# The Leben RS30-EQ RIAA, 6X5GT & ECC81 Tubes *April 21, 2025 — Kasper Bergholt* In addition to a Leben tube amplifier, I’m also satisfied owner of Leben’s only RIAA so far, the Leben RS-30EQ, which both looks and sounds stunningly well. Goldring 2400 cartridge mounted on a Pro-Ject X2 tonearm, which feeds into the Leben RS30-EQ RIAA. Pentax SMC-A 50mm lens on Pentax *istD S. The RS-30EQ RIAA is based on a circuit including a single 6X5GT rectifier tube and two 12AT7s Jan Philips tubes. The European designation for the 12AT7 is ECC81. Jan CHS 6X5XT/G – U.S. Army / U.S. Navy. Acceptance date June 1945. Produced by Sylvania Electric Products for the US Navy & Army. Co-designated 6X5GT/G & VT-126B. Nikon D3 & Carl Zeiss Milvus 50mm. 6X5GT rectifier tubes Beautiful vintage 6X5GT rectifier tube from RCA (Radio Corporation of America). For use in for example Lebens’ RS30-EQ RIAA. The image shows a vintage 6X5GT rectifier tube from the American manufacturer RCA, Radio Corporation of America. The 6X5GT is used in a rectifier role in a range of high-end audio designs, for example Leben and  Audio Note UK (not to be confused with Japanese Audio Note Kondo, which I briefly introduce in this blogpost on the a Sunbuck Kondo Audio Note KSL-M7 clone. Leben RS30-EQ Riaa with ECC81 & 6X5GT tubes. The ECC81s are from Telefunken and was an upgrade I made from the Electro Harmonix ECC81 the RIAA came with. The 6X5GT is the Hytron rectifier tube the RIAA came with originally. Substituting 6X5GT tubes with Bendix 5852  tubes – not a good idea! In different fora (and by certain vendors) it’s suggested to use a Bendix 5852 as drop-in replacement for the 6X5 or 6X5GT, and, in addition, that the Bendix 5852 should be the holy grail of tube rectification (e.g. in Audio Note DACs). A word of warning though: The Bendix 5852 draws 1.2 ampere, whereas the 6X5GT draws half of that (0.6 ampere). This means that the Bendix 5852 presumably will sound different (and better to some), but might be too heavy a load for the equipment’s transformer. Ambience shot of Leben tube amplifier showing of four EL34 tubes in the front and three transformers behind the EL34 tubes. 12AT7Ts/ECC81s in the RS30-EQ I was of the impression that Jan Philips 12AT7 (ECC81) tubes were installed from the factory in my Leben RIAA, which I bought about a year ago. I detected a general over-leanness in my setup (Leben CS-600, Leben RS-30EQ RIAA, Pro-Ject X2 Carbon, Goldring 2400 cartridge & silver cables from Yannis Tomé Analogue Audio Cables). Goldring 2400 cartrdige hovering over acrylic platter on a Pro-Ject X2 Carbon turntable. I thought the output tubes in the amplifier were to blame, or the silver cables or the Goldring 2400, which made me start looking for a set of NOS EL34 tubes instead of the 6L6/5881 Sovtek tubes the amplifier came with from the factory. Also see: Copenhagen artist & photographer, Kasper Bergholt Tube box for vintage Telefunken ECC81 (US designation: 12AT7)  tube for use in  my Leben RS-30EQ. Comparative listening: the Leben RIAA vs Marantz 65CD-II To calibrate my listening experience, I got a cheap Marantz CD65II CD player on eBay. After a couple of hours warm-up time it sounds astonishingly good despite being, or perhaps because of, being 35 years old. I used the same interconnect cable (Gaia series) that I use for the RIAA, which leaves  three things to affect the sound: the tonearm cable, the cartridge and the Leben RS30-EQ itself. 12AT7 NOS (New Old Stock) tubes for use in Leben RS30-EQ Riaa. Two for use and one spare. Electro Harmonix 12AT7EH/ECC81 vs New Old Stock Leben has recently switched from Jan Philips military grade tubes to RFT Germany 12AT7 tubes in the RS30-EQ RIAA thought. But when I took off the cover to look at the tube compliments, they  were from modern Electro Harmonix (type: 12AT7-EH ) tubes made in Russia, and not NOS / vintage GE’s as I had expected. By all means fine tubes, I don’t know much about them, but definitely calls for some experiments. 12AT7EH tube from Russian manufacturer Electro-Harmonix. Present-day production in my Leben RS30-EQ (which I acquired around a year ago). I think this indicates that NOS/NIB tubes are getting scarcer and more expensive – especially if the setup requires a closely matched pair. On my wish & to-do list is trying New Old Stock Siemens Halske triple-mica tubes for the RIAA, as I’ve had good results with this producer in my old tube-based preamplifier (an Audio Note M1). JAN CHS 6X5GT/G from June 1945 6X5GT rectifier tubes in original boxes. Marked Jan CH ‘6X5GT/G VT-126B. Acceptance date 6-45. US Army. They are rarely seen in pairs with identical serial numbers. For use in for example the Leben RS-30EQ and some tube-based DACs from Audio Note UK. Tubes in the RS-28CX preamplifier with inbuilt RIAA In the Facebook Leben Hi-Fi group tubes are often debated as they have an influence on sound, some tubes in some positions more than others. Recently, there was a thread mentioning that Leben seems to have switched to newly produced tubes in the RS-28CX dedicated preamplifier. Sunlit corner of a Pro-Ject X2 turntable Instead of New Old Stock General Electric J.A.N 6CG7 tubes in the line stage, new tubes from Electro-Harmonix. The phono stage, that is identical as I understand it to the RS-28CX uses two ECC81/12AT7 tubes. Here there’s been some recent changes too, where Leben has changed from General Electric ECC81/12AT7 tubes to ones from the German produced RFT. I can recommend the group for anyone seeking advice on all things related to Leben range of products, and Leben’s distributor towards Western countries, distributor, Yoshi Hontani, participates occasionally. Four Telefunken ECC81 &¨¨ Siemens E81CC tubes for use in Leben RS30-EQ RIAA. Leben RS30-EQ specifications Tubes: JAN 12AT7A (General Electric) X 2. 6X5GT (General Electric).Gain: 23.5dBRIAA curve: less than+/-0.2%Input impedance: 47KohmMax input: 400mV (2Khz.)Output voltage: 175mVPower consumption: 17WWeight: 6 kilosDimensions: 340(W) x 140(H) x 240 (d) mm New Old Stock 6X5GT/G tube produced by Sylvania.