably been an ongoing delight.

When the Altec A5 Voice of the Theatre loudspeakers displaced my Harbeth Super HL5's from my AV room, the Leben CS-600 & Harbeth's became my the system in my master bedroom.

Now the Leben CS-600 is back in my AV room, with the Altec A5's, so I can try it with the new Sophia Electric EL34-ST vacuum tubes.

You can use a bunch of different tubes in the Leben CS-600 because of its adjustable cathode resistor and plate voltage settings, but primarily it is intended to be used with 6L6GC's or EL34 tubes.

For those who are into tube rolling, I've posted a settings table for the different tubes you can use in the CS-600 here.

In addition to it's gorgeous exterior, the Leben CS-600 is able to hold its own against pretty much anything out there.

Jonathan Halpern (Tone Imports) has had huge success winning ‘best sound of show’ praise (1, 2) with his Leben CS-600 at a number of hi-fi shows, impressing such hardened audio writers as Stephen Mejias, John Atkinson, Robert Deutsch, John Marks, and Art Dudley, for example, while shaming much larger & more expensive systems with his David versus Goliath system approach.

What kind of vacuum tubes was Jonathan using in his Leben CS-600 that garnered such impressive praise? If you guessed it was EL34’s you’re exactly right, and that's what piqued my interest in giving the new Sophia Electric EL34-ST vacuum tubes a go in the CS-600.

I played the CS-600 with the 5881 tubes I've been using in it for a couple of albums, to get a feel for its performance with my Altec A5 Voice of the Theatre loudspeakers, before switching to the Sophia Electric EL34-ST vacuum tubes.

Oh, by the way, the tube complement in my CS-600 is as follows:

• Four National Electronics 5881 power tubes.
• A NOS General Electric 6Cj3/6DW4B 'dumper tube' (allows for a gradually increasing supply of high voltage (B-Voltage) to the output tubes on turn-on in order to protect them from damage and extend their life).
• Four NOS Sylvania twin-triode 6CS7's for the first-stage of amplification (my favorite NOS 6CS7, but getting hard to find).

I should point out that with the 5881 power tubes the CS-600 is good for 32 watts, and with EL34's 28 watts.

That's not a lot of power, but the CS-600 is able to effectively drive even less sensitive speakers like my Harbeth's quite easily, and with the sensitive Altec A5 Voice of the Theatre loudspeakers it's more than enough!

I powered down the CS-600, removed the 5881 tubes, flipped the cathode resistor & plate voltage switches to their EL34 settings, and installed the Sophia Electric EL34-ST vacuum tubes in the CS-600.

I powered back up the Leben CS-600 with the new complement of Sophia Electric EL34-ST tubes and let it warm up.

The Sophia Electric EL34-ST tubes are too tall to be able to put the top back on the CS-600, so it'll be going topless for a while.

The Sophia Electric EL34-ST vacuum tubes are the very last review in my review queue right now, so it'll be quite a while before their review for Positive Feedback will be ready, but that'll give me plenty of time to interview Richard about their construction and his inspiration for their design.

As I get some time on them and get a handle on how they're performing, I'll check in from time-to-time with an update on their performance in the Leben CS-600.

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As always, thanks for stopping by, and may the tone be with you!