First DIY project, RIAA problem.

[kasn]

I'm new to DIY audio and wanted to build a phono stage since mine is broken. I can measure an amplified signal at my RCA output connections but when I plug it in to my amplifier (an old Marantz) the signal disappears and I can't measure anything and there is no sound. When i unplug the output RCA from the amplifier I again can measure a signal with my multimeter. Anyone has any idea why this is and how to fix it?

Thanks

kasn

[stratus46]

Originally Posted by kasn

I'm new to DIY audio and wanted to build a phono stage since mine is broken. I can measure an amplified signal at my RCA output connections but when I plug it in to my amplifier (an old Marantz) the signal disappears and I can't measure anything and there is no sound. When i unplug the output RCA from the amplifier I again can measure a signal with my multimeter. Anyone has any idea why this is and how to fix it?

Thanks

kasn

Schematic needed. Tubes? Opamps? Discrete transistors? Cactus needle into a big horn?

G²

[kasn]

Its based on the Velleman kit K2573 (Velleman Inc.) and I know the outlet I try to plug the phonostage in to is working sense I use that outlet for my CD-player and that's working fine. Thanks for the quick reply.

[stratus46]

Originally Posted by kasn

Its based on the Velleman kit K2573 (Velleman Inc.) and I know the outlet I try to plug the phonostage in to is working sense I use that outlet for my CD-player and that's working fine. Thanks for the quick reply.

Is the CD on the _same_ input as the preamp or another input?

Two recommendations:

1: add a small value resistor (22 to 100 ohms) in series with the outputs C6 and C10. This will reduce capacitive loading on the opamp and prevent oscillations.

2: use a regulated power supply as any variations on the AC line Voltage will add low frequency thumps in the output. If you run on a pair of 9 Volt batteries you won't need a regulator.

G²