Mastering Compressor

As a mastering compressor, IRON is inspired by the legendary vintage tube compressors à la Fairchild, Collins or Gates and has been developed in a way to give modern productions more energy and power with the advantages of the 120V technology.

Input & Output

Input and output levels are switchable in a control range of +/- 12dB. An increase of the input level leads to more intensive compression. When mastering full scale material, the reduction can be useful. The output is used to adjust the level ratios of input and output.

Attack & Release

The time parameters Attack and Release are switchable in six steps from Slow to Fast. The times vary depending on the rectifier circuit selected.

Side Chain EQs

With the side chain EQs, compression can be focused on frequency ranges. In addition to an inserted EQ, there are four internal EQ presets with a partly complex frequency response.


The tube stage is controlled by a rectifier circuit. There are six diode control characteristics generated by germanium, silicon and LED diodes or combinations thereof.

Variable-Bias Limiter/Compressor

The IRON Mastering Compressor is a variable-bias (variable µ) limiter/compressor from the basic concept.

IRON works on the principle of the bias controlled remote cutoff tube. Parallel to this, a medium-variable-bias triode (sharp-cutoff tube) with a steeper characteristic is connected. The tube bias voltage (BIAS) can be adjusted in three steps.

The tubes are integrated into special Lundahl manufactured balanced high-level double core mu-metal-iron transformers.

AirBass & Tape Roll-Off

The compressor is followed by a passive filter network with two equalizer presets: AirBass and Tape Roll-off.

The AirBass filter boosts low and high frequencies by about 1.5 dB and the Tape Roll-Off filter emulates the typical frequency response of a tape machine.


All functions can be set via switches and the threshold via a rasterized potentiometer which makes recall easy.

The settings of Threshold, Bias, Attack, Release, Rectifier and Side-Chain-EQs are transferred from the right side (channel 2) to the left side in Link Mode, in which the compressor operates with summed control signals.


Channels 1 and 2 are activated with the large illuminated IDEC switches.

In Auto Bypass mode, the channels are automatically switched on and off, which leads to a more objective assessment.

The Interval control is used to adjust the time window continuously between two and 20 seconds.

Play Video
Jonathan Wyner of M-Works Mastering talks about PQ and Iron
Play Video
Michael Romanowski: Grammy-Nominated Mastering Engineer - Warren Huart: Produce Like A Pro
Play Video
In the studio with Simon Phillips
Play Video
This video introduces you to the entire mastering series.

The 120V Technology

What exactly is that?

And what does it do?

Good questions need good answers. And that’s what the 120V video gives you.

Play Video


Tape Op
Studio Magazin

Other Mastering Series Products

Mastering D/A Converter
Mastering M/S Processor
Mastering Router
16-channel Monitor Controller
Mastering Console
Mastering Equalizer
Passive Mastering Equalizer
Play Video
Replacement of defective fuses for 115V
Play Video
Replacement of defective fuses for 230V
Play Video
Changing the mains voltage from 115V to 230V
Play Video
Changing the mains voltage from 230V to 115V


Analog inputs & output; XLR (balanced)

Maximum input & output gain
32.5 dBu
Input impedance
Output impedance
75 Ω
Frequency range (-3 dB)
10 Hz – 40 kHz
Common mode rejection (0dBu, 1kHz)
> 80 dB
Crosstalk (1 kHz)
-108 dBu
THD (+10 dBu)
0.002 %
Noise (A-weighted)
-98 dBu

Internal Linear Power Supply with Shielded Toroidal Transformer

Operating voltage for analog audio
+/- 60 V
Operating voltage for relays and LEDs
+ 12 V

Mains Power Supply

Mains voltage (selectable, see fuse chamber)
230 V AC / 50; 115 V AC / 60 Hz
Fuse for 230 V
T 1 A
Fuse for 115 V
T 2 A
Power consumption
max. 40 VA

Dimensions & Weight

W x H x D (width x height x depth)
482 x 132 x 300 mm
19 x 5.2 x 11.8 inch
Unit weight
11 kg
24.25 lbs
Shipping weight (incl. packaging)
12.9 kg
28.44 lbs

Referenz: 0 dBu = 0,775V. Technische Änderungen vorbehalten.


Due to Covid19 there are no events scheduled at this time.

What does it actually mean …

In Stock!

The product is in stock in our warehouse in Niederkrüchten, Germany, and will be shipped the same or next working day.

We process the orders after receipt of the order and update the stock in the online shop regularly. If the product is no longer available at short notice due to high order volume, you naturally have the right to withdraw from the purchase (see Right of Withdrawal).

In any case, you will receive an e-mail with details of the delivery and the estimated delivery time.

Available soon!

The product is not in stock in our warehouse in Niederkrüchten, Germany. Usually it will be available again within 5 working days.

Due to the current pandemic and the associated worldwide shortage of components, delivery times may be significantly delayed in some cases.

In any case, you will receive an e-mail with the details of the delivery and the estimated delivery time.

Of course you have the right to withdraw from your purchase (see Right of Withdrawal).

Product Condition


Brand-new product from the current product portfolio.


Demo, exhibit or return item.
In original packaging, incl. manuals and full warranty.
Only slight to no signs of use.


Demo, exhibit or return item.
In original packaging, incl. manuals and legal warranty.
In some cases clear signs of use, which are documented in photos.


"New Old Stock"
After discontinuation of a product still available new products with full warranty.