Output Transformers: Discussion of basic principles
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The output transformer is the core of a valve amplifier The right image shows a stereo amplifier leakage Both output trannys are put into rotation to 90deg trans feed network to avoid picking snoring induced network tranny trannys external magnetic field output contribute most of the distortion in a cAMP valve and a limited bandwidth.
Valve amp manufacturers trannys purchase of transformer winding transformer winding business is an extension of the assembly industry and rotation Few people working in companies winding transformers have knowledge of electronics and valve amps Most manufacturers valve amps have an academic understanding of basic output trannys but often have limited understanding or incorrect physical processors or how they are made.
Academic formulas for the calculation of the design output trannys is available in many books of texts and websites There is no need to repeat this page academic information that is readily available This page provides an overview of physics that governs the performance of output trannys and helps provide a perspective that academic text often fail.
Release trannys are the most costly and the most intense part of the work of one ampere valve for each outlet transsexual, depending on the size takes about 1 to 2 hours for winding, together with stratifications, heated in oven, soaked in resin and cured overnight, cleaned, painted, connected external son, fitted dress caps, packaged and sent to one amp valve manufacturer a tedious task to say the least the right image is a simple analogy of an output tranny.
B represents historically the battery B is the supply voltage to the center tap CT of the primary winding of the 560V supply outlet trans DC is connected to the CT center tap of the primary winding The amplified audio from the two outlet valves, push pull is opposite the 180deg Phase 300VAC 300VAC 600V AC is through the primary winding.
Depending on the design of trans there may be 2000 turns of wire in the primary and 90 turns of the secondary winding 22 a step down ratio 600V AC 22 AC 27V in a 8 Valve AMPS naturally have a high output impedance and output voltage will automatically increase to try to maintain a constant power of the speaker as the output voltage increases, especially at high power, a transsexual without sufficient inductance at low frequencies can easily saturate create an intense distortion avoid the base saturation, the primary turns should be the maximum number and the basic mass should be as large as possible for a given frame size.
In the past, when the only valve technology existed, materials are expensive compared to working out a transsexual for a 100 Watt amp valve was about 10 to 20 in number 5 for materials, 5 for work and little the majority of profit output trannys were minimum size made from less expensive materials Only a few valve amps Hi-end had trannys output that were made with the best quality materials.
Early stratification document trannys amps for valve mainly used the less expensive, lower voltage rating of enameled copper wire and insulating impregnated paper thickness between each layer of the winding layers of paper enabled trans winding high speed automated machines, reducing labor and keeping costs under control poor insulation paper and poor enamel coating on the burning compatible wireless occur between windings.
Extreme high voltages are generated across the primary winding if the speaker is disconnected while the music plays Ignite between windings has been a major problem with the valve guitar amps.
A disproportionate of the window space is consumed by an insulation of the paper layer which limits the total number of turns to enable the transformer has a sufficient inductance to obtain a good bass response with a limited window area the wire must be thinner causing additional losses in the DC resistance of the wire space occupied by a thick paper insulation causes the leakage inductance, which reduces the efficiency of trans.
Modern materials for high voltage thin polyester Mylar, Kapton insulation and Nomax including high voltage hardened enamel wire used in electric motors were easily available from 1960 the use of these insulating materials of superior quality does not require the superposition of the paper between each layer of winding pictures above modern sector and output windings tranny shows the high voltage thin insulation is used only between the primary and secondary windings, minimizing the space occupied by the insulation, which allows the maximum mass of the copper wire to fill the space of the window.
But very few manufacturers of valve amps were are aware of the physical design of the transsexual output, therefore the insulation of top quality and high voltage wire coated with enamel, including cores C were rarely used trannys output were made at a budget and when the technology solid state came the era of valve technology ended.
Today, an output tranny for a 100 Watt amp valve is about 50 to 100 for materials, labor force 100, 100 earnings final price of about 200 to 600 but because of alchemical beliefs imagined magical bygone perceptions of brand names and components, many output trannys today are still using the same methods and materials at low cost as in the past.
