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Wednesday, July 28, 2021

D3a Phono and 10Y Line Stage.


The D3a phono and 10Y line stages are my best selling units. Earlier this month I showed the assembly steps of power supplies for such preamps. Here some photos of the completed units.

The line stage is finished with black anodised metal plates in teak wood.

The phono comes with gold anodised metal plates in smoked eucalyptus.

Drop me an email if you want me to build one of these or any other of my amp designs for you.

Best regards


Thursday, July 22, 2021

Making of 45 Drives 45 Mono Amps - Part 2


In the last post I showed the assembly process of the new 45 Drives 45 mono amps. Here is the finished pair.

Gold anodised metal plates in smoked eucalyptus chassis.

This confguration with a second 45 acting as input tube gives the full flory of the 45 tube.

A couple of days testing and then they will ship to their new owner.

Best regards


Thursday, July 15, 2021

Making of 45 Drives 45 Mono Amps - Part 1


A new pair of Single Ended 45 mono amps with 45 Driver is in the making.

The 45 which goes into the left socket serves as driver tube and is connected to the 45 on the right through an interstage transformer. The 4 sockets in the back are for 6AX4 TV damper tubes configured as a full ave bridge rectifier.

The top metal plates anodised in gold.

Sockets and some resistors added.

Filament chokes, critical capacitors and she input transformer are mounted directly to the top plate for short signal wiring.

The top part ready to be attached to the next level.

Next comes a sub plate which holds the transformers, some choked and capacitors.

Attaching the next level to the top part:

The power supplies (high voltage and filaments) are located on a sub plate which mounts at the bottom.

The amp is tested like this before it is inserted into the wooden enclosure.

Stay tuned for part 2 which will show the finished amps.

Best regards


Saturday, July 10, 2021

Tube of the Month : The 416D


After last months post about the 6EN4, let's continue with another rather uncommon tube this month. I present to you the 416D.

The 416D is a planar triode developed by Western Electric for very high frequency applications in the range of several GHz.

The 416D does not come in the common glass bulb but is housed in a shell composed of ceramic and metal. The metal parts of the housing also serve as connections to electrodes. There are 4 versions from 416A to 416D. The tube is an indirectly heated triode. It has a 6.3V heater which consumes 1.85A. The Western Electric data sheet of the 416B lists an amplification factor of 200 coupled with a transconductance of 50.000 micromhos. A candidate for a phono stage maybe if you dare to cope with the unusual base and shape and need to connect to the shell. I have never seen any suitable socket and connection accessories for this tube so you probably would have to make your own. But could be worth a try and I heard from some DIYers that they used this tube for auto applications.

The pin extending from the top connects to the plate. The upper metal ring is the grid connection and the major part  of the housing connects to the cathode which also connects to a base pin. The heater is powered through two of the base pins.

The datasheets I found do not show any plate curves, so I cooked up an adaptor to use it in an octal socket on the tube tracer. Here are the plate curves which have been taken using 0.5V steps on the grid.

Not exactly a linear tube but linearity is not of importance in high frequency applications. 

The 416D I have came wrapped in padding material packed in plain white boxes.

What an interesting tube. If you have used this and have some experience with it, please let me know.

Best regards


Friday, July 2, 2021

Peek into the Workshop : Preamp Power Supplies Assembly


I have been a bit lazy with posts recently. I'll try to show more in the next weeks. Here a peek into the workshop.

A phono stage and a line stage are in the process of being finished. Started with the power supplies.

The top plates with tube sockets and resistors mounted.

Next the power transformers and oil capacitors.

The heater and filament transformers are mounted on the bottom side:

Wiring up the transformers:

Adding the chokes:

Adding the caps for the heater and filament supplies.

Proper operation gets tested before the preamps go into the enclosure and front and back plates are mounted.

Finished PSUs:

Back sides:

Next the signal sections will be built.

Best regards