6n6p Kit Manual

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6n6p Kit Manual

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  • Lampizator Kit 6NxPApplication Manual

    By Lukasz Fikus

    This kit represents a very well known and tested application of tube triodes in audio amplification stage.It is so universal and versatile that the number of possible applications is very large. It can work with tens of different tubes and tens of different sources.

    This design is very immune to power supply quality problems, very stable, and very tolerant of parameters, loads and errors.

    We believe that properly implemented KIT can be a part of any high end system, however ambitious and / or expensive.

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  • TUBES: This kit has been designed with the 6N6P tube in mind, but it will work for all

    tubes which have: 6,3 V heaters on pin 4 and 5 Anodes on pins 1 and 6 Grids on pinsd 2 and 7 Cathodes on pins 3 and 8 Pin 9 is grounded and in soviet tubes it represents the screen between two

    triodes.These tubes are: noval, triodes, dual type (two identical triodes in one bottle.)They are indirectly heated and share one common heater circuit.

    Possible tube types are: 6N6P, 6N30P (not recommended), 6N6P-I (Impulse variant, not recommended), 6N1P (all variants), 6N2P, ecc88, e88cc, 6dj9, 6922

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  • APPLICATIONS:This kit can be used as:CD player lampizator with U-Out DAC type and I type DACDVD lampizatorDAC Lampizator or simply output stagePreamplifier stageAmplifier input stageOther, like tuner stage, sound-card lampizator, I-Phone amplifier etc.

    TOOLSTo complete this kit we need:Soldering iron of 40-60 W, preferably a DC stationSolder with lead (no silver and no ROHS solders please)Wire strippersUtility knifeUniversal meter

    An oscilloscope is very good but not strictly necessary.

    If you buy your first oscilloscope, get a 50 MHz type or faster and CRT display, NEVCER LCD.

    CIRCUIT PARAMETERSThere are three main circuit detrmining parameters:1. Heater current2. Anode idle current (bias current)3. Input signal volume and amplification

    HEATINGWhen we roll tubes all three of the above will change but the circuit will still play. It will not get damaged or damage tubes.

    Ad1. Heater current is a function of tube heater resistance connected to the 6,3 V supply. 6N6P, its sister 6N6P-I and brother 6N30P draw circa 0,8 A per tube. That is the largest load of all noval tubes known to me. Consequently: AC heaters will have a voltage sagging of transformer secondary, AD unregulated supplies will need very small recistor in CRC and of a large wattage (5 W). The regulated circuits will require a 6,3 V DC regulator with large heatsink and only one tube per regulator can be used. For stereo pair use two regulators fed from one common 6A bridge and with at least 6800 uF /16 V cap after the bridge. 20 000 uF would be better.

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  • For AC heaters we need dedicated circuits from transformer secondary with precisely 6,3 V AC under the load. Since the load is only circa 10 Ohm (on hot tube 10 Ohm, on cold - 1,5 Ohm !) Our secondary winding must be rated at at least 2 A per tube supplied. Without load such transformer secondary will measure circa 7 V AC.

    The board has heaters SEPARATELY for both tubes. You should connect them in parallel for using a common 6,3 V heater source.

    For the music - it does not matter if the heaters are AC or DC. DC will not hum but require more parts, more work, more skills and they have more potential areas that can get damaged. I encourage you to start from AC heaters and finish the project. Later you can convert to DC heating.

    For one common heater supply (AC or DC) connect parallel heaters: 6,3 (left hole) of one tube to 6,3 terminal left hole of second tube, and the same for right holes.If our transformer has a slightly too high AC windings, we can add resistors which will reduce heater voltage. R6 and R7 are on PCB (marked 1 Ohm) just to drop heater voltage.If say out voltage AC on pins 5 and 4 of tube are 7,3 V that means we have one volt too much. OVERHEATING DESTROYS TUBES! If the tube is 6N6P so it will draw 0,8 A, from ohms law to drop 1V we need that the current of 0,8 will generate a drop of 1V on resistance of Rx , so Rx = U/ I = 1 / 0,8 = 1,25 Ohm. We decide to split this value in half and add TWO resistors of 0,6 Ohm in place of R7 and R6 (and in other tube of course R6_1 and R7_1).

    The yellow capacitor (use only one, even if the PCB has place for two) is for creating a virtual point of earth reference for the heater circuit. It connects the pin 4 or 5 to ground.

    If we want to build a DC regulated heater, we use:- 4 A (or bigger) bridge, followed by 10 000 uF/10 V cap (or 16 V), followed by the 5 V

    regulator, with a cap after regulator min. 100 uF/6,3 V (can be as big as 10 000 uF - this does not matter).

