The sound of the 300B Class A single-ended output amplifier has fascinated many audiophiles. To date, there are still many experienced audiophiles in Hong Kong and Taiwan who enjoy playing it tirelessly. Some people even describe it as the highest state of fever. However, the power of less than ten watts restricts the use of some inefficient high-quality speakers. This is a great regret. If there is a sound quality of 300B single-ended output, and the efficiency, dynamics, damping, and resolution of the push-pull output exceed its excellent amplifier, I believe it is the dream of many enthusiasts.
After more than a year of repeated production and adjustment, the author finally produced this super dual monomer class A push-pull tube amplifier. Dedicated to audiophiles at this time. If you are a DIY burner, after reading this article patiently, you can't help it without scratching your palm.
In order to save you a lot of trouble in the production process, I will introduce some necessary experience here.
Circuit characteristics, this machine adopts one-stage SRPP voltage amplification, one-stage long tail inverter circuit, and FU-7 double-tube parallel amplification. I tried to insert a first-level cathode output device after the inverter circuit, in order to reduce the load of the inverter circuit and improve the driving force. As a result, the mid and low frequencies were richer, but the gold velvet-like high-frequency treble could not be found and had to be removed. This measure is often used in some low-end amplifier circuits, but the motor does not work here. As long as the gain is sufficient, one more level is better than one less level.
The first stage uses 12AU7 [6N4] for SRPP amplification, and its high frequency response is good, and the tone is relatively neutral. Use 6N4
It can make the voltage level have enough gain, and the "bile taste" is more intense. 6DJ8 [6N11] can get higher resolution here. But the gain is not enough, and the "charm" is also less.
The second stage uses 6SN7H [6N8P] plus balanced current source to form a long tail inverter circuit. There is a gain of about 15db. The addition of the balanced current source is beneficial to balance the two arms of the inverter circuit and reduce distortion. The working current of the inverter stage is very important for the sound quality of the whole machine. Adjust R12 can choose between 4-8MA, the author chooses 5MA. If the value is too large or too small, it has a crucial impact on both treble and bass.
The third power output stage uses four FU-7 parallel push-pull outputs. The use of FU-7 is not just for cheap, but more importantly, his vocal performance ability is not far behind the famous 300B. Another point is that the machine adopts a dual-tube parallel output. Generally speaking, after bile ducts are connected in parallel, the mid-low frequency of the sound orientation becomes thicker and the high frequency becomes masked, and the resolution decreases to varying degrees. Different bile ducts have their own differences. The overall performance after EL34, KT88, and parallel connection has been tried. Except for the increase in output power, the overall performance is not as good as a single tube. However, when the FU-7 is used in parallel with a single tube and a single tube when the load is about 6000 Euros, the difference in high frequency is minimal, the mid-frequency texture is increased, and the human voice is more abundant. Dynamics, control power, and increased output power are naturally expected. Each FU-7 works at 470V 50MA, power consumption is about 23W, close to FU
The maximum anode dissipation power of -7 is 25W, but as long as you choose genuine tubes, there is no problem. The author's prototype has been used for a year without any aging phenomenon, not to mention his price is only a quarter of KT88. FU-7 is one of the most valuable bile ducts.
FU-7 is connected as a triode connection method, and its sound quality has long been finalized. Although there is a little less masculine masculinity, a part of it can be supplemented by using two tubes in parallel.
Because the open-loop characteristics of the whole machine are very good, the large loop feedback value of this machine is low. It effectively reduces the negative effects of transient distortion and high frequency phase shift caused by large loop feedback. This makes the unit have a very good transient response.
The whole machine has only one level of capacitive coupling, the capacity is very small, and the impact on sound quality is not very large. A supplementary capacitor can be used. I use WEMA capacitors, which are neutral and have good resolution.
The output transformer is the key to the success or failure of a tube amplifier. This machine uses high-quality iron core and oxygen-free copper wire to wind itself. As long as it is meticulous and careful, according to the picture is correct, the success rate is extremely high. It's much better than some fake output products.
The size of the iron core is larger and the low frequency is better, but the magnetic flux leakage, leakage inductance and distributed capacitance are large, and the high frequency frequency response decreases. The iron core is smaller, the mid-high frequency is good, but the mid-low frequency is worse, and the sound is thin. After numerous experiments, the author carefully wound the 4X6 iron core according to the picture. Good frequency response was achieved. Hearing is also very beautiful.
The power supply part is very important. This machine is a dual-unit design, and two power supply cows need to be made. I use 450W
The iron core is conventionally wound. No longer. The choke is a burden, as long as the DC ripple of the power supply is small enough, it is not better. After the rectification, in addition to the electrolytic capacitor used in the first stage of filtering, all other filtering capacitors use CBB60 polypropylene capacitors and then add a 0.68 CBB small capacitor. Multiple motor starting capacitors 30UF / 500V can be used in parallel. If the space of the bottom plate is large enough, it is better to replace the first-stage filter capacitor with CBB. But the capacity should be sufficient, not less than 90UF /
500V. You will find that this is a beautiful "trick". The author often adopts this method when trying to power a bile machine, and has tried many times and tried many times. In terms of medium frequency texture, the resolution is obviously better than "high-speed electrolysis" and "audio-specific electrolysis". Once again, the capacity must be large enough, and there must be a margin for the withstand voltage, otherwise the power supply with unfiltered filter will seriously affect the sound quality.
