![]() ![]() If you don’t like it, then there is a solution called the Zobel network. You may or may not like the sound of transformer overshoot. Most transformers designed for audio usually have the peak of the overshoot in the higher frequencies, outside of 20kHz – but it doesn’t mean you won’t hear it. The frequency and the level of overshoot depend on many factors and different transformers have different reactance. ![]() And because it is also wound around itself, with primary and secondary all bundled up tight, there is also a capacitive relationship.Īll this adds up to the reactive element of the transformer and it is usually measured and heard as a ringing or “overshoot” in the high frequencies. Its bobbin is wound around magnetic material and this makes it inductive as the audio passing through it. Transformers physically have some resistance in their windings, because it’s made up of long and thin wires. Unterminated, the transformer is naked and natural. UNTERMINATED simply means that there is no load on the secondary of the transformer, thereby relying on the following device, such as a DAW or an outboard unit, to load it. Today, the idea of pro-audio gear having 600 ohms has stuck even though it has nothing to do with how pro-audio must work. Because communication across the country was far more important than recording or reproducing music, the audio world borrowed transformers from the telephone industry up until the 1970s. The 600 ohms was established back in the days of analog telephones as the nominal impedance between transmission lines. This is easier to drive for the average pro audio devices output. If the TransDrive contains transformers with a 1:2 ratio, with the secondary loaded at 10k ohms going into these units, then the primary input impedance would be 2500 ohms, or 2.5k ohms. In another example, the Apogee Symphony I/O MkII specifications say the line input impedance is 10k ohms, which is the same for the line input of older Neve console modules. This would be a heavy load for the average pro-audio devices output. So if there’s a load of 600 ohms on the secondary, the input impedance looking into the primary would look like 150 ohms. 1 squared is still 1, and 2 squared is 4. To find out what the input impedance is, we square the ratio numbers. This is an important point often misunderstood in the pro-audio world.Ī transformer’s input impedance is dependent on the load on its secondary, whether resistive or reactive.Īlso, a transformer’s impedance is related to the square of its turns ratio.įor example, if we set up the TransDrive at PRL/SERIES using a 1:2 ratio transformer loaded, then we can expect an audio gain of +6dB. Transformers do not have an intrinsic input impedance transformers have a reflective impedance. We shall first establish some simple electronics rules. Following the inverse of the rule, halving the audio voltage would yield a loss -6dB. The third setting is SERIES/PRL, which the TransDrive® set up the primary in SERIES, and the secondary in PARALLEL, essentially the opposite of the first position for a 2:1 ratio. ![]() You can expect a near unity gain in this setting. The second setting is SERIES/SERIES sets up the windings in an equal ratio of 1:1, thereby no gain is attained, although some small amount of level loss is expected due to insertion loss. This would be a 1:2 ratio and as a rule of audio calculation, anytime you double voltage, you get a step up gain of +6dB. With the first position PRL/SERIES, the TransDrive would set up the primary in PARALLEL, meaning that the two windings double up, and the secondary would be in SERIES, meaning that the windings are one after each other. A transformer with at least two primary and two secondary windings would be preferred and this would give us some options as follows: This means PARALLEL and SERIES, and it’s a way of setting up the primary (the input) and secondary (the output) ratios. ![]()
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