Hello dear radio amateurs! I want to tell you about the creation of my first audio amplifier using tubes. I chose a single-cycle circuit, fortunately there were famous GU-50, allowing you to get up to a couple of tens of watts per channel. I don’t believe that for any serious listener they might not be enough for a small room. The driver for them also requires a solid one - I used common ones 6P15P. The anode current is high - about 0.09 A. It is set by adjusting the bias voltage on R15. I decided to abandon auto-bias so as not to lose precious watts :) Selecting the driver current using R16. All voltages in control points shown. Regular rectifier - diode bridge and capacitors, with small P-filters based on low-resistance resistors. Tests have shown that it is not necessary to install a choke - the background is practically inaudible, but it makes sense to separate the power supply into channels separately so that signals do not leak through the anode lines. Further, in fact, herself ULF circuit, which also contains all the data on transformers.

Photos of the ultrasonic unit assembly process

This design of the sidewalls is not without reason - it is convenient to turn over. Underneath the film is mirror-cut laser-cut stainless steel. Industrial CNC machine for laser cutting of metal, load the AUTOCAD file into it, and voila - everything is clean and smooth!

Of course, I didn’t cut it myself, my friends helped me. There is another set, I don't need it. Lamps in 400 V 85 mA mode. By the way, if I set the current to 90 mA, the anodes begin to turn red.

And here he is - a monster! The cross-section of the transformer is 35x55 = 19.25 centimeters square.

I did the first option appearance amplifier, and... somewhat disappointed, it turned out to be some kind of cuttlefish. Maybe it would be necessary to paint the wooden parts more evenly, and then cover them with spray varnish...

This is the only problem I have, I can’t cover it evenly, I sanded it three times. Then kind people advised me to try painting the wood with black paint - black with a shiny panel looks cool.

Amplifier housing - take two

I used aerosol cans of paint for this. Sold at the market or in a car dealership. There are plenty of them there - any color, glossy and matte.

As for the plate, there’s just a hole there, I decided to cover it with something, I disassembled the Korean monitor from 1997 (how well assembled, the whole circuit is in an aluminum screen, and I pulled the mosfets with all my heart) and the product number is stamped on this screen. Cut it out, closed the hole, cool!

You also need to install green eyes - for visual indication of the sound signal. It turned out like a cabinet with glasses!

So, what we end up with: he really sings!

No, brothers - you need to hear this! It's warmed up, you can't get up if you fall! It is better to hear once than to read 100 times - this is exactly the case. That's all for now, I was with you rv3dun.

Briefly, mostly photos (re-uploaded in good quality). I’ll say right away that I had little experience and knowledge in radio engineering and made a lot of mistakes. Not being a fanatical lover of warm tube sound, the assembly process itself was interesting to me.

The hardest part is finding the output transformers. I bought myself ready-made ones from the TU-100M amplifier (I didn’t choose for a long time, I took what they had). The frame was made from an aluminum profile and the strength margin was a little overdone.

Upper part The body was made of 3mm steel. Holes for transformers and lamps were laser cut. The bottom was also cut from 2mm steel with ventilation holes:

Front panel made from a piece of aluminum:

Scheme

The final amplifier is assembled using a push-pull circuit using two G-807 lamps. Pre-amplifier contains two amplification stages assembled on a 6N9S double triode ( foreign analogue 6SL7).

Advantages of 6N9S:
1) The lamp was originally designed for audio applications;
2) Two triodes in a cylinder;
3) High linearity;
4) Wide distribution, low price.

Disadvantages of 6N9S:
1) High internal resistance.

The pre-terminal amplifier (an intermediate link between single-ended and push-pull amplifiers) is assembled using a phase-inverted circuit on a 6N9S double triode; its main purpose is to form two mutually antiphase, equal in amplitude signals from the input signal. In the TU-100M circuit, the lamp amplifies the input signal and the voltage amplified by it is supplied to the lamp grid of the first arm push-pull amplifier.

Part of the output voltage of the first lamp of the phase-inverted amplifier is supplied to the input of the second lamp of this amplifier. The voltage amplified by the second lamp of the phase-inverted amplifier is supplied to the grid of the lamp of the second arm of the push-pull
amplifier Thus, for the first arm of a push-pull amplifier the signal passes through one tube, and for the second through two.

It would be better if the voltage applied to the input of the first arm was equal to the voltage at the input of the second arm. I made a slightly different circuit, with a modified phase inversion stage.

