I did not get that far yet but the link below links to a build with those transformers, page 8 has some measurements on the whole amp
De Tsaar GM70 single ended versterker
De Tsaar GM70 single ended versterker
The output power, load and THD of the triodes are interconnected. 18W maximum for 6C33C are possible (210v, 0.28a), but no one will listen.
?????? ??????? 6?33?
Calculation of modes 6С33С(Расчет режимов 6С33С).However, lowering the load resistance from 810 Ohm to 450 Ohm will increase the removed power by 1.3 times, i.e. up to 23.5 W, perhaps this is the limit for 6С33С in SE.But that's theory.
I usually used 6С33C in light duty class A, 155v 0.25a 8w max, OTL and PP 16w, otherwise it is very hot.
I think 6C33C is not very suitable for SE, because of large distortions.
It does not show a 10kHz square wave, near to full power (80%) distortion and frequency response at 20Hz and 20kHz.From this information you can understand the quality of the OPT and the amplifier.
Last edited:
As the output power increases, the distortion of the output transformer increases and narrows bandwidth:
diytube.com • View topic - Transformer Shootout- Hammond vs Magnequest vs Dynaco vs HW
diytube.com • View topic - Transformer Shootout- Hammond vs Magnequest vs Dynaco vs HW
Commercial amplifier. They wrote and showed all the data, except for the power vs distortion graph.
6С33С can give different results vs different load + -, there are 6С33С of different quality,but all 6С33С have greater non-linearity vs DHT.
Another graph for 6C33C, power versus distortion,Page 13:
http://www.metaleater.narod.ru/simplex.pdf
6С33С can give different results vs different load + -, there are 6С33С of different quality,but all 6С33С have greater non-linearity vs DHT.
Another graph for 6C33C, power versus distortion,Page 13:
http://www.metaleater.narod.ru/simplex.pdf
B. Aloia made a 6C33C-B SE that was capable of 30W RMS at 3% THD without exceeding specs. This was available as a kit. The guy is now 81 but the schematics can be found online.
Anyway, with standard simpler SE designs it is easy to get 12-20W with THD of 3% or less. Lower power for longer life.
The only real problem of 6C33 is that it needs to be really selected but it's not difficult as it's still rather common.
It really depends on how the amplifier is made. There are DHT SE with lots of distortion too as there are 6C33 amps that deliver 12-15W with less than 1.5-2% THD. Distortion at 1W is typically 0.3% or less which is more than good enough. More powerful designs might sacrifice a bit of linearity at low power but still THD is of the order of 0.5% @1W.
It's all about using a good design in all aspects and optimizing.
Lamm ML2.2 monoblock power amplifier Measurements | Stereophile.com
Not really a big problem if tubes are selected. The selection aims precisely to avoid faulty tubes by comprehensive test and inspection. In fact, I remember that when Aloia launched his kit reliability of 6C33 was the only issue and it was solved with careful selection.
The GM70 is worse regarding filament supply....60 VA! 211 a lot better, IMHO. Golden Dragon brand make good replicas of 845 and 211. That would be my choice for this kind of DHT if economy is important. In UK, Billington have their own rebranded (Billington Gold) Chinese 211 and 845 and these are also good. Very very close to originals regarding performance....
The GM70 is worse regarding filament supply....60 VA! 211 a lot better, IMHO. Golden Dragon brand make good replicas of 845 and 211. That would be my choice for this kind of DHT if economy is important. In UK, Billington have their own rebranded (Billington Gold) Chinese 211 and 845 and these are also good. Very very close to originals regarding performance....
Last edited:
Yes, 6С33С have really poor efficiency, ratio Pa/Pf=1.5,for GM70 Pa/Pf=2.08.
For a long time, 6С33С was produced at the Svetlana factory in Leningrad. It was a military order and the 6С33С were of high quality. Then, in the early -70s, the military order was greatly reduced and the 6С33С were transferred to the factory in Ulyanovsk and the quality of the lamps became much worse.
I saw the Lamm specification, there are even more amazing specifications of commercial amplifiers.
Mistral 1 Mono Bloc Power Amp
Specifications
• Single Ended RMS 20W
• THD : 0.1% (15W, 1kHz), 1.5% (20W, 1kHz)
I don't know what 6C33C they do it on. I have 25 new tubes from the Ulyanovsk factory.
One of them is killed!, # 24, the rest cannot be paired:
I overcome the instability of 6C33C for SE - I do automatic current control.
Attachments
I have a box full of 6C33C tubes that I ran through my curve tracer. They were all fine, and I don't need all of them. I am not sure if I kept the data, but I could repeat some of the tracing / matching. Are you looking for something specific?