If you are blowing tubes, I would recommend doing some checks on your amp before damaging anything else.
(1) Measure filament voltage at the tube pins (4 and 5 DANGER, Potentially Lethal voltages present on other pins!).). It should be 6.3Vac rms +/- 0.3Vrms. I suspect you will find it is higher than 6.6V and probably close to 7.
(2) Measure the B+ high voltage supply and compare this to the manufacturers specification and tube data sheets (Caution do not do this unless you are familiar with HV measurements and comfortable doing so. DANGER, Lethal voltages present!).
The chinese amps are notorious for not being properly made for the mains AC supply that exists in various countries around the world. They run excessive voltage on tube filaments and plates resulting in blown tubes, etc.
There are several ways to reduce the voltage. The best is a 1:1 transformer with taps that allow you to configure the input for the desired output to match your line voltage requirments. Another alternative is a Variac that will allow you to adjust the voltage to your amp.
It is also possible to add a small value resistor in series with the filament supply to drop this down to within spec if the HV is acceptable. (This requires soldering skills, and appropriate safety cautions.)
(1) Measure filament voltage at the tube pins (4 and 5 DANGER, Potentially Lethal voltages present on other pins!).). It should be 6.3Vac rms +/- 0.3Vrms. I suspect you will find it is higher than 6.6V and probably close to 7.
(2) Measure the B+ high voltage supply and compare this to the manufacturers specification and tube data sheets (Caution do not do this unless you are familiar with HV measurements and comfortable doing so. DANGER, Lethal voltages present!).
The chinese amps are notorious for not being properly made for the mains AC supply that exists in various countries around the world. They run excessive voltage on tube filaments and plates resulting in blown tubes, etc.
There are several ways to reduce the voltage. The best is a 1:1 transformer with taps that allow you to configure the input for the desired output to match your line voltage requirments. Another alternative is a Variac that will allow you to adjust the voltage to your amp.
It is also possible to add a small value resistor in series with the filament supply to drop this down to within spec if the HV is acceptable. (This requires soldering skills, and appropriate safety cautions.)
Soviet Union had centralized planning, so it was decided on the top of government stages, which production do people want to consume. The rest was planned in accordance with changed requirements. Octal tubes were called obsolete, and miniature tubes required to replace them.
6Н1П tube was offered to designers as a new miniature tube to replace considered as obsolete octal tube 6Н8С that was equivalent to 6SN7. 6Н2П was offered as a replacement of considered as obsolete 6Н9С, equivalent to 6SL7. 6П1П was offered instead of 6П6С (6V6), and so on.
6Н1П tube was offered to designers as a new miniature tube to replace considered as obsolete octal tube 6Н8С that was equivalent to 6SN7. 6Н2П was offered as a replacement of considered as obsolete 6Н9С, equivalent to 6SL7. 6П1П was offered instead of 6П6С (6V6), and so on.
Below are some values to consider - courtesy of info found on Broskie's Tubecad journal. One can see that optimizing the idle currents requires a lot of tinkering of the cathode resistors...not a huge deal however.
Looks lik the 6N1P is happiest at 5 or less mA. I had been running 6CG7 at 7mA and then the 6DJ8 at 10mA at 250V. The 6CG7 is very smooth but the 6DJ8's have a little more gain which I prefer - Aikido 5687 pre. Be sure to measure the actual voltage across Rk...it will vary by tube type so dont always assume its 3.1V for example. This will ensure you have your exact idle current.
Tube mu rp Rk Ik(mA) B+ Input Gain Input Gain dBs
6N1P 39.8 12200 328 3.0 200 19.4 25.8
6N1P 36.00 9480 221 5.0 250 17.7 25.0
6N1P 35.00 956 642 5.0 300 17.1 24.7
6CG7 21.10 8960 397 5.0 200 10.4 20.3
6CG7 21.00 9250 626 5.0 250 10.3 20.2
6CG7 20.80 9840 1000 4.5 300 10.1 20.1
6CG7 21.40 8370 470 7.3 300 10.5 20.4
6CG7 21.90 7530 243 10.0 300 10.8 20.7
6CG7 21.80 7680 352 10.0 350 10.7 20.6
6DJ8 30.00 2960 205 10.0 200 14.9 23.4
6DJ8 29.60 3060 291 10.0 250 14.6 23.3
6DJ8 28.60 3980 673 5.0 250 14.0 22.9
6DJ8 28.30 4080 845 5.0 300 13.8 22.8
6DJ8 28.90 3400 481 8.0 300 14.2 23.0
Looks lik the 6N1P is happiest at 5 or less mA. I had been running 6CG7 at 7mA and then the 6DJ8 at 10mA at 250V. The 6CG7 is very smooth but the 6DJ8's have a little more gain which I prefer - Aikido 5687 pre. Be sure to measure the actual voltage across Rk...it will vary by tube type so dont always assume its 3.1V for example. This will ensure you have your exact idle current.
Tube mu rp Rk Ik(mA) B+ Input Gain Input Gain dBs
6N1P 39.8 12200 328 3.0 200 19.4 25.8
6N1P 36.00 9480 221 5.0 250 17.7 25.0
6N1P 35.00 956 642 5.0 300 17.1 24.7
6CG7 21.10 8960 397 5.0 200 10.4 20.3
6CG7 21.00 9250 626 5.0 250 10.3 20.2
6CG7 20.80 9840 1000 4.5 300 10.1 20.1
6CG7 21.40 8370 470 7.3 300 10.5 20.4
6CG7 21.90 7530 243 10.0 300 10.8 20.7
6CG7 21.80 7680 352 10.0 350 10.7 20.6
6DJ8 30.00 2960 205 10.0 200 14.9 23.4
6DJ8 29.60 3060 291 10.0 250 14.6 23.3
6DJ8 28.60 3980 673 5.0 250 14.0 22.9
6DJ8 28.30 4080 845 5.0 300 13.8 22.8
6DJ8 28.90 3400 481 8.0 300 14.2 23.0
Thxs cj
I have the Broskie manual and it had 3 or 5 mA but then I looked at the data sheet which threw me off because it had a scale up to 30mA!!!!
5mA appeared to be too low.
I'll measure across the resistor as you said. Thxs.
May end up going back to my 6N6P with the LED bias which I like a lot.
I have the Broskie manual and it had 3 or 5 mA but then I looked at the data sheet which threw me off because it had a scale up to 30mA!!!!
5mA appeared to be too low.
I'll measure across the resistor as you said. Thxs.
May end up going back to my 6N6P with the LED bias which I like a lot.
I second everything that has been said about NOT replacing 6N1's with 6922's.
Various experiments I have undertaken show that where an amp has been designed for 6N1 it is better to try various builds of the same, even by the same manufacturer to find the 'sweet' one. I found that 6922's and ECC88's can easily go into HF oscillation.
Various experiments I have undertaken show that where an amp has been designed for 6N1 it is better to try various builds of the same, even by the same manufacturer to find the 'sweet' one. I found that 6922's and ECC88's can easily go into HF oscillation.
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