Advantages:
1) Reduced requirements for supply voltage filtering;
2) Extremely low level noise;
3) Equal output voltages of the shoulders.

I found another option on the forums:

Sockets for lamps 6N9S:

The amplifier housing contains a DAC with the ability to connect to a computer via USB:

Adjustment option:

Transformer screens, first sketches on paper:

Cut from 2mm steel:

After filing and sanding:

Some more photos:

Cleaned it up a bit:

Price: unreasonably expensive.
It’s easier to buy ready-made for 4-5 thousand rubles. But if anyone needs it, I can send you files for cutting and for printed circuit boards.

Hello to all lovers of good sound! People always ask me which one is vintage tube amplifier better sound. Although stone amps have many great features, many music lovers and audiophiles feel that these amps cannot provide the same great sound quality. This also applies to such a product category as: vintage tube amplifier.

However, not all vintage tube amps are good. By the way, there are only a very small number of tube amplifiers that were created in the late 1960s to the 80s, and they sound good, and are considered one of the best electronics, both in sound and in overall design.
There are many vintage tube amps you can buy, but only a few are good.

These include products from Dynaco, Marantz and Harman Kardon.

However, you shouldn’t rejoice ahead of time, because a vintage tube amplifier with good sound will cost big money, it is much easier to buy a new lamp or hybrid amplifier with a guarantee, free shipping, without thinking how long it will last and what needs to be changed in it.

One of the most popular tube amplifiers ever produced is the Dynaco Stereo 70, or ST-70 for short. More than 300,000 units of these were sold.

The Dynaco ST-70 tube amplifier can be purchased at a price of 60,000 rubles.

Originally released in 1959.
The Dynaco ST-70 has 35 watts per channel with a simple yet very sophisticated design. It uses four EL34 output tubes, a pair of 7199 input tubes, and GZ34/5AR4 tubes. This is considered to be one of the finest vintage tube amplifiers.

The Dynaco ST-70 tube amplifier offers good high quality sound at a relatively low price. As a result, it was one of the few tube amplifiers that remained in production and sold well, even after the market turned its attention to solid-state technology.

Due to its initial low cost and large quantity units produced, the Dynaco ST-70 remains an affordable vintage tube amplifier.

Julius Futterman was the very first to make a tube amplifier without output transformers. However, his work was then continued at New York Audio Labs.

The Futterman H3 OTL tube amplifier can be purchased at a price of 160,000 rubles.

A little history

Before the appearance transistor amplifiers nominal impedance of most high quality speaker systems was 16 ohms. For this there were good reasons, since, all other things being equal, a higher impedance speaker is more efficient, and the crossover design is not as complex or non-existent.

The reason for the move to lower impedance speakers in acoustics today is, of course, the fact that voltage-limited transistor amplifiers provide more power to such speakers.

First introduced in 1961, the McIntosh MC275 tube amplifier is one of the most beloved and renowned vintage tube amplifiers among music lovers and audiophiles. Its name comes from the fact that it uses two 75-watt amplifiers, which gives it quite a lot of power that is not available from a regular tube amp.

Amplifier McIntosh MC275

The MC275 is also built with four KT88 output tubes, which allow the amplifier to work well with a variety of musical styles.

The McIntosh MC275 tube amplifier can be purchased at a price of 100,000 rubles.

The popularity of the vintage McIntosh MC275 tube amplifier led to the fact that in 2011. They also released . as a 50th anniversary issue.

There were a lot of them produced limited quantity, this special edition is a great opportunity for collectors to own a factory version of one of the greatest tube amps of all time. By the way, the vintage tube amplifier McIntosh MC275 is also the ancestor of the modern McIntosh MC275 Mk IV.

Marantz 8B

The tube amplifier was released in 1961 as a redesigned version of the Marantz 8, which itself was updated version Marantz 7. Developer Sid Smith then introduced the pinnacle of ultra-linear Class A amplifier circuitry.

Amplifier Marantz 8B

The Marantz 8B tube amplifier can be purchased at a price of 80,000 rubles.

The vintage Marantz 8B tube amplifier uses a pair of EL34 tubes with a high-power pentode with an output of 35 watts per channel. This tube amplifier produces full and colorful sound with...

This rather interesting vintage tube amplifier uses 2 pcs at the output. pentodes 6550. But the power of the “lamp” is 75 W per channel.

