F602 Tube Compressor - Compressor Fredenstein - Free user manual and instructions

Product Type	Tube Compressor (500 series module)
Product Name	Fredenstein F602 Tube Compressor
Form Factor	API 500 series single slot
Dimensions (approx.)	5.25 x 1.5 x 6 inches (133 x 38 x 152 mm)
Weight (approx.)	1.2 kg (2.6 lbs)
Tube Type	6386LGP remote cutoff double triode
Input Circuit	Transformer-less, high clarity
Output Transformer	Lundahl, adds character
Output Impedance	20 ohms (very low)
Maximum Output Current	±200 mA
Frequency Response	20 Hz - 20 kHz, ±1 dB
Distortion	< 0.01%
Signal-to-Noise Ratio	> 90 dB at 0 dB gain
Make-up Gain	0 to +20 dB
Threshold Range	-25 dB to +9 dB
Compression Ratio	2:1 to 20:1 (limiting)
Attack Time	250 µs to 15.5 ms
Release Time	12 ms to 5 s (auto mode available)
Mix Control	Blend of compressed and uncompressed signal
Knee Selection	Hard-knee or soft-knee (switchable)
Link Capability	Up to 10 units for multichannel operation
Bypass	True hard bypass (active even when powered down)
Standby Switch	Powers down tube to extend life (yellow LED)
Indicators	VU meter (gain reduction/output level), Clip LED (>+24 dBu), Over-temperature (OT) LED
Power Requirements	+16 V @ 250 mA, -16 V @ 200 mA (max 8W)
Max Input Level	+24 dBu
Max Output Level	+26 dBu
Input Impedance	> 10 kOhm
Reference Level	0 dB = +4 dBu (American studio standard)
Over-Temperature Protection	Auto standby if internal temp > 76°C
Compatibility	Fredenstein Bento boxes recommended; not compatible with third-party modules using same link interconnect (PIN 6)
Manufacturer	Fredenstein Professional Audio, Taiwan (German-American design)

Frequently Asked Questions - F602 Tube Compressor Fredenstein

What type of tube does the F602 use?

The F602 uses a 6386LGP remote cutoff double triode tube, commonly found in vintage designs from Gates, Fairchild, and GE.

Can the F602 be used in any 500 series rack?

It is designed for API 500 series but consumes up to 8W. Ensure your rack can supply +16V @ 250mA and -16V @ 200mA. Fredenstein racks are recommended. It cannot coexist with third-party modules using PIN 6 for link interconnect.

How do I connect multiple F602 units for stereo or multichannel operation?

Up to 10 units can be linked via the LINK switch. Use the link interconnect in compatible racks. In Fredenstein Bento boxes, turn off link switches for third-party modules and only enable them between F602 units.

What is the difference between hard-knee and soft-knee compression?

Hard-knee applies full compression above the threshold. Soft-knee gradually increases compression as the signal approaches the threshold, reaching full ratio at 3 dB of gain reduction. Switchable via the SOFT switch.

How does the automatic release mode work?

When the release control is turned fully counterclockwise, a switch engages automatic mode. The release time adjusts dynamically based on the program material and input level.

What is the function of the Mix control?

The Mix control blends the compressed and uncompressed (dry) signals. Fully counterclockwise outputs only compressed, fully clockwise only dry. This allows parallel compression without external routing.

How do I read the VU meter?

By default, the VU meter shows gain reduction. If the VU switch (upper position, LED on) is engaged, it displays output level instead.

What does the Clip LED indicate?

The Clip LED lights when the output level exceeds +24 dBu, indicating potential clipping.

How can I extend the tube life?

Use the STANDBY switch to power down the tube when not in use. The yellow LED indicates standby mode. This prolongs tube life while the rack remains powered.

What should I do if the OT LED lights up?

The OT (over-temperature) LED indicates internal temperature exceeds 76°C. The unit automatically activates standby to cool down. Ensure adequate airflow in your rack to prevent this.

USER MANUAL F602 Tube Compressor Fredenstein

Black silhouette of a human ear with the letter F inside, no text or symbols present.

Fredenstein

Professional Audio

F602 TUBE COMPRESSOR

Operating Manual

Fredenstein F602 Tube Compressor

The F602 Compressor is a true variable transconductance (often falsely called “variable mu”) high performance tool for professional recording and mastering engineers. The F602 features the original remote cutoff double triode tube used in many vintage designs (Gates, Fairchild, and GE to name a few) called 6386LGP. The signal path is very short and delivers the smoothness you would expect from a great piece of vintage equipment. The innovative transformer-less input circuit yields clarity while the Lundahl output transformer adds character. The extreme low output impedance with its high current design allows even the most difficult and complex loads to be driven without sonic impact. A wet (compressed) and try (uncompressed) mixer further enhances the flexibility of the F602 Tube Compressor. In addition a true hard bypass, which also works, if the unit is powered down, was implemented as well as a standby switch allowing to shutdown the tube circuitry if the F602 is not in use while the rack is still powered, therefore extending the tube life cycle.

