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Sunday, January 16, 2022

Tube of the Month : The 6AW8A


Over the years I kept buying tubes which I found interesting based on their tube data but which are completely unknown in the audio world. One of these is the 6AW8A.

The 6AW8A has a triode and a pentode section. The triode section caught my attention due to the technical parameters which seemed interesting for audio use.

The 6AW8A is a 9 pin miniature tube. The pinout is shown on the left. It has a 6,3V heater which needs 0,6A. It is suitable for series connected heating in a 600mA heater string as well as parallel heating. There is also a version called 8AW8A which has a 8,4V/450mA heater. The 6AW8A has a high mu triode section and a sharp cut off pentode. The characteristics of the triode section are quite interesting. It has a high amplification factor of 70, similar to that of a 6SL7 but at a much lower plate resistance of only 17500 Ohms.  That's what made me buy a bunch of 6AW8A and put them into the box 'interesting tubes to be checked for use in audio later'. Well the check later turned out to be more than 20 years now while the 6AW8A had been lingering in tube drawers. I don't know if I well ever get to actually use the 6AW8A in a project but at last I pulled it out for a closer look and a tube of the month post. For the complete technical specs see the General Electric data sheet. As always let's have a look at the plate curves, starting with the triode section:

And here the curves taken with a tracer:

The pentode section:

The pentode triode wired:

A very interesting tube indeed and definitely deserves more attention.

Here we have a General Electric 6AW8A.


Here the three grids of the pentode are nicely visible:

Sylvania 6AW8A:

A very interesting tube. Both sections should be well useable for audio. Maybe a phono stage?

Best regards


Saturday, January 8, 2022

First Amps of 2022 : Silver TM300B Mono Blocks


The first pair of amps of 2022 got finished. A pair of Monoblocks using the TM300B as output tube and the ER801A as driver.

The amplifiers are fully transformer coupled using silver transformers throughout.

In this case Lundahl input transformers and Tribute interstage and output transformers.

A peek to the internals. First the underside of the top plate which carries a pair of filament chokes which feed the DHTs the capacitors which are most critical to the signal path and the input transformer

On the next level below is the module which carries the Tribute transformers, both silver wound on finemet cores.

And on the bottom the power supply module.

After completion of final testing these amps will be delivered to their new owner.

If you are interested in getting your own set of TM300B amps or amps with other output tubes, drop me a message.

Best regards


Friday, December 31, 2021

Happy New Year!


Another year comes to its end.

A year filled with music, amplifier building and tubes.

This year Deutsche Elektronenröhren Manufaktur GmbH introduced two new tubes.

An ELROG ER5U4G for which we received many requests. And since it is basically the same tube with different base we also launched an ER5Z3.

New tube developments will not end here. We already have two new variants in development due to be launched next year.

More about these when they are ready for release.

Also many new projects in the pipe on the amplifier building side. Here a peek into work in progress for amps and preamps to be shipped next year.

It seems 2022 will be the year of the 300B since I already have 5 pairs of 300B mono blocks to be delivered next year. The first a pair with all silver transformers due to be delivered in January. The interest in the 300B amps seems to be mainly fuelled by the option to equip them with the TM300B.

This set of all out 300B mono blocks will be adequately driven by a Silver 10Y differential line stage.

So the soldering iron will not get any rest next year.

Today we have fantastic weather here in Lindau.

So let me finish this post with some impressions from my home town.

Many thanks to all of you and wish your families and yourselves

Frohes neues Jahr
Happy New Year
Bonne Année
Feliz año nuevo