The Audio Research 76A tube amplifier can be purchased at a price of 80,000 rubles.

However, the Audio Research 76A amplifier uses a very difficult to control power supply.

This tube amp is quite heavy, but I really liked its performance. This one is not bad for its detail and high resolution.

Harman Kardon Citation II is recognized as one of the most elegant and attractive vintage tube amplifiers, which is prized by collectors, and is also one of the clearest and most accurate in sound. This is partly due to the bandwidth being higher than the audible range, which consequently eliminates artifacts such as phase shift at high frequencies.

The Harman Kardon Citation II tube amplifier can be purchased at a price starting from 90,000 rubles.

The vintage Harman Kardon Citation II tube amplifier is built with KT88 output tubes and is rated at 60 watts per channel. The unit has multiple controls for precise adjustments, including output tube bias controls and balance controls alternating current, as well as a meter on the back of the tube amplifier to reveal the current levels for each.

However, the Harman Kardon Citation II produces a fairly crisp and dry sound that is generally different from the mellow sound of most tube amps, but with some distortion. Like other amps on this list, the Citation II is very difficult to find and buy in excellent condition; it is much easier to buy a new tube amp or a hybrid with a similar one.

The main innovation of this vintage amplifier is that it is built according to Tim de Paravinci's design, namely the output stage is made using a symmetrical bridge circuit. When turned on, the anode, as well as the screen grid and cathode, have all their coils on the output transformer itself.

The EAR 509 amplifier was created for use in professional studios. High fidelity audio in studios makes it ideal for home audio playback.

Nowadays, EAR Yoshino 509 has been released in a new version, despite its high power, it has been improved without sacrificing sound, and has a compact design.

The new tube amplifier EAR Yoshino 509 can be purchased at a price of 800,000 rubles.

Accurately set the operating offset. The 4 LEDs let you know when it's set to equal intensity, allowing you to easily adjust the bias when it is.

In the late 60s, William Zane Johnson began making and selling a converted Dynaco ST-70 amplifier. Many transistor amplifiers were created in the 70s. However, the all-tube Dynaco D70, in 1983, forever set the standard for Audio Research amplifier sound quality.

The Audio Research Reference 600 tube amplifier can be purchased at a price starting from 2,000,000 rubles.

However, in 1995, Johnson made an amplifier that became very famous, namely the Audio Research Reference 600. This later evolved into the Audio Research Reference 610T, with its 600 Watts!

With its appearance, this amplifier plunged the audio world into .

The price of the Audio Note Ongaku amplifier at the time of release was $60,000!

However, in 1988, Hiroyashi Kondo's single-ended amplifier had an output power of 27 W and set an incredible price record for tube amplifiers.

The Audio Note Ongaku was the first mass-produced amplifier and used all components: transformers, capacitors and wires that were made by hand.

Significantly newer in design than several other amplifiers, the Cary Audio CAD-805 was first released in 1991. This vintage tube amplifier marked the beginning of a new type of high-quality amplifier.

The Cary Audio CAD-805 tube amplifier can be purchased at a price of 300,000 rubles.

Despite early skepticism, the Cary Audio CAD-805 tube amplifier ultimately won over critics with its ability to deliver on nearly every aspect music track, enhancing each instrument and creating a clear and precise listening experience. Its success led to the creation of other triode amplifiers, but the CAD-805 remains outstanding in its class.

The Cary CAD-805 amplifier returned single-ended amplifiers to their place of honor. It has the build quality of McIntosh amplifiers and is the originator of the phrase "single-ended mid-range magic."

Results. While vintage tube amps can provide excellent sound quality, not all of them, but only a very, very small portion of them, are more fragile than their newer counterparts and require a higher level of maintenance. Because of their age, vintage tube amplifiers should be thoroughly inspected before purchase, and you should ensure that they function properly.

Be sure to also listen to the tube amp at low volume. This highlights any shortcomings or advantages in the operation of the device and also gives the buyer a clearer understanding of the general sound.

Advice!!! In any case, to avoid headaches, it is better to buy a new tube amplifier or a hybrid one.

Refurbished tube amplifiers

The popularity of vintage tube amps has led to the creation of replacement parts and repairs for many older tube amps. In turn, this has increased the number of refurbished tube amplifiers on the market. Remanufactured tube amplifiers must be cleaned and rebuilt using new components. They are designed to look and perform just like new product, as much as possible. While remanufactured and rebuilt tube amplifiers can provide many years of excellent use, it is important to investigate the nature of the work done.

