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Friday, March 16, 2018

The 45 / 2A3 Single Ended Amplifier


I haven't built any of those since a while, here is a new version of a single ended stereo amplifier which can use either a 45 or 2A3.

The amplifier comes in two chassis, one for the amp itself and a separate power supply. Here the amplifier section:

It is interesting how the requests for landscape style chassis have increased lately.

Here a top view of the amp:

The selector switch for the output tubes is hidden in the corner between the tubes and the transformers. The output tubes are AC heated. Hum can be nulled through hum bucker pots. This particular build has both balanced and RCA inputs selectable by the switch between the driver tubes (6N7), alternatively the 6J5 can be used as driver without any mods. The use of the 6J5 results in about 3dB less gain.

The bias current of the output tubes is monitored through vintage panel meters.

Check out these beauties, vintage meters made by Weston in perfect condition, hard to find these days.

The complete set with power supply:

The amplifier is transformer coupled with Tango transformers. Balanced to SE conversion from the XLR inputs is done through Lundahl input transformers.

The power supply uses 4 TV Damper tubes in a full wave bridge arrangement. A trusted concept which is used in most of my amps and preamps.

Multiple choke / capacitor filter stages with oil caps throughout. No electrolytic caps or silicon in this amplifier.

Best regards


Friday, March 9, 2018

The 6AH4 Line Stage


Since I mostly write about the 10Y linestages (those are also requested more often) many are not aware that I also offer a smaller, single chassis linestage using indirectly heated tubes like the 6AH4.

Depending on the gain requirements this linestage can also be built with the 6J5 or 27.

This version has a slightly different design than the 6J5 linestage.

The tubes are prominently displayed at the front with all capacitors and the power transformer mounted on the top plate. The 6BY5 rectifier resides in the left corner at the back.

Here some impressions from the internals. The top plate with sockets and parts mounted and wired:

All chokes and the line output transformers reside on a separate plate, in this particular build there are also two input transformers to offer a set of XLR inputs.

The transformer volume controls are then directly mounted on the front plate by the volume control switch. Here the preamp powered up for the first time in the workshop system:

A compact solution for those who do not have the space for a 2 chassis preamp and it comes at about half the cost compared to the 10Y line.

Best regards


Monday, March 5, 2018

Some New Colours


Just received the metal plates for a D3a phono and 10Y linestage in some crazy new colours. Purple and orange.

These units will be shown at the High End show in Munich this year.

Best regards


Monday, February 26, 2018

The 46 drives 46 Amplifiers - Part 2


In part 1 about these new mono blocks I showed some initial assembly steps and gave a hint how the final amps will look like. In the meantime the pair is finished.

The set consists of two chassis, one per mono block.

Two stage, a 46 driving another 46 through an interstage transformer.

The 4 rectifiers in the back are a full wave bridge using 4 TV damper tubes into a choke filtered supply.

Here some more photos of the assembly process:

The top plate with all parts mounted and wired up on the underside shown above. Then the next level is mounted underneath:

And the final level contains the power transformers and DC filament supplies. Unfortunately I forgot to take a photo with the last module mounted since I was eager to finish and test the amp.

One of the amps in operation.

Now of course the question 'how do they sound?'

People who read my blog regularly know that I am reluctant to provide subjective sound descriptions. Especially of my own creations.

But these amps really surprised me. The previous, simpler builds of 46 amps were already stunning. But these are simply outstanding.

The 46 has a very special character which draws you into the music. It simply does everything right.

Sometimes more of a good thing can be too much, so the question was would a 46 drive 46 amp provide too much '46ness'?

These amps prove that the concept works. It brings everything to the next level. I can say with confidence that these are probably the best sounding amps I built so far, although they are not even using silver transformers as my other top of the line amps. But there is a caveat.

1.25w is all you get from a 46, yes just 1250 milliwatts.

With the right speakers those are the most glorious milliwatts.


Now the question is what would  an all silver version of these amps sound like?

Needless to say I am very happy how these turned out. Since these monos will be shipped to their owner soon, I already ordered the chassis materials for another pair for myself.

Best regards


Wednesday, February 21, 2018

The Octal Preamplifier


since I mostly write about my separate phono and linestages, many people are not aware that I also have a full function preamp in the offering which has a phono stage integrated. The Octal Preamplifier.

The Octal Preamp has a transformer coupled lien stage with auto former volume control. In this Mk2 version the linestage uses the 6AH4 triode.

The phono section is a LC coupled circuit with passive split RC RIAA.

6SC7 is used as input tube and 6N7 in the second stage.

Signal section and power supply are in separate chassis.

In this case the preamp is built in the classic landscape chassis but could be done in portrait stye as well.

A lower cost alternative to my D3A and 10Y combo.

Best regards