Tube of the Month : The 46 (revisited)

Hi!

As mentioned in the previous post about the recently built single ended amplifier, the 46 deserves more attention. So I selected it as tube of the month.

Since the 46 was already tube of the month way back in 2011, this is a revisit. That first post was a bit short and in the meantime there are a few more 46 tubes in my collection to show.

The 46 is called a dual grid power amplifier tube hence it has a 5 pin base. This is not to be confused with a tetrode since the 46 is only meant to be used as triode. Depending on how the second grid adjacent to the plate is connected, a triode with different parameters is obtained. By tying both grids together we get a triode with high amplification factor which is meant to be used as output triode in a Class B push pull stage. Two tubes in such a configuration deliver 10W output power. Such an amp design is shown in the RCA data sheet. Since the tubes would be operated near zero grid bias, such an output stage would require some significant driving power. Here the other operating mode of the tube comes into play. When the second grid is tied to the plate the resulting triode is very similar to a 45. As transformer coupled driver stage it can deliver 1.25 Watts into the grids of the output tubes.
Of course it can also be used as a single ended output stage this way. But the 1250 milliWatts is all you can get out of one. Even less than the flea power a 45 does provide, which can be pushed to deliver almost 2 Watts. But those 1250 mW are simply stunning. As I have written in the last post: The quality of the 46 is actually not really a secret. It has been repeatedly reported from different people that they prefer the 46 over the 45. I myself used the 46 almost 20 years ago and found it to be a great performer. But still it stayed below the radar of most amplifier builders. Maybe it is the extremely low power which prevented people from using it or the fact that it is not a 'real' triode with the two grids. But that is nonsense. Maybe it is the second grid which has something to do with the special sound of this tube. Many people are fond of tubes with mesh plates. It could be the combination of second grid and plate tied together which mimics some of the characteristics of a mesh plate. Or maybe it is simply the extremely low output power which means that an amp with this tube is almost always operated near the max and produces a pleasantly sounding amount of second harmonic distortion. Whatever the reason is, when you listen to this tube you will not worry about it and simply enjoy. After all it is a directly heated tube and when connected as Class A output triode it has nicely linear plate curves as can be seen in the data sheet curve diagrams and a photo of the screen shot of some actual curves taken with the tracer:

Let's have a look at some 46 tubes.

Here we have the ST shape variety made by Sylvania which is a bit larger in size than the 45.

Nice green leaf logo printed on the base.

National Union:

Three different varieties from this manufacturer:

Tung-Sol:

These, like almost all 46 tubes I saw, have an unusually large amount of getter in them. Almost covering the whole bulb up to the shoulder.

A Tung-Sol VT-63, the military designation of the 46:

Here we have a nice row of General Electric 46s:

Similarly large getter area as seen in other tubes:

Two different varieties:

Close up to the plate:

Raytheon:

The base:

View from the top:

Close Up showing the electrodes:

here a quite unusual 46 made in France by TSF:

These have less getter than the US-made tubes we saw above:

The tubes are branded 'Dario':

Some close ups:

And of course there were plenty 46 made by RCA:

The top:

Cunningham branded 46 made by RCA:

Some details:

Interesting detail in the photo above: The vertical grid support rods are of different metal between the two grids.

And finally some globe 46 tubes:

Interestingly the globe 46 don't have the 3 letter designations like the 45 which was named 245 or 345 before introduction of the ST-shape glass.

These globes are simply beautiful.

Some details of globe 46s:

These have a combination  of mica disc and glass piece for alignment of the electrodes.

Engraved bases:

Some more photos of globe tubes to enjoy:

Cunningham C-46 with beaten up box:

RCA-46 with spec sheet:

Being a tube manufacturer myself now, of course the ELROG 300B, 211 and 845 are among my very favourite directly heated tubes along with 10Y, 801A and 45 and now also the 46.

If you are up for a new amplifier and if your speakers are very sensitive, the 46 might be an excellent alternative outside of the mainstream!

I hope that I will get the chance to build more amps with this tube and a 46 squared (46 drives 46) would be something worthwhile to explore!

Best regards

Thomas

The 46 Back in Black!

Hi!

As much as I like building multi chassis amps with silver/finemet transformers and large transmitting triodes, I also enjoy doing more budget stuff like the amp I am presenting today. A stereo single ended power amp with the 46 as output tube.

This amp is in the classic landscape layout:

It comes in the same black and silver color combination as a 6CB5A amp I built last year and it will be used in the same system as that amp as part of an active set up with the 46 powering the midrange or highs.

Pricing for such amps starts below 4.000,- Euros.

This particular amp has balanced inputs but of course it can be built with RCA inputs as well.

This is actually only the second 46 amplifier I built so far. By coincidence I just had the first one back for service. The first one has a similar style. Only some construction details have been improved in the meantime. Here a photo of the older one:

I always knew that the 46 is a great tube. The first time I used it is almost 20 years ago. I had excellent results using it as driver in a 211 amp. The amp above was serial number 46 of my amps so I used the 46 tube as a gag. However it sounded simply great.

