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Sunday, April 26, 2015

Mercury Vapour Madness


I am getting quite a few requests for amps with power supplies using mercury vapour rectifiers lately. Like the recently shown Octal Preamp and 6CB5A power amp.

This time it is a set of power supplies which are meant to be used with SE 300B mono blocks. The amps itself still need to be built as I am waiting for some custom transformers for them. But the PSUs are already finished.

These use a set of 866A mercury vapour tubes.

The 866A is simply stunning with it's large bottle and intense blue glow.

Here is one power supply operating with a previously built 300B amp:

Another view:

The greenish tint in these pictures is due to he light conditions during night. In reality it is blue.

Top view of the PSU:

Front view:

The hybrid arrangement with the two 6AX4 in the rectifier bridge provides a slow warm up which can be nicely seen in this video clip:

The blue glow comes on gradually as the heaters of the 6AX4s warm up and the TV dampers start to conduct. Another video from a different angle:

And a video taken in total darkness:

A photo showing the hybrid bridge:

Close up to the 866A:

Best regards


Sunday, April 19, 2015

45 / 2A3 Mono Amplifiers


Here is a set of just finished Mono Blocks which can be used either with 45 or 2A3 as output tube. The driver is also selectable between 10Y and 45.

The amps share the same circuit and transformers as a previous set of similar amps. Just a different amplifier chassis layout as used in my most recent builds.

The wood is smoked eucalyptus which is a very dark brown, almost black. All transformer covers and oil capacitors are varnished in a graphite grey metallic tone.

The two amplifier chassis with 45 in the driver tube sockets:

Interstage and output transformers are Tango of which I still have some stock. The input transformer is the silver version of Lundahl LL7903 which I use in most of my all DHT amplifiers.

The power supply chassis:

Top view:

The amplifier chassis:

Top view:

These amplifiers reminded me again what a great tube the 45 is.

It simply is the queen of tone. Those who are blessed with efficient speakers should give this tube a listen. Especially in globe fashion.

I already described the sound of the different tube combinations here. So I won't go into that again.

The amp with a 10Y in the driver socket:

Besides the 10Y, a 801A can be used as driver as well.

2A3 as output tube:

45s are still available as NOS or good used tubes, despite many claims that the supply dries up. This tube has been produced in large quantities over decades and is still easy to find. Also in my experience they last quite long if run conservatively. The situation with 2A3 is a bit different. Bi-plate versions can be found rather easy, but the mono plates got very expensive and scarce.

So no excuse not to consider such an amp if speakers with a matching sensitivity are available.

Best regards


Tuesday, April 14, 2015

VinylSavor at the Munich High End Fair 2015


Time flies! The next High End show opens in a month in Munich, May 14 - 17. I will exhibit again with the same partners as last year, Wolf von Langa and PrimaryControl.

We will exhibit in the same room as last year: F231c / Atrium 4.

There will be different 300B amplifiers on demo using the Elrog ER300B tubes. Preamplifiers will be an updated version of the 10Y line stage and the latest LCR phono with EC8020 tubes.

See you in Munich!


Thursday, April 9, 2015

Tube of the Month : The E55L (revisited)


Since I used the E55L in a headphone amp recently, this is a good opportunity to have a closer look at the tube again. The first tube of the month post about the E55L did not show any photos of the internals, so it is time to revisit it.

Technical details of the tube have already been covered in the first post. So this one will just show photos.

Philips Miniwatt E55L:


Another Amperex:



For closer inspection of the internals I picked the Amperex with green letters. A close up before it is getting destroyed:

The glass removed:

Peeking into the side opening of the pate already gives an idea of the fine structures of the grids:

The top with the getter ring:

Side view:

A close up showing the pins going through the glass:

The plate removed from the system:

This leaves the remaining assembly exposed, cathode, control and screen grids and beam forming plate:

A close up to the rod which holds the screen grid:

The heater wire inside the cathode:

Heater wire partially pulled out:

Close up:

The heater:

Cathode and control grid:

The control grid wires are extremely fine and barely visible:

A human hair in comparison:

A close up shows what a marvellous piece of engineering the control grid structure is:

Cathode and control grid separated:

More views of the grid:

And lastly a few photos of glowing EL55s:

Best regards