Legendary Tube Opto Compression

The SA-1B5 is a meticulously reverse engineered replica of the legendary Danish 1B opto compressor. Being a popular request for many years and with many companies attempting to recreate it, we decided it was time to bring this piece of history into a 500 series format operating at the same voltage and with the exact same sound as its big brother.

Thanks to the careful selection of parts and a proprietary matching circuit we have been able to make this unit an identical match to the original. The same frequency response, tone, top end and time constants were achieved.

At Stam, we do many things differently, and one of them is that our ears are the ultimate decision maker. We spent hundreds of hours listening to every component and how it affected this circuit so that we could fully reproduce the silky top end and “grabiness” of this vintage gem. Despite being famous for being a transparent compressor, the 1B circuit imparts a subtle but unique coloration and character thanks to the transformers, tubes and opto element, that when combined, produce an articulate, silky and smooth compression.

The Iron

Getting the correct transformers was a critical piece of recreating the tone of an original. After testing dozens of prototypes we decided in favor of 2 different recreations. Each SA-1B5 is packed with a custom-made input transformer in the USA and a Swedish-made Lundahl output transformer, both which precisely replicate the original ratios, frequency response and THD.

The Opto Element

The opto element was the trickiest part to get right. After auditioning many variations and hundreds of hours of measuring and listening tests we decided to request a custom-made opto element to be created for Stam Audio. It was critical for the time constants to be the same. We also produced a proprietary circuit to match them so that each SA-1B5 has the same attack and release times as an old 1B comp.

Added Features

Hand-made