Elektroda.com
Elektroda.com
X

Search our partners

Find the latest content on electronic components. Datasheets.com
Elektroda.com

Budget PCL82 stereo tube amplifier

pawelr98 5325 16
This content has been translated » The original version can be found here
  • Hello

    I would like to present my stereo tube amplifier, built on two PCL82 tubes. It is a very budget amplifier, the cost of production did not exceed around PLN 150.

    Let's start from the beginning.
    August 2020, Dominican fair in Gdańsk, while digging through the piles of antiques, I found two brand new PCL82 lamps, still in boxes. Lamps intact, price PLN 2 / piece, inside one box there is even a bill from 1975.

    Budget PCL82 stereo tube amplifier

    Budget PCL82 stereo tube amplifier

    I decided to buy such lamps, because why not, PLN 4 no money and the lamps looked new. Later measurement on the meter showed the emission in both cases slightly above the catalog, i.e. the lamps are really new. One Telam, the other Polamp.
    In addition to them, I also bought two used PCL86, they were supposed to be in this amplifier, but the emission measurement showed very high consumption, the emission of pentodes around 30-40%, which is total dead bodies.

    We had to wait a while for the parts for further construction, but I decided to go for a very cheap option, loudspeaker transformers from aliexpress. 5k? / 4-8? ratio, power 3W.

    Budget PCL82 stereo tube amplifier

    90-a pair of zlotys for two transformers? I take.

    Here's what these transformers look like in real life

    Budget PCL82 stereo tube amplifier
    Budget PCL82 stereo tube amplifier
    Budget PCL82 stereo tube amplifier

    There is a gap, the performance is so-so, but we won't complain, after all, it is supposed to be a budget amplifier, not an audiophile's dream. Primary resistance approx. 500 ?.
    By the way, I will notice that by connecting the 8? loudspeaker to the 4? tap, we get a load impedance of 10k?, which allows the use of very cheap and easily available PCL84 (or any lower power tube) in audio applications (for PCL84 such "atypical" load impedances were used, if you believe the catalog who described such a use).

    As a housing I bought an ELGIG E145 with dimensions of 50mmx140mmx160mm (height, width, length). It cost me PLN 21.

    First thing, cutting holes for lamps and fixing transformers.
    Budget PCL82 stereo tube amplifier
    Cutting holes with a dremel is average, he slipped and made a scratch, difficult, it is right behind the lamp so not very visible. In the future I will buy a larger diameter conical drill for making holes for lamps.

    Then drilling holes in the panels for banana connectors for speakers and phono sockets.
    Budget PCL82 stereo tube amplifier

    Passing OK
    Budget PCL82 stereo tube amplifier

    We go on, power.
    The main "innovation" of this amplifier is to circumvent the problem of an expensive power transformer by using a flyback pulse power supply.
    Here I refer to this thread:
    https://www.elektroda.pl/rtvforum/topic3690608.html#19238925

    Generally, P-lamps are very suitable for switching power supply, due to the low losses on the diodes (low current) and the possibility of series filing (one thin winding).
    UCL82 where the current is only 100mA would be even more advantageous.

    The lamps are heated from the first tap (12w) of 48 secondary turns.
    Voltage about 40V + resistors 30? 10W and 10? 2W in order to break the voltage, the current around 310mA, i.e. we are within ? 5%.
    As for the anode ones, we have 185V, which is enough.

    There was some perturbation along the way with the determination of the appropriate primary current. This power supply works all the time with a constant key current, the voltage feedback basically does not work.
    Budget PCL82 stereo tube amplifier

    The power supply after the first try-outs.

    Budget PCL82 stereo tube amplifier

    Then the beam from the cinch to the potentiometer at the front (logarithmic 2x50k? ;) .

    Budget PCL82 stereo tube amplifier

    When it comes to construction, it is a simple matter, we solder directly to lamp sockets and other construction elements.

    Budget PCL82 stereo tube amplifier

    The interior looks like this:

    Budget PCL82 stereo tube amplifier


    Budget PCL82 stereo tube amplifier

    The glow is detachable through the usual 4.8mm slides, so you can easily disconnect, then unscrew the volume potentiometer and the connection to the loudspeaker sockets. The serviceability is also fairly maintained.