Find out if restoration has been done previous owner or a professional electronics retailer or repair shop. Examine a remanufactured tube amplifier in the same way as a standard used item to ensure it is functioning properly. Although these items often sell for higher prices than the standard ones used, they may be worth the cost.

However, you shouldn’t rejoice ahead of time, because a vintage tube amplifier with a good sound will cost a lot of money, it’s much easier to buy a new tube or hybrid amplifier with a guarantee, free shipping, without thinking about how long it will last at the same price as a vintage tube amplifier or in good quality

Listen to some onlinetracksright there on the Zvukomania website

For any questions, write to me by email. mail: [email protected] or VK

Many music lovers prefer to listen to their favorite tunes using tube amplifiers. What are the specifics of these devices? Based on what criteria you can choose optimal model corresponding device?

What is interesting about tube

An amplifier is one of the key components of the acoustic infrastructure, which is responsible for increasing the power of the signals coming from sound sources, switching the corresponding devices, adjusting the volume level, and also transmitting the signal, the power of which is amplified, to audio equipment designed to play tunes.

Tube amplifiers use radio tubes as a key element of circuitry. They perform the function of reinforcing elements. Typically, tube amplifiers provide less distortion. As many music lovers note, the corresponding devices are characterized by warmer, softer playback of melodies - especially when playing mid-range and high frequencies.

Another major advantage of a tube amplifier is that in many cases it provides a richer sound compared, for example, with transistor devices. This is possible thanks to the unique properties of the lamps themselves, which, for example, are adapted to function without auxiliary correction, which is necessary to maintain the operation of semiconductor devices.

Single-cycle and push-pull devices

Lamp devices are most often classified into 2 main categories - class A and class AB. The former are also called single-cycle. In them, amplifying elements stimulate an increase in the power of both half-waves in the signal - both positive and negative. The second devices are also called push-pull. In them, each subsequent cascade of increasing power involves the use of different elements- one can be responsible for the positive half-wave, while the other can be responsible for the negative half-wave. Class AB amplifiers are usually more economical and efficient, and often more powerful. But discussions sometimes arise on this issue among music lovers.

The devices under consideration in many cases are much more expensive than their transistor counterparts, despite the fact that their design is quite simple. Many music lovers assemble the corresponding devices themselves - however, you need to try to find best schemes tube amplifiers - on 6P3S, for example, or other popular tubes. For connoisseurs of music played using the devices in question, their price often becomes secondary - if the decision is made not to build an amplifier, but to buy it. At the same time, the characteristics, of course, play an undeniably significant role when choosing a device. Let's look at what they can be, as well as examples popular models corresponding type of device.

Amplifier ProLogue EL34: characteristics and reviews

According to many experts, the best tube amplifier, or, according to at least, related to the leaders according to the corresponding criterion (of those related to budget segment) - ProLogue Classic EL34 device. This device can operate using two types of lamps - the actual EL34 or KT88. In this case, the user does not have to reconfigure the amplifier.

According to experts - reviews reflecting their opinions can be found on many thematic portals - one of the main advantages of the device is that it is equipped with interfaces that allow the load to be applied to the lamp smoothly, which helps to increase its service life. The amplifier is equipped with an efficient device. It has quite a large power, which is 35 W.

Triode Amplifiers

Another amplifier that belongs to the budget category is the TRV-35 device, produced by the Japanese brand Triode. The fact that it is assembled in Japan largely determines the quality of the corresponding product. The amplifier is versatile - perhaps the best tube amplifier in its segment from this point of view. The lamps that can be used on the device are EL34; in some cases, it is possible to use ElectroHarmonix elements manufactured in Russia.

According to experts, among the most notable options of the amplifier in question is the ability to connect to modern home theaters.

Other famous product Japanese brand Triode - TRX-P6L device. As some experts note, this device- the best tube amplifier in the Triode line in terms of functionality. Thus, it contains, in particular, a four-band equalizer, which is designed to optimize the timbre of the melody, taking into account the specific acoustic environment in the room, as well as the parameters of the sound systems used. The device about which we're talking about, allows you to use different categories of lamps - EL34, also KT88. The device is equipped with a reverse interaction depth regulator. The amplifier can operate in 2 modes - triode and ultralinear.

