— OYNACE poy UN eyez: |) leviaeiia arg OUTPUT Sse en Be QULJNACO INE. 2020 serorson sx, prisdsprn, 2.191215.DYNACO SUPER FIDELITY OUTPUT TRANSFORMERS ‘The now line of DYNACO output transformers incorpor- ‘ates the first basic advance in output transformer design since the introduction of interleaved windings. All DYNACO models feature para-coupled windings, © design by Dovid Hofler an which patents are pending ‘hovel arrangement provides an accurately balanced coil with tight coupling between the various sections and {8 choice of parameters which furnish superior quality at moderate cost. The low distortion which results from the pora-coupled design gives greater definition of musical deteil-enalogous 10 the way in which complex coupling of lens elements can provide greater resolution of photo. ‘grophic detail. The basic aim in the design of DYNACO transformers was to provide the finest pessible performance under octual udio operoting conditions as well as under steady stote laboratory test conditions. This geal was ieved by building into the transformers a large mar- gin of performance copabilities, over thot normally expected in an ouiput tronsformor. One rosult of this policy is thet the design is not eritical on tube balance, ‘ond circuits can be simplified and maintenance. mini mized by omission of components which are used solely for the purpose of bolancing currents in the output transformer Recognition of the important fact thet output transform: fers ore intended to operete with loudspeaker loads rather than resistive loads clone led to design fectures which preserve the quality of performance even when the load impedence shifts such os hop ‘of the audio spectrum with loudspeaker loads. The sul stantial reserve of power handling capability which is built into every DYNACO Super-Fidelity output trons former permits full undistorted power transmission ot frequency extremes. Most better grade transformers can deliver a reasonable amount of power in the middle of the audio band. Unfortunately however, in most units the distortion at high levels increase sharply at the ends of the band, This is not true for DYNACO transformers since the para-coupled arrangement reduces middle and high Frequency distortion, while © massive core of thin gouge grain oriented stool provides distortionloss transmission of high lovel, low frequency signal components Modern high fidelity amplifier ciruits incorporate sub stantial proportions of negative feedback, primarily to reduce distortion to extremely low lovels. However, there is.@ penalty which is incurred in the use of lorge amounts of feedback-problems of instability are introduced, and «large part of these problems are due to the detrimen: tal phase characterises of the output transformer used “Amplifiers which do not hove sufficient margin of stobil- ity under feedback conditions tend to get “bloopy”” and muddy of low frequencies and harsh and strident at high frequencies. The remedy requires close control of the ‘amplifier and transformer phose characteristics even ot frequencies for removed from the audio band. Advanced pulse techniques hove been incorporated into the design ond production of DYNACO Super-Fidelity transformers to make the phase choracteristcs suitable for omplifiers with high proportions of feedback. The gain in margin of stability which accrues from this design technique mekes on audible improvement in listening ‘quality. The best test for inherent stability under feed back conditions is the use of the square wave test~both ‘on the transformer alone and on the complete amplifier with loudspeoker load. The superiority. of DYNACO, fransformers is readily confirmed in this square wove: fest by noting the straight sides and flat top of the wavelorm and the absence of ripples and spikes, even at high frequencies. DYNACO Super-Fidelity transformers ore built to give consistent, long lasting performance. Such fectures as 3000 volt insulation, vacuum impregnation, high temper- ‘ture potting compound, end rigorous production precision winding. The design, the materials, and the Fabrication are the finest available; ond they provi the finest performanes. CIRCUITS FOR DYNACO TRANSFORMERS The high performance capabilities of DYNACO Super- Fidelity transformers will improve any circuit in. which thete transformers are used. As a general rule they can be inserted in any high quality