The Stereo 300B amplifier, Part 1

Hi!

More new stuff in the pipe line! After several sets of 300B mono block amplifiers it is about time to scale down a bit. Coming up is a stereo single ended 300B amp. These are some of the parts of the signal chassis.

The chassis will be in a similar style as the 300B monos. It will also have a separate power supply. Both amplifier channels will share a common chassis and they will get a common supply in a separate chassis. Output transformers are Hashimoto. The reduction from 4 to 2 chassis does not have enough room for a directly heated driver stage. So I am resorting on an indirect heated tube, the 6SN7.

Updates will be posted as the assembly progresses. Stay tuned!

Best regards

Thomas

Tube Box Art, Part 18 : Westinghouse

Hi!

One of the major players in vacuum tube manufacturing history is still missing from the Tube Box Art series: Westinghouse.

Let's start with some of their earlier boxes:

These contain type 26 triodes:

A 45 DHT and a 6CB5 beam power tetrode in different style boxes:

A 2A3 and an octal tube in gold/black/white boxes:

A 6BY5 TV damper box:

6AX4 TV damper boxes:

These are rather modern and bland:

And finally some beautiful boxes of 816 mercury vapour rectifiers:

The 816 is the small sister of the impressive 866A.

This tube will be covered in it's own Tube of the Month article soon!

Best regards

Thomas

The 300B Line Stage - Part 1

Hi!

So far the 10Y has been my favourite line stage tube. But I often get inquiries for line stages using the 300B. With the availability of the Elrog ER300B and it's superior resolution, this might have become feasible. So I am going to test it with a prototype.

Tribute has wound some suitable OPTVCs for this project. These are some massive beasts the size of power amp output transformers.

Just waiting for some chassis material to arrive before the assembly of the line stage starts. I will report about the results. Stay tuned!

Best regards

Thomas

Elrog ER300B update 5

Hi!

It's been a while since the last update about the ER300B. 

In the meantime I received more feedback from users of the tube which I'd like to share. But first I am happy to announce that the data sheet for the ER300B is now finally released. Please click on the link to download it. Many people have asked for this since my initial report about the tubes which mentioned some deviations from the Western Electric specs. Now the characterisation is complete and the data sheet is released. The main differences to the WE 300B are the increased plate resistance of 950 Ohms vs. the 700 Ohms of the WE and the reduced amplification factor of 3.3. There is also an Application Note for the ER300B which explains the impact of this and the optimal use. This can also be downloaded by following the link. 

Here are the plate curves from the data sheet:

Note the extension of the curve set into quite high voltage territory. The design of the ER300B is derived from the ER845 and is capable of higher plate voltages than the WE. I am planning some new amplifiers which take advantage of the parameters of the Elrog tubes.

But all this technical stuff is boring for many people and they are more interested in the performance of these tubes in actual amplifiers. Here a feedback which I received from Theo from Norway:

I have run the Elrogs for a couple of hours now. I totally agree with your impression. I have used 300B tubes from new production WE, EML, TJ, JJ and EH, and this is another world to me. Even in my modest DRD 300B they play so beautiful. I could be analytical in my description, but right now that side of the brain is on holiday. I just enjoy what they do with the music. 

I thank you from my heart for the effort you have made to get this tube into production.

Here a photo of Theo's DRD 300B monos:

The impressions above were only after a few hours of listening. After some more listening Theo provided another update:

I have listened more with the Elrogs in place now, and I can't find a single drawback comparing to the other 300B tubes I have. They have the same sweetness. 

Bass is bigger and more controlled, more details which is beautifully integrated into the music, more presence, wider and deeper soundspace. They just sound more alive, in the room. The other 300B's become very dull by comparison. 

If this is representative to thoriated tungsten, I am a fan:-)

Thanks to Theo for sharing his impressions and the photo of his beautifully built monos. Next we have a quick comment from Ngan from Hong Kong:

After a few hours the sound more more relax and refine, i felt nothing tube can come close this 300B at the moment, very balance at all frequency spectrum...

Ngan uses the Elrogs in amps which he built himself:

And finally the comments from Ivar, also from Norway about his impressions of the tubes. Ivar uses them in parallel single ended monos:

Here are my impressions, right out of the box, replacing Western Electric 300B tubes:

• The Elrogs are way better in the bass, the control and resolution is just in a different league, WE are soft and unresolved in comparison.
• My impression is that the Elrogs are much more dynamic than the WE.
• The Elrogs are highly resolving from bottom to top, very smooth sounding, very natural highs, I think the WE have too much sparkle in the top. 
• Good perspective and 3d properties with Elrog, better than WE, Elrog puts the soundstage at a larger distance than the WE. WE are quite close and "up in the face" which I do not like too much.
• The Elrogs are more open, they have a leaner sound and more delicate colours in a way.
• The WE seems to have a little more harmonic richness, or "magic" or euforic colour or whatever it can be called. The Elrog tubes outperform the WE in all other respects. I do not think the WE colouring is correct, but it is a very alluring and appealing property.

Thanks to Theo, Ngan and Ivar for sharing their impressions!

If you are interested in these tubes please drop me an email. Delivery time is currently about 5-6 weeks from order placement. My contact information can be found under the link Impressum / Contact.

Best regards

Thomas

Yet Another SE 300B Amplifier, Part 2

Hi!

Beginning of last month I showed my latest 300B mono amps using Tamura amorphous core output transformers. They were lacking matching power supplies and I used them with the PSUs of another set of amplifiers. Now the power supplies in a matching color scheme are finished.

They come with the capacitors in the same metallic white. The transformer covers are graphite grey to match the Tango interstage transformers on the amplifiers. Here is the entire set of 4 chassis:

Front view of one of the power supplies:

Side view:

To allow some experimentation with the operating points of the Elrog 300B. I added an array of switches which allows selection of different taps of the power transformers, which results in different B+ voltages.

While at it I also made the DC filament supplies for output and driver tubes adjustable over a wide range to be able to use different tubes.

Top view of the PSU:

One channel:

More about this amp in an upcoming post. Stay tuned!

Best regards

Thomas