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Old 14th August 2010, 07:07 PM   #1
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Default gain block pcb's

The review of the Hammond H100 organ at Harmony Central is correct, they do have problems maintaining contact with their tubes at loud volume levels. I've tried replacing one tube socket, the hammond uses the mounting ring to connect 4-8 grounds on each tube, and commercial sockets do not have such a thing. I've bought a gold socket, a plate of brass, a .875" punch that is really .890", and now I need a $195 nibbler tool to make the notched tabs around the edge of the socket ring. Bleah- it is time to modernize with something that has soldered connections and doesn't heat the room so badly.
I'm happy with the speakers, two 8" for vibrato-mid, and a 15" for bass. All are 8 ohms.
The three channel power amp is another issue, discussed under the "Output capacitors, objective and subjective results" thread of solid state amps. I'm going to build the mosfet single supply amp listed there in three channels, with connectors compatible with the Hammond wire harness.
Now I need to replace the preamp. It has at least three sound buss inputs, plus control inputs for various "attack" types, plus local controls for click silencing, signal nulling, etc. Anybody that is really interested can see the H-100 service manual at archive.org. Hammond does it all with 6 12AX7's. I'm happy with the op amp gain circuits of my RA-88a mixer, using 33078 or 4560 or tl082 or any compatible op amp. However, that device is no longer available and has ground plane everywhere around they didn't use, and I need to install one-shots for gating and attack, envelope generators, keyclick oscillator, various other things.
So does anybody in the western hemisphere sell little PCB's that put the DIP package op-amp, the power supply inputs, filter and coupling caps, feedback and gain resistors and capacitors, on a little board that you could put 3 to 6 on a perf board and enclose in the special purpose stuff. I don't need huge slider pots either, the gain is going to be set and forget for an organ preamp. I don't mind doing a little point to point wiring, but doing the bread and butter stuff six times seems a little stupid. Nor do I need some kind of 104 db s/n wonder, particularly. I've visited a couple of vendor sites at the bottom, Planet 10 is a cool guy but he seems to sell speakers.
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Last edited by indianajo; 14th August 2010 at 07:19 PM.
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Old 14th September 2010, 02:39 PM   #2
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Well, Paccio answered my question by having a problem with a kit under musical instruments. See the link http://www.diyaudio.com/forums/music...ion-pedal.html. The vendor is tonepad.com, the pcb is microstereo amp. Op amps seems to be a 7102, never heard of it, but it is a start.
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Old 17th September 2010, 12:01 PM   #3
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My first post so hope this works. Dont know if this is what you are looking for but try Elliott Sound Products - The Audio Pages (Main Index) This guy sell circuit boards and has a simple gain stage for a pre amp, project 88. He also has circuit experience in the music industry so may be helpful with your project. Gotta do some soldering though....
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Old 17th September 2010, 02:01 PM   #4
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thanks for the elliot listing. He has interesting projects, but being located in Australia his pack cost, shipping etc are necessarily relatively expensive to the USA. Tonepad has some obvious failures, including no power supply decoupling capacitor holes on the PCB (mxr project), but his $11 pcb and $2 shipping (first class mail) from El Salvador couldn't be beat here. I need some kind of soldering aid like a pcb on DIP or SIP packages: my vision is not what it was when I was forty. I made a solder bridge on the RA88a when I put the DIP sockets in , took me a couple of hours and 6" focus reading glasses to find it.
Welcome to posting here. Been watching "inspector Lewis" "Masterpiece "series on TV, lots of shots of interesting Oxford UK buildings and canal boats.
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