DISCLAIMER

DISCLAIMER: Vacuum tube circuits work with dangerously high voltages. Do not attempt to build circuits presented on this site if you do not have the required experience and skills to work with such voltages. I assume no responsibility whatsoever for any damage caused by the usage of my circuits.

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Sunday, December 31, 2017

Happy New Year!

Hi!

It is December 31st. Time to review the year and look ahead into 2018.




2017 was the 7th year of the VinylSavor blog. In January 2018 it is the 10th anniversary since I started audio as a business, five of those as a full time job. The tube manufacturing operation under Deutsche Elektronenröhren Manufaktur GmbH is in it's second year.




Starting tube manufacturing was a tube amplifier builder's dream come true and still is and still sometimes appears somewhat unreal to have this capability at hand. Yet it demanded it's toll in time diverted from the amplifier building and also the blog did not get as many updates as I wished.




But it was worth it, not only did we prove that we were able to continue the manufacturing of the ELROG tubes but we also managed to vastly improve the quality and reliability. With the change of the 211 and 845 construction to the 'inverted' style with the internals mounted at the top we not only eliminated some of the heat dissipation issues of the older tubes in certain amplifiers.




We also addressed the complaints of some people who prefer to have a clear view of the internals and especially the bright thoriated tungsten glow.






The activities did not stop with the improvements and reworking of all tube types. We introduced a total of 4 new tubes to the product portfolio.





The 242 and 284 which are molybdenum plate variants of the 211 and 845.




And two rectifiers. The ER274A and ER274B.




The development will not stop there. Two more types had been announced and are in development right now with a release expected beginning of the new year.




Replicas of the type 50 triode and the 801A, the latter also meant as replacement of the 10Y.  More new types are planned. One of them a directly heated driver tube optimised to drive a 845 output tube.




The main reason why I did not show 845 amplifiers on my blog yet was the lack of really great driver tubes for it. This will change in 2018. So expect more 845 amplifiers to be shown. As a start to kick off the 845 lineup a first set of entry level mono blocks were finished this month.




Besides these some other notable new builds of 2017:




The differential 300B amps got an ultimate all silver version to complete the ultimate differential line up from phono to power amps. These were publicly demoed at the Munich High End.




Another new introduction during that show was the new variable EQ mono phono stage for 78rpm record payback.




The 78rpm sessions during the show received a lot of positive feedback and it is planned to repeat this in similar form during the 2018 High End.




2017 was the 4th time for VinylSavor to attend this fair and the 1st time for Deutsche Elektronenröhren Manufaktur GmbH. In August I attended the Hong Kong AV show for the first time with the help of Emmanuel Lebreton of baoling alternative audio. The Hong Kong show was a great experience and we plan to do it again in 2018.




It has been a great year and I would like to thank the readers of my blog, customers and partners and last but not least the staff of Deutsche Elektronenröhren Manufaktur GmbH for all the hard work. A lot of plans and ideas are already in place for 2018. Stay tuned for updates about new amplifier builds and new developments from the tube factory!




Happy new year to all of you and your families!

Thomas








Tuesday, December 26, 2017

845 Mono Amplifiers - Part 3

Hi!

Here some photos of the finished 845 mono amplifiers.




The amps are now housed in walnut chassis and are completed and tested.




Both mono blocks side by side:




Each amp weighs in above 40kg. And yes these are my 'entry level' 845 amps.




The next level up will come in 4 chassis, each amp will get a separate power supply.




More photos and some impressions about the sound in part 4.  Stay tuned!

Best regards

Thomas




Friday, December 15, 2017

Tube of the Month : The 6FW5

Hi!

This month's tube is a nice low cost alternative to output triodes. The 6FW5.




The 6FW5 was designed as horizontal deflection amplifier for TV sets but it can be used for other purposes as well, for example as output tube in an audio amplifier.

The tube has an Octal base. The pinout is shown on the left. It is a beam pentode, which means the grid nr. 3 is a beam forming element. The beam forming plate is internally connected to the cathode. Unlike most tubes designed for this application it does not have a top cap. I have played around with this tube many years ago in a single ended amp and remember getting about 3-4W output power in triode mode. I have heard reports from people who got good results with the tube in screen driven mode. In triode connection the parameters are somewhat similar to the 2A3. In fact I heard rumours that Sylvania sold 6B4Gs in the 1980ies which were
6FW5s triode connected in the base and with the cathode connected to the heater to 'emulate' a directly heated triode. The absence of a top cap and rather modest heater current of 1.2A make this an attractive candidate for a low budget single ended amp. The plate dissipation is rated at 17.5W but as with many TV tubes this can probably be pushed a little beyond and will still last. The 6FW5 received some fame during the late 1990ies when JC Morrison published a circuit of a screen driven amp with it. But interest in this tube seems to have faded in the recent years. So it's time to give it some attention again. The complete technical data can be found in the General Electric data sheet. Let's have a look at the plate curves, pentode mode first:






And triode connected:




Looks quite good. Slap on a 6N7 as driver and you have a nice little two stage single ended amp.




All 6FW5s I have are branded International Servicemaster. Most likely made by one of the big manufacturers, RCA or GE.




The tube has a nice little bottle, which looks a bit chubby.




They look very well made.






The top:




Let's open one up to see the internal construction:




With the glass removed we have a better view of the details.







Now we pull out the heater wire:






The plate removed from the assembly:





Beam plate, grids nr 1 and 2 and the cathode:




In the close up it can be seen how well the two grids are aligned.




Grid 2 is in the 'shadow' of grid 1.





View from the side:





The cathode is internally connected to the beam plate:





The screen grid (grid nr 2):





It is carbon coated for better heat dissipation.




The control grid (grid nr 1):




It appears to be gold plated to suppress secondary emission.




Gold plating avoids that barium from the cathode can get deposited on it.




Beam plate and cathode without the grids:





The tube with the heater lit up:







A very well made tube with rugged construction which can probably take a lot of abuse.


Best regards

Thomas