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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Wednesday, December 31, 2014

Happy New Year!

Hi!

2014 is coming to it's end and this is the time to look back at what happened throughout this year and also to look ahead into 2015. It's been another great year filled with music, great sound and many exciting projects.





Rereading last years Happy New Year post, I realised that many projects which had been planned got done. Others had not and are still awaiting to be brought to life.





The highlight of 2014 was the introduction of the Elrog ER300B. It surpassed the expectations and enabled a new level of sound quality from 300B amps. I finished 3 different 300B amps using this tube and more will follow next year. I will continue to post user feedbacks from the tube and hope to visit the Elrog factory again soon. Of course I will share a report about it.




The 801A amps which I announced end of last year got finished. See a post about them here.




Also silver was indeed an important topic of 2014 with several amplifiers and preamplifiers built using silver wound transformers. The pure 45 bliss silver amps are still holding the title of my best sounding amps so far, if used with the right speakers.For more demanding speakers and louder listening levels, it is the silver 211/211. This ranking may be a surprise since I wrote such glorious reviews about the ER300B. It is still the overall amp and parts quality which determines the final result. The output tube is only one part of the picture. The ranking will surely change once an all silver 300B amp has been built.





On the preamp side the silver/finemet 10Y line stage was a highlight and again proved the sound qualities of silver wound transformers. This was also the first time I was using finemet core transformers and this will be a big topic in 2015 with several amps using finemet interstage and output transformers in the planning.






Another topic which had been pending and finally proceeded in 2014 was differential/balanced circuits. Not in form of the differential EC8020 phono stage as mentioned end of last year, but I began with the differential 10Y line stage. It turned out great and showed the potential of the concept. So a differential phono has to follow and this will hopefully happen in 2015. But before that I will finish a single ended EC8020 phono with an improved biasing scheme. This is in progress and should get completed in January.




I am often asked about push pull power amps. Although by far the most amps I built are single ended, I am not dogmatic about this topology and will also explore this field further. The differential preamps will get their counterparts in form of push pull/differential power amps. Not sure if this will happen in 2015 or rather in 2016.




On the lower cost side there were also some new things. First the cost optimised D3a LCR phonos. Then I digged out some sleeper tubes: The 6GE5 for use as power tube, the 6AG9 as suitable driver for it and the 6BE3 as matching rectifier. Two different amps have been shown with these tubes.




There had been some great events this year. The High End in Munich was a great experience. I will be exhibiting again in Munich in 2015 with Wolf and Bernd and hope to meet and talk to some of you there. The ETF in Berlin was an absolute blast and I am looking forward to ETF.15 in Denmark.




And finally there was the journey through the world of 78rpm Shellac records which culminated in the Shellac presentation at the ETF hosted by my friend Frank whom I am thankful for introducing me to this.

The webshop for parts and kits which I wanted to set up got postponed a bit but is definitely going online soon. This year I started to upload some videos which seem to be quite popular. I need to work on my skills however and improve them. Here a short video from the lake, with some waves hitting the small island called Hoy.





Many thanks to all of you for a great year and all the best to you and your families for 2015!

Thomas



Thursday, December 25, 2014

6GE5 Stereo Amplifier, Part 1 : Circuit

Hi!

In previous posts schematic and assembly steps of transformer coupled mono blocks with the 6GE5 as output tube have been shown. As promised a cost optimised version will also be presented in form of a stereo amplifier.




Going stereo instead of two mono blocks is already a considerable cost saving measure with minimal impact on sound quality. To reduce cost further we need to let go of the interstage transformer and use RC coupling in the driver stage instead. Next is the reduction of the number of chokes which requires to go for a cap input filter instead of choke input. And lastly the exchange of oil caps with electrolytics. Here is the schematic:




I wanted to keep the ultra path connection in the output stage, hence two separate chokes for each channel to isolate them. All other capacitors are electrolytic. The first cap after the rectifier sees the highest voltage peaks, hence two 22uF/350V caps in series. This results in 11uF capacitance which is still reasonably low and does not stress the rectifiers too much. The two 150uF caps after the chokes can be implemented with 3 47uF in parallel as I did. These caps can also be increased but the 150uF proved sufficient for quiet operation. The bypass caps at the cathode resistors of the 6GE5 are needed to suppress any residual ripple which would otherwise be coupled from the high voltage to the cathode. The driver stage is a standard RC coupled stage.

A rather simple circuit which is easy to build. I will show the completed amp in the second part and will also offer this version as a kit. Stay tuned!

