You bought a Boyuu A10 amplifier, you know that a Chinese man put it in for you.
In the description you read:
Use 0.35, 96-60 large power core manufacturing, design power of 200W to ensure adequate power and low temperature rise.(HIFI EXQUIS) - IT'S A LIE!
You have a transformer 96-50 Take a look, please BouyyA10 — imgbb.com BoyuuA10 — imgbb.com Bouyy-A10 — imgbb.com
sooner or later it will burn you smoking.
In the description you read:
Use 0.35, 96-60 large power core manufacturing, design power of 200W to ensure adequate power and low temperature rise.(HIFI EXQUIS) - IT'S A LIE!
You have a transformer 96-50 Take a look, please BouyyA10 — imgbb.com BoyuuA10 — imgbb.com Bouyy-A10 — imgbb.com
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
sooner or later it will burn you smoking.
Hello,
I really liked this thread so far. I have a proposal to cascode the parallel input tube to compensate for the miller capacitances. I propose a simple NPN transistor because of space and power concerns as well as the upper element doesn't add anything to the signal.
Benefits are:
- higher bandwidth
- more linear phase in audio band
- higher slew rate
- lower Rout of first stage (1/3 @same power)
- less distorsion (ok, FFT looks worse)
I simulated it in LTSpice. I add the scematic and some pictures. Green is the cascoded and blue is the original signal. Would this work?
I really liked this thread so far. I have a proposal to cascode the parallel input tube to compensate for the miller capacitances. I propose a simple NPN transistor because of space and power concerns as well as the upper element doesn't add anything to the signal.
Benefits are:
- higher bandwidth
- more linear phase in audio band
- higher slew rate
- lower Rout of first stage (1/3 @same power)
- less distorsion (ok, FFT looks worse)
I simulated it in LTSpice. I add the scematic and some pictures. Green is the cascoded and blue is the original signal. Would this work?
Attachments
Cascode input:
C16 220nF and R6 10k will be -3 dB at 72 Hz, and -1 dB at 144Hz. R6 will cause the KT66 to draw very high plate current. It is DC coupled from the plates of the input tubes to the control grid.
Are you using R6 for Schade Negative Feedback? That is what R6 effectively is.
R12 75k? Cascode collector is very high impedance, that is in parallel with R12, 75k That has to drive the KT66 miller capacitance (higher C in triode mode than in Pentode mode). It also has to drive the node of R6, C16, and control grid.
What does R2 dummy resistor do? Are you going to use 100 Ohm grid stopper resistors for each 6N2P grid? R17. There are no individual 1680 Ohm self bias resistors for the two input triode cathodes, current may not be balanced. It will need individual bypass caps.
Non Cascode input:
R20 has to drive the miller C of the input tubes. May need a lower value. Instead take out R20. Put a 1k Ohm grid stopper resistor on each input grid (right at the tube socket tab). R3 Dummy, what does it do? R17. There are no individual 1680 Ohm self bias resistors for the two input triode cathodes, current may not be balanced. It will need individual bypass caps.
The triode input stage is a lower impedance drive for the triode wired KT66, Good.
Power supply:
I do not use capacitors across HV diodes. Instead use a higher voltage diode if needed. Once, when I had troubles with 1000V diodes, I just went ahead and used Hexfred 8A 1200V diodes there (expensive, and overkill, but they should not die, and the supply was quiet). I use power strips with transient suppressors.
Put bleeder resistors across one of the B+ caps. Safety first.
C16 220nF and R6 10k will be -3 dB at 72 Hz, and -1 dB at 144Hz. R6 will cause the KT66 to draw very high plate current. It is DC coupled from the plates of the input tubes to the control grid.
Are you using R6 for Schade Negative Feedback? That is what R6 effectively is.
R12 75k? Cascode collector is very high impedance, that is in parallel with R12, 75k That has to drive the KT66 miller capacitance (higher C in triode mode than in Pentode mode). It also has to drive the node of R6, C16, and control grid.
What does R2 dummy resistor do? Are you going to use 100 Ohm grid stopper resistors for each 6N2P grid? R17. There are no individual 1680 Ohm self bias resistors for the two input triode cathodes, current may not be balanced. It will need individual bypass caps.
Non Cascode input:
R20 has to drive the miller C of the input tubes. May need a lower value. Instead take out R20. Put a 1k Ohm grid stopper resistor on each input grid (right at the tube socket tab). R3 Dummy, what does it do? R17. There are no individual 1680 Ohm self bias resistors for the two input triode cathodes, current may not be balanced. It will need individual bypass caps.
The triode input stage is a lower impedance drive for the triode wired KT66, Good.
Power supply:
I do not use capacitors across HV diodes. Instead use a higher voltage diode if needed. Once, when I had troubles with 1000V diodes, I just went ahead and used Hexfred 8A 1200V diodes there (expensive, and overkill, but they should not die, and the supply was quiet). I use power strips with transient suppressors.
Put bleeder resistors across one of the B+ caps. Safety first.
DonQ,
You have just a little under 300V B+.
I use 2 each 25k 5W wire-wound resistors in series.
That is 10W total.
300V / 50k = 6mA
6mA x 300V = 1.8W
10W/1.8W = 5.5 x margin.
The resistors will be relatively cool.
You could use 2 each 25k 3 W resistors (6 W total), but the margin would only be 3.33.
The resistors will be a bit on the warm side.
You have just a little under 300V B+.
I use 2 each 25k 5W wire-wound resistors in series.
That is 10W total.
300V / 50k = 6mA
6mA x 300V = 1.8W
10W/1.8W = 5.5 x margin.
The resistors will be relatively cool.
You could use 2 each 25k 3 W resistors (6 W total), but the margin would only be 3.33.
The resistors will be a bit on the warm side.
Hi - yes, I've tried KT77, 6CA7, 350C, 6P3P and 6L6. All just a straight drop-in without any mods at all.
Can't say I particulalry noticed any difference between any of them!! Maybe because my top-end ears response is lacking nowadays after years of concerts, industry and other loud environments....
BachAudioDK,
Max DC current is an unknown spec.
Which factor are you concerned with?
Examples:
1. The DC current that will degrade or destroy the primary wire.
2. The DC current that will cause large distortion at 20Hz (due to saturation).
3. The DC current that will cause large distortion at 80Hz (due to saturation).
3, 2, and 1 are at increasing DC current levels, in that order.
Max DC current is an unknown spec.
Which factor are you concerned with?
Examples:
1. The DC current that will degrade or destroy the primary wire.
2. The DC current that will cause large distortion at 20Hz (due to saturation).
3. The DC current that will cause large distortion at 80Hz (due to saturation).
3, 2, and 1 are at increasing DC current levels, in that order.
Last edited:
I just bought a used A9
What tubes can I try / without any modes ?
I will be running Klipsch Heresies 1 on the 4 ohm tapas these are really a 6ohm speaker
I will try the 8ohm taps as well
I only want to roll the tubes with out doing any modes as doing the mods is over my hear. Also I’m in the states and will be running at US voltage
What tubes can I try / without any modes ?
I will be running Klipsch Heresies 1 on the 4 ohm tapas these are really a 6ohm speaker
I will try the 8ohm taps as well
I only want to roll the tubes with out doing any modes as doing the mods is over my hear. Also I’m in the states and will be running at US voltage
