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I have a pair of push pull parallel el84 output transformers from what is I believe a Hammond Organ amplifier. The model number is C512-025947A and C512-xxxxxxx. The 2 are identical in dimensions but I have not measure the primary impedance. Since they are both for PPPEL84 I am guessing it is about 2K. I don't know what the exact application of the opt in the amp so I am concerned if I might be limiting my planned amplifier's frequency response or other sonic aspect by using these for an audio amplifier. If anyone can help with this I would be most appreciative. best regards, Dak
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If other parameters are usable, Organ outputs are usually decent. They have to be as they are making sound for a full range instrument with various effects too..
Alan organs were the fantastic amp wise
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The Mind has No Firewall~ U.S. Army War College.
You might find posts #4 and #9 useful which indicate 3.5k. Of course, it depends on the output independence.
ray
Hi and thank you for the link. Good info there, but no one tried to make an audio amp out of the opt. It also looks like since my 2 opts have different second numbers they may be of slightly different impedances and I will need to check that. I do have a pair EICO HF32 that I could take the opt from and use in my project but they are much bigger than the Hammond units. I am not sure if my chassis will support that. Too many choices, too little time. Cheers, Dak
I don't recall any Hammonds that used a PPP output stage, but I could be wrong. I'm mostly familiar with the M100 series that I own, and just a few others. That aside, I think the first priority in your case is to determine the output Z. Many of the old tube organs used 16 ohm speakers. Assuming the primary is 4K (not 2K), you could test the transformer to determine the turns ratio. Alternately, there are lots of Hammond schematics out there on the Net, and you could search for one that uses four EL84s in the output. The schematic should tell you the speaker impedance, and might even include the factory part number of the output transformer. Once all that is sorted out, you'll probably have to test the frequency response yourself in order to know for sure if it's suitable. I have several Hammond amps that I'm planning to scavenge, but no chance yet to qualify the transformers. There's always the possibility they won't be useful for anything other than musical instrument amps.
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I measured the impedance on the 2 trannys and 1 measured 3500 at 8 ohm and the other measured 3600 for a 4 ohm load. I thought my project was a bust but I thought I had another PPPel84 opt so I checked my inventory and I found a to the one that measures 3500ohm at 8 ohms! It even has the same part number. Well, it looks like I can at least see how these Hammond sound as an audio amp in a few weeks. cheers, Dak
Hi TK, I will measure the primary impedance to see if the 2 outputs are the same and also their value. I have no means to test frequency response other than my ears, and I am afraid that those instruments are bandwidth limited.
I was going to build the amp on the original Hammond chassis which has a humongous power trans on it and a lot of real estate for other components. It also has dual rectifiers, and 11 noval tube sockets which is perfect for an imitation Croft series 5 power amp. I already stripped out the chassis and am playing with my transformers to see how I can situate everything. So, that brings me to my current situation of deciding if I can use these opts from Hammond or if I need to go to the EICO trans. Maybe, I should just build it with the Hammond iron and see how it sounds? I guess I need to measure them first to see if they are same. tc and br, dak
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