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Fender Twin 73 IR Pack

1973 Fender Twin (Silverface) combo amp impulse pack
Fender Twin 73 IR Pack is a pack of impulses (IR) that can be used with our A+ CabZone LE cabsim or with any other cabinet simulator, either hardware or software. The impulses were recorded and edited by the Shift Line team in St. Petersburg, Russia. This is the fourth instalment in the series of impulse packs presented on our website; this time, the impulses were recorded from a 1973 Fender Twin combo.

Impulse format is mono 24bit 48kHz WAVE PCM1, non-compressed. Impulse length is 1000 samples (around 20ms), which is enough to recreate a true-to-life frequency response of the cabinet while eliminating the effect of the room or any unwanted reflections. All impulses in the pack have been normalized to the same volume level.
This pack is distributed on the Pay-What-You-Want basis: this means you name your own price. No matter how much you pay (if anything), the files are always available for you to download.


The 1973 Fender Twin (Silverface) with JBL D120F speakers is one of the best clean amps ever — in our opinion, at least. However, it also works great for all sorts of crunch, breakup and mid-gain, and it tends to take fuzz and distortion pedals really well. This isn't supposed to be a classic metal amp, but it's frequently used even in those genres.

So what's so remarkable about the '73 Twin?
First and foremost, it has an open back cabinet with two 12-inch JBL D120F speakers, resulting in a characteristic peak at 4kHz. This resonance acts as a peculiar "presence" filter that highlights the glassy sound of a Strat or enriches the thick Les Paul tone. Its effect varies from one impulse to another but it's present in all of them. This way, you can choose the impulse you like best. Another perk of this cab is that Fender spring reverbs sound amazing into it, providing the authentic surf sound.

We firmly believe that even in a pair of two impulses recorded from the same amp model, each impulse will be unique in its own way. We used two mics to record this impulse pack: a Sennheiser e906 and a Lomo 19A19. The Twin's power amp was also used. Each of the 10 impulses in the pack has its own mic positions, combinations and balance.


CabZone LE: Unpack the archive into the root directory of a blank MicroSD card. An AFX folder should appear on the card along with text description files.

Twin MkIIIS: Copy the needed impulses into the appropriate folders on the SD card. Remember to delete any old files in the folders beforehand.

All impulses in the pack have a mono 24bit 48kHZ WAVE PCM1 non-compressed format and are adapted to working with our devices (A+ CabZone LE cabsim and Shift Line Twin MkIIIS tube preamp). Of course, you can also use them in any device or software which supports that format.

Mic positioning schematics

Fender Twin Impulse Pack Scheme

Details on each impulse

The impulses in the pack have the necessary minimum frequency correction. Each impulse is a snapshot of a particular "cab/mic/preamp" combination. The positions of the Sennheiser e906 and the Lomo 19A19 are not always identical; in some impulses, the left speaker was used, while others took advantage of the right one. The most characteristic feature of the Lomo 19A19 is its wide frequency response resulting in a more "open" sound, while the Sennheiser e906 tends to be more focused. For a busy mix, impulses using the Sennheiser might be preferable; at the same time, those using the Lomo 19A19 would work great for laid-back atmospheric parts.

For easier navigation, the name of each impulse reflects the position and type of the mic used.
Dome edge: This pair of impulses was recorded with a mic aimed at the edge of the protective dome and placed 10cm from the speaker. This mic positioning might result in the most genuine impression of using the combo in real life. Despite the almost identical mic placement, the general frequency response curve is quite different between the two impulses.
  • 01 Twin73 dome edge L19: The Lomo 19A19 has a boost at 80Hz and a scoop at 380Hz, as well as a significant high frequency rolloff over 10kHz. This impulse works great for clean sound and gives it a bit of "body" due to the scooped low mids.
  • 02 Twin73 dome edge e609: Unlike the Lomo, the Sennheiser e906 has a low mids boost around 600Hz and a slight scoop at 2kHz. The high end rolloff begins at 7kHz. This makes the sound "rounder" and "softer", which should work well with light overdrive.

Center: This pair of impulses was recorded with a mic aimed at the center of the protective dome and placed 10cm from the speaker. In this position, both mics strongly highlight the 4kHz resonance, which results in a cutting sound that will never get lost in the mix. The general response of both mics in this position is quite similar, but the nuances will let you choose the one that fits your music best (depending on the rest of your signal chain starting with the guitar).
  • 03 Twin73 center L19: The Lomo 19A19 has a more open (both in terms of bass and treble) and more uniform sound than the Sennheiser.
  • 04 Twin73 center e609: Due to a slightly reduced low end response, the Sennheiser e906 results in a slightly brighter sound.

Cone20: This pair of impulses was recorded with a mic aimed at the center of the speaker cone and placed 20cm from the grill cloth. This positioning provides a good general impression of the combo's sound; however, the 4kHz is slightly subdued with either mic here. This pair must have the most uniform frequency response out of the whole pack: between 250Hz and 2800Hz, there are no significant frequency jumps.
  • 05 Twin73 cone20 L19: The Lomo 19A19 shows its characteristic open low end and even has a slight boost around 60Hz. The 4kHz peak is mild and 2dB quieter than with the Sennheiser.
  • 06 Twin73 cone20 e609: Despite having a less open high end, the Sennheiser e906 provides a slightly brighter sound in this position. This is due to the steeper low end rolloff around 90Hz and a more pronounced peak at 4kHz.

Cone: This pair of impulses was recorded with a mic aimed at the center of the speaker cone and placed 5cm from the grill cloth. This close positioning results in a more focused overall sound; at the same time, the 4kHz resonance is more pronounced and the general frequency balance is shifted towards the low end. These two impulses will work great if you need to tame an excessively wild distortion pedal.
  • 07 Twin73 cone L19: As usual, the Lomo 19A19 has a slightly wider frequency response and has slight filtering around the 1kHz mark.
  • 08 Twin73 cone e609: The Sennheiser e906 is more focused and has slight filtering around 500Hz.

Mic sums: The impulses in this pair were recorded from different positions. The thing they have in common is that both have an impulse recorded from the back of the cabinet. Since the Twin has an open back cab, it is common practice to record impulses from two points and later to mix them for greater "body" or for frequency correction.
  • 09 Twin73 cab plusback L19: The Lomo 19A19 was placed 50cm from the center of the cabinet in front and also 50 cm behind it. The two signals were then phase-aligned and mixed in 50/50 proportion. The result is interesting, albeit unexpected. A number of mild scoops emerged in the frequency response curve, while the overall sound became a bit "boxy", which can be used as an artistic tool.
  • 10 Twin73 dome edge plusback e609: The Sennheiser e906 was first placed at the edge of the protective dome (15cm from the grill cloth) and then behind the cab at an angle of 45 degrees. The two signals were then phase-aligned and mixed in 50/50 proportion. Unlike the Lomo impulse, this one sounds quite natural and has a pronounced high mids boost. This is a great impulse for blues playing.

Terms of Use

Commercial use of the Shift Line Fender Twin 73 IR Pack or its parts (such as implementing it in third-party hardware or software) is possible with our permission. Please contact us at

Our devices in which the impulses can be used