Now I had some time to listen to the old amp after servicing it and to this new one. The 46 definitely deserves more attention. In fact it beats the 45 in terms of sheer fun, musicality and tone. The only drawback ist that you only get 1.25W out of it. Not more. A Watt and a quarter. That's it. But as has been said before: The first Watt counts. And with the right speaker this amp is stunning.

Does it have the resolution and refinement of an Elrog 300B? No of course not. Also not the authority a well implemented 211 or 845 can produce. But it is the kind of amp which you will forgive it's weaknesses and enjoy.

I will cover the 46 again in the upcoming tube of the month post since it is such a great tube. But now some more details about this amp. The rectifier section uses my usual TV dampers:

Everything is mounted in a single chassis which saves cost and space. Here the top plate:

Capacitors, resistors and mains transformer mounted and pre wired:

The output tubes are AC heated from a separate filament transformer which is added to the lower right corner:

Input, interstage and output transformers as well as the chokes are mounted on a separate plate:

Here the inside of the finished amp:

The amp with globe 46 tubes:

After the results from this little gem, I am wondering how a 46 amp would perform with silver transformers and a driver with directly heated tubes like 10Y, or maybe another 46.

It is surprising how loud you can play with only 1.25W. It can make my Wolf von Langa B&W speakers go really loud with deep and well controlled bass.

Stay tuned for more about the 46!

Best regards

Thomas

SE 211 Amplifier Production

Hi!

A quick glimpse into my workshop showing the current work in progress.

3 Pairs of 211 drive 211 single ended amps are being built. Similar to the 211/211 amps shown last year.

The photo above shows the pre assembled sub modules which go inside the wooden chassis. The top plates for one set of amps are already done. Since each mono block has its separate chassis a total of 12 chassis to be assembled and tested.

The large stack in the back are the modules for high voltage smoothing. 3 chokes and plenty of oil caps:

The shorter stack in front are the modules with the final filter chokes which will reside in the amp chassis. On the right two stacks of modules with the large vacuum varnished B+ transformer and the separate DC filament supplies for driver and output tubes.

The modules with the Tribute output and interstage transformers:

NOS paper in oil caps for the critical sections.

The amp chassis will of course be equipped with Elrog ER211 tubes:

Alternatively these amps can also use the new ER242C.

While one set of the amps will get a similar hybrid rectifier as the amps from last year, the two others will use a bridge with 4 6AU4 TV dampers for rectification:

This is a similar arrangement as in the recently finished differential 300B amps.

The first set of these amps is due to be finished this month and the others will be done in January.

Best regards

Thomas

ELROG ER242C - 211 With Molybdenum Plate

Update: We received pre orders for the entire first lot which is planned. So we cannot accept any more pre orders for the ER242C at this time. Another lot will probably be started around October 2017.


Hi!

Since I wrote about the future of the Elrog tubes, I am often asked if there will be new developments. I am very happy to announce a new Elrog tube type, the ER242C, a replica of the Western Electric 242C.

The 242 was first introduced by Western Electric as 242A with metal plate. It was later replaced by the 242B which had a graphite plate. In it's final release as 242C the plate was metal again using molybdenum and with a maximum plate dissipation increased to 100W.

It is basically a 211 with metal plate and increased plate dissipation. It can be used in any 211 amplifier without changes.

The photos show prototypes of the ER242C. These are without the characteristic black area and don't have any printing on the glass yet. The final version will get the same blackened area and the printing, similar to the 211:

Here a close up to show the different plates:

Molybdenum is very difficult to work with. After many trials we came up with a 4 piece plate structure which is assembled together with screws.

In normal operation the plates glow orange:

The plates are intended to be operated like that.

Here the tubes are working in my 801A/211 mono blocks.

Some close ups to the beautiful orange glow:

Quite a sight to behold!

We will do a first limited production run of about 20 pairs next year In February / March. If you are interested to get a pair, we are starting to accept pre-orders for the ELROG ER242C. Due to the difficult forming and assembly process of the molybdenum plate structure, these tubes will have a 50% price premium over the standard ER211.

Orders from within the European Union will be handled directly be us. Please contact me by email or phone. Contact information can be found under the Impressum link.

If you are in  the US or Canada you can buy Elrog tubes and pre-order the ER242C through George Lenz of tubesUSA.

I am happy to announce two new distributors for ELROG tubes:

For China, Hong Kong and Taiwan contact Emmanuel Lebreton.

Robert Lai of Live Acoustics represents Elrog in Singapore.

All other regions will be served directly. If you are interested to represent the Elrog brand in your area, please contact me. I hope to announce more distributors soon.

The sound of the molybdenum plate tubes is beautiful. They improve on the qualities of the ER211 with added ambience and resolution. Of course the subjective sound impression of these can vary between different amplifiers and different people might have different perceptions.

I expect the first batch of ER242C tubes to be reserved very quickly. Depending on demand and feedback from the first users we will occasionally make batches of these and might introduce molybdenum plates also as an option for the ER300B

Stay tuned for more news from the tube factory and for new tube type introductions!


Best regards

Thomas