Valve Tweaks

Warning – danger Will Robinson!

This page was posted when I was still resident of Audiofoolsville via Chickasaw Falls.  The only proper valve tweak is this:


I am not a valve nut.  Solid state amplifiers are clearly superior in every way.  This page simply relates to some valve gear that I suffered with for a long time, but which have since been decommissioned or otherwise relegated to the junkpile.

These brass “tube anchors” were recommended for pre-amps.  I used heat transfer paste to conduct heat to them more efficiently.  Otherwise there would be an insulative air gap due to the imperfect roundness of the mating surfaces.  They greatly increase the effective mass of the valves to ensure that they won’t microphone.  The large surface area dissipates heat better than if the valves were “naked” too, so they last longer.

These 1960’s Tung-Sol 6GK5s (I think manufactured by Sylvania or RCA) have been in use in these anchors for about 10 years and still tested as new on my Sencore tester.  The green wires in the photo connect the anchors to the chassis to conduct any charge to ground.  They don’t form a loop.

Downside:  Longer warm-up time.

Great for line stages but not suitable for output valves.

For cooling output valves, there is another way:

These are black coated copper with very fine louvres (hard to see in the photo) and act by conduction and natural convection.   I won’t mention the brand name because the same people push a lot of pseudo-scientific bull (allegedly cryogenically treated valves for example) and if these coolers were used as recommended they would cause your valves to burn out pretty quickly.  They came with absurd “socks” which were cut from lengths of braided Kevlar tubing which were intended to fit between the coolers and the valves to “improve” thermal efficiency – yeah just like fibreglass roof insulation batts keep your room cool in winter – not!  Anyway I threw them in the garbage and used something that would actually conduct heat rather than blanket it –  computer CPU-to-heatsink thermal paste (used by computer over-clockers) called Silver Ice (or something like that) smeared onto the inside faces between each fin.  Also, they were supplied with just a pair of very cheap and thin low quality O-rings which I replaced with three fatter high temperature-rated ones.  The copper is very thin and fragile and three O-rings press them agaist the glass more evenly than two.

Those SED “Winged-C” EL34s (real Svetlana) have been in use for about 5 years so far with the coolers fitted and still pass emission quality and grid leakage tests as new.  These things throw off a lot of heat, but have no impact whatsoever on sound quality other than preserving it.

Also good for line stages and power amp input stages are these old IERC valve shields:

They come in different sizes.  Here they are installed on the input and phase splitter stages of a C-J power amp.  In old valve radios (or whetever they were intended for) there would have been studs at the valve sockets to receive the bottom clips.  Here they just sit in the 1 inch cover plate holes to form an annular chimney around the glass.  There is a metal insert (just visible in the front right one) with a multitude of spring fingers to centre the valves.  The metal tubes shield the valves from external interference.  I can’t say I hear a sonic benefit, but the valves certainly last a long time in them.



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