I’ve just picked up four 6cs7 tubes for my Leben CS-600 amplifier. The Leben CS-600, often called the tube roller’s dream, uses four of these in the driver stage. A wide range of output tubes is possible – mine came with 6L6GC (equivalent to 5881 tubes from the Russian brand Sovtek).
Images of 6cs7 vacuum tubes tested on a Hickok 600A
The Sylvania tubes in the image gallery above have been measured on a Hickok 600A tube tester by a professional in Canada. NOS (New Old Stock) values are in the range of 2200/4500, the lowest number for triode 1 and the higher for triode 2. These specific tubes have been measured according to American standards in microohms.
Note that the tubes should not measure identically for each side. Each triode differs in value, which is in contrast to most driver / preamp tubes, for example the ECC82 and ECC81 tubes, where each triode has the same value, and generally speaking, the closer values, the better.
Tube 1 – 2275/4700;
Tube 2 – 2325/4850;
Tube 3 – 2350/4900;
Tube 4 – 2325/4800;
This is considered extremely well-matched.
Use in other other audio products
The image gallery show-cased above showcases a set of perfectly matched tubes, commonly referred to as a ‘quad,’ produced by the American manufacturer Sylvania. The text on the boxes contain the words ‘Electronic tube’, Made in the USA, the brand name Sylvania and, lastly, the characteristic logo consisting of af Z-like ‘S’.
Originally designed for use in televisions and radios, the 6cs7 tube sees limited use in audio applications, but Leben’s chief designer and owner, Mr. Taku Hyodo, who is often referred as one of the eight best amplifier designers in Japan, has always had a fondness for it, presumably because of its high degree of linearity and robust design. In general, Leben favour American tubes.
In addition to being used in the Leben CS-600 and the Leben 600P, 6cs7 tubes have been used in the SRA-3S headphone by Stax, the General Electrics RIAA UPX-003A from the beginning of the 70s and the 5B7 Bassman guitar amplifier from American producer Fender in addition to a range of do-it-yourselves designs.
A tube few and far between
The supply of NOS (New Old Stock) 6cs7 tubes has become quickly depleted the last couple of years. The American reseller of vacuum tubes known as “The Tube Store” has addressed this issue on their website, providing a notice stating that their supply is nearly depleted, and as a result they are no longer able to offer matched pairs or quads of these tubes:
“Note to Leben [CS-600] amplifier owners, we do not have matched sets at this time. These tubes are very difficult to find. Only odds and ends of various brands available,” The Tube Store, March, 2023.
Difference between the Leben CS-600 and the CS-600X
Facing the listener both the CS-600 and the CS-600X feature four driver tubes in a row. In a row behind are the four driver tubes.
In the Leben CS-600 amplifier, all four driver tubes are of the this type. In the CS-600X design, there are two 12AU7A tubes and two 12BH7A tubes. From left to right, the distribution is: 12AU7A; 12HB7A; 12AU7A and 12BH7A.
The different positions in the Leben CS-600 according to Yoshi Hontani
I’ve corresponded with Yoshi Hontani, Leben’s Japanese distributor and general contact facing the English-speaking world, who described the role of the different tubes position as:
Two left tubes are for left channel; and two right tubes are for right channel, which gives us:
Tube 1 (from left) is first stage for left channel;
Tube 2 (from left) is second stage for left channel;
Tube 3 (from left) is first stage for right channel;
Tube 4 (from left) is second stage for right channel;
The selection of driver tubes for the CS-600X is a lot, lot larger, offering both the option of NOS vacuum tubes and modern productions
Many people, though, seem to prefer the sonic signature of the CS-600 to the CS-600X.
Another difference is the type of damper tube used in the amplifier design. The CS-600 uses a C6J3 tube, while the CS-600X uses a 6DN3.
Also see: 6X5GT and 12AT7 tubes in the Leben RS-30EQ RIAA
Precision Machines from Leben Audio / Hi-Fi Company
Output tubes in the Leben CS-600 & CS-600X
The output stage is configurable through two switches that each have two positions. Through different settings, the amplifier is compatible with a wide selection of tubes – some of which are famous ones, for example the 6L6/5881 and the EL34 of which some NOS (New Old Stock) productions often are labeled ‘the holy grail’ of audio reproduction.
There is a wide selection of tubes currently in production from different manufacturers. In addition to the 6L6/5881 and EL34, the CS-600’s are compatible with KT77, 6L6GB, 350B, KT66, KT88 and 6550A tubes. Some of the tubes are considerable larger than for example the 6L6/5881 & EL34, so the lid cannot be on when operating those.
In that way, the design accommodates both tube collectors who were lucky (or clever) to buy NOS tubes when the prices were at a completely different level from what they are now for the best tubes from the best brands.
People who are either not interested in spending too much on tubes or are perfectly content with the tubes the amplifiers comes with directly from the Leben factory.
How many watts do the CS-600 & CS-600X deliverWhen using EL34 tubes the both amplifiiers are listed at 28 watts, and with 6L6GC 32 watts.
.
C6J3 damper tube used in Leben CS-600
The Leben CS-600 and the Leben CS-600X feature so-called damper tubes in their designs. The CS-600 utilizes a C6J3 tube, and the CS-600X uses a ‘6CM3’.The
Substitutes for the 6cs7 tube: ECC81 or ECC82?
The last 6cs7 tubes were, to my knowledge, produced in the 80’s, which stands in contrast to for example ECC81 (12AT7) and ECC82 12AU7) tubes which are currently produced due to a larger market as they are used in a wide range of RIAA’s, preamplifiers and amplifiers.
The use of NOS 6cs7 tube traced back to the first amplifier Leben produced and brought to the market, the Leben RS35-A (1995)m´, and then on to the Leben CS-600P.