    The regulator must have aluminum heatsink surface not smaller than the green project PCB for example. The larger the better.The head of the regulator must be insulated from heatsink by mica or teflon washer and the screw must be insulated by a collar type washer as well. The center leg of 7805 regulator must have two series diodes to ground, with both plus marks towards ground. These two diodes change the output from 5V to 6,25 V ideal for heaters.

    Ground (minus) of the regulated system must be connected to PCB ground.

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  • BIAS CURRENT:Bias current of the SRPP system is determined by Rk of upper and lower triode (both must be the same R values and types !)Our system can handle Rk from 140 - 1000 Ohm range (1/8 W or more) We recommend values between 240 and 380 Ohms.This value will fit all tubes listed.

    ATTENTION: the PCB has silkscreen mark of 1K, please ignore it.

    The cathode resistors are marked R1 and R4.

    The bias, depending on tube type, will be from the range of 10 mA to 1 mA. 6N6P will draw 10 mA and ecc88 will draw circa 3 mA of anode current. (at circa 275 Ohms in cathodes).

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  • GRID INPUTThe signal from the source must get to the grid to make the tube play. The grid pins (2 and 7) are connected to something.Pin 2 is connected to the reference point below its Cathode resistor which makes it a CURRENT SOURCE (upper triode)The pin 7 is grounded by a Grid resistor Rg.(note that it is also connected to a reference point below its cathode resistor like the upper one).This grid resistor R5 must be small enough to set the grid on ground level (from 1 Mega Ohm down to 0 Ohm are acceptable for that criteria) , but large enough in order not to influence incoming signal (2K to infinity is accepted). The compromise resistance is usually set at 250k-600 K Ohms. R5 on PCB silkscreen is marked 1K, please ignore it.

    A keen experimentator may try to ground the grid with a wire and send input signal directly to cathode Pin8 , it is very interesting.

    SIGNAL INPUTWe have infinite number of scenarios, depending on tube application, volume of source signal, impedance of source, cables used, etc.

    Scenario 1 - we need full amplification of Voltage (maximum that the tube circuit can offer.We send the source signal to Input+1 point. We short R3, Nothing is in R2.The amplification is full. 6N6 offers lowest amplification in SRPP - circa 10-20 times depending on many factors.ECC88, E88cc, 6dj9, 6922, 6N1P tubes offer medium amplification between 30 and 50 times.6N2P offers circa 100X amplification.

    Scenario 2: If we need less amplification, say in a DAC the chip has a 2 V pp signal strength and we desire circa the same on output, we must use L-Pad divider.R3 and R5 form the L-pad.

    The design criteria of L pad are: R3 plus R5 must be larger than 20 K and smaller than 100KR3 must be 4 to 10 times larger than R5.R5 is no longer around 250k-300K like before.The factor of 4 means small attenuation, factor of 10 means over 11 times attenuation (much).

    Example: we use 6N6P and a DAC with 2 v PP output and we want a 3 V PP output at the end of the Lampizator.We choose R5 = 10 K and R3 = 47 KSum = 57 K which is OK.

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  • Ratio of reduction is: (R3+r5)/R5 = (47k+10k)/10k = 5,7 times, a perfect match for 6N6P.

    Scenario 3 - like Scenario 2 but our DAC likes a strong bias of output stage:Reduce the both R by the factor of 10R5 = 1 k and R3 = 4k7Ratio is the same but small resistance of R3 plus R5 (5k7) gives stronger bias of DAC.

    Scenario 4- I out DAC (current DAC like TDA1541 or AD1865 or PCM63, 1702, 1704 or 1794 or 1798 (new Lampucera).

    In this scenario: there is no input capacitor between DAC output and tube input grid (pin7). The Rg (R5) between tube grid and ground becomes the voltage converter for the DAC.The Rin (R3) is shorted.The Rg (R5) has a value recommended for the given chip. 82 Ohms for TDA 1541A, 280 Ohms for TDA1543, and so on.The tube should be of high amplification, the best being 6N2P or E88cc / Ecc88.

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  • PREAMPLIFIER SCENARIOthe pre configuration should have input impedance of maximum value, so R5 plus R3 should give around 100K (if we dont use a pot) . Low amplification tube is the best so lets choose 6N6P. Since we need no L-pad attenuator, the pot takes care of attenuation. So we install a pot (100k Log type) at the input after RCA and then from center tap of the pot (wiper) we go directly to tube grid. To tame oscillations we install 1K resistor (between 1K and 10 k whatever you have) directly at R3 (R_input) and R5 becomes as high as we can find. 500K (max. 1 Meg) is OK. (no less