I bring to your attention a well-reproducible, proven, tube ULF circuit with parallel connection of lamps, based on an entry-level ULF. I once became interested in the circuit of an entry-level tube ULF. I repeated it and was pleased with the result. After some thought, I decided to remake this circuit into a more powerful version. In the stereo version it turned out to be two more lamps, but it's worth it. The 6n3p lamp has two independent lamps in its cylinder. It was decided to assemble a circuit 6n3p + 6p14p + 6p14p. Through trial and error, I found out that it is most advisable to use both halves of 6n3p, for each 6p14p, which in turn are connected together by anodes. Many authors of similar articles suggest parallel connection of the same pentodes, both at the input and at the output. This circuit design does not provide any noticeable increase in watts. In addition, noticeable sound distortions appear and it is quite difficult to get rid of them. Still, the lamp is different, even if both are new and did not work. And we have to complicate the OOS, which also does not lead to anything good.
In the process of a little adjustment, I got rid of OOS completely. I didn't notice any difference by ear. However, in the version with one 6p14p OOS is still needed. The result was an ULF with a maximum output power of about 8.8 W. If the 6p14p inputs are connected together and sent further according to the circuit, then in this option the maximum power is only 5.7 watts. The only thing worth mentioning is that in this circuit you need to select pentodes. If you have to install which ones, an AC background will appear. Or squeaks at low volumes. Accordingly, 6n3p ideally should have two normal halves, and not so that one is used and the other is new. The result from such a lamp will be the same, even if 6p14p are selected. In general, a dozen 6p14p and three 6n3p were enough for me, and I chose the most optimal ones.
Now about the output transformers. If you have TVZ, you can immediately remove them away. They are not suitable at all, since the output impedance with such a connection is very different from the usual one on one 6p14p. A lot of trances were ruined, rewound and abandoned. In the end, trances of the OSM-0.016 brand caught my eye. It was with them that I got simply excellent results! Some use OSM-0.16. Why do you need such a 160 watt trans? If the output power is limited to 9 watts. 16 cotton trances are more than enough. If there are none, then take the iron from TVK-110. Don’t be too lazy to completely wind the outlet on it from scratch. It's worth it.
Now about winding. We wind it like this: the first layer of the secondary is 90 turns of 0.47 wire, then 1500 turns of the primary with 0.18 wire. Then another layer of secondary 90 turns of 0.47 wire and another 700 turns of primary of the same wire. I did not place paper gaskets between the windings; in order to save space, I laid two layers of opaque tape. The transparent one is very inconvenient to wind. And the advantage of this solution: the winding is securely glued. Does not create any noise during operation. We connect the primary into the afterbirth, the secondary in parallel. If the iron is from TVK, then instead of the last 700 turns you wind 1200 turns. I note that no matter how you look at it, the primary will have to be wound turn to turn, otherwise all the windings will not fit. We do not place any paper gaskets between the iron halves! Dimensions of the assembled OSM: 50 mm height, iron thickness 32 mm. TVK is slightly thinner. I am posting photos of OSM and TVK.
We read all other nuances in the entry-level ULF article. The voltage table is the same, do not forget, taking into account that the power supply here is 320 volts. Personally, I didn't pick them up at all. I set the norm only to 6n3p. I've been using this one for a couple of years now. It works 12 hours a day, there are no complaints or breakdowns. Works flawlessly. Very good lows, deep and good HF sound.
A few words about the details. All wiring is 6n3p resistors 0.125, except for the anode ones. It needs something more powerful. It is better to find a double imported variable resistor. I took it from an old Chinese car radio. Domestic ones are no good, uneven adjustment across the channels, and even create all sorts of noises. As for decorations, I installed a 6e1p indicator lamp.
Separately about network trance. I have a rewound TS-100, I still have to blow on seven lamps, they consume a decent amount of filament current. The iron gets very hot. In general, electronic transformers after home-winding are very suitable. But there is one minus: you have to install a bunch of filter chains. If you use it only for incandescent, then no filters are needed and it takes up much less space.
