New Amp set-up for Allen 632-D --Expression pedals and Relay/Attenuator questions

[SoBeMisha]

Good Day Everyone: Due to an old, non-functioning amp rack, on recommendation from a pro I purchased a Behringer Europower 4 channel amp for my 632-3D. The amp seems to do the trick--to an extent. I'm without expression pedals, hence without much volume despite the amp. I was told by an Allen rep that he could fix that and he told me I would not have expression pedals with the current set-up. I'm wondering, though, if anyone has some experience with this. The attached photos are of the outputs from the DAC boards directly to the amp. The top DAC board's outputs originally went directly to the connections below the expression pedals (photo included). The lower DAC board channels its outputs into inputs on the pictured attenuator/relay box, then outputs from there to the connections below the expression pedals..

I am wondering if I take the lower DAC board's original routing--through the Relay/Attenuator and connect those out connections (rather than directly from the DAC) to the amp. Will that engage the expression pedals? Is there are reason I should use the Relay/Attenuator box? I'm not sure that box is working--we were having troubles connecting to the original connections (any advice there, too, would be helpful). We were having trouble getting sound through the original connections. I'm not technical, certainly do not want to harm the organ. I hope this makes sense--not very technical here and I am brand new to the old Allen organs. Thank you for any help/insights you may have! BTW, red connections = flute, black = Main. The original connections look straight forward, but we could not get sound--not sure if it was the connections or perhaps the relay/attenuator box is out. Thank you!!

[Admin]

You have several potential problems.

• The signal level out of the DACs may not be enough to drive your new amps. Some models of the Allen S-100 amps had a preamp stage to raise the level.
• The DACS are designed to work into an input impedance much higher than found in conventional amplifiers. This is necessary for the expression pedals to work.
• The expression pedals are designed to shunt the signal to attenuate it. You're currently bypassing them and getting the maximum signal level into your amplifier. Connecting the expression pedals will not increase your level.

You need to restore the original signal path of DAC -> Attenuation Relay -> Expression box as your first order of business. Make sure that the signal is being passed by the attenuator/relay box. Then try inserting a 22k resistor in series with the connections from the expression box to the amplifiers to isolate the expression pedals from the input impedance of the amplifiers. That should restore the expression, but the level will likely remain low. If so, you'll need to add preamplifier stages prior to the amplifiers.

Alternatively, fix the amplifier rack. Use the Forum's Advanced Search and search for the tags S-100 and S100 to pull up threads and schematics on the amplifiers.

http://www.organforum.com/forums/sho...len-amp-repair
http://www.organforum.com/forums/sho...mplifier-codes
http://www.organforum.com/forums/sho...fier-Schematic

[SoBeMisha]

Very helpful. Thank you!

[John Vanderlee]

S100 Amps are easy to get. Another thing to consider is that most commercial amplifiers seem to roll off below 20 Hz. If the organ has a 32' stop it needs to produce 16 Hz at low C. Allen's Amplifiers are made to do that. I guess most mfrs figure if it reproduces Bass guitars it's good enough!

[michaelhoddy]

S100 Amps are easy to get. Another thing to consider is that most commercial amplifiers seem to roll off below 20 Hz. If the organ has a 32' stop it needs to produce 16 Hz at low C. Allen's Amplifiers are made to do that. I guess most mfrs figure if it reproduces Bass guitars it's good enough!

Most measured reference specs are 20 Hz to 20 kHz, but most decent commercial power amps actually perform well beyond that. As an example, the inexpensive, common, and decidedly non-specialized and non-exotic QSC RMX and CMX-series amps are only down -3dB at 5 Hz, flat at 20 Hz, and down an imperceptible amount at 16 Hz. This type of performance is common in many other amps.

The non-linearity of even most purpose-built organ pedal speakers at 20 Hz is far more of a typical contributing factor than the ability of the amplifier to drive those frequencies.

[SoBeMisha]

Organ to Amp connections for Allen 632-3D

Good Evening Everyone:

First, thank you to everyone who has answered my questions. Very helpful. Regarding the terminal connections on my organ for the amp connections--to which I will be connecting to S-100 amps--can anyone tell me to which screw each wire should be connected? There are markings, but a little confusing. Here are photos of the terminals--Great-Choir is in a box on the left, Swell-Pedal are in a box to the right. Channels 1-4 start at the right box with #1 and #2 and the second box #3 and #4. I'm going to be using new wires for the amps and speakers--the others are 40 years old so I think it is time. I hope the photos below are helpful. The first photo are the two boxes. The second photos are closer for more detail. The third is of the original connections that went to the amps #1-#4. The photo of the wires are the four channel connections which I am replacing with new wire But, I need to know which wire goes where. The original connections used coaxial wire to the amps. I'm guessing it is pretty straight forward, but any insights will be helpful. Thank you!

[SoBeMisha]

Good News! My Allen 632-3D is up and running. Thank you all for the information. It was helpful. The man from whom I purchased refurbished amps told me exactly what I needed to do. Thanks again everyone!