Output-Transformerless (OTL) Tube Output
An OTL tube output stage drives its load without an output transformer.
Also called: Output Transformerless (OTL)
OTL means output-transformerless. This describes the coupling arrangement of a tube amplifier, separately from amplifier class or single-ended versus push-pull operation.
Output-Transformerless (OTL) Tube Output — Headphone Amp
For a tube headphone amplifier, OTL means the headphone load is driven without a matching output transformer. Output impedance and available current therefore matter when matching headphones.
Compare the stated supported load and power, rather than assuming every headphone is suitable. A transformerless solid-state amplifier is not what this tube-specific field describes.
Output-Transformerless (OTL) Tube Output — Power Amp
For a tube power amplifier, OTL means the speaker output has no output transformer. The circuit must deliver the required voltage and current to the loudspeaker load by another arrangement.
Check the specified load range and output capability. Both single-ended and push-pull OTL designs exist, and silence about an output transformer does not establish that an amplifier is OTL.