    As for the scheme:

    Budget PCL82 stereo tube amplifier

    Nothing revealing, a simple amplifier based on a combination tube. I would also like to remind you that the potentiometer has 2x50k?, also the input impedance is significantly lowered compared to a traditional tube amp.
    The pentode does not have a capacitor in the cathode, because PCL82 itself is not a king of no distortion (from what I have read, the catalog data is significantly exaggerated in favor), so it is worth giving some negative feedback, also to reduce the gain that we have underneath abundance.

    The amplifier looks not bad, although it is a subjective matter, it is definitely not without flaws and distortions, but for PLN 150 I do not complain.

    Budget PCL82 stereo tube amplifier
    Budget PCL82 stereo tube amplifier
    Budget PCL82 stereo tube amplifier
    Budget PCL82 stereo tube amplifier

    I still add a video presentation


    Link

    Music: ??? ? - ? ?? ? ?

    There is a slight hum, but it's not very noticeable.
    Live sound is definitely better than in the movie shot with the phone.
    And you have to get the potentiometer knob, that's all and so much.


    I built and presented this amplifier, because many people think that a tube amplifier is something expensive and requires components for a lot of money. I built it cheaply, using normally available components, I didn't spend much, and I also have my "tinsel" playing in the room.

    Cool! Ranking DIY
    Can you write similar article? Send message to me and you will get SD card 64GB.
    About Author
    pawelr98
    Level 39  
    Offline 
    pawelr98 wrote 5608 posts with rating 700, helped 370 times. Live in city Bydgoszcz. Been with us since 2009 year.
  • #2
    szeryf3
    Level 22  
    All the time I thought that I have to spend over PLN 1,000 on a tube amplifier. and you have a nice device at a really low price.
  • #3
    Ostry23
    Level 18  
    pawelr98 wrote:
    In the future, I will buy a larger diameter conical drill for making holes for lamps

    It was my first thought after seeing these holes, but then I saw that everything was covered by the lamp holders, so it turned out nice in the end. In my only lamp holder, the sockets are on the PCB located just below the top wall, so the holes had to be even (and I'm not very happy anyway, because the processing of this steel was very ungrateful).

    Did you leave these wires for measurements soldered to the resistor in the power supply? It doesn't look very good.
    And I still have doubts about this spring. I understand that she has to fasten everything mechanically. And is it not too close to the output of this electrolyte? You are not afraid of short circuits.
    And .. do you have PE on the housing?

    And now, lest it be that I'm just complaining - in fact you did it very cheaply and decently. And if it still plays, it's cool at all :)
  • #4
    conisl
    Level 10  
    Hello,

    As for a home-made design, the amplifier looks pretty good.

    There used to be a safety rule that in the lower position of the power switch, the device should be turned off. You can see in the photos that this item is turned on.

    Regards
  • #5
    szeryf3
    Level 22  
    Tell me what did you measure the lamps?
  • #6
    398216 Usunięty
    Level 43  
    pawelr98 wrote:
    A slight hum is heard
    And how do you run the wires from the sockets with cables in the screen?
    The spring is not shown in the diagram as it is in the photos?
  • #7
    pawelr98
    Level 39  
    Ostry23 wrote:

    Did you leave these wires for measurements soldered to the resistor in the power supply? It doesn't look very good.
    And I still have doubts about this spring. I understand that she has to fasten everything mechanically. And is it not too close to the output of this electrolyte? You are not afraid of short circuits.
    And .. do you have PE on the housing?


    The wires were cut as I had already established the primary current.
    As far as I remember, there are 4 resistors of 3.92 ? in parallel.

    The spring is a mechanical fastening, although it is not the only one that holds the resistor, because the copper wire itself is mounted in an eyelet connector screwed to the housing.
    This wire is at the same potential as the spring, i.e. at the ground potential. It is simply a ground point where the signal ground and the cathode and mesh resistors are connected. The incandescence is carried out separately because the series resistor is on the ground side.

    The electrolyte, as you can see, the minus has an open, because why insulate something that has nothing to short-circuit, while the plus of the capacitor, where we have about 170V, has a stretched heat-shrinkable tube so that there is no short circuit.

    There is no PE, the three-core cable did not fit into the factory passage through the housing. At most, I can add a housing ground terminal and a third PE conductor attached parallel to the current two-wire.

    The mains potential cables are double insulated, each has a stretched heat shrink tube, the power supply is mechanically mounted on distances and I took care of decent separation gaps between the paths from the mounting points to the housing.

