Interfaces

SoundCard

 

 

 

 

 

Audio Amplification from FT1000MP to SoundCard Input

I don't know about you folks, but I can never seem to get enough audio from the FT1000MP to drive my soundcard properly, even when I boost the input control all the way up. I believe there are probably other solutions equally good, but Phil, IC8POF has found a very good solution (a preamp) that he built and is using is his station. His instructions and pictures are attached.

Solution: You have had luck in that I have solved it already some years ago for my old radio a Drake TR7 and then my first FT1000 and now on the new FT1000mkVF. I used the first version of the AFpreamp some 20 years ago between my first computer a Sinclair ZX Spectrum and an FT902dm.

This MicPreamp (see schematic) is a part of a complete 2 radio-switcher unit for my nowadays setup : FT1000 and FT1000mkVF. It is fine to switch between the 2 radios but the buttons are doubled, but this is another story HI HA HO :--)) (see picture of this circuit)

Now on the circuit: I have taken it from an old microphone preamp-compressor kit. print one or both pages so you do not need to have the pc on during the reading. (see picture of circuit).

The signal at AF-OUTof the RTX is about 50 millivolt PeP very low for the Soundblaster input. This circuit drives it up to 6 volts, but already 500 millivolt are quite enough for the SBL input before overdriving it.

You need very few parts and I use the same numbering as on the circuit. I have used the half of an mc1458 (double 741),but you can use an 741 or equiv. too. Refer just on the first half opamp ic1a:

R1 input potentiometer , not trimmer because I can setup it from the outside whenever is it needed. I used a 1megaohm but 100kohm or even 47kohm are ok too.

C1-C4 input and output capacitors: I used 2 x 1microfarad-polyesther(mylar too, not elkos) but 100nF are ok too.R2 any value from 4700 to 10000 ohm, I had an 8200 at hand.C2 R3 R4 R5 are same values, I have omitted the C3 because no improvement on the output signal was noted. As you see in the photos all is mounted almost flying.

It is needed:
1 piece of AF cable from AF out to preamp
1 piece of AF cable to SBL on rear of the PC
2 mini stereo jacks with left-right pins soldered togheter
1 small alu-box

If someone needs stereo then should build 2 preamps and run 2 wires cable from AFout to the SBL. But never needed till now at my side for such stereo setup.

This preamp is very useful every time one needs to look\work at audio signals on the PC even with the volume tied to zero on the front.

Of course this circuit is of use during digital modes. Therefore my circuit comprehends also all the switching needed to and from the SBL. All possible switching for the rig microphones: handmic and or headset mic\hear. Mixing mic with SBL output and mic to SBL input. Also connecting a table recorder to rig AFout and SBL so do not need to have the PC on for recording.

All these are doubled by the radio switcher an 2 position\11 ways switch (RF too).

I would now only need a good HAM fellow how could write a little program to get synchronized both FT1000 via CAT. It should not be too complicated for a programmer. Of course If you need more info I am ready to pass them.

Phil IC8POF



 



 

This site was last updated 08/21/07