Another notable device produced under the Triode brand is the VP-300BD amplifier. Many music lovers ask a common question: “Single-cycle or push-pull tube amplifier - which is better?” They can, by choosing the VP-300BD, which belongs to the devices of the first type, remain very satisfied with the purchased device. The device in question is triode, classified as an amplifier open type. It can be noted that the output stage of the device operates on 300B triodes, which are classified as direct channel.

Audio Research VSi60

Among the most famous brands producing tube amplifiers is the American corporation Audio Research. Its most technologically advanced products include the VSi60 device. Many music lovers are convinced that tube amplifiers are better than transistor ones, and the device produced by an American company makes it possible to put forward a strong argument in favor of devices of the first type: according to experts, the amplifier in question provides the most impressive sound scale, quite comparable to the performance of transistor devices. Main lamps it works with American device, — KT120. Volume control for the one in question

Amplifiers Unison Research

Another well-known brand manufacturer of the devices in question is Unison Research. To the very effective solutions, which were developed by this corporation, can be attributed to the S6 amplifier. It is arguably the best tube amplifier, or at least one of the leading solutions, in terms of its combination of characteristics typical of a Class A device: high power of 35 W, as well as a significant damping factor. The device uses 2 direct-channel triodes located in each channel.

As experts note, the amplifier in question is characterized by the highest sound quality in terms of detail and purity of the reproduced melody.

The next well-known product produced under the Unison Research brand is the P70 amplifier. In turn, it is two-stroke. Music lovers who wonder why a single-ended tube amplifier plays better than a push-pull amplifier somewhat change their perception of the effectiveness of the corresponding devices after listening to music while using the device in question. The developers of the P70 amplifier managed to provide exceptional high quality sound with a very impressive device power - more than 70 W.

As experts note, the device can connect to an acoustic infrastructure that forms a fairly impressive load. The device in question is also characterized by genre versatility. If we consider the best tube amplifiers for listening to rock music, the P70 device can rightfully be classified as a leading solution.

Among the well-known single-cycle products manufactured under the Unison Research brand is the Preludio device. It also operates in Class A. It uses powerful KT88 tetrodes. The power of the device is 14 W. Therefore, the amplifier requires connection to an acoustic infrastructure that has sufficient high level sensitivity.

McIntosh

Another well-known brand that produces amplifiers is the American corporation McIntosh. Many music lovers, wondering which tube amplifier is better, first of all associate the highest quality products with those devices that are manufactured under the McIntosh brand. This corporation is among the most recognizable manufacturers in the world. audio equipment in the Hi-End segment.

It may be noted that the MC275 product from McIntosh first appeared on the market in 1961. Since then, it has undergone a number of improvements, but is still produced under the historical name. In principle, this amplifier belongs to the legendary devices, among best products in the world in the Hi-End segment. The device uses KT88 lamps. The amplifier power is 75 W in stereo playback mode.

Audio Note

Another famous brand in the amplifier market - Audio Note. Among its most popular products is Meishu Phono. Perhaps this is the best tube amplifier in its segment, if we consider the corresponding devices from the point of view of maintaining the purity of technology. So, it does not involve a single semiconductor. The structure of the device’s power supply contains 3 transformers, 3 kenotrons, and 2 chokes. The output stage uses 300B triodes. The amplifier design includes an effective tube phono preamplifier. The device in question has a rather modest power, which is 9 watts. Nevertheless, the device is compatible with many modern types floor acoustic equipment.

Determining the best tube sound amplifier based on the subjective perception of its operation is quite difficult. However, you can get closer to solving such a problem by comparing certain device models according to their main characteristics, as well as analyzing the relevant parameters.

Choosing the best amplifier: model comparison parameters

What parameters can be considered as key? According to modern experts, the most important characteristics V in this case can be:

Harmonic distortion level;

Signal to noise ratio;

Support for communication standards;

Energy consumption level.

In turn, these parameters can be compared with the price of the device.

Choosing an amplifier: power

As for the first indicator - power, it can be presented in the widest range of values. Optimal for solving most problems that characterize the use of a tube amplifier is an indicator of about 35 W. But many music lovers welcome an increase in this value - for example, up to 50 W.

