SPL Lundahl Line Input Transformer Kit

Sound benefits
We think a good part of the "warmth" that is commonly associated with vintage gear comes from transformers -- and not only from tube circuits. With transformers low end and lower mids sound rounder, full-bodied with more punch. The top end gets a silky touch and benefits from improved presence without sounding boosted.
Reasons are reduced odd harmonics (which produce harsh top end imressions) and a slower characteristic compared to electronic stages (which causes a more voluminous sound). We recommend transformers since we experience their sound as refinement without disadvantage in any application.

Transformers in preamps
Used in preamps or channel strips, the input transformers add ca. 14dB (depending on the microphone) of gain. This must be added to the scaled values. The additional passive gain relieves the complete unit permanently at any gain level, thus improves signal quality.
That's why the input transformer is more important in preamps, but to benefit from all possible sonic improvement and operational safety, both input and output should be equipped with transformers. If SPL preamps only offer an input transformer option, the simple reason is not enough space ... if a unit offers an transformer option for inputs and outputs, we recommend to replace all electronically balanced stages.

Operational safety
Transformers transmit the signal by induction. This means there is no static connection (like a wire) to transmit the signal. This protects the unit from damage caused by power failures in the input/output connections. In addition, hum problems are effectively avoided if balanced connections are used throughout. Transformers are a must for units used in facilities that need highest operational safety (e.g. broadcasters). Another notable advantage for many live and recording applications is that much longer cable lengths are possible with no loss in sound quality.