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Friday, January 28, 2022

Silver 10Y Differential Line Preamplifier


Here some photos of a recently finished all silver differential 10Y line stage.

This represents the very best I have to offer in terms of line level pre amplification.

A fully differential circuit with a total of 14 silver wound transformers and inductors.

This particular set is used to drive the recently shown silver TM300B mono amplifiers.

It shares the same circuit and parts with previously finished differential 10Y preamps.

As standard three balanced inputs are included each with its own set of silver input transformers. Each input can be configured for different gain. Each input can also be configured for use with RCA connectors. Standard is XLR.

More or less inputs are possible on request. Both XLR and RCA outputs are standard.

Best regards


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