Konnichiwa,
Given that you don't really need the low source impedance of the gyrator (having 1,000uF after it) you might simply make an "electronic choke" circuit, which can be in the negative line, use N-Channel devices and allows a defined and reasonable "DCR" as well....
Very nice work.
Nice one. Looks like I have to try this one....
Sayonara
altor said:You are right, but I have no high voltage "p" mosfets, but have a huge quantity of the 200-800v N-mosfets
Given that you don't really need the low source impedance of the gyrator (having 1,000uF after it) you might simply make an "electronic choke" circuit, which can be in the negative line, use N-Channel devices and allows a defined and reasonable "DCR" as well....
altor said:
Very nice work.
altor said:
Nice one. Looks like I have to try this one....
Sayonara
The max continous current is specified as 0.6A, the average current of each tube is 0.8A when pushing the amplifier to the limit with a continous sinewave which is not a normal situation when playing music where average power is 10 - 20dB lower than peak so in reality it is not a problem.
That is too bad, can you explain why?
Regards Hans
For me it is not clear what you mean by that statement, are you saying that Svetlana 6C33c are better than others?
Most of the 6C33C I have used are made at the Ulyanov factory and have been 100% reliable. I had one earlier tube that I believe was made at Svetlana but that failed on first power up with a short between cathode and grid, but it is the only failure I have had of more than 30 tubes.
Regards Hans
Hi
I have build a stereo single ended tube amp with 4 * 6c33, with homemade transformers, with multiple primary windings instead of direct parallel tubes for higher output power..
my homepage is in danish but feel free to email me about questions.
www.micro-io.dk
best regards
Kim Olesen
I have build a stereo single ended tube amp with 4 * 6c33, with homemade transformers, with multiple primary windings instead of direct parallel tubes for higher output power..
my homepage is in danish but feel free to email me about questions.
www.micro-io.dk
best regards
Kim Olesen
dimitri said:
I know
But I say about 80th, not 90th....
And I didn't see any problems with "-B" marked tubes of 80th, even at 80W plate power (i'm not use this mode, but tested).
Some tubes without "-B" were drifted even at 62-64W, even with autobias. One of these tubes, when the power was higher then 53W - after 15min has near 800mA plate current with -100v at the grid!
Dimitri wrote:
So how can we interpret this?, are tubes manufactured before 1975 good or is it enough to look for tubes manufactured before 1991?
All the 6C33C I have used are manufactured between these years, I am really doubtful if there are any 6C33C manufactured after 1991.
Victor Khomenko at BAT has explained that they discover faults in about 1% of all 6C33C tubes and the most common fault is a grid to cathode short, however for tubes that survives the burn in and the first few hours of service the service life is very long, I have the same experience.
Altor wrote:
and also:
So how can we interpret this?, are tubes manufactured before 1975 good or is it enough to look for tubes manufactured before 1991?
All the 6C33C I have used are manufactured between these years, I am really doubtful if there are any 6C33C manufactured after 1991.
Victor Khomenko at BAT has explained that they discover faults in about 1% of all 6C33C tubes and the most common fault is a grid to cathode short, however for tubes that survives the burn in and the first few hours of service the service life is very long, I have the same experience.
Altor wrote:
Even more sense then to follow the advice not to exceed 40-45W of anode dissipation with fixed bias for long life.
Hi
The power dissipation of the tube an its temperature has a big influence on it's lifetime. At 60w the lifetime is around 700h and at 45w 2000h, keeping it below temperature limits will also increase lifetime (some datasheet say more than 3000h).
Keep the tube cool by placing them so that they have a 3inch radius each, this will give them space to radiate the heat to.
The four tubes i use, is un matched an they dont drift more than a +- 3ma, and it takes 15 to 20 minutes to settle after power up.
(i will check production year when i get home, think they are Ul'janovsk , found on ebay 40$)
Best regards Kim Olesen
www.micro-io.dk /fotogalleri
The power dissipation of the tube an its temperature has a big influence on it's lifetime. At 60w the lifetime is around 700h and at 45w 2000h, keeping it below temperature limits will also increase lifetime (some datasheet say more than 3000h).
Keep the tube cool by placing them so that they have a 3inch radius each, this will give them space to radiate the heat to.
The four tubes i use, is un matched an they dont drift more than a +- 3ma, and it takes 15 to 20 minutes to settle after power up.
(i will check production year when i get home, think they are Ul'janovsk , found on ebay 40$)
Best regards Kim Olesen
www.micro-io.dk /fotogalleri
I can see that we will never agree about this issue but let me ask you how long life you expect from a 6C33C? I have used the same tubes without adjustment in my OTL for more than 6 years with daily usage.
One more question, what alternative tubes do you recommend for an OTL that can operate with a peak current of more than 2.5A?
Regards Hans
Hi
The "hour rating" is only to get an idea of how long it keeps it's data ratings. Many plasma screens are said to have a lifetime of 10000hours, so if the tubes will run as long as that, i would be happy.
Best regards
Kim Olesen
www.micro-io.dk
The "hour rating" is only to get an idea of how long it keeps it's data ratings. Many plasma screens are said to have a lifetime of 10000hours, so if the tubes will run as long as that, i would be happy.
Best regards
Kim Olesen
www.micro-io.dk
KimBOlesen wrote:
Yes I know, and for 6C33C it includes severe vibration requirements aso. How much disspation do you run your tubes on, I can see from the circuit diagram that you seem to run the tubes at 300V but at what current?
The requirements and stress on the tubes is very different in an OTL and a SET amp.
In the OTL you have relatively low average dissipation, in my case less than 40W but the peak current requirements are very high e.g ~2.5A when giving 25W in 8ohm.
Even when playing close to clipping the dissipation doesn't much exceed the one at idle as the peak to average of ordinary music is very high, at least 10dB but more close to 20dB.
In a SET however it is completely different with max anode dissipation at idle.
Another requirement in an OTL amp is that you want minimum DC drift as you want to use direct coupling to the speaker.
Regards Hans
Yes I know, and for 6C33C it includes severe vibration requirements aso. How much disspation do you run your tubes on, I can see from the circuit diagram that you seem to run the tubes at 300V but at what current?
The requirements and stress on the tubes is very different in an OTL and a SET amp.
In the OTL you have relatively low average dissipation, in my case less than 40W but the peak current requirements are very high e.g ~2.5A when giving 25W in 8ohm.
Even when playing close to clipping the dissipation doesn't much exceed the one at idle as the peak to average of ordinary music is very high, at least 10dB but more close to 20dB.
In a SET however it is completely different with max anode dissipation at idle.
Another requirement in an OTL amp is that you want minimum DC drift as you want to use direct coupling to the speaker.
Regards Hans
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.