One question that customers often ask us is whether the ASD-1 and ASD-2 spring reverb pedals will work with a particular spring tank they already own. The spring tank may have come from an old amplifier they aren’t using anymore, and they don’t know anything about the specifications. While spring tanks typically don’t list the specifications on them, they do usually have a seven-digit code on them that will tell you everything you need to know. This article teaches you how to read spring reverb tank codes so you can determine if your spring tank will work for a given application.
In this article we will use a spring tank with the code 8EB3C1B as an example, which is one of the spring tanks that will work with the Analog Spring Driver effect pedals.
The first digit will be the number 4, 8, or 9. This specifies the length and the number of springs. 4 = 16.75” with 2 springs, 8 = 9.25” with 3 springs, and 9 = 16.75” with 3 springs. Some manufacturers will say that they are 4-spring tanks and use a code that starts with 4. That is because instead of using two long springs, they use two sets of two springs that are connected at their ends. The 8EB3C1B spring tank example is a 9.25”, 3-spring tank.
The second digit specifies the input impedance and will be a letter from A – F. A=8-10 ohms, B=150-190 ohms, C=200-240 ohms, D=250-310 ohms, E=600-800 ohms, and F=1475-1925 ohms. The 8EB3C1B spring tank example has an input impedance between 600 – 800 ohms.
The third digit specifies the output impedance and will be a letter A -C. A=500-600 ohms, B=2250-2575 ohms, C=10000-12000 ohms. The 8EB3C1B spring tank example has a output impedance between 2250 – 2575 ohms.
The fourth digit specifies the reverb decay time and will be a number 1 – 3. 1=1.2 – 2 second short decay, 2=1.75 – 3 second medium decay, and 3=2.75 – 4 second long decay. The 8EB3C1B spring tank example is a long decay tank.
The fifth digit specifies whether the RCA connector jacks are grounded or insulated. A=Input grounded/output grounded, B=Input grounded/output insulated, C=Input insulated/output grounded, D=Input insulated/output insulated, and E=No outer channel. The 8EB3C1B spring tank example has an insulated input and a grounded output.
The sixth digit will almost always be the number 1, which means that no locking device is present.
The seventh digit specifies the recommended direction that the spring tank should be mounted. A=Horizontal with the open side up, B=Horizontal with the open side down, C=Vertical with the jacks facing up, D=Vertical, with the jacks facing down, E=On end with the input jack facing up, F=On end with the output jack facing up. The 8EB3C1B spring tank example is a tank that should be mounted with the open side facing down.
The below table can be used as a reference guide to determine the specifications of your spring tank.