List of radioelements
| Designation | Type | Denomination | Quantity | Note | Shop | My notepad | |
|---|---|---|---|---|---|---|---|
| First scheme | |||||||
| VL1 | Double triode | 6N3P | 1 | To notepad | |||
| Diode | D223 | 1 | To notepad | ||||
| Capacitor | 0.1 µF 400 V | 1 | To notepad | ||||
| Capacitor | 0.1 µF | 1 | To notepad | ||||
| Resistor | 1 | Selection | To notepad | ||||
| Resistor | 1 MOhm | 1 | To notepad | ||||
| Resistor | 470 kOhm | 1 | To notepad | ||||
| Resistor | 3 kOhm | 1 | To notepad | ||||
| Second scheme | |||||||
| VL1 | Double triode | 6N3P | 1 | To notepad | |||
| VL1, VL2 | Output pentode | 6P14P | 2 | To notepad | |||
| Capacitor | 0.068 µF | 2 | To notepad | ||||
| 100 µF 350 V | 1 | To notepad | |||||
| Capacitor | 1 µF | 2 | To notepad | ||||
| Electrolytic capacitor | 330 µF 400 V | 1 | To notepad | ||||
| Capacitor | 0.1 µF | 1 | To notepad | ||||
| Variable resistor | 470 kOhm | 1 | To notepad | ||||
| Resistor | 390 kOhm | 2 | To notepad | ||||
| Resistor | 120 kOhm | 1 | To notepad | ||||
| Resistor | 220 kOhm | 1 | To notepad | ||||
| Resistor | 750 Ohm | 2 | 0.5 W | To notepad | |||
| Resistor | 47 kOhm | 2 | To notepad | ||||
| Resistor | 3.9 kOhm | 1 | |||||
I bring to your attention a well-reproducible, proven, tube ULF circuit with parallel connection of lamps, based on an entry-level ULF. I once became interested in the circuit of an entry-level tube ULF. I repeated it and was pleased with the result.
After some thought, I decided to remake this circuit into a more powerful version. In the stereo version it turned out to be two more lamps, but it's worth it. The 6n3p lamp has two independent lamps in its cylinder. It was decided to put together a circuit 6n3p +6p14p+6p14p. Through trial and error, I found out that it is most advisable to use both halves of 6n3p, for each 6p14p, which in turn are connected together by anodes.
Many authors of similar articles suggest parallel connection of the same pentodes, both at the input and at the output. This circuit design does not provide any noticeable increase in watts. In addition, noticeable sound distortions appear and it is quite difficult to get rid of them. Still, the lamp is different, even if both are new and did not work. And we have to complicate the OOS, which also does not lead to anything good.
ULF circuit with parallel connection of lamps
In the process of a little adjustment, I got rid of OOS completely. I didn't notice any difference by ear. However, in the version with one 6p14p OOS is still needed. The result was an ULF with a maximum output power of about 8.8 W. If the 6p14p inputs are connected together and sent further according to the circuit, then in this option the maximum power is only 5.7 watts. The only thing worth mentioning is that in this circuit you need to select pentodes.
If you have to install which ones, an AC background will appear. Or squeaks at low volumes. Accordingly, 6n3p ideally should have two normal halves, and not so that one is used and the other is new. The result from such a lamp will be the same, even if 6p14p are selected. In general, a dozen 6p14p and three 6n3p were enough for me, and I chose the most optimal ones.
Tube amplifier parts
Now about the output transformers. If you have TVZ, you can immediately remove them away. They are not suitable at all, since the output impedance with such a connection is very different from the usual one on one 6p14p. A lot of trances were ruined, rewound and abandoned. In the end, trances of the OSM-0.016 brand caught my eye. It was with them that I got simply excellent results! Some use OSM-0.16. Why do you need such a 160 watt trans? If the output power is limited to 9 watts. 16 cotton trances are more than enough. If there are none, then take the iron from TVK-110. Don’t be too lazy to completely wind the outlet on it from scratch. It's worth it.
Now about winding. We wind it like this: the first layer of the secondary is 90 turns of 0.47 wire, then 1500 turns of the primary with 0.18 wire. Then another layer of secondary 90 turns of 0.47 wire and another 700 turns of primary of the same wire. I did not put paper gaskets between the windings; in order to save space, I laid two layers of opaque tape.
The transparent one is very inconvenient to wind. And the advantage of this solution: the winding is securely glued. Does not create any noise during operation. We connect the primary into the afterbirth, the secondary in parallel. If the iron is from TVK, then instead of the last 700 turns you wind 1200 turns.
