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Adding a reverb unit to replace spring unit

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  • Foster
    replied
    A follow-up on reverb units: I purchased a Behringer guitar pedal unit, and after fitting 500k resistors to drop the Gulbransen levels, it is working well.
    Thanks for the help from everyone.
    Foster

    Leave a comment:


  • jbird604
    replied
    I haven't seen that one or tried it on an organ. All digital reverbs are basically similar in operation, so could work. However, it may be awkward -- for example, I don't see any on/off switch except for the footswitch. And no wet/dry balance control. (It probably has a preset amount of dry that passes through, and the "E. level" knob controls the amount of wet signal in the mix, but no way to completely eliminate the dry signal. The typical reverb has a wet/dry balance or possibly a "dry defeat" setting or switch.) Also, I don't see any dedicated input and output level controls, which one normally has to tinker with to get a digital unit to replace a spring.

    All that said, it won't hurt to try it, if you don't mind risking the $40. Could be that the preset parameters and levels are perfectly good for an organ reverb. But if you find it doesn't fit the application, just going up the scale a bit to one of the nanoverb-like minis from several sources ought to get you the controls you need. I can't find it on line right now, but I used to buy a unit called (I think) the FX-800 from Behringer for $69, and it had all the features and controls I needed to install it on a number of church organs and home organs.

    Leave a comment:


  • Foster
    replied
    Many thanks John.
    Amazon sell the Donner unit for about $40.00, and I have
    watched the video on how it works but only with a guitar, and sounds good.

    Leave a comment:


  • jbird604
    replied
    Yes, no, maybe...

    (1) Yes you can use an inexpensive digital reverb device. The Alesis Nanoverb is perhaps the most popular, and there is or was an inexpensive Behringer effects generator that also featured about 16 different types of effects that cost a little less. Anything that will accept a basic line-level or lower level signal, with a mono input and mono output. (The reverb system in older organs is always mono, but even if a reverb unit has stereo outputs, as the Nanoverb and others do, you can use it as a mono reverb too.)

    (2) As to connectors, you will need adapters to couple the existing RCA plugs to the 1/4" jacks found on most all digital reverbs. But that's not much trouble. There are little adapters that cost less than a dollar that have a male RCA jack on one end, and the other end is a 1/4" mono phone plug. A pair of those should get you hooked up. But.........

    (3) Maybe on the impedance (and level) question. In general, digital reverb units expect a "line level" signal on the input. The signal that the organ sends to the spring reverb may in fact be a fairly high level signal, as the reverb spring's transducer basically amounts to a miniature "speaker" attached to one end of the spring. So start with the Input Level on the reverb unit turned all the way down, and just open it a crack to see if it's going to overload the unit. If you can't open it more than a crack while playing a full registration and full chords with pedals without making the reverb go into overload (red blinking light), you'll have to wire in a resistor in series with the input. Possibly about a 100K resistor, but maybe smaller, maybe larger. Trial and error will tell you what you need.

    And on the OUTPUT end, the reverb unit is going to be delivering a rather strong signal level, approximately standard line level, so maybe a volt or so with a typical playing situation going on. That would be more than the "recovery amp" in the organ's circuitry is expecting to receive from the pickup coil on the reverb spring, which probably puts out only a fraction of a volt, maybe just a few millivolts, more like a microphone.

    So after establishing the best setting on the INPUT end of your digital reverb, start with the OUTPUT level just barely cracked open and see if it overloads the reverb recovery system in the organ. You should not get an overbearing amount of reverb, and there shouldn't be any distortion on the reverbed signal. If need be, you can wire in a resistor in series with the output, just like with the input. Start with 100K and see if that works. If not, go up or down in resistance as needed.

    BTW, before you get started, be sure the wet/dry mix knob or control on the reverb unit is set all the way to WET. You do NOT want any of the "dry" signal getting recirculated through the organ's reverb system. You only want the digital reverb unit to contribute "wet" signal to the system.

    Use the other controls on the reverb system as needed to get the desired type of reverb. Most will have a variety of available reverb effects, along with a parameter knob that will fine tune the effect.

    Good luck!

    Leave a comment:


  • Foster
    started a topic Adding a reverb unit to replace spring unit

    Adding a reverb unit to replace spring unit

    Can I use a budget guitar reverb unit, to replace the spring reverb on my Gulbransen Theatrum 3218 ?
    I will need a unit which can run on a mains voltage supply, and need to be able to set it up to my satisfaction, and not have to be fiddled with, as it would be best if it lived inside the console, replacing the spring unit.

    Also, will I be able to just plug the in/out connectors to the unit, or am I going to have problems with the impedances ?
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