Best regards

Thomas

Monday, December 22, 2014

300B Drives 300B, Part 2

Hi!

The new single ended 300B mono blocks with 300B driver are finished.




The Elrog ER300B casts a beautiful light onto the top metal plate with shadow 'beams' coming out at either side of the tube.

The complete set of amps with power supplies:




As is obvious, chassis layout and construction style are similar to the 10Y/300B amps.

The basic character of these 300B/300B amps is quite similar to that of the 10Y/300B. The 300B drivers give a warmer more full bodied sound.




Probably more a matter of taste which amp to prefer.




Light show in the dark:





I made a short video as well:




Best regards

Thomas



Thursday, December 18, 2014

6GE5 Mono Amps, Part 2 : Assembly

Hi!

Part 1 about the 6GE5 Monos showed the circuit. In this post I am presenting the assembly steps of the amplifiers.





So far the amps which received the most positive feedback for the design are my 211/6HS5 mono blocks.  So I reused some of the design aspects of those 211 amps for the layout of the 6GE5 Monos:




All the capacitors in the circuit are place in a single row on the left side. The 6GE5 output tube at the front in the middle and the 6AG9 driver beside it. Two separate power transformers are hidden under the black covers. Since the heater windings of the power transformer used does not supply enough current for all the tubes, I used a separate heater transformer for the signal tubes. The 6BE3 rectifiers are placed at the back side.

This is the top mounting plate with just the 12-Pin tube sockets installed:




Most of the resistors in the design are directly mounted to the bottom side of the plate:




All remaining resistors are soldered to the terminal strip.




Mounting of the power transformers:





Most of the wiring done:




Adding the capacitors:





The chokes, output and interstage transformers go inside the chassis:






The finished amp:




The two monos side by side:




Top view:




I have been using these amps for some time and am very happy with the result. Power output is about 4W. Solid frequency response. As mentioned in part 1, I am making a parts kits available for these.

Iron set (power transformers, chokes, output and interstage transformers):

Mono block       EUR 740,- (EU incl. VAT) / EUR 622,- (outside EU)
Stereo version    EUR 1120,- (EU incl. VAT) / EUR 941,- (outside EU)

Iron Set plus oil caps:

Mono block       EUR 860,- (EU incl. VAT) / EUR 722,- (outside EU)
Stereo version    EUR 1360,- (EU incl. VAT) / EUR 1142,- (outside EU)

Full parts kit (excluding chassis and wire):

Mono block       EUR 975,- (EU incl. VAT) / EUR 819,- (outside EU)
Stereo version    EUR 1525,- (EU incl. VAT) / EUR 1281,- (outside EU)

Too expensive? Stay tuned for the entry level version of this amp with just a single choke and RC coupled driver instead of the interstage transformer.

Best regards

Thomas



Monday, December 15, 2014

Elrog ER300B Update 4

Hi!

Another shipment of ER300Bs came in today. All tubes have been retested for matching plate curves and op points. The tubes will be shipped with a measurement protocol of the plate current at a specific operating point.





Almost all remaining pre orders will be shipped this week. The rest will be shipped before the end of the year from the next batch. Some pairs from the next batch are still available. Place your pre order now to secure your pair. After that batch I will not receive more tubes for at least a month.


In the meantime I am getting feedback from the first users of the tube. One such impression was already posted in the previous update.

Cheah from Malaysia was the very first person who put in an order for the ER300B. He just received his pair and plugged them into an amplifier which was built by himself:




This is his feedback:


The ER300B is truly amazing ! 
Just listen to the first few notes form the ER300b already notice the ER300b is out performing the others 300b I own. 
With ER300b music fill with energy and impact. It's portray a rock solid staging and  3d imaging. Tonality is very natural, as good as 45 but with more energy and the ER300b have a deeper sound in every instruments. This tubes are very balance from highs to lows. It's give the right amount of well define bass. 
With ER300b, my amp like double its power. Even with complex music, this tube can handle well, will not out of power.
It's hard to describe the ER300b sound with words until you listen to one. If you are saying ER300b is the best sounding tube you ever listen to, I'm 100% agree with you.


Thanks a lot to Cheah for his feedback and for the photos of his beautiful mono blocks!






Next I have some comments from Michael from Germany who uses 2 pairs ER300B in his Nagra 300p amplifier. I translated them to english:

In the meantime I listened to the Elrogs closely. The waiting was well worth it. During the 40 years of my HiFi hobby I did a lot of 'investments'... the Elrogs are clearly among the lucky ones.

