Danelectro DSR-1 Spring King by John Eppstein
This is to my knowledge the cheapest true spring reverb available. And for what it is, it ain't bad. Added to any of my small, reverbless guitar amps it adds an authentic spring reverb sound. As such, it does what I need it to do. It even features a kick plate for that "thunderstorm" effect. Knobs for Volume, Tone, and Reverb. On-off switch.
But it's not without some issues.
First, as there is no acoustic isolation of the reverb tank it could be prone to feedback with larger amplifiers. This might be able to be dealt with by packing the inside of the box around the tank with some sort of damping material, but I have not tried it. The problem is probably exacerbated by the fact that this unit uses a very small, Chinese made tank rather than the more expensive (and bulkier) Hammond or Accutronics units found in most guitar amps. The fact that the tank is much shorter physically means that the springs must operate at a much lower tension to achieve the same delay times, making the spring more sensitive to feedback.
The other issue has to do with power. The unit has provisions for either a 9V battery or a power supply but they might as well have left out the battery because it's pretty useless unless you own a battery factory. This unit devours batteries in a very short time and is very demanding on the type of battery used - the el cheapo battery supplied with the unit doesn't really work properly. Even a good brand only is good for a couple of hours.
When the battery goes out the device does something that might make you think it's defective, but it isn't. The problem is that it oscillates, producing a high pitched tone. I had experienced a similar problem with other effects devices in the past, so rather than returning the pedal I replaced the battery and the problem was solved - however the short battery life means that if you use this pedal you will want to use a power supply so you don't go broke buying batteries. It uses a standard 9V supply and works just fine sharing supply with my Boss Echo, Boss Tremolo, and Peterson StroboStomp.
At a street price under $150, this is a unit worthy of consideration if you can use a device with its quirks. It works pretty well for me with my 5 to 15 watt amplifiers and I don't need it with my Twin Reverb. And it does make my Fender Pro Junior sound like a Fender Reverb amp.