Commissioning: 1. Adjust the four grid negative pressure adjustment potentiometers to make the current corresponding to the four FU-7s be 50MA, and adjust it again after working for one hour.
2. Adjust the resistance of the balancing current source R12 so that the current of the inverter stage is 5MA.
3. The current of the SRPP amplifier stage should not be lower than 3MA, otherwise the sound effect will be reduced, and the resistance R3 can be increased or decreased to reach it.
4. The filaments of 12AU7 and 6SN7H are not grounded, but the 100V + voltage is taken out through the partial voltage, which is added to the two ends of the filament through two flat resistors. The circuit diagram is not drawn, and the reader can design it by himself. This is because the cathode potential of both stages is above 100V, which exceeds the maximum cathode filament voltage.
5. Proofread the negative feedback phase. Since the negative feedback amount of this unit is very small, it is not necessarily howling when the phase is reversed. You can shortly open the negative feedback experiment. If the music sound becomes louder after disconnection, it means that the feedback phase is correct. The two input terminals of the output cow can be replaced.
Note that when there is no signal, if the FU-7 screen is red and the tweeter has irregular noise, it means that there is high frequency self-excitation. The top screen lead of the FU-7 can be wound around five times to form a small inductance, which can generally be solved.
6. Inverted-phase power supply 380V can be increased to 430V. The dynamics are greater and the control is better, but the sound is a bit harder.
This machine can be directly connected to the CD player. Then connect to the predecessor, but it is a bit more addictive!
The main performance test of this machine:
Power: 35X2 8 Euro Distortion: 0.5% 1KHZ 5W
Frequency response: 18--30000Hz plus or minus 3db
After more than a year of repeated production and adjustment, the author finally produced this super dual monomer class A push-pull tube amplifier. Dedicated to audiophiles at this time. If you are a DIY burner, after reading this article patiently, you can't help it without scratching your palm.
In order to save you a lot of trouble in the production process, I will introduce some necessary experience here.
Circuit characteristics, this machine adopts one-stage SRPP voltage amplification, one-stage long tail inverter circuit, and FU-7 double-tube parallel amplification. I tried to insert a first-level cathode output device after the inverter circuit, in order to reduce the load of the inverter circuit and improve the driving force. As a result, the mid and low frequencies were richer, but the gold velvet-like high-frequency treble could not be found and had to be removed. This measure is often used in some low-end amplifier circuits, but the motor does not work here. As long as the gain is sufficient, one more level is better than one less level.
The first stage uses 12AU7 [6N4] for SRPP amplification, and its high frequency response is good, and the tone is relatively neutral. Use 6N4
It can make the voltage level have enough gain, and the "bile taste" is more intense. 6DJ8 [6N11] can get higher resolution here. But the gain is not enough, and the "charm" is also less.
The second stage uses 6SN7H [6N8P] plus balanced current source to form a long tail inverter circuit. There is a gain of about 15db. The addition of the balanced current source is beneficial to balance the two arms of the inverter circuit and reduce distortion. The working current of the inverter stage is very important for the sound quality of the whole machine. Adjust R12 can choose between 4-8MA, the author chooses 5MA. If the value is too large or too small, it has a crucial impact on both treble and bass.
The third power output stage uses four FU-7 parallel push-pull outputs. The use of FU-7 is not just for cheap, but more importantly, his vocal performance ability is not far behind the famous 300B. Another point is that the machine adopts a dual-tube parallel output. Generally speaking, after bile ducts are connected in parallel, the mid-low frequency of the sound orientation becomes thicker and the high frequency becomes masked, and the resolution decreases to varying degrees. Different bile ducts have their own differences. The overall performance after EL34, KT88, and parallel connection has been tried. Except for the increase in output power, the overall performance is not as good as a single tube. However, when the FU-7 is used in parallel with a single tube and a single tube when the load is about 6000 Euros, the difference in high frequency is minimal, the mid-frequency texture is increased, and the human voice is more abundant. Dynamics, control power, and increased output power are naturally expected. Each FU-7 works at 470V 50MA, power consumption is about 23W, close to FU
The maximum anode dissipation power of -7 is 25W, but as long as you choose genuine tubes, there is no problem. The author's prototype has been used for a year without any aging phenomenon, not to mention his price is only a quarter of KT88. FU-7 is one of the most valuable bile ducts.
FU-7 is connected as a triode connection method, and its sound quality has long been finalized. Although there is a little less masculine masculinity, a part of it can be supplemented by using two tubes in parallel.
Because the open-loop characteristics of the whole machine are very good, the large loop feedback value of this machine is low. It effectively reduces the negative effects of transient distortion and high frequency phase shift caused by large loop feedback. This makes the unit have a very good transient response.