In most of the windings are wound trannys output layer through the coil interleaving the primary and secondary windings enables trans to obtain a high frequency response The primary windings are connected in series with secondary windings are essentially connected in parallel the secondary windings are often taken to resolve the 8 or 4 impedance output is the symbol for transformer windings which are rotated 90deg in one of the coil windings are assembled in sandwich image below is an experimental valve amps with output trannys wound Pi final design was 8 Primaries sandwiched between 9 wound Secondaries Pi trannys 100 are symmetrically balanced and have a response to high frequency 2 x greater than a trans exit wound of the conventional diaper.
Pi winding is commonly used in ferrite core trannys transferring energy at very high frequencies, as seen in the switching mode power supplies and Rf winding Pi amplifiers is also the preferred method to construct an audio output trans winding Pi output trannys are not known to have been used in the Ampere audio valve One possible reason is the high tooling and costs mount further commercialization of audiophile products, especially tube amps, is driven by names brand, romantic nostalgia and reviews, not engineering or performance.
Toroidal output trannys are now used in some tube amps in the past trannys toroidal x 2 were more than trannys employment insurance because of the high cost of winding machinery toroidal Today, labor is expensive compared to cost of a winding machine toroid winding Many processors now have toroidal machinery EI and toroidal are now about the same cost of construction.
Trannys toroidal have a higher magnetic coupling between windings But a toroidal core can easily saturate at low frequencies creating an intolerable distortion Therefore, the mass of the toroidal core must be greater than a conventional EI trans for the same power to avoid risk saturation of the toroid core are forgiving of any direct or alternating current audio imbalance in the primary windings of the two outlet valves must be completely biased with exactly the same current and have exactly the same gain when driven Providing these conditions are met, a toroidal transsexual will outperform a classical trans EI.
4-way valve active tower below peak is an active valve collar 4 so as to trannys using output toroidal as in the above picture are 5100 Watt Ultra linear amps using KT88s The two amps at the bottom the frame are connected in parallel to give 200 Watts the frame is divided in the center one side of the left frame of the peak side of the power supply also uses trannys toroidal across the peak right side frame are trannys toroidal output.
Right peak shows trannys output and an active filter.
Trans-Hi 5 kHz - 50 kHz The two mid-range output trannys The great low cross at the base of the chassis is able to 5Hz.
The rise three small coils torus above the high bass output are trans to filter peak B on the left shows the opposite side power supply chassis.
The small high power toroidal trans -20V and -100V is for electronic circuits crossover and driver output KT88 valves.
Below the upper small toroidal power is the power core and toroidal choke 12 filaments 6V DC heating power supply.
The 2 large toroidal trannys create electric 560V B Power at B is built from 3 x 188V supplies in series.
The four-way intersection of steps and active pilots are solid state to ensure a balanced signal without distortion is perfect issued KT88 output valves Each followed two LEDs to allow the quiescent current through the KT88s to calibrate.
Ampere Valve require tailored valve outlet to provide the best performance This is similar to having pistons equilibrated in a vehicle engine, it is essential that the quiescent current through the output valves calibrating a 10R resistance exactly is placed series with each cathode voltage to the negative bias grids is adjusted 500mV appears in each resistor 10R 500mV through 10R 50mA valves are then driven at full power and the current through the valves will increase to about 150mA two valves must be perfectly equal in both quiescent and full power condition All current imbalance between the valves will result in the iron core of the trans partially magnetized DC inductance will be reduced, the bass response will be reduced and the core saturates easily at low frequencies.
Many early TETRODE valve amps and Hi-Fi almost every valve guitar amps are configured tetrode tetrode mode In operating outlet valves screens are connected to a second filtered feed B power supply.
The first of the output transsexual is connected to the anodes of inlet valves Transvestite designed to operate tetrode only need 3 son primary center tap of the TC to food B and 2 to son Trannys anodes designed for guitar amplifiers tetrode operation are often made as cheaply as possible but there are exceptions.
Ultra linear output trannys intended to be applied Ultralinear are often manufactured from high quality material and have multiple primary secondary interleaving outlet valves of screens are connected to the primary windings Ultralinear provides the same high power as configuration Tetrode with a higher power and performance inter -modulation a triode configuration the power supply for the amplifiers must be linear Ultra control, smooth and ripple free.
