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SM2558 Active Stereo Summing Mixer


  • Mix and Match HRK 500 Products!
500 Units 2 4 6
Discount -10% -15% -20%

Available Until Stock Last




SM2558 | Active Stereo Discrete 10 Inputs 500 Summing Mixer

  • Stereo Summing Mixer in a Single 500 Slot!

  • Adds Warmth, Details, Space and Enhances the Mix

  • 10 Active Summing Inputs in Total

  • Real-Time Monitoring and Recording

  • Flexible Stereo Mix-Bus Routing: L, R, L+R

  • Vintage Console Mode

  • Discrete Class-A British Summing Opamps

  • Discrete Class-A Transformer Drivers

  • HRK Active Transformers

  • Selected NOS Discrete Components

  • Studio-Grade Texas Instruments Opamps

  • Output Adapter Included

  • Direct Sale – Save on Distributors Fee!

SM2558 | Fully Featured Stereo Summing Mixer

The SM2558 is an Active Stereo Discrete Summing Mixer unit which fits in a single 500 rack space.

The SM2558 has a total of 10 active balanced summing inputs which can be used to mix any music material in the Outside-the-Box Analogue Domain.

The Direct Monitoring feature helps to save the outputs of an audio interface and provides seamless workflow without the latency!

The stereo summing bus section is based on the Discrete Operational Amplifiers made with NOS transistors.

The Outputs of the SM2558 are coupled with custom HRK Transformers powered by Class A Discrete Drivers.

Flexible routing allows to assign summing inputs to channel LEFT, RIGHT or LEFT + RIGHT summing bus.

The Vintage Console Mode adds more harmonics by increasing the saturation of the output transformers.

The SM2558 is a compact, yet fully functional summing mixer, with features which can be found only in very expensive studio mixers!

Direct Sale allows us the keep the price low and passes the saving on the distributor fees to our Customers!


Use the SM2558 with a Simple Audio Interface!

The SM2558 can be used even without the D25 split cable, with a simple two-channel audio interface.

The front panel TRS inputs can be used to process any stereo signal.

Simply connect the inputs and outputs of your interface, run any track or finished the mix with SM2558 and get the analogue warmth of Class A Discrete Circuitry and Output Transformers.

All you need are the standard TRS cables!


Discrete Operational Amplifiers Summing Bus

The analogue summing of all 10 inputs is processed with the Class A Discrete Operational Amplifiers.

The Opamps used in the SM2558 are inspired by the famous British design from the ’70s.

The SM2558 Discrete Opamps are made with selected NOS components.


Vintage Console Mode

The Vintage Console Mode adds the harmonics to the signal by saturating the output transformers, typical for the vintage mixing consoles.

The output transformers are not overdriven by the higher signal level.

Special Class A Discrete, open feedback circuitry is used to power the output transformers.

Such solution ensures the high fidelity of the processed mix, equal signal levels and prevents the digital clipping.

The signal is enriched with even harmonics resulting in enhanced bottom-end, space between the mix elements and vivid sound scene.

The Vintage Console Mode can be engaged by the switch on the front panel.


Direct Monitoring

The Direct Monitoring feature helps to save the outputs of an audio interface.

The Direct Monitoring function allows to edit, listen and process the mix at the same time without the latency.

The MON switch converts the front panel TRS sockets into the Direct Monitoring outputs.

The front panel TRS sockets mirror the signal available on the main rear panel outputs.

You can connect the studio monitors and use all interface outputs for mixing.

No cable switching, just seamless workflow without the latency!


The use of the 500 single slot in a stereo configuration.

It might be counter-intuitive to use a single slot of the 500 rack in stereo mode. Nonetheless, it is absolutely possible and completely safe.

The 500 rack rear panel XLR input connector is nothing more than a straight-wire connection between the XLR socket and the 500 module PCB edge connector. Therefore, it can be easily converted to the output with the included XLR male-to-male adapter.

The picture below shows the arrangement of the rear panel XLR connectors. The XLR male-to-male adapter is included with the SM2558.