The whole machine has only one level of capacitive coupling, the capacity is very small, and the impact on sound quality is not very large. A supplementary capacitor can be used. I use WEMA capacitors, which are neutral and have good resolution.
The output transformer is the key to the success or failure of a tube amplifier. This machine uses high-quality iron core and oxygen-free copper wire to wind itself. As long as it is meticulous and careful, according to the picture is correct, the success rate is extremely high. It's much better than some fake output products.
The size of the iron core is larger and the low frequency is better, but the magnetic flux leakage, leakage inductance and distributed capacitance are large, and the high frequency frequency response decreases. The iron core is smaller, the mid-high frequency is good, but the mid-low frequency is worse, and the sound is thin. After numerous experiments, the author carefully wound the 4X6 iron core according to the picture. Good frequency response was achieved. Hearing is also very beautiful.
The power supply part is very important. This machine is a dual-unit design, and two power supply cows need to be made. I use 450W
The iron core is conventionally wound. No longer. The choke is a burden, as long as the DC ripple of the power supply is small enough, it is not better. After the rectification, in addition to the electrolytic capacitor used in the first stage of filtering, all other filtering capacitors use CBB60 polypropylene capacitors and then add a 0.68 CBB small capacitor. Multiple motor starting capacitors 30UF / 500V can be used in parallel. If the space of the bottom plate is large enough, it is better to replace the first-stage filter capacitor with CBB. But the capacity should be sufficient, not less than 90UF /
500V. You will find that this is a beautiful "trick". The author often adopts this method when trying to power a bile machine, and has tried many times and tried many times. In terms of medium frequency texture, the resolution is obviously better than "high-speed electrolysis" and "audio-specific electrolysis". Once again, the capacity must be large enough, and there must be a margin for the withstand voltage, otherwise the power supply with unfiltered filter will seriously affect the sound quality.
Commissioning: 1. Adjust the four grid negative pressure adjustment potentiometers to make the current corresponding to the four FU-7s be 50MA, and adjust it again after working for one hour.
2. Adjust the resistance of the balancing current source R12 so that the current of the inverter stage is 5MA.
3. The current of the SRPP amplifier stage should not be lower than 3MA, otherwise the sound effect will be reduced, and the resistance R3 can be increased or decreased to reach it.
4. The filaments of 12AU7 and 6SN7H are not grounded, but the 100V + voltage is taken out through the partial voltage, which is added to the two ends of the filament through two flat resistors. The circuit diagram is not drawn, and the reader can design it by himself. This is because the cathode potential of both stages is above 100V, which exceeds the maximum cathode filament voltage.
5. Proofread the negative feedback phase. Since the negative feedback amount of this unit is very small, it is not necessarily howling when the phase is reversed. You can shortly open the negative feedback experiment. If the music sound becomes louder after disconnection, it means that the feedback phase is correct. The two input terminals of the output cow can be replaced.
Note that when there is no signal, if the FU-7 screen is red and the tweeter has irregular noise, it means that there is high frequency self-excitation. The top screen lead of the FU-7 can be wound around five times to form a small inductance, which can generally be solved.
6. Inverted-phase power supply 380V can be increased to 430V. The dynamics are greater and the control is better, but the sound is a bit harder.
This machine can be directly connected to the CD player. Then connect to the predecessor, but it is a bit more addictive!
The main performance test of this machine:
Power: 35X2 8 Euro Distortion: 0.5% 1KHZ 5W
Frequency response: 18--30000Hz plus or minus 3db
Touchless Sensor-Makes it germ Free
Environment Friendly-Prevents Contamination
Ideal fit for Kitchen/Bathroom/Bedroom
As users hands or debris enter the zone 6 inches (15cm) from the infrared sensor on top of the dustbin, the lid will automatically open.
The Lid will remain open if hand or debris is within the 6 inch (15cm) range of the infrared sensor. Lid will close 7 seconds after users hands move away.
The new touch switch panel has higher stability and efficiency. you can use it effortlessly. There are [OPEN" & [CLOSE" buttons for manual operation, and there is a ON/OFF power switch on the back of the dustbin.
The new removable plastic rim is easy to lift out, and the plastic ring helps leave no excess plastic bag visible (w/o liner).
Two liners (30L+20L) for easy recycling
Features:
-100% [Hands-Free" operation.
-[Germ-Free"-Prevents cross-contamination
- Trash Bag Retainer Ring stops full, heavy bag from falling in and keeps bag ends neatly out of view
-Rubber feet keeps this trash can in place and protects floors from scratches
-Removable hard ABS plastic head for easy cleaning
-Uses 4 AA-Sized batteries 1.5V(LR6) (Not included)
-Low energy-consuming
-Multiple colors to satisfy your different requirements.
-Capacity:30L+20L
-Dimensions: 34W x 48 L x 64H CM
-1 Year Manufacturer`s Warranty included
Rectangular Sensor Automatic Dustbin 2-Compartment 30L+20L
Automatic Dustbin,Hand Sensing Dustbin,Hotel Dustbin,Environmental Dustbin
NINGBO ZIXING ELECTRONIC CO.,LTD. , https://www.zixingautobin.com