I note that no matter how you look at it, the primary will have to be wound turn to turn, otherwise all the windings will not fit. We do not place any paper gaskets between the iron halves! Dimensions of the assembled OSM: 50 mm height, iron thickness 32 mm. TVK is slightly thinner. I am posting photos of OSM and TVK.
We read all other nuances in the entry-level ULF article. The voltage table is the same, do not forget, taking into account that the power supply here is 320 volts. Personally, I didn't pick them up at all. I set the norm only to 6n3p. I've been using this one for a couple of years now. It works 12 hours a day, there are no complaints or breakdowns. Works flawlessly. Very good lows, deep and good HF sound.
A few words about the details. All wiring is 6n3p resistors 0.125, except for the anode ones. It needs something more powerful. It is better to find a double imported variable resistor. I took it from an old Chinese car radio. Domestic ones are no good, uneven adjustment across the channels, and even create all sorts of noises. As for decorations, I installed a 6e1p indicator lamp.
Separately about network trance. I have it rewound TS-100, you still have to blow on seven lamps; they consume a decent amount of filament current. The iron gets very hot.
In general, electronic transformers after home-winding are very suitable. But there is one minus: you have to install a bunch of filter chains. If you use it only for incandescent, then no filters are needed and it takes up much less space.
The output power of a single-ended ULF can be increased by parallel connecting one or more lamps to the output stage lamp. Thus, at the same supply and anode voltage, the anode current and, accordingly, the output power of the cascade increases two or more times. An example of parallel connection of an additional lamp in the final stage of a single-ended ULF is shown in rice. 1.
Fig.1. Schematic diagram of a single-cycle ULF on one (a) and two (b) pentodes
In the scheme under consideration ( rice. 1, a) the so-called ultralinear connection of the pentode is used, a characteristic feature of which is the connection of the cathode to the protective grid. The pentode shielding grid is connected to pin 2 of the output transformer Tpl, with the number of turns between pins 2 and 3 being approximately 43% of the number of turns between pins 1 and 3. The Tpl transformer is designed so that the impedance of the primary winding (pins 1-3) is equal to the value of the load resistance determined for each lamp according to the catalog specification. So, for example, for an EL34 lamp this resistance is approximately 3 kOhm. The automatic bias voltage is generated across resistor R3, which is shunted by electrolytic capacitor C2.
When connecting an additional lamp (or lamps) in parallel to the lamp of the ULF output stage, you will need to adjust the values of some elements. So, for example, when connecting one additional lamp ( rice. 1, b) the resistance value of resistor R3 in the automatic bias circuit should be reduced by approximately two times compared to the previously considered circuit ( rice. 1, a), and the value of the capacitance of the shunt capacitor C2 is doubled.
This is explained by the fact that when two lamps are connected in parallel, the cathode current doubles. It should be noted that the power of resistor R3 should also be doubled, that is, from 5 to 10 W. To achieve a twofold increase in output power, it will also be necessary to reduce the impedance of the primary winding of the transformer Tpl by half.
Theoretically, in a similar way, a larger number of similar lamps with almost identical parameters can be connected in parallel with the output stage lamp. Therefore, on sale you can find already selected pairs and even fours of lamps for use in parallel connection of the ULF output stage. As in a single-cycle tube ULF, you can increase the output power of a push-pull amplifier by parallel connecting one or more tubes to the output stage lamps. At the same supply and anode voltage, the anode current and, accordingly, the output power of the cascade increases two or more times. We will explain the features of such a connection using the example of a simple push-pull power amplifier, the circuit diagram of which is shown in.
rice. 2
This amplifier consists of two identical channels, each of which is based on the single-ended amplifier discussed earlier. An example of parallel connection of additional lamps in the final stage of such a push-pull ULF is shown in rice. 3.
Fig.3. Schematic diagram of a simple push-pull power amplifier with parallel connection of lamps
When choosing the parameters of elements for a push-pull tube ULF with parallel connection of lamps, all the comments and recommendations mentioned earlier for a single-ended circuit are valid.
Almost every radio amateur who takes his first steps in mastering tube ULFs starts with a simple one on 6P14P. This scheme is really simple and unpretentious. It works well when assembled without errors, the dimensions are small, the sound is pleasant.
