The Black 300B Mono Amplifiers - Part 2

 Hi!

The all black single ended 300B mono amplifiers are finished.

This set consists of 4 portrait style chassis.

Two mono blocks, each with outboard power supply.

The driver tube is an ELROG ER801A, old production 801A tubes can of course be used as well.

The output tube is ELROG ER300B which can be substituted by any other 300B tube.

The output tube is placed between interstage and output transformer for short signal wiring.

All signal transformers are silver wound on finemet cores, made for me by Tribute.

Of course both the driver and output tubes are DC heated for hum free operation and best sound. This is done by separate elaborate choke filtered filament supplies for each tube.

The power supplies use a bridge rectifier scheme with two 866A mercury vapour tubes, augmented by a pair of 6AX4 TV dampers for slow ramp up of the high voltage. 836 vacuum rectifiers can be used instead of the 866As as well.

The 866As have an eerie blue glow when in operation.

Together with the bright light from the thoriated tungsten filaments of the ELROG tubes this is quite a show.

Email me if you are interested in such an amplifier.

Best regards

Thomas

Stereo 300B Amplifier in Tower Chassis

Hi!

Here is a newly finished project. A new implementation of the Stereo 300B amp.

This is a similar implementation as the stereo 300B amp in portrait style chassis which served as the main amp at last years High End demo.

Like the portrait version it is split into 2 chassis.

I always prefer to go for a separate power supply rather than mono blocks.

This allows for a healthily over designed power supply rather than two wimpy ones which need to be sized to fit into the chassis with the amp.

Since the tower chassis offers more space this version received some upgrades compared to the portrait style amp.

It uses the same output transformers but larger interstage transformers.

The power supply uses a hybrid rectifier set up with two 836 and two 6AU4 tubes.

The driver tubes are 6SN7 as in the portrait version.

The large chassis allowed for a design with just the tubes on top and all other components inside.

For this version a special type of veneer was chosen.

It is called 'maple carbon effect'.

It makes a nice contrast with the gold coloured top plates.

The veneer has an almost silver like touch which is nicely picked up by using silver anodised handles.

The upgraded interstage transformers and beefier power supply improved the sound quality by a distinctive step over the smaller portrait style amp (which is already very good sounding).

Best regards

Thomas