Academic original text said that the screens must be connected to a 42 position paper of the primary winding to reach the maximum power of the original text refers only to graphics and did not take into consideration how an output transsexual is wound is difficult to obtain mechanically perfect symmetry with 42 tap positions on both sides of the center tap However, 50 may easily be achieved if a trade off is in fact, the mechanical symmetry of the primary windings, must come first also, the theoretical difference between 42 and 50 is too small for a hearing difference or measured to detect.
The figurers distortion and frequency response of the amplifier valve are often specified to 1 Watt Most trannys output can easily reach a bandwidth of 20 Hz to 20 kHz to 1 Watt But this bandwidth is rarely reached full power response low frequency at full power is directly proportional to the number of primary turns and the mass of the iron core.
Above 2kHz the iron core has little effect on the high frequency response is directly dependent interleaving the primary and secondary windings However, if the trans has a wide base and a large number of primary turns him that possible to achieve sub-bass at full power, then the large surface area of the windings causes an increase in capacitance between the primary and secondary restricting the high-frequency therefore response, a small core with fewer turns promotes high frequency response .
The coil and the core in the right peak is trans 100 Watt output, one 5in a and a core half inches with a stack about 2 inches 3kg mass of the majority of this size output trannys have about 2000 primary turns with the man winding technique and compaction hermetically wire, the primary coil may be increased to 2500 or 3000 the total resistance dc primary should not exceed 100R, thread 0 36mm or more can be used the secondary windings parallels can be 1 or 1 1mm 2mm secondary resistance DC 0 1R.
There is no way to wind transsexual perfect Few of highly qualified people who find themselves trannys and have different techniques to achieve the target inductance of the transsexual varies depending on the basis of mass and quality and number of primary windings the goal is for the inductance is as high as possible the image below is a list of consistent basic formulas for those who wish to exit trannys.
Academic formulas for calculating the output tranny design are available in many books of texts and websites Those who trannys output will already be overwhelmed by mathematics and there is no need to repeat this page the academic information that is readily available This page is intended to provide an overview of physics that govern the performance of output trannys, a perspective that academic text often fail.
The impedance ratio is the square of the transformation ratio.
Impedance ratio between understanding is primary and secondary difficult for those who are technical and nearly impossible to understand for those who do not hope that this explanation will be easier for those who are interested.
Fine text states that a pair of KT88s in push-pull class AB, based on a supply voltage B 560V deliver 100 Watts Under this condition, the output transsexual primary impedance is indicated as 4K5 The impedance of 4K5 is a academic figure and represents the highest impedance plate plate will allow 100 watts to get a plaque just means Anode Anode to this theoretical figure of 100 implies 4K5 transformer efficiency with zero losses.
A pair of KT88s rarely reach 100 Watts in the real world, the average is of 80 to 90 Watts also the impedance plate may vary between 3k 5k with little change to the available power.
Our sample output trans 4 primary windings 600 revolutions per winding of a total of 2400 turns.
4K5 plate plaque enclosure 8 562 5 562 5 23 7 turns ratio primary turns 23 2400 7101 secondary turns.
This academic process requires the formula repeating several times for each change calculation Another way to view this process is done by the calculation related to the physical output trans The voltage ratio between the two is the same primary and secondary the transformation ratio.
A general rule for the push-pull class AB amplifiers valve The RMS voltage across the primary winding is 1 x B 1 Supply voltage at full power.
1 1 x 560V AC 616V DC 100 Watts in a 28V RMS 8 speaker 616 Turns Ratio 28 22 2400 22 109 primary turns to secondary turns.
There is a small difference in 8 secondary turns between the two calculations This second formula does not look the plate impedance Therefore, the calculation is more convenient to use by reversing the last calculation of a January 22 report processing by the first formula, we can see that the plate reflected on the impedance plate was reduced to.
A difference in turns ratio 23 7 1 22 1 leads to a small difference in secondary turns 8 This small difference causes a large change in reflected Academic plate to the plate impedance.
The right image shows a speaker impedance 8 has an average well above 8 Two and three-way loudspeaker boxes HiFi trying to keep as close as possible overall impedance 8 also the son connectors add additional strength.
Output trannys are not 100 effective basic losses, leakage inductance, resistance continues copper wire, contribute to the increase in overall plate reflects impedance plate, above the academic figure Therefore, second formula represents almost real conditions, but it is wise to be familiar with both approaches and cross each method.
Output transformers Valve Amps, Valve, amplifiers, output transformers.