The input impedance of the short tank is close enough. (10 Ohm vs 8 Ohm)

That figure is also only at 1kHz. It will drop a little at lower frequencies and rises almost exponentionally towards higher frequencies.
If the longer tank is 8 Ohm at 1000 Hz, I guess the short tank will be 8 Ohm around 800 or 900 Hz. So, it doesn't matter all that much as far as the driving circuit is concerned.

I mounted a long and a short tank (Accutronics 4AB3C1B and 8AB3C1B) in one enclosure and they're wired to a 4PDT toggle switch, so I can easily switch between the two.

The long tank is bright and drippy and is the best choice surfy tones. When people talk about spring reverb, they generally mean this tank and its typical sound and tone.

The short tank sounds very lush, darker, fuller, less metallic, a lot less drippy. It sounds more like a hall reverb. It is also a lot louder (much more output), probably because it has 3 springs and 3 transducers.

Last edited: Oct 28, 2018 16:54:09

I really cannot get a drippy, surfy tone out of that short 3 spring tank.

A while ago I modded my Vox Pathfinder 15R and Marshall MG15CDR. They both have a rather cheaply made, short, two spring tank inside and despite the length I could make them very drippy by adjusting the recovery circuit.

I recently also added a spring tank to a Marshall MG10CD and created the drive and recovery circuit from scratch and I was (again) surprised how much the drip depends on the drive and recovery circuit rather than the tank itself.

But there's no denying that the long tanks are easier to make them drip and their drip definitely sounds 'better' (or maybe just more familiar)

I think though that the longer the spring the harder it becomes to make it not drip, while the shorter the spring the harder it is to make it drip.
I once made an 8 meter longer spring reverb in my basement and the only sound it made was "piew... piew...", a very high pitched drip.
It looked and sounded similar to this:
https://www.youtube.com/watch?v=-6J0hacr1WU

Last edited: Oct 28, 2018 19:06:13

I've been working on my Surfybear/Surfy Trem project for a while now, and because I'm using the cabinet of an old radio, I have to use a short tank. It definitely gets drippy (to my ears), but I also find that it is too much reverb. Perhaps there's no such thing as too much reverb, but it really is overwhelming and I have to turn mix and dwell down quite low to the range of 2-3 to have it be a nice saturated level rather than way more reverb than guitar.

So j Flanders comment on the short tanks makes sense. My question is whether there is any way to tame this, like by changing pot values, throwing a resistor or capacitor into the circuit somewhere, or who knows what. I am building it so that I can hook up a long tank externally, so at some point I can A/B the tanks, and if I need to add some other switch in the circuit, that's not big deal.

I've been waiting to post this up for so long... I didn't want to join the forum until I had some more content to share. You can look at my profile to see my other posts that talk about my gear and the band that I use it in.

This pedal is brought into the chain with an effects loop pedal, and had the tank mounted under my pedal board. It's awesome.

I use a clean boost after the reverb pedal (not shown in this photo) to be able to match the volume of the pedal to the amp when the reverb is engaged. Again, these two pedals are brought into my signal by the small black effects loop pedal on my board.

Taifighter wrote:

I've been waiting to post this up for so long... I didn't want to join the forum until I had some more content to share. You can look at my profile to see my other posts that talk about my gear and the band that I use it in.

This pedal is brought into the chain with an effects loop pedal, and had the tank mounted under my pedal board. It's awesome.

I use a clean boost after the reverb pedal (not shown in this photo) to be able to match the volume of the pedal to the amp when the reverb is engaged. Again, these two pedals are brought into my signal by the small black effects loop pedal on my board.

I would be curious to see how you have it mounted under your pedalboard as I have thought of doing something similar...

LaFleur wrote:

Cool! I had the same idea to save some space on the pedalboard. What is the size of the housing for the Surfy Bear circuit?

Some pics of my board are at the top of page 103. I used a double wide housing from Amazon 4.7 x 3.7 x 1.2 inches. After looking again there are pre painted boxes available, I might switch mine out!

It produces quite a lot of heat.

I mounted it inside a relatively small Hammond box, which I covered with Fender tweed fabric. No vent holes.

I didn't want to drill a hole in the enclosure and have an 'ugly' screw on the outside which normally secures the pcb heat-pad to the enclosure serving as the heatsink.
So, I made a large custom metal plate inside the box and screwed the pcb to that. The metal plate itself acts as the heatsink but the plate is also in contact with the hammond box.
But with the tweed covering and no vent holes the heat builds up inside the pedal and the heat transfer to the surrounding air outside the box is probably poor.

It has been in use on a daily basis for a couple of years without a problem.
Sometimes I forget to turn it off and it has been on for more than 24 hours straight.

Just sharing my personal experience and the 'risk' I took, not recommending it.

Edit: It looks like taifighter above did the same thing. Maybe he screwed it to the bottom of the box? Seems unlikely. I don't see a screw on the front though. Maybe it's just 'floating' inside?

Last edited: Dec 16, 2018 18:36:13

Use proper heat sink tape or compound between the fets and whatever you had dissipating their heat.

Thanks guys, I searched like crazy and came up empty... mostly because I wasn't sure what the stuff was called.