Platenspeler.Com |
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Platenspeler.Com |
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This is an "in-between" project. Recently I modified the Geenkloon with better components and now it found a semi-permanent position in my HiFi setup. But with only one input on the amps, the Geenkloon is not in the position to allow connection of multiple sources.
At about the same time I realized this (maybe only) shortcoming of the Geenkloon, I got some nice OPA627 opamps from a forum colleague and these amps screamed for use.
And as I have several cheap switches around I decided that I might as well start a project for an input chooser that could evolve into a full-blown pre-amp based on the OPA627 over time.
First version of this amp will be a passive pre-amp, which contains a 12-step attenuator and a 3-input chooser. So what did I use:
| #nr | Descr | Val | Price |
| 1 | Aluminum Housing (Conrad 522970-44) | € 18.66 | |
| 1 | Lorlin 4 * 3 switch | ||
| 4 | Red chassis input connector | € 6.00 | |
| 4 | Black chassis input connector | € 6.00 | |
| 1 | Microphone cable shielded | 1 meter | € 2.00 |
| 1 | Attenuator switch (conrad 709379-44) | € 3.22 | |
| 24 | Resistors for attenuator | (see next page) | € 6.00 |
I want the preamp to be able to drive power amps on a certain distance. therefore a buffer as described on page 3 will be the final result of this project. I'll use the OPA 627 as the driver for the preamp, it may not be the most powerful amp in this catagory but I like its sound and in my experience the OPA627 should be able to drive a load of a couple of kilo-ohms without problems.