    Nevertheless, I like the current state on average and I intend to design this power supply from scratch so that it is on one laminate (currently 3) and has stabilization of the filament current.
    szeryf3 wrote:
    Tell me what did you measure the lamps?

    https://www.elektroda.pl/rtvforum/topic3533672.html
    Simple and convenient.
    We test as a diode, the results of PCL82 measurements as triodes (i.e. we have a curve for Us1 = 0V, which corresponds to a diode) are on the Internet. I treat the measurement as more coarse in order to determine whether the lamp is still fit for work or not.

    You need to have a regulated high voltage (or at least some adjustable resistor in the anode) and a filament voltage source. Nothing else is needed. 100-pair volts may not be much, but the emissions can be estimated.


    398216 Usunięty wrote:
    pawelr98 wrote:
    A slight hum is heard
    And how do you run the wires from the sockets with cables in the screen?
    The spring is not shown in the diagram as it is in the photos?


    As I wrote above, the spring is only a mechanical fastening, also not included in the electronic diagram.
    I honestly did not check if shielded cables would give anything, because I do not have them in stock now.
    Earlier, I checked the short circuit of the triode grid to ground and there was still hum. Also, either I did not run the ground or the power interference. The enclosure is entirely on ground potential.


    szeryf3 wrote:
    All the time I thought that I need to spend over 1,000,000 on a tube amplifier.zl. and you have a nice device at a really low price.


    There is a lot of "audiophile element" in "tube making" and hence the prices and views that cheap tube amplifiers cannot be built.

    I used to buy Chinese transformers, Polish 5k? / 8? Sizei, and now they cost PLN 115-120 / piece.
    However, the basis is to bypass very typical tubes for audio, which make money, i.e. EL84 / 6P14P, EL34, 6L6, ECC83 / 82 and a few others.
    PCL86 is still quite decently priced and offers decent parameters.

    It is also worth looking at 6P1P, i.e. the Soviet 6V6 clone in a Noval plinth, 6P18P i.e. the Soviet EL82 clone, although better because it is more powerful, you can also use it interchangeably with EL84 because the outputs are the same (so EL84 kits fit). We change ECC82 to 6N1P-EW, ECC83 to 6N2P-EW and suddenly the prices of the whole fun drop very quickly.

    But the most interesting are amplifiers on horizontal deflection tubes.
    Such cheap PL500 / 504, according to various publications in push-pull circuits, can achieve high power with low distortions. They cost a few zlotys, 19W anode admission power and a high allowable cathode current (they work well for lower supply voltages better than the usual EL34).

    When it comes to power supply, if someone does not feel strong enough to make a pulse power supply, you can order a 50VA 2x50V toroid for pln toroids. Voltage doubler, connect the glow with copper wire and it's ready, we have "traditional" power supply in reasonable money.

    Several dozen zlotys of savings here, several dozen there and you can build yourself cheaply.
  • #8
    conisl
    Level 10  
    pawelr98 wrote:
    ECC82 is replaced with 6N1P-EW, ECC83 with 6N2P-EW


    I do not recommend 6N1P lamps, they have a filament current of 600mA, better to give 6N2P (300mA filament current).
  • #9
    pawelr98
    Level 39  
    conisl wrote:
    pawelr98 wrote:
    ECC82 is replaced with 6N1P-EW, ECC83 with 6N2P-EW


    I do not recommend 6N1P lamps, they have a filament current of 600mA, better to give 6N2P (300mA filament current).


    Except that these tubes are different, the 6N1P is a triode with a lower internal resistance, more suited to the ECC82, i.e. for use as drivers.
    The 6N2P is a close counterpart to the ECC83.

    Of course, I'd like to avoid all lamps with an incandescent lamp of 6.3V or the same incandescent lamps in series, as long as the voltage was higher at the same current.

    However, for amplifiers, where there are more tubes, a completely different topology of the power supply is better. Instead of the flyback, which is great at generating high voltages from a small number of turns, go for a half bridge. We rewind the usual ATX transformer and you can light a lot of lamps without any problems. The output voltage is, say, constant (it does not depend on the load as much as in the flyback), we have an alternating waveform, you can easily use a multiplier (fewer turns on the high voltage winding) and you can straighten the glow on a two-diode rectifier, which allows you to break down the power losses into more items.

