Urei LA-4 Compressor/Limiter Pair (Siret Mod)

A Classic Optical Workhorse with a more modern sound.

The Urei LA-4 has always been the quiet sibling of the LA-2A and LA-3A. Same optical lineage, same smooth levelling behavior, but held back by the realities of 1970s integrated circuit design. Stock units can sound a little dark, a little veiled, and a little noisy when pushed.

The Siret Mod is what happens when you take that classic opto heart and give it some fresh air.

Inside, the original RC4136 quad op-amp is replaced with modern high-slew, low-noise circuitry that finally lets the optical cell breathe. Power supply rails are rebuilt, the entire audio path is re-capped, and the unit is recalibrated from the ground up. What you get is not a different compressor, you get the LA-4 that modern productions cal for.



The difference is immediate:

- the top end opens up.

- the midrange steps forward.

- the low end tightens.

- the noise floor drops by a shocking margin.



Instead of haze on vocals or bass, the modded unit delivers a warm, clear and beautifully transparent tone with the same unmistakable LA-series levelling action. Transients are faster, the stereo image snaps into focus, and the unit handles hotter material without folding in the highs.

Engineers who rarely touched their stock LA-4s often describe the modded version as a “secret weapon” opto. Smooth on vocals, authoritative on bass, gentle on guitars, and clean enough for mix-bus glue. It’s still an LA-4, but finally operating at full bandwidth and full musicality.

US and EU parcels ship via UPS, ETA 1-7 working days from pickup day zero. That also applies to most locations worldwide.

All shipments are fully insured.

Bigger shipments requiring pallets or custom made crates ship to US, CA, JP, CN, AU and other outside of EU locations via DHL Air Freight, ETA is normally approx. 7-14 working days from pickup day zero.

Big shipments inside EU ship via different freight companies, recently mostly via ACE Logistics. Freight forwarders can use different courier companies for deliveries to final destinations.

Palletising and crating time can vary depending on the size of the shipment and packaging queue. We pack all our shipments with great care.

You are most welcome to pick your order up yourself from our Retrosonic Pro Audio showroom, studio and warehouse in Tallinn, Estonia.

We ship worldwide – contact us for a personal shipping quote or any other questions.

VAT (Value Added Tax) can be deducted if you have a company with a valid EU VAT number or if you're based outside of the EU. Non-EU buyers pay all and any import tax and duty as regulated by their local customs.