My little Nagra 300p power amplifier improved in pretty much every aspect. Apparent is especially the increased transparency without any harshness or embellishment. Also a nicely balanced sound stage. The tubes which came with the amplifier cannot reach the dynamics and the sovereignty in the bass. I never would have expected such a strong and at the same time refined bass from my amp or any other 300B. All in all it sounds effortless and well-balanced and as such is more music and less machine. Many thanks for this!





Many thanks also to Michael for sharing his experience with the Elrog tubes. Here is the original german Text:


Inzwischen habe ich die Elrog's eingehend gehört. Das Warten hat sich allemal gelohnt. Im Laufe meines bald 40 jährigen HiFi-Hobbys habe ich sicher viel Le(e)hr-
geld bezahlt....die Elrog's gehören eindeutig zu den glücklichen Investitionen!

Meine kleine NAGRA 300p Endstufe hat in nahezu allen Belangen zugelegt.
Auffällig sind insbesondere die gesteigerte Durchsichtigkeit ohne Schärfe oder 
Schönfärberei und der sehr schön ausbalancierte Raum. An die Dynamik und
die souveräne Gelassenheit in den tiefen Lagen kommen die serienmäßigen
JJ's bei weitem nicht 'ran. Einen derartig kräftigen und zugleich feinen Bass
hätte ich meinem Verstärker und auch irgendeiner 300b nicht zugetraut.
Insgesamt klingt das sehr mühelos und ausgewogen und ist damit ein
Stück mehr Musik und weniger Maschine; vielen Dank dafür!


It is great to have feedback about the tubes in such very different amplifiers. I will post more feedback as it comes in. Stay tuned!

Best regards

Thomas

Friday, December 12, 2014

Tube of the Month : The 6BE3

Hi!

This post concludes the trilogy about the tubes used in the recently shown 6GE5 amplifier. Since the signal tubes both are 12-Pin compactron types it was only natural to select the rectifier from that series as well. And the chosen tube was the 6BE3.





Why another TV damper? Besides the various Octal types and the Novar 6CJ3, I already covered a 12-Pin compactron damper in the tube of the month series, the 6CG3.

The 6CG3 would actually be a bit overpowered for this amp. The 6GE5 only draws about 50mA. Even for a stereo version and taking additional current for driver and bleeder resistor into account, the 6CG3 would still be oversized. This is not a bad thing but it has the draw back of rather high heater current. The 6BE3 heater only draws 1.2A. The 6BE3 shares the same pinout with the 6CG3 which is shown on the left. It has a DC current capability of 200mA. This doubles when two of them are used in a full wave configuration. This is plenty even if some derating is taken into account since the 6BE3, as most TV dampers, was never specified for mains rectifier service.
Like all TV dampers, the 6BE3 was designed for extremely high peak inverse voltage. 5kV in this case. Again this needs to be derated for mains rectification. A derating to 50% still leaves a higher peak inverse voltage rating than most classic rectifiers. The 6BE3 is quite similar in it's characteristics to the 6AX4, the TV damper which I mostly use in power supplies. For the complete set of electrical parameters, please see the General Electric data sheet. While I have seen some 12-Pin compactors used in audio amplifiers, I never heard of anybody using a 6BE3 in the power supply. That's why they are sitting in the warehouses of tube dealers and collect dust. They can be bought for next to nothing, which makes them the perfect companion for the 6GE5 and 6AG9 in an amplifier. Here a photo of two 6BE3 in operation:




The 6BE3 was made by all the major manufacturers.

RCA:





Sylvania:






Sylvania / PhilipsECG:




Zenith branded (made by Sylvania):




General Electric:




DuMont:




Tung-Sol:




The characteristics of the 6BE3 are very close to the 6BZ3. In such cases it was a common practice to  combine the types and label tubes with both designations:




6BE3/6BZ3 made in Japan:





These came in a bulk pack of 50 pieces:




Now let's take this one apart to see how it is constructed inside:





Removing the glass reveals a better view of the plate structure:




The top side:




The white spiral provides isolation between the heater wire and the cathode.




Removing the heater with it's isolation spiral:




Close up:




The cathode:




The plate:






A 6BE3 in operation:




A close up to the heater :




I hope you enjoyed the last Tube of the Month post of 2014. Stay tuned for many more tubes to be covered in this series in the next year!

Best regards

Thomas