

API 535-LA Line Amp
Modeled after API's highly prized console-based 325 booster cards, the 535 can both amplify and attenuate incoming and outgoing signals for ultimate flexibility - all while providing API's trademark warmth and tone.
The 535 excels at adding warmth to a variety of signals. Warm up digital signals of all kinds, add tone to keyboard rigs, or add warmth to any mix.
Audio playback devices, mic preamps, or audio processing devices that do not have their own level control will also benefit from the added tone and control of the 535-LA.
The 535-LA also includes a balanced input, a polarity switch, a 20dB pad for incoming signal attenuation and a three position toggle switch, which allows for different output gain levels from the transformer. This is designed to drive long balanced lines with low distortion just as the 325 booster card does. Output gain range is from 6dB to 45dB. The 535 utilizes the discrete 2510 and 2520 Op-Amps along with API's proprietary transformers to create the unique, warm and reliable sound that API users expect. Like all API products, the 535-LA features API's unique 5 year warranty.
- Continuously variable detented input level trim
- Polarity button
- 20dB Input Pad
- Calibrated Level mode
- Output Ratio selector
- Clip LED indicator
- Continuously variable Output Gain
- Audio circuit uses the famous 2510 and 2520 Op-Amps
Product Overview
Product Specifications
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Shipping Information
We provide free shipping on most items and Next Day delivery on all orders completed before 12pm (noon!) so you don’t have to pay extra or wait long to start enjoying your new equipment.
We use DPD to ship the majority of our orders within the UK. International locations will vary, learn more here.
Product Support
We work with some of the world’s leading audio manufacturers to provide everything from the trusted studio classics to modern, innovative technologies that help you to push sonic boundaries. We pride ourselves on offering the best support both before and after sale. If you have any questions, please get in touch.

API 535-LA Line Amp
New Gear FAQs
Are all new items in stock?
With such a wide range of products we cant stock everything at all times.
The product page will display if an item is in stock. If it is marked as pre-order, you can place your order as normal and await its arrival into stock.
Please get in touch for an estimated shipping date. This may vary depending on stocking level with the manufacturer and/or distributor.
What warranty do you get with new gear?
Minimum 1 year manufacturer's warranty. Some manufacturers may also extend this (please see their respective websites for more information).
Can I part exchange used gear towards new gear?
Of course! Whether youre just looking to sell unused gear or looking to upgrade, get in touch here to discuss.
Can I test the equipment before I buy it?
We have a demo room at MNPA HQ where you are welcome to come and try out the equipment we have in stock. We’re not a shop and open to the general public so please get in touch via our Contact Form to book an appointment before coming to see us.
