Please call us for the latest inventory, and we can often outsource these tubes for you. This s dated military vintage redbase is a very good, very rare dual triode. Rugged 4 support posts, 10, hr. The real vintage RCA red full octal base deal, built like a tank, awesome tube! These have the JAN military labels and all have passed mil spec, they may outlast you and your equipment. These are great matched pairs!

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This month I am presenting a high mu dual triode. The 6SL7. The 6SL7 could be regarded as the high mu companion to the medium mu 6SN7. Like the 6SN7 it became quite popular during the ies among audio amplifier builders. It went through a similar popularity cycle as the 6SN7. After being overused and often in applications for which it is not well suited, it went a bit of fashion. It shares the same octal base and pinout with the 6SN7. To some tube rollers this made it seem compatible and it was often tried as an alternative to get more gain.

While the 6SL7 might work in some circuits designed for the 6SN7 and provide a bit higher gain, it really is a different animal and should only be used in circuits which are designed for it. The heater operates at the same 6. As mentioned above it is a high mu triode with an amplification factor of 70 vs the 20 of the 6SN7. But that high amplification factor comes at a cost. The 6SL7 has a plate resistance of 44kOhms which is more than 6 times higher than the rp of the 6SN7.

It also operates at a lower current, typically around 2ma. For complete technical data please see the data sheet. This high plate resistance which comes with a rather low transconductance probably is the reason why it lost popularity a bit when higher transconductance tubes became more fashionable. But this does not make it a bad tube. For example as first stage in a phono preamplifier.

Correctly implemented the 6SL7 gives a nice warm and smooth sound. As it does for example in my Octal Preamplifier Mk1. The 6SL7 has also been used as driver tube for small triodes like the 45 or 71A. With both sections wired in parallel to halve the plate resistance this can work well and offer the possibility to build a simple two stage amplifier.

I prefer it in small signal applications like phono stages. But it can still be found at reasonable prices if you look around a bit.

The tube has been made by all the major manufacturers and NOS specimens are still around in large numbers. These have a nice low loss micanol base. Another version which only has a different color printing on the base.

But that is unjustified. They can perform just as well as the full base versions if the tube is healthy and measures well. Like the 6SN7, the 6SL7 has an improved industrial 4 digit version, the This is probably the most sought after variant. Simply stunning looking with the ox blood coloured base. A lot of extra bracing was added to improve shock resistance.

This was done to make the tube usable in aircraft and space applications. Wether this is of any advantage in audio is of course questionable. The certainly looks good though.


valvula 6sl7 5691 novinhas

NOS Siemens appeared suddenly out of nowhere, in massive quantities, in crispy new boxes, that look like made yesterday. The printing is so clear and bright, also that looks like printed on it just yesterday too. Not with all tunes, but sure with 6SL7, the plate system inside, unveils the manufacturer. These Siemens are are displayed with this text: "must have been made by Sylvania, for Siemens". Oh, yes


6SL7 Tubes


FLUKE 190 062 PDF


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