What is the difference between 2springs and 3springs reverb tank?

[psychepool]

There is a problem with the reverb tank of my diy amplifier so I am going to replace it with a new one.

It is a tube-driven circuit and uses the Hammond 1750A, so 8 ohm input impedance is needed.
However, among the 3spring tanks, there was no 8 ohm, so I was using 10 ohm.
The 2spring tanks have 8ohm, so I considering to buy 2spring type.

I want to know what the difference between 2 spring and 3 spring is.
I knew it was decay time, but I can’t certain about it

I used medium size tank due to the small head cabinet size.

[martin manning]

See: https://www.amplifiedparts.com/tech-cor ... d-compared

"Three Springs vs. Two Springs
Any amp using a two spring tank may have its tank replaced by a three spring tank of the same impedance code (for example, 4AB3C1B vs.9AB3C1B) and vice versa. This will also change the sound characteristics of the reverberation effect. Three spring tanks have a more smoothed out flutter with a bigger, fuller sounding reverb effect and more lows. Two spring tanks have more flutter and grit, they also seem to capture that vintage 1960s vibe better."

[TUBEDUDE]

The 10 Ohm is perfectly fine for an 8 Ohm output. The impedance is a variable commodity, depending on frequency. As a coil based device the impedance increases with frequency. Impedance is typically listed @ 1 kHz. At 5kHz it has climbed up to 20 Ohms or so.

[psychepool]

Thanks for your answers. I don’t want surf type spring sound so I would like to use the 3 spring type as I used it.

[samrock55]

Thanks for the info!

[Stevem]

You can make a nice improvement in any tank by elimination and play that there may be between the transducer and the iron core that passes thru it .
You pack a short section of a tooth pick in there and then place a few drops of super glue on it to retain it.

Some tanks especially vintage ones have huge amounts of play on one or both transducer size.

[teemuk]

Generally each spring is a delay line with its unique characteristics (spring lenghts and tensions are different in each spring). 3-spring tank has one delay line more so it adds a "fuller" and more complex reverb effect with more reverb artifacts.
Decay time, I guess, is more dependent on spring length. Three short springs may have shorter decay than one long spring.

[martin manning]

Decay time, I guess, is more dependent on spring length. Three short springs may have shorter decay than one long spring.

It's complicated. I would guess the natural frequency of the springs themselves needs to be in some range to sound natural, which will constrain the spring design to certain combinations of spring diameter, wire diameter, pitch, and number of turns. The decay envelope then depends on damping coefficient, which is damping (due to air, mostly) divided by the spring mass (which is a function of all the parameters above).