    Anyway, I already have a prototype of such a power supply, it is just waiting for me to use it in another, large amplifier, this time push-pull.
  • #10
    Olkus
    Level 21  
    Everything is nice, the only thing that could be faulted are the unshielded cables and the average aesthetics of the power supply. 150 zlotys for the amplifier is not bad, but mine on the ECL82 exceeded 200 zlotys.

    Regards.
  • #11
    And!
    Admin of Design group
    What is the Dominican Fair in Gdańsk?

    It is necessary to work on the appearance, even if these knobs will give a lot in terms of the overall effect :)
  • #12
    pawelr98
    Level 39  
    And! wrote:
    What is the Dominican Fair in Gdańsk?

    https://pl.wikipedia.org/wiki/Gda%C5%84ski_Jarmark_%C5%9Bw._Dominika

    Such an event, where there are antiques fairs, you can look for antiques, including radios, electron tubes or other electronic equipment.

    The nice old man literally had a whole basket of electron tubes, and seeing my interest, he also took another box from the "back room" for me to dig and pick something. I shot then a new one 6N2P from 1958.

    What's most important, a lot of people don't know what they're selling, so you can dig up some curiosities. The Lord divided the price according to the size of the lamp, PLN 2 small (nowal plinth), PLN 5 for a large one (magnoval / octal). It didn't matter if we were buying EL84 or PCF82.
  • #13
    Ostry23
    Level 18  
    pawelr98 wrote:
    The electrolyte, as you can see, the minus is uncovered, because why insulate something that has nothing to short-circuit with, while the plus of the capacitor, where we have about 170V, has a stretched heat-shrinkable tube, so that there is no short circuit

    Ok, you are absolved :)

    pawelr98 wrote:
    There is no PE, the three-core cable did not fit into the factory passage through the housing. At most, I can add a housing ground terminal and a third PE conductor attached parallel to the current two-wire.

    The mains potential cables are double insulated, each has a stretched heat shrink tube, the power supply is mechanically mounted on distances and I took care of decent separation gaps between the paths from the mounting points to the housing.

    Ok. Double insulation, so you made equipment in protection class II. Ie. do you have heat shrink tubing along the entire length of these wires? Because it is not clear from the photos.
    But if it's what you say, it's cool. Just the photos themselves, without that description, suggested something else.

    I once bought a simple guitar amplifier with a clean channel on Allegro, DIY with 30 elements crosswise. U-shaped sheet metal casing with 2 nicely sanded side boards. From the outside it even looked nice, but inside there was one big spider, but with virtually no insulation. Bare wires and elements arranged in space. And held in this position only by the (poor) stiffness of the joints. Come on, horror :)
  • #14
    tytka
    Level 20  
    pawelr98 wrote:
    Nevertheless, I like the current state on average and I intend to design this power supply from scratch so that it is on one laminate (currently 3) and has stabilization of the filament current.


    Well, I even like the current state of the interior less than the average. But from the outside, you only add a knob and it's really OK

    You figured it out very sparingly (I'm wondering if not too much), but the effect is quite complete. (Thought you might be a production accountant :) )
  • #15
    398216 Usunięty
    Level 43  
    pawelr98 wrote:
    the spring is only a mechanical fastening
    "1001 patents for the use of a spring". Yours is 1002 a patent. Haven't heard about mounting strips? You could even make one yourself on your knee (a strip of laminate with cuts every 0.5 cm for soldering the tips plus two 3.2 mm holes for screws. The mounting was more secure, and the aesthetics would also gain a bit.
    By the way - from what I can see (?) The spring is sticking to the screw threads. Have you thought where it will fall as it will fall from this thread? From practice and Murphy's Law it follows that where he does the most damage.
  • #16
    żarówka rtęciowa
    Level 37  
    Hello

    Olkus wrote:
    Everything is nice, the only thing you could find fault with are unshielded cables


    They are not always needed, especially with high value signals of 1V and more.

    As for the driver tube, PCC85 or PCC88 (E88CC) double triodes can be used in amplifiers with P-series output tubes.
  • #17
    olaf x
    Level 32  
    Functional and simple, it is known that the greater the complexity, the greater the likelihood that something will go wrong. Even if the end result will be much better.
    I will probably commit something like that, although only art for the sake of art, but to make my dreams come true, as recently as the nixie clock, which has waited 30 years for it :P