NOTE: If your 500 rack has any built-in extra routing features, remember to disable any routing options before the use of SM2558.

User Manual – Read before using the SM2558:

SM2558 User Manual

ALL HRK Products Are Brand New - Assembled and Fully Tested

All HRK Products are tested with the industry’s best audio measuring equipment – The Audio Precision

Audio Precision is an industry leader in providing high-quality audio testing equipment. They are renowned for their test systems’ precision, reliability, and versatility.

When testing studio audio devices, Audio Precision’s equipment can assess parameters like frequency response, harmonic distortion, intermodulation distortion, phase response, signal-to-noise ratio, and cross talk. In-depth and accurate testing allows the identification of even the smallest issues in audio quality, enabling corrections and improvements that can significantly elevate the overall product quality.

In conclusion, using Audio Precision test equipment is an excellent way to ensure that all HRK products are performing at their best, meeting the standards required for the Professional Studio Applications.


Stereo Buss Operation

All Items are dispatched from Poland in the European Union within 1-3 working days.

Country / RegionShipping CostCustoms FeeVAT
All 27 European Union Countries – Delivery Time: 2-7 Days

– 14.99USD for orders below 249USD

– FREE shipping for orders over 249USD

NO Customs Fees– Yes, for personal orders- Not charged with the EU VAT number
United Kingdom – Delivery Time: 3-7 Days

– 14.99USD for orders below 249USD

– FREE shipping for orders over 249USD

No VAT ChargeHMRC collects the VAT or additional Fees if applicable.
USA, Canada – Delivery Time: 5-10 Days

– 14.99USD for orders below 249USD

– FREE shipping for orders over 249USD

NO Customs Fees for orders up to 800USD – charged by the USA Customs OfficeNo VAT charge.
Australia, Japan, South Korea –  Delivery Time: 5-14 Days

– 19.99USD for orders below 299USD

– FREE shipping for orders over 299USD

There is no info available – refer to local regulations.No VAT charge.
Switzerland Delivery Time: 3-7 Days

– 14.99USD for orders below 249USD

– FREE shipping for orders over 249USD

There is no info available – refer to local regulations.No VAT charge.
Norway Delivery Time: 3-7 Days

– 14.99USD for orders below 249USD

– FREE shipping for orders over 249USD

There is no info available – refer to local regulations.No VAT charge.
Worldwide Destination Delivery Time: 3-14 Days– 29.99USDRefer to local regulations.No VAT charge.

EU Customers

EU Customers will not pay any extra customs fees.

Business customers with a valid EU VAT number will not have to pay VAT tax.

Please enter your EU VAT Number at checkout and the VAT will be deducted from the Total Payment. The VAT number is automatically checked in the VIES database.

For personal orders from the EU, VAT will be added at checkout.

UK Custmers

We ship directly to United Kingdom.

UK VAT tax is collected by HRMC

Non-EU Customers

Customers from outside the EU purchase items with no VAT.

Please select the destination country and the VAT will be removed automatically.

If the VAT is not removed, please email customer service via the contact form and a custom invoice will be issued.

USA and Canada

Orders from the USA below 800USD are FREE from customs tax.

We ship directly to the USA and Canada

Payment Options:

You can pay for your order with any Credit Card or Apple Pay!

PayPal – We do not use PayPal as a payment method.

7 Days Return Policy

Our return policy is a part of the general Terms & Conditions, which you must acknowledge at the checkout. We stand by fair rules and a win-win approach.
We understand that our customers may wish to return the product and we provide such an option.
However, because we are a small company, we can’t afford to run a grade B outlet shop like big distributors and provide a 30 day return period. We can’t also scrap every returned unit.
We can charge our customers more to offset the cost of the returns, and this is what major distributors do. Or we can keep our prices low and hope that our customers will appreciate our policy.
This is why we provide the 7 days test period after receiving the package with the ordered items. If you wish to return the item, we will accept the return request, provided that the item is not damaged.

If the item is damaged during transport, we will do our best to help you and provide a replacement product.