But after listening to such an amplifier for some time, you begin to understand that the power of one lamp is clearly not enough. And it’s not a matter of the desire to turn up the music at full blast so that the neighbors can hear, but the need to have a certain power reserve for high-quality playback of low-frequency sounds. The easiest way out is to add another similar lamp to the output stage, connecting it in parallel with the already installed one.This inclusion of lamps makes it possible to reduce the internal resistance of the lamps, which has a positive effect on the output impedance of the amplifier and increases the ULF power by reducing the transformation ratio in the transformer.
Schematic diagram of ULF on two 6P14P lamps
Exit The current power is 6 watts.
Reproducible frequency range 35-35000 Hz.
5% distortion at maximum power.
Input voltage 1 volt.
This circuit is set up in almost the same way as a single-lamp circuit, only you need to achieve equality of the currents flowing through the output lamps. I had EL84 - these are analogues of the Soviet 6P14P, and I used them. In my version, I set one EL84 lamp to 54mA, and the other to 55mA. At the input 6n2p - 7.5mA. I selected all the ratings: according to the cathodes and the open mode at 220 k (replaced the circuit in front of the grids with the EL84 housing by 500 k). Now the ULF works great: it turned out with deep highs, normal mids, normal lows.
When setting up (setting the anode voltage and current), you must not exceed the power on the lamp - approximately 15 watts will be the limit. We measure the current of each lamp by the voltage drop at 10 Ohms - R3 R4; if necessary, they can be used to balance the currents.
One more thing. To parallel the lamps, you need to reduce the load resistance, that is, reduce the estimated number of turns of the output audio transformer by approximately 30%, otherwise there will be no noticeable increase in power.
Finished the job. Input: Tungsram PCC88 current 2 mA. The output of all 4 x EL84s was set to 40mA. Works great. Speakers with 25-G speakers pump normally. True, for a weak tube ULF this is a heavy speaker.
A more sensitive one is needed, for example 10gd36 or similar. The room is 12 sq. meters sounds quite decent, but undoubtedly weaker than a two-stroke. At 350 volts anode the difference is noticeable - it costs 1 lamp or 2. The power increase is about 50%. Assembly and testing - Ma$ter.
Recently on the Internet I saw an interesting circuit of a class “A” tube amplifier, with 6p45s pentodes at the output. The scheme was simple and had good recommendations from those who repeated it. But I decided to slightly change the electrical circuit by installing 6P41S, since despite the lower power, it does not have an inconvenient contact on top for supplying anode voltage.The driver contains 6p14p. In the output stage I used automatic bias, which has proven itself to be excellent for its simplicity and stability of parameters.
Power to the ULF comes from a mains transformer, rectifier and inductor. The transformer chose TSSh-170, but TS-160, TS-180 can also be installed here. In general, anyone capable of providing up to 300V 0.3A anode and 6.3V 3A filament voltage. Throttle - ready from .
For the case I used an unnecessary Chinese 20-watt speaker. We will disassemble the AC and cut out the necessary windows.
The lamps should be on top; we install them on a metal base - a sheet of two-millimeter aluminum, with cut-out round windows for the panels. At the back we cut out a window for the panel of sockets and connectors. Electromagnetic interference from devices is absolutely inaudible - you can safely repeat the idea with wood.
We attach sound transformers, a choke, and high-voltage electrolytes to a wooden base using screws. And we assemble the lamps and trim on the top aluminum cover. All connections must be as short as possible, since they carry significant currents and voltages.
After assembling everything, we test the power supply. Don’t forget to solder a 2 watt 200-500 kOhm discharge resistor to the anode output, parallel to the filter capacitor. After making sure that the power supply output has the required voltage, the capacitors do not explode, and the diodes do not heat up, we connect the amplifier.
The speakers must also be connected, as a strong hum or whistle will indicate problems and assembly errors.
We immediately measure the current consumption of each lamp by monitoring the voltage drop across the cathode resistors. By touching the input jack with a screwdriver, you can hear the background. This means the cascade is working properly.
In comparing this single-ended amplifier with a similar one with a 6P14P at the output, I was convinced of the significant advantage of the first.
The power is noticeably higher, which already allows you to listen to the bass. True, the treble is somewhat weak, but overall the sound is pleasant and not tiring.
