Making of a 801A / 211 amplifier, Part 1: Layout

Hi!

As already mentioned in previous posts, several single ended 211 amplifiers are planned. The first one is a variation of an amplifier which I already built several years ago, but with some improvements. It will use ELROG ER211 output tubes and a 801A as driver. So it will be an all-DHT amplifier with throated tungsten filament triodes throughout. This first post shows the planning of the layout.

Tango X10S output transformers and NC20 interstage transformers will be used. Oil capacitors throughout and extensive passive filtering of all voltages with chokes, including the filaments.  Due to the size and amount of components this dictates splitting up into mono blocks with separate power supplies. So 4 chassis in total. I would have preferred to even use separate PSU chassis for plate supply and filament supply. But the person who requested the amp insisted on only 4 chassis. The photo above shows the main components which have to fit to the amplifier chassis.

I like to place the components which should go onto the top of the chassis on the floor and move them around until a good layout emerges:

Besides the tubes themselves, the Tango transformers should not be hidden and shown on the top plate. I have some of the oil caps varnished in a beautiful metallic effect white, so they go on top as well.

This leaves the 4 chokes and two more capacitors which will be placed inside the chassis. Each tube gets a separate B+ and filament smoothing choke. Once the placement of components has been decided upon, the layout for the metal plate can be done:

The power supply will be a bit more difficult since it uses more heavy components:

Three power transformers. My newly developed mains transformer for 211 or 845 amps and separate filament transformers for the 211 and 801A. These have been described in a post about my new mains transformers. In addition 4 B+ chokes, 2 each for the 211 and 801A plate supplies and 2 filament chokes, one for each tube. In addition some smoothing caps. These are only the big components. There is some more stuff like Schottky diodes ans caps for the filament supplies as well as some resistors. And of course the rectifier tubes.

Arranging everything such that it fits into the anticipated chassis size was difficult. Finally the decision was made to place all power transformers on top along with the rectifier tubes:

Separate covers for each transformer. The transformer covers are described in a previous post here.

The rectifiers placed in the front so that they are well visible. The arrangement of the covers leaves some room behind the high voltage transformer for the connectors:

The layout of the metal plate for the power supply:

The assembly steps will be shown next. Stay tuned!


Best regards

Thomas

Cool Links : www.scheu-analog.de

Hi!

I am often asked about the analogue front end I am using. After the European Triode Festival (ETF) I stayed for another day in Berlin and visited the manufacturer of my turntables: Scheu Analog

The picture above shows the main page of their web site : scheu-analog.de This gives a nice overview of all their products.

In October I had the pleasure to meet Ulla Scheu at the Cool Gales Bath Audio Fest where we demoed our equipment together. Ulla continued to run the business after the tragic death of her husband Thomas Scheu who founded the company. She maintained the legacy of her husband and further established the brand which is well known throughout the world in the audio community. I met a warm hearted woman in Ulla who is passionate about her products. During the event in Bath we agreed to meet up again soon. So I took the opportunity while I was in Berlin and visited her company.


Upon entering the workshop I saw many objects of beauty either in the assembly or testing stage or in preparation for shipment. Here a Cello Classic, the entry level turntable:

A Scheu Diamond with a base made from slate,being prepared for shipment:

The storage room has rows and rows of shelves with parts waiting to be used for one of Ulla's music making machines:

Of course there are also shelves full of records in the listening room:

In the listening room there is a picture showing Ulla with the musician Katie Melua:

Katie is using a Scheu turntable. She has good taste!

One of the work desks at which motor units are assembled:

Note the cloth gloves which are always in reach to handle the motor units with shiny chrome finish.

I got my first Scheu turntable almost 15 years ago when the brand was only known to insiders and the turntables were sold as kits. That turntable has been continuously in use since then. I took to several events for demos and moved it around a lot. It is still playing robustly and sounds like when it was new. That's what I admire about the Scheu products, their robustness and longevity. This holds true as well for the second turntable which I got about 8 or 9 years ago, the Premier Mk2. In the meantime The product line is considerable enhanced and not only contains several lines of turntables but also three tonearms and a range of cartridges which are made for Scheu by Benz Micro.
Ulla brought an awesome pink coloured Diamond to the event in Bath, which I couldn't get off my mind since then. So I had to get one and while I stayed in Berlin we discussed the details of my pink Diamond. While I visited a friend in Berlin, I had the chance to listen to some Shellac recordings which caught my interest (this will be covered in another story). So my new turntable will have to have two tonearm bases one for a tonearm equipped with a stereo cartridge and the other for a mono cartridge for shellacs. Ulla also committed to make a custom motor unit which will allow 78rpm which is needed for shellac playback besides the usual 45 and 33 1/3.

Some photos of a pink Diamond:

The base with the platter taken off:

The bearing:

I can't wait to get my third Scheu turntable which will be used in my workshop.

It has been a great experience to finally visit the creator of my turntables. Thanks a lot to Ulla for the hospitality and for showing her company.

Best regards

Thomas

Tube of the Month: The 211 (revisited)

Hi!

The 211 / VT4C was already covered extensively in the Tube of the Month of July last year. Judging by the clicks that post received and still receives, it is by far the most popular post of the Tube of the Month series. Therefore this tube deserves a revisit, especially since there is now a newly manufactured 211 of at least equal quality as the NOS tubes. The ELROG ER211.

For information about the company Elrog, please read my visit report. Since my visit there I became affiliated with the company and I am selling their products. I also have some 211 amplifiers in the making which will use this tube. I already wrote a report about the sound of these tubes here and also posted some user feedback here.

There are some reports floating around on the net about reliability issues with Elrog tubes. These had occurred with early prototypes which have been handed to a few companies. Some of these early prototypes leaked out onto the market and are occasionally being offered. These early tubes can be identified by their slimmer glass which has about the same diameter as the base. This caused some thermal issues. It also took a while to get the degassing process under control. These prototypes have never been intended to be given into end users hands.

These early problems have been fully resolved and the tubes are in stable production in their final version since earlier this year. You can easily spot a legit Elrog tube by the glass which is bulging over the base:

Besides the standard version the tubes are now also available with silver wiring in the base. These are identified by the red dot between the pins:

Each tube carries a unique serial number which is embossed on a small metal plate inside the glass:

Since I don't have a dud tube of this type for dissecting, Dr. Schaffernicht of Elrog was so kind to send some parts to show how the tube is constructed.

The glass enclosures are cut farm raw tubes and as initial step one end is formed like this:

This is the assembly of filament and grid:

A close up of the bottom part:

The filament hook:

Connection of the outer ends of the filament:

Welding of an electrode to the pin which goes through the glass bottom:

Glass bottom :

A close up of the filament:

The grid:

The graphite plate:

A comparison between General Electric 211 / VT4C and ELROG ER211:

Close up showing the bases and details of internal construction:

In the Elrog tube the electrode is mounted close to the base while it is closer to the top in the GE. This results in different heat distribution. The Elrog gets hotter at the base. But a well constructed amplifier is able to cope with this heat distribution.


The tops:

Clearly the Elrog is not a mere copy of the General Electric but a complete new development of it's own. Which it also shows through it's exceptional sound quality.

Several amplifiers which will use these tubes are in the making. Both with directly heated driver stages. One of them using a 801A as driver and the other will use a ER211 as driver. Stay tuned for updates about these amps.

Until end of this year, readers of my blog can get the tubes at a special year's end price. Contact me to get a quote. My contact details can be found under the link Impressum / Contact at the top left of this site.

Best regards

Thomas