All rights of photos and text reserved. Usage of photos or text from my blog on other websites or for any other purpose only with prior permission. If you want to use any material from my blog please contact me by email.

Thursday, April 19, 2012

Tube of the Month: The 183/483


This months tube is a quite uncommon directly heated triode, the 183/483.

This tube exisits junder two designations 183 and 483. The photo above shows a pair 483s branded Marvin. apparently this tube was only manufactured over a short peroid. While the RCA RC13 receiving tube databook does not list it yet, the RC14 lists it as 'replacement type' which means it is not recommended to design new equipment for it. RC15 lists it as discontinued type. So probably only a few radio sets used this tube.

The 183/483 is very similar to the 45. It has the same UX4 base. It has an amplification factor of 3 while the mu of the 45 is 3.5. The plate resistance is 1750 Ohm at a 250V plate voltage and 30mA current. This is very close to the values of the 45: 1600 Ohms at 34 mA. So it would work in a circuit designed for the 45. Only the filament voltage differs. It is 5V, double the value of the 45. Filament current is 1.25A, slight.ly lower than the 1.5A of the 45, but at double the filament voltage this is a significantly higher filament power requirement. Both can provide a power output of about 2sw in single ended. I have not found any databook which shows plate curves of this tube, so I measured it on a curve tracer:

Very linear as one would expect from a directly heated triode designed for audio purposes.
Construction is quite similar to that of the 45. Only the size of the bottle is bigger. The 183/483 comes in the same bottle as a 2A3. below a photo which shows a 2A3, 483 and 45 in comparison.

The filament follows the same 'M' shape as that of the 45, with two filament support on the top:

A very interesting tube, but since not many seem to be available not really recommended for DIY use. If you have some in your stash. It might make sense to adapt the filament voltage in a 45 amp to allow to use these. I do not have many 183/483 myself, so I'll probably never use them in an amp. Since little can be read about this type, I found it worthwhile to give it a place in the tube of the month series. Maybe somebody with some more information about this tube can provide details about it's history and background.

Best regards


Thursday, April 12, 2012

The Modular Preamplifier, Part 9 : 10Y Linestage Chassis Design


The two different linestages of the modular preamp concept did not progress as I would have liked. I hope to show the completed preamps soon. In the meantime I got the wooden frames for the 10Y linestage which differs from the other modules since it has the tubes, transformers and caps on top of the chassis.

Here some pictures of the chassis concept. The inside is still empty and needs to be wired up.

This one is quite tricky to assemble since no screws extend to the top or front. There are quite a few parts which have to go inside: Two chokes for B+, two filament chokes and input transformers.

The volume control at the right for 24 2dB steps from the Tribute lineout / volume control transformers. The linestage has 4 inputs. Two regular high impedance inputs for all kinds of sources and two separate low impedance transformer coupled inputs with different step up ratios, providing 21 or 12dB gain.

The transformer inputs are meant to be used with low output impedance sources. Especially the yet to be planned and built all DHT phono stage. DHTs are known for their low gain, so any additional possibility to amplify the signal is needed for that.

All inputs, outputs and the power supply connector on the back side, along with a ground lift switch and separate ground connections to chassis and signal ground:

My apologies to Pieter and all who are waiting for my assessment of the sound of these new volume control transformers. I will report back as soon as the linestage is finished which will take a little more time. I hope you enjoy these photos in the meantime.

I quite like this new appearance and will adopt the same style to other components. The all DHT phono will have a similar look and I'm thinking about power amps in this style.

Of course the external power supply of this linestage will have a matching design, with caps, transformers and rectifiers on the top side.

Best regards


Saturday, April 7, 2012

Tube Box Art, Part 6: Marconi


In this tube box art article I will show my favorite tube box of all. The packaging of a british Marconi MS4B tube.

Isn't this a stunning box with it's black and violet colors and gold decoration?

I found this tube many years ago in an antique shop. They had it prominently displayed in the window. I had to get it before somebody else does.

Marconi was a british tube manufacturer (valves in british english) founded in 1919 and later renamed to Marconi-Osram-Valves (MOV).

The MS4B which is in the box is an indirectly heated pentode with the european B5 base. I have only this single one of these. This is one of the very few cases when I bought a tube just because of the box.

This has been my favorite tube box ever since, so it deserves it's own tube box art post.

The photo on the right shows the bottom of the box, with the somewhat funny remark to open it at the other end. You can open the box at both ends without any probelm.

This box again is a nice example of remarkably beautiful box designs in the early years of vacuum tubes.

The photo below shows a side of the box with patent licence information.

Stay tuned for more tube box art. The next article will cover a famous american brand with a very distinctive motif on their boxes.

Best regards