At the same time, many modern high-tech devices of the corresponding type work excellently at a power of about 12 W. Of course, in many cases they require connection to a high-performance acoustic infrastructure. But the use of effective audio equipment is one of the mandatory attributes of using, in fact, the devices in question. Why a tube amplifier is better than more modern modifications of devices is a question that is not particularly relevant for many music lovers, since they have repeatedly been convinced in practice of the objective superiority of the corresponding devices in terms of key parameters. And therefore testing and practical use They try to carry out testing of tube amplifiers on pre-prepared equipment that meets the highest requirements.

Frequency

Regarding frequency response amplifier - it is highly desirable that it be in the range from 20 to 20 thousand Hz. Although, it should be noted that it is quite rare that modern manufacturers of the devices in question supply amplifiers to the markets that do not meet this criterion. It is difficult to find equipment in the Hi-End segment that would not reach specified parameters frequencies. One way or another, when purchasing a tube amplifier, for example, from a little-known brand, it makes sense to check the frequency range in which it supports.

Harmonic distortion

As for harmonic distortion, it is desirable that it does not exceed 0.6%. Actually, the lower this indicator, the better the sound. The best tube amplifier in a given segment is often determined primarily by harmonic distortion. It’s worth noting right away that the corresponding indicator is not the most significant from the point of view of ensuring good quality sound. However, this parameter characterizes the response of the acoustic infrastructure to the input signal. It is quite difficult in practice to ensure that the acoustic response is stimulated during measurement in the same way as it is done during playback. real signals. But modern tube amplifier brands are trying to ensure the lowest harmonic distortion. Prestigious device models are capable of providing it at a level not exceeding 0.1%. Of course, their cost may be incomparably higher than competing models that have a higher harmonic distortion rate, but for a music lover, the issue of price in this case may be of secondary importance.

Signal to noise ratio

The next parameter is the signal-to-noise ratio; in modern tube amplifiers it most often corresponds to 90 dB or more. Generally given value can be considered very common when comparing the characteristics of different devices, even if presented in different segments. Therefore, if the task is to choose a good single-ended tube amplifier or, for example, a push-pull amplifier, then the parameter under consideration will not always objectively reflect the competitiveness of a particular device. One way or another, the higher the corresponding indicator, the better. It is desirable that it be at least 70. Some top amplifier models provide a signal to noise ratio of more than 100 dB. But their price, as in the case of harmonic distortion, can be impressive.

Other parameters

The remaining parameters - support for certain communication standards, power consumption - are significant, but secondary. It makes sense to pay attention to them, all other things being equal, according to the indicators that we discussed above. One way or another, for a modern amplifier, it can be considered typical to have support for a sufficient number of stereo pairs - about 4, audio outputs for recording sound. Regarding power consumption, the optimal figure is about 280 W.

Of course, when considering the question of which tube amplifier is better, many subjective factors also play a role. Most often, music lovers evaluate the corresponding devices based on their design, build quality, sound level, and ergonomics.

All of the above parameters can be compared with the price of the device, which can be presented in a very wide range of values. But a person for whom the question of why a tube amplifier is better than a transistor one is not particularly relevant, since he knows the answer to it, the price, as we noted above, cannot always be considered as the most significant criterion when choosing a device for listening to his favorite tunes.

This was developed somewhere in the late 80s. During this time it has shown itself to be worthy and versatile: suitable for amateurs high-quality sound(composed for himself), and for musicians who need power.

Brief lyrical introduction. At one time, the amplifier published in the magazine "Radio" in 1972 was very popular. I also repeated this pattern. Its disadvantages are known to many who repeated it: low linearity, weak stability at low frequency, insufficient stability at high frequency (which is why a corrective air conditioner was introduced into the circuit), a narrow frequency range, and something else that I don’t remember now. And most importantly, the sound left much to be desired.

I couldn’t stand this at home: my ears are not official :) The first thing I started the modernization with was replacing the output trance. The changes made to the output trance suggested themselves - tighten the connection of the windings feedback(ultralinear) with the remaining windings, which reduces Kg by higher frequencies, and improve the frequency and phase characteristics of the output stage. In the version that I used in the new design, it was possible to expand the frequency range, increase HF stability, and lower the output impedance. The sound has noticeably improved, but now the entire circuit design (a clone of the so-called “Williamson circuit”) began to seem far-fetched in Hi-Fi - it was done somehow “head-on”, the weak link remained weak stability with OOS at infra-low frequencies, increased nonlinear and frequency distortions (especially at HF).