Up to ten units can be linked together to form a true multichannel compressor. The engineer can easily change the compression characteristics by tuning threshold, ratio, attack and release times as well as selecting an automatic release mode, which adjusts the release time dynamically according to the source material and input level. The main compression behavior can be switched between hard- and soft-knee. Up to 20dB of make-up gain is provided to compensate for the gain reduction. The VU meter is selectable between gain reduction and output level. A clip LED indicates output levels above +24dBu.

The whole package is delivered a single space API 500 series form factor. Due to the high power-consumption of about 8W, not all lunch-boxes and racks are suitable for this module. Of course, Fredenstein boxes and racks are well equipped to handle these loads. As all Fredenstein products, the F602 is designed by a German-American team and manufactured in Taiwan.

Fredenstein F602 Tube Compressor

Overview:

Rotary Controls:

THR : Threshold Control

VU : if the VU-switch is in the upper position (LED is on), the VU meter shows the output level instead of gain reduction.

SOFT : if the SOFT-switch is in the upper position (LED is on), the compressor works in the soft knee mode.

LINK : Enables multichannel link capability indicated by a blue LED.

STANDBY : Powers down the tube to increase its life expectancy, if not in use. Indicated by a yellow LED.

BYPASS : True hard bypass function, also active when powered down

Indicators:

CLIP : Lit, if output level exceeds +24 dBu

OT : Internal Temperature exceeds 76 °C, the unit automatically activates standby mode.

Fredenstein F602 Tube Compressor

Installation:

Please power down your rack or box first, before inserting the F602. Since the F602 uses the link interconnect in the box or rack, it cannot coexist with any other third-party modules using the same link interconnect (PIN 6 on the edge connector). If you are using a Fredenstein Bento box, please turn off the compressor link switches to any third party module(s), only turn the link switches on between F602 modules.

Other third party equipment not using the link interconnect, such as most Mic-Pres and EQs etc, can be used simultaneously with the F602 in any enclosure. The power requirements are maximum +16V, +250mA and -16V -200mA. Please make sure, in case you don't use a Fredenstein Bento, that your box or rack can support the required currents. Please consult your third party documentation in case of any doubt. To prevent high internal temperatures leading to over temperature shutdowns, please make sure you have enough airflow through your lunchbox or rack.

To understand the function of the F602, let's discuss first some terms:

Hard-Knee characteristics means the compressor will evenly compress all signal above the Threshold as set by the Compression Ratio control. Soft-Knee means that the compressor will start softly when the Threshold is almost reached with a reduced Compression Ratio. Then it will increase the Compression Ratio until the Gain Reduction reaches 3 dB and the full Compression Ratio is applied.

When using very fast release times < 100 ms, you will get audible artifacts on low frequency signals, so be careful when tracking a bass or using it as a buss compressor on a mix as an example not to choose an ultra fast release time unless you want artifacts for artistic reasons.

Fredenstein F602 Tube Compressor

User Controls:

Threshold Control:

Determines the input level at which the compressor is activated. If turned completely counter clockwise, a switch engages and the compression is turned off.

Compression Ratio:

The amount of increase in output level relatively to the threshold level. Minimum is 2:1, maximum is 20:1 (limiting).

Release Control:

If the signal drops below threshold, the release time determines how fast the compressor falls back to 0 dB gain reduction. If turned completely counter clockwise, a switch engages and the release time is set to automatic mode depending on the program material. The range is 12 ms to 5s.

Attack Control:

Determines how fast the compressor reacts to signals above threshold.

Mix Control:

The mix control allows the user to select a ratio between the compressed and uncompressed signal. If turned completely counter clockwise, a switch engages and only the compressed signal will be on the output, if turned completely clockwise only the uncompressed (input) signal is present on the output.

Level Control:

Make-up gain can be applied in the range of 0 to +20dB to compensate for the gain reduction.

Technical Data:

Reference Level : 0 db = +4 dBu (American Studio Standard)

Make-up Gain : 0 to +20 dB

Threshold : -25 dB to +9 dB

Attack Time Range : 250 us to 15.5 ms

Release Time Range : 12 ms to 5 s

Compressions Ratio : 2:1 to 20:1

Frequency Response : 20Hz - 20,000Hz, +/- 1dB

Distortion : < 0.01%

S/N Ratio : > 90dB at 0dB gain

Input Impedance : > 10KOhm

Max. Input Level : +24 dBu

Output Impedance : 20 Ohm

Max. Output Current : +/- 200 mA

Max. Output Level : + 26 dBu

Power Consumption : +16 V +250 mA, -16V -200 mA

Contact Info:

Fredenstein Professional Audio

by Orion Communication

7F-1, No. 582, Ruei Guang Rd.

Neihu District

Taipei 114

Taiwan

Phone : [phone]

Email: [e-mail]

Web : www.fredenstein.com