The New Stereo Single Ended 300B Power Amplifier - Part 2

 Hi!

In part 1 about the new Stereo Power amp in tower chassis, I showed the initial construction steps. Here photos of the finished amplifier.

It contains the entire amplifier including power supply in a single chassis 305*305mm, 400 mm high (plus height of tubes and feet.

The amp is configured for 8 Ohm speakers. Driver tubes are 6SN7 with both halves in parallel to get lower impedance. The drivers are transformer coupled to the output. Rectification is done with a bridge of 6AX4 damper diodes.

It already arrived in its new home where it will be used as part of a multi amplifier system together with 801A drive 300B monos.

So a matching color scheme was used to fit with the amps which were already in place.

Best regards

Thomas

Stereo Single Ended 45 amplifier

 Hi!

below some photos of a recently finished 45 amp.

It is a stereo amplifier with the power supply integrated.

This represents my entry level in amplification with the 45 tube.

Tube rectification with two 6AX4 TV damper tubes. A pair of 6N7 as driver tubes is interstage transformer coupled to the output tubes.

All transformers and chokes, except the main power transformer reside inside the chassis.

The two trim pots between the output tubes are hum buckers to minimise residual hum from the AC heated 45s.

This enables a hum free operation except on extremely sensitive speakers for which I would recommend the DC heated version of the 45 amps. On my 98dB speakers no hum whatsoever was audible.

Best regards

Thomas

The New 6CB5A Amplifiers

 Hi!

Last month I showed the initial construction steps of the new 6CB5A amps. In the meantime they are finished.

The amplifiers are constructed in tower style with dark wooden enclosures.

The amps are laid out as mirror images of each other.

The tube complement consists of a 6N7 driving a single ended 6CB5A wired in triode and a full ave bridge of 4 6AX4 diodes.

This yields 8W of glorious single ended power. Output taps are available for 4, 8 and 16 Ohm speakers.

Here a photo of the naked amp without the enclosures showing the vertical assembly technique:

The amps will now test run for a few days before they are shipped to their new owner.

Best regards

Thomas

Making of 6CB5A Mono Amplifiers - Part 1

 Hi!

I just started assembly of 2 single ended 6CB5A amplifiers and will share the construction process.

Readers of my blog will know that I have a long history with the 6CB5A tube and always proposed it as an interesting alternative to the more mainstream tubes.

I have built numerous versions of this amplifier which uses a 6N7 as driver and a rectifier bridge with 6AX4 TV Dampers.

This time it is a fully fleshed out pair of mono blocks built in the floor standing tower style chassis, as used in recent amplifiers like the last Stereo 300B amp I built.

Once the bare metal plates arrive the assembly can begin. Here we see the 2 top plates which are mirrored to each other this time, and all the bits and pieces needed for the internals:

Mounting the tube sockets and some initial wiring:

The top plate with all parts mounted and wired:

The next level below the top plate carries the interstage and output transformers and some capacitors:

Below that another capacitor bank and filter chokes:

And on the bottom the mains power transformer and another 2 chokes:

All the sub assemblies of one channel:

Completion of the amps will continue when some missing parts arrive. Stay tuned for part 2 which will show the final steps of assembly and finished amplifiers.

Best regards

Thomas

The 2A3 Mono Amplifiers

 Hi!

In the last post I showed the making of the 2A3 amplifiers. Here photos of the finished set.

Each amplifier has an outboard power supply. Here we see one channel, amplifier and PSU:

4 chassis in total:

The power supply uses 4 TV Dampers in a full wave bridge configuration.

On these photos 6AX4 are plugged in.

Any compatible type can be used, for example 6DQ4, 6DA4, 6W4, and many others.

The power amp uses a 6N7 as driver tube which is interstage transformer coupled to the 2A3 output tube.

Of course all types of 6N7 tubes can be used, for example the 6N7G in shoulder type glass:

Or the 6N7GT, with straight glass bulb, here an RCA with smoked glass:

Or a Sylvania with clear glass:

Here a Tung-Sol with blacked glass:

Also the metal shell 6N7 is useable, here a Ken-Rad:

And as a bonus 6J5 can be used as well without any modifications. Here a Sylvania with metal base:

The 6J5 will give about 3dB less gain compared to the 6N7.

This set delivers about 3.5 single ended Watts per channel.

This amp uses DC filament supplies for the 2A3 for absolute hum free operation even on the most sensitive speakers.

If you are interested in such a set of amps or any other, send me an email.

Best regards

Thomas