Dual Channel Field Coil Power Supply

Hi!

Here some photos of a custom field coil power supply.

It has two independent supplies. Neutrik PowerCon connectors for the outputs.

Each of the two supplies can be independently adjusted in small steps via the switch bank. From about 10V to almost 16V.

The power supply under test with dummy resistors:

Best regards

Thomas

The D3a LCR Phono ... Back in Black

Hi!

Here some photos of a newly finished LCR Phono Stage with the D3a tubes.

Finished with silver metal plates in black chassis and with black transformer covers and capacitors.

The same as the previously finished one but in black.

Except this one is partially equipped with silver transformers.

4 of the 8 signal transformers are silver wound.

The power supply uses 4 6AX4 tubes in a full wave bridge rectifier configuration.

Best regards

Thomas

Tube of the Month : The 12AY7

Hi!

This month's tube is a miniature (noval) twin triode for low level applications, the 12AY7.

I have stashed away some 12AY7 many years ago and used it in one of my very early phono stage builds. But later stuck with my other favourite tubes and these collected dust in the drawer. But since it is an interesting tube it deserves it's own post.

As mentioned above the 12AY7 was specifically developed for low noise performance in applications working at low levels, which makes it an interesting candidate for the first stage in phono or microphone preamplifiers. The General Electric data sheet lists an operating point specifically for such low level applications. The tube has a 9 pin noval base. As the prefix '12' indicates the heater voltage is 12.6V and only needs 150mA. The heater has a center tap which is connected to pin 9. This enables parallel connection of the heater halves which results in a 6.3V/300mA heater. The 12AY7 has an amplification factor of 44 which comes with a plate resistance of 25kOhm. Here the plate curve diagram from the data sheet:

And actual curves taken from a sample:

Let's start with a 12AY7 made by RCA:

Some views from different angles:

Next we have a Tung-Sol:

And lastly Sylvania:

The RCA 12AY7 shows a nice glow in operation.

Best regards

Thomas

10Y Line Preamplifier

Hi!

Here some photos of the first new gear built in 2020.

A 10Y Linestage in a very unique color combination.

Gold anodised metal plates, metallic graphite grey transformer covers and capacitors. Wood chassis in a special veneer called silver carbon effect maple.

Center mounted toggle on off switch instead of the rotary switch which I normally use.

No power indicator LED. The glow of the ELROG ER801A is sufficient to show that power is turned on.

I got a small batch of wooden chassis made in this veneer. If you want a line or phono stage in this wood, please contact me.

Best regards

Thomas