Further improvement resulted in the complete abandonment of this scheme. Many different circuit solutions were tried. Attempts to find best option led to the solution I propose. At the input, I used a cascode UA with high linearity, then a phase-inverted cascade with a divided load, which has the highest linearity. At the same time, I connected them directly to reduce phase shifts along the signal path. At the output, however, the familiar ultralinear output stage with minor changes(for the purpose of ease of adjustment and increased stability), and, as already mentioned, with an improved output trance. In the diagram, I conventionally divided the preliminary stages, a bunch of triodes in which is actually my know-how;), and the output stage, instead of which you can connect any suitable one. With a properly manufactured and adjusted amplifier, the maximum amplitudes on the control grids of the output lamps should be at least 80V at a load of 47k. And this made it possible to fully pump up the 6P45S. And what is important, with all its advantages, the scheme turned out to be even easier than that, from which I had to leave.

The result is an amplifier with a sound that (with proper measures) can easily qualify for hi-end ;) The amplifier is absolutely stable, so it can be used both with deep OOS and without it at all - the linearity of all stages ensures low distortion and open loop OOS.

From two 6P3S, I managed to get >150 watts, from two 6P45S - >220 ;), and in the version with grid currents (especially for musicians) - 400 watts of peak power! But that diagram is already noticeably different from the one given.

I can’t give detailed parameters of the amplifier now - I haven’t measured it for a long time. For those who need sound and not parameters, I have given enough information for repetition, and if it is really necessary, I can (albeit at great cost) re-measure them. I would probably try it on for a magazine. And here it will do :o)

As for setup, it is simple:

1. collect standard scheme parameter measurements;
2. disable OOS;
3. turn on the power and warm up the cathodes;
4. resistors R10 and R11 set the quiescent currents of the output. lamps 30...60mA (0.06...0.12V at the cathodes), but always identical;
5. without supplying a signal to the input, use the R2 regulator to set the cathode of the bass reflex to 105V;
6. apply a signal to the input until the load voltage reaches 15 volts (for a 6-ohm variant);
7. resistor R9 sets the minimum of the 2nd harmonic at the output;
8. restore OOS (optional).

Point 7 can be skipped if you replace R8 and R9 with one with a resistance of 12k (this may not even affect the quality in any way, especially with OOS).

To power the amplifier, additional voltages were needed: 410V (10mA/channel) and stabilized 68V (b/t). The diagram shows one of the options for obtaining them from the available ones. Here you can do it in different ways. For example, I have a stub source. +220V to power the preamplifier, so I got +68 as a divider.

At one time, the scheme was shrouded in trade secrets :). Now please - let anyone who wants to try it. I repeat that the UN-FI combination is universal and can be used to drive various PP output stages (triode, pentode, class A, AB). For each specific case, you may have to recalculate some elements, which is done very easily. This is how I can help those in need.

P.S: Priboy amplifiers lend themselves well to such modifications - the quality improves noticeably.

List of radioelements

Designation	Type	Denomination	Quantity	Note	Shop	My notepad
	Radio lamp	6N1P	2			To notepad
	Radio lamp	6P45S	2			To notepad
C1, C5, C6	Capacitor	1 µF	3			To notepad
C2	Electrolytic capacitor	47 µF	1			To notepad
C3	Capacitor	0.1 µF	1			To notepad
C4	Capacitor	0.047 µF	1			To notepad
R1	Resistor	220 kOhm	1	0.5 W		To notepad
R2, R9	Trimmer resistor.	4.7 kOhm	2			To notepad
R3	Resistor	100 Ohm	1	0.5 W		To notepad
R3	Resistor	100 kOhm	1	2 W. By mistake in the circuit two resistors are named as R3		To notepad
R4	Resistor	2 MOhm	1	0.5 W		To notepad
R6	Resistor	1 MOhm	1	0.5 W		To notepad
R7	Resistor	12 kOhm	1	2 W		To notepad
R8	Resistor	10 kOhm	1	0.5 W		To notepad
R10, R11	Trimmer resistor	22 kOhm	2			To notepad
R12, R13	Resistor	47 kOhm	2	0.5 W		To notepad
R14, R15	Resistor	1 kOhm	2	0.5 W		To notepad
R16, R17	Resistor	22 kOhm	2	1 W		To notepad
R18, R19	Resistor	2 ohm	2	2 W		To notepad
R20	Resistor	2.7 kOhm	1	1 W		To notepad
R21, R22	Resistor	68 Ohm	2	2 W		To notepad
	Discharger		1