circuit configuration in- cluding Williamson,” “ultra linear,” “multi-loop,” or any other with gratifying improvement in amplifier stability and distortion characteristics. However, the benefits available from a given transformer are bounded by the circuit in which it is used. Therefore, we recom- mend some specific circuit arrangements which have bbeen carefully designed and tested to insure maximum User setisfaction The circuits shown are suggested for “those who roll their own,” either in complete amplifier construction or in modernization nd conversion of older equipment or moderate-fidelity commercial equipment. The DYNACO circuit, os used in the DYNAKIT Merk I, was designed to match the outstanding characteristics Of the A-431 tronsformer. The simplicity, stability, and ‘uality of this circuit ore unequalled by any regardless of complexity oF cost. The thousands of people who have Williamson type ‘ompiifiers, in any of the popular versions, can now modernize them to improve the amplifier stability chor- tcteristcs and fo increase their power output to over 50 watts as shown in figure 2. This modernization and con- version, using the DYNACO A.431 transformer, makes ‘an improvement in quality which is audible even to the Untrained ear since there i greater cleanliness and smoothness of the sound, Figure 3 illustrates o low power circuit (12 watts of less than 1° IM distortion) which is similar t0 that used in ‘many of the medium priced commercial amplifiers. Either EL-84's or tubes of the 6¥6 and 6AQS type can be used in this configuration with the A410 iransformor. The use of this super-fdelity transformer in commercial grade equipment makes a substentiel improvement in transient response o+ well as drastically lowering the distortion Most commercial amplifiers can be greatly improved merely by ditect substitution of the A-dI0 for amplifiers Of the 6V6 type or the A420 for amplifier of the 5881 616, and KT-66 type without any other circuit changes. The 120wat A.441 translormer is designed specifically to be used in applications requiring 0 tightly coupled tertiary winding for screen feedback, cathode looding, or for balanced feedback to earlier stages. With 6550 tubes using 600 plote volts, 350 screen volts, ond 35 volts of fixed bias, it is practical to get 100’ watts of leon ovlput with superb listening quality. The output stage can be readily driven from Williomson-type cir cuits of the modernized type.DVM AC OL oc ae TRANSFORMERS: . ato a0 mae nat ast A470 B30" Impedance 000 ohm cr | daha | 200eRmv« 4300 ohms ‘ae woe, teuee Bowe | eis 04, 8,18 sec ‘oitit or an Unditored pone Bete iste | 30 warts 60 wons 129 wows 240 wots 240 wows 70 wotts 20 cps to 20 ke 15 watts 30 warts 60 watts, 120 wotts 120 wots: 35 watts minimum ie | etebdem | krebocy | etdocm | ttabsem | = tab dons | 1 db 6 oo cqwency rvponie | 10.60 be v0 60 4 to 40 ke tok te 60 ke 10 60 ke SiniGecled 27/849 aaanaia | anes s7faxeaid | srimxaaa | 3.9/4 23.072 eaa/a high | 242 hom | x5 high £8 high 8. Hah 21/2 high sesara'sanes: | ee paaxzia | aaaaaze | 40312 axa 23/4 21/4 Weight 5 ths 7 ts Vet ak 23 ibs 7 ibs ‘Asplicotion vs, E84, Kr6's 6550's, KT-88"s, | feces te” | tpn por Lads, o saass sae fae oss Krants, | écarre B38, 0 scars eats, or or ELBA's scars 50 pm KT core Noreen $20.95 $26.95 $29.95) $59.95. $26.95 ‘ati higher in the West), sees A units have tops on primary win [All units ore furnished in heavy gauge steel cans with 12° color code stude with mounting herdwor Units are conserys hpended for uses Wither overleue mer any amount of unbalanced op Tormers. ‘For aptimum low distortion reproduction, the de bal P=782 power transformer oz vsed im Dynakit Mark I 410:0-58-410, 200 mo; Sv, Tee aETMT SGA igh erica $200" (Ps Construction}. 10:708 power tansformer for ute with A451 in 120 wo GET aa. Weight 14 Ibs. Not price $23.00, (Furnished in vertical end sh C-354 choke (200 mo) Nor price $2.80, C-492 choke (400 ma} Net price $6.60 sd only invert 192 except A441 which has tightly coupled tertiary winding. 1de ond steel mounting ely designed end can hondle tice the de current of the tube types recom: tion will orm the trans | (ould be kept within 10%, a; 6.24, 4a, Weight 9 Ibe: J nounting end shell amplifier cirevit: 410-0-55-410, 400 ma; $¥, 60) Is oalyhe | MODELS A410, 4-420, A-431, AMS! and A470 (BROWN LEAD IS 49 OUTPUT) (WHITE LEAD IS 70V OUTPUT ON A-431-707