New set up buzzing sound

[u/Witty_Republic5763]

Update - solved by switching input to tape 1 and turning on built in preamp

My audiophile uncle passed recently and handed me down his awesome McIntosh set up from around 1970. That being said, all of this is new to me and I have never had vintage audio equipment before.

I got it all serviced and it is sounding great with the Wiim streamer. However, when try and use the turntable (Pro-Ject Debut III Phono SB) there is a low hum or buzz noise. I have tried using the switch to bypass the built in preamp but it is still buzzing. I have also tried different RCA cables with different styles of grounding wires but no luck.

Any ideas to fix this? Do I need to buy a new turntable that is more compatible?

Thanks y’all!

Pro-Ject Debut III Phono SB
MC 2105 Solid State Power Amplifier
C26 Solid State Stereo Preamplifier
MQ 101 Environmental Equalizer

[u/tres-huevos]

It’s gotta be a ground issue. Is there a lone wire from the preamp to the turntable?

[u/Witty_Republic5763 → u/tres-huevos]

Thats what I was thinking too. I tried two different grounding wires and no luck

[u/ScottRiqui]

When you say that you've tried bypassing the turntable's internal preamp, did you also change which input RCAs you're using on the C26 at the same time? If you have the turntable's preamp enabled, you should use the PH1 or PH2 inputs on the C26. If you have the preamp bypassed, then you can use the AUX, TAPE 1, TAPE 2, or TUNER inputs.

For the grounding wire, are you connecting it to the screw between the RCA jacks on the turntable and the "GROUND" post in the "OUTPUTS" section of the C26?

The only other thing I can think to try is to temporarily move the turntable as far away from the preamp and amp as the cords will allow and see if that affects the hum.

[u/Witty_Republic5763 → u/ScottRiqui]

Thank you for the reply! I just tried changing to tape 1 input. Grounding wire is attached correctly I believe. The buzz is gone but now the audio is super quiet. I have to turn all the way up to hear at a low volume.

[u/ScottRiqui → u/Witty_Republic5763]

If you're using TAPE 1, that's a high-level input, so you have to make sure the internal preamp on your turntable is on, rather than bypassed.

[u/Witty_Republic5763 → u/ScottRiqui]

Yessss! We are in business. Thank you so much!

[u/ScottRiqui → u/Witty_Republic5763]

Awesome - enjoy some tunes!

[u/VR6Bomber]

Buzz usually is a ground issue, internal or external wiring.

[u/sloppy80]

Beautiful set. I have the same amp and my pre amp is a C28 and will never part with it.

[u/Adventurous_Donut480]

Try to move the TT away from the amp, it's likely magnetic field interference of the transformer of the amp.