Reverb tank ohm question

Dan0h

Dan0h

Well-known member
Ok gurus. I need help.

Can someone explain what the input impedance of a reverb tank does? The Supro has a Mod 9” tank with 1925 ohm input. I was looking at getting a 16” long tank to drop in but the input impedance on that is only 800 ohms. What would this do sound wise? Could I damage the tube driver pushing it? Just curious. Thinking it’s be a great low cost mod at under $30 to go from small to large tank. Thank you in advance for any insight.
 
Clearly the answer is to run 2 tanks in series. Jk.
In this amplified parts article, it recommends matching them as closely as possible.
I believe going to less than half would result in saturating the coils and probably not sound good.
I'm also no expert and shouldn't be your deciding factor but from an EE standpoint, that's what makes sense.
Edit, spellun
 
It's hard to tell without looking at a schematic exactly what it would do, but generally matching reverb tank impedances is like matching speaker impedances. It doesn't have to be an exact match, but if it's that far off then it could potentially damage something. If your driver is expecting a light load like 1925Ω and it's presented with a much heavier load like 800Ω, it's going to have to work more than twice as hard to provide the current necessary to drive it, which could damage the reverb driver (not sure if transformer or directly tube-driven, though with that high of impedance I would expect the latter).

What's the model number of the tank in there right now? I'm seeing a MOD 9FB2A1C that's a 16" tank with a 1925Ω input, most likely a drop-in replacement.
 
Bricksnbeatles said:
as far as 16” tanks go…

This fits your spec:


Close match, if you need long decay:


Click to expand...
That’s the medium I was looking at too. I was hoping to find a Short delay time version in 16” but that’s where I run into the ohm mismatch which sounds like something to avoid for sure. For $30 it’s worth a try. The current tank is 9” and long and the decay time is very very long hoping to cut it down a little bit. I guess I could put something to slightly muffle the springs and see if that works. Sorta regretting selling off my surfy bear now. The decay control was great.
 
I ended up ordering a couple tanks and will experiment when they arrive. Starting to wonder if I have a bad tube or wrong tank because this reverb sounds ok but no where near what the YouTube videos sound like for this amp. Lots of background decay that’s a bit gnarly sounding almost distorted. My Sproing pedal sounds 10x better which is concerning.
 
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