The modernly produced ECC81 & ECC82 produced by JJ Electronics (Slovakian-based), TAD, Tung-Sol and Mullard are not equivalent to and / or replaceable with the 6cs7.
Leben Hi-Fi Stereo Company (by many also referred to as Leben Audio Company) have been fond of 6cs7 tubes from the beginning. This tube was used in Leben’s first amplifier produced under own name, that is the Leben RS35-A (produced from 1995), so in that regard very little has changed in close to 25 years.
Image showing the amplifier’s 6CJ3 damper tube
6cs7 datasheets from Tung-Sol, RCA & General Electric
Tung-Sol ~ 6CS7
RCA (Radio Corporation of America) ~ 6CS7
General Electric ~ 6CS7
6cs7 vacuum tubes for sale near me
As mentioned previously, 6cs7 tubes are becoming increasingly difficult to source. But you might be able to get some from the following suppliers, most of which are US based. The only European seller Tube Amp Doctor currently only stocks two General Electric New Old Stock.
Another option would be to visit shops that offer repairs of vintage equipment. You could also get lucky at a yard sale if you’re in the US or the UK.
You migt be lucky to find 6cs7 tubes here:
- Tube Amp Doctor
- Tube World Express
- eBay (various listing both US & Europe)
- The Tube Store
- Acme Tube Supply
- Parts Connexion
- Tubes Unlimited
- VintElec
- RF Parts
- Reverb (various US listings)
- TubeDepot
- Viva Tubes
- World Tube Company
- Altana Tubes
- Bangy Bang
- Vacuum Tube Superstore
- NessTone Tube Sales
Tubes incoming: GE Canada, black plate, O-getter, Marconi
Matched quad of GE Canada, black plate, O-getter marked Marconi from the early 60s are on their way to me from Canada. Some of the tubes are rebranded as ‘Admiral’, but the construction of all the tubes is the same. They’ve been tested by a professional operator on a Hickok 600A tube tester with the following scores:
Tube 1 – 2300 4850
Tube 2 – 2325 4800
Tube 3 – 2275 4750
Tube 4 – 2350 4800
Where New Old Stock value 2200/4500.
Further reading on circuitry of the CS-600 & 600P
Grzegorz Makarewicz, who runs the trioda.com blog, has written a comprehensive analysis of the Leben CS-600P model, which includes lots of pictures of the amplifier seen from the back, the front and the bottom, in addition to a full complete diagram that visually shows circuitry. The CS-600P’s driver stage should be around 95% identical to the CS-600’s.
A short history of Leben Hi-Fi Company
Leben Hi-Fi Stereo Company, established in 1995, is a Japanese manufacturer of tube preamplifiers, integrated tube amplifiers, preamplifiers and, so far, a single RIAA. The brand’s name, Lebel, is a loan-word from German translating into the intransitive verbal forms ‘to live’ or ‘to be alive’ or ‘to exist’. Newer models containt the tag line ‘A motion sound’ adding a further feeling of experiencing music in a Haruki Murakami-like atmosphere.
Mr. Taku Hyodo, an experienced audio engineer having worked for Luxman in the past, a collector of new old stock vacuum tubes, for example 3CSS, 12AT7, E288CC and 6L6GC and a music lover with a professional background playing the guitar, is the founder of Leben Hi Fi Stereo Company.
At 60, Mr. Taku Hyodo left Luxman in 1979 to establish hos own company, “Kouri Denki Corporation”, which produced a range of electronic components. He kept designing and constructing amplifiers under the ‘KFH’ brand name – primarily custom-made products for café, bars and restaurants.
Mr. Taku Hyodo’s first commercial product to see a broader market was the ‘Triode 33’ power amplifier released in 1991 followed by the RS-35A 6L6GC tube-based power amplifier under the Leben brand in 1995.
Leben released the RS-28C preamplifier (equipped with E288CC tubes) in 1998.
To cater to a wider range of audiophiles, Leben subsequently introduced a series of more affordable amplifiers: the CS-200, CS-250, CS-300, and CS-300X, released in 2001, 2002, 2003, and 2005, respectively. These amplifiers allowed a broader audience to experience the unique sound quality associated with Leben products. In 2005, Leben released the CS-600 integrated amplifier, which is the focal point of this blog post, featuring the 6CS7 tube. The CS-600 was succeeded by the CS-600X in 2019, with most of the design remaining the same, except for the type of driver tubes.
Point to point wired tube amplifiers is rarely seen nowadays, as it required a skillset few modern workers have in a today’s world marked by mass production.
Leben is one of few amplifier manufacturers that feature amplifier designs of this type thanks to a highly skilled number of employees working in the company’s quarters in Nishi-Koya in Amagasi City.
Leben tube amplifiers are amongst the most popular brand of tube amplifiers known for their high design quality, quality of components, workmanship and their get the design right from start-approach – combined with a very reasonable pricing.
They are known for their exceptional design quality, top-notch components, meticulous workmanship, and their commitment to getting the design right from the beginning, Leben is widely recognized as a popular and reputable brand in the industry. Additionally, these amplifiers are reasonably priced, making them an attractive choice for customers even though priced has seen a noticably increase in recent years concurrent with general lebels of inflation.
Looking for free images of vacuum tubes?
I am currently tasked with documenting and archiving various vacuum tubes for the Swiss Radiomuseum and Wikipedia. The best images will be made available on Pbase, where they can be freely utilized under a creative commons license for non-commercial purposes.
Access the image collection here: Images of Vacuum Tubes | Pbase Gallery
If you’re looking for images of other vacuum tubes or higher-resolution images, feel free to reach out and we’ll probably be able to work something out.