6C33C-B on 8W

[Tyimo]

Hi!
Usually everyone wants to get the most out of this tube, e.g. 16W.
But what would be the ideal operating parameters for just a 8W version?
Greets:
Tyimo

 

[tubes4all]

I guess you already have seen this datasheet: http://www.jogis-roehrenbude.de/Russian/6C33C/6C33C-B-6S33S-VExtendedDatasheetMB.pdf

Stay below 45W (for both anodes) and below 250V and service life will be a lot better. Go for a Ra between 800-1200 Ohm (preferable a transformer with an Rdc lower then 15 Ohm)

I personally like fixed bias for this tube but that is not the easiest way (steep tube, 1 volt differance on the grid makes a huge difference in current)

 

[acg]

You only need to use one triode for 8w. Sounds a little better that way too in my experience.

 

[Pyka]

It is recommended to try to work with a half heater (half cathode), which can reduce the heat generation and the anode characteristics are more linear.

 

[Tyimo]

Thanks for that Extended datasheet!
The reason that I want only 8 W is because for me it's enough, + less heat and longer operational time.
Yes , I know that only one side has better sound but I want to use both with less stress.

 

[SVStube]

In this amplifier, I use the mode of 300-320 V, 55-56 W of anode power.
The maximum output power of the amplifier is more than 18 W, the output resistance is 1.25 Ohms at a load of 4 Ohms.
I can get an output of more than 20 watts, but I have to choose the tubes.
The sound is great.
https://sound-design-atelier.com/amplifier-2

 

[tubes4all]

In this amplifier, I use the mode of 300-320 V, 55-56 W of anode power.
The maximum output power of the amplifier is more than 18 W, the output resistance is 1.25 Ohms at a load of 4 Ohms.
I can get an output of more than 20 watts, but I have to choose the tubes.
The sound is great.

This is an autobias amplifier i guess.

 

[tubes4all]

It is recommended to try to work with a half heater (half cathode), which can reduce the heat generation and the anode characteristics are more linear.

Did you measered the linearity your self? From the datasheets it’s hard to tell.
The difference cannot be great anyway because almost nothing changes, only 1 or 2 heaters are on the rest is the same. (Ri changes)

 

[Pyka]

Did you measered the linearity your self? From the datasheets it’s hard to tell.
The difference cannot be great anyway because almost nothing changes, only 1 or 2 heaters are on the rest is the same. (Ri changes)

You can compare the curves below. Full heater on the left, half heater on the right.

 

[tubes4all]

You can compare the curves below. Full heater on the left, half heater on the right.

View attachment 1077562

Because of different scales i cannot make any decisions about linearity.

 

[SVStube]

This is an autobias amplifier i guess.

No, there's an electronic bias system

 

[SVStube]

I couldn't get good linearity at more than 6-8 W using conventional circuitry. The cathode winding in the output transformer solves the problem. At the same time, getting a good 20 W is not a problem.

 

[tubes4all]

No, there's an electronic bias system

What about tube life, 300-320V and 50-55W is not recommend.

 

[SVStube]

What about tube life, 300-320V and 50-55W is not recommend.

Several amplifiers have been working for about 10 years without problems. Electronic bias and soft start extend the life of the tubes many times over.

 

[tubes4all]

Several amplifiers have been working for about 10 years without problems. Electronic bias and soft start extend the life of the tubes many times over.

Very good job!

I am also very happy with this tube, very reliable. I used about 200-220V and 50W dissipation. Never had a broken tube (exept when i made a mistake myself). However, after 1000h i checked the amplifier with a new tube and i discovered that a new tube sound a little bit fresher. Just a little bit. The older tube was still good enough in my opinion.

 

[PRR]

Because of different scales i cannot make any decisions about linearity.

 

[SVStube]

Print at different scales and look through to the sunthrough pictures, if this is important to you.

 

[mbrennwa]

This curve comparison is nice! However, the individual curves look like they were hand drawn using a curve ruler (take a look at the somewhat irregular spacing between the curves). These curves are not the best basis to assess the linearity. Are there any proper curves out there to compare full/half heater?

 

[tubes4all]

Print at different scales and look through to the sunthrough pictures, if this is important to you.

Thanks for scaling.
The differences are to small and the graphs not super good so for me i go for the double filament.

 

[acg]

Thanks for scaling.
The differences are to small and the graphs not super good so for me i go for the double filament.

My advice, if you need more than two or three watts for maximum listening volume, go with both sides, you will likely have better sound. I only need watt, so one triode is just fine.