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Hum

My analog setup consists of a Garrard 301, Ortofon tonearm, and Koetsu Rosewood cartridge. The phono stage is a Synthesis Roma 79 DC, the preamp is a Synthesis Roma 117 DC, and the power amps are Synthesis monoblocks.

 

I absolutely love the system and the music it produces. However, I do have one issue: there is a noticeable hum during dead air or before the stylus touches down on the record. Once the music starts, it largely disappears into the background. My digital front end is completely silent.

 

I’m looking for some insight into what might be causing this hum and possible solutions to eliminate or reduce it. Any advice would be greatly appreciated.

 

Thank you for your help.
 

John

curtisvill
lewm
14,675 posts
 

If everything is grounded to everything, try disconnecting some ground wires. If TT, tonearm, and phono are not grounded to each other, try grounding them to each other. In addition to what noromance suggested, any major appliances that share the AC supply can put EMI back on the line. Try also turning TT motor off. It can also emit EMI, either through the air or on the AC line.

curtisvill OP
75 posts
 

If I turn off the turntable, the hum still exists. I will check my grounding wire to make sure all is well. Appreciate the advice.

grk
283 posts
 

AI Overview

A humming noise from the Synthesis Roma 79DC phono preamplifier is a very common issue, almost always related to grounding discrepancies, electromagnetic interference (EMI), or an induction loop. Because phono signals are incredibly low and highly amplified, they are exceptionally sensitive to external noise. 

YouTube·Analogholic +2

To effectively troubleshoot and eliminate the hum, follow these steps starting with the easiest checks:

 

1. Check Your Grounding Connections

 

  • Turntable Ground: Ensure the ground wire from your turntable is securely fastened to the dedicated ground post on the back of the Synthesis Roma 79DC.

     

  • Multiple Grounds: If everything in your rack is heavily grounded, having too many grounds can create a loop. Try disconnecting the turntable ground wire temporarily to see if the hum stops. 

    Gearspace

  • System Grounding: Sometimes connecting the Roma’s ground lug to your amplifier’s chassis can help break inductively coupled loops. 

    Reddit·r/turntables

2. Relocate and Shield Cables

 

  • Routing: Make sure your phono interconnect cables (the RCA cables between your turntable and the Roma) are not running parallel to any AC power cords. If they have to cross, ensure they cross at a 90-degree angle.
  • Distance: Move the Synthesis Roma 79DC as far away from your main power amplifier and its power supply as your cables allow.
  • Proximity to Interference: Ensure there are no Wi-Fi routers, modems, or major appliances near the phono stage. 

    Reddit·r/turntables +6

3. Diagnose via Isolation (The "Victory Dance" Test)

 

  • Power down your entire system and disconnect all source devices (like your turntable) from the Roma.
  • Turn the amplifier back on. If the hum is entirely gone, the noise is being introduced by your turntable or its cables.
  • If the hum is still there with nothing plugged into the inputs, the issue may be a ground loop in your AC lines. Try plugging all components (turntable, preamp, and power amp) into the exact same power strip or wall outlet to eliminate potential differences in ground potential. 

    YouTube·FireWalk +1

4. Check for Transformer Induction

 

  • Tube phono preamps are susceptible to hum induced by the electromagnetic fields of massive power transformers. Try placing a non-inductive piece of shielding (or even just lifting the unit a few inches on foam) to see if the noise volume changes. 

    YouTube·Analogholic +2

For tips on how to identify the three primary types of hum (ground loop, connection, and induction) so you can narrow down your specific problem:

Related video thumbnail

44s

How to Diagnose and Solve Hum & Buzz in Your Audio

Morley

YouTube · Aug 2, 2023

If you’d like, let me know more about your setup so we can pinpoint the exact cause:

 

  • Is your turntable powered by a standard wall wart or an aftermarket power supply?
  • Are you using shielded, high-quality RCA cables between the turntable and the Roma?
  • Does the hum change in volume when you adjust the preamp’s volume or only when you get close to the speakers? 

    Reddit·r/turntables +1

Good luck!

Addendum:  could also be a bad tube or tubes.

spatialking's avatar
spatialking
670 posts
 

One thing not mentioned is the proper wiring of the electrical outlet.  Make sure neutral and earth is not reversed, likewise line and neutral. 

I had this problem when I moved into this house. Line and neutral were swapped at the outlet. I had a lot of hum problems until I sorted it out. 

audphile1's avatar
audphile1
7,934 posts
 

@curtisvill lets start with easy things…

1. Make sure your phono stage is plugged into the same outlet you’re running your preamp out of. Running phono and preamp on two different circuits can create a ground loop and that will manifest itself as hum. Check that you are using proper 3 prong power cords on phono and preamp  

2. reroute all power cords away from the phono cables that are input and output of your phono stage

3. Move all wifi extenders, routers and other devices that generate EMI/RFI away from the phono stage and from cables that run in and out of phono stage 

4. make sure your phono stage is positioned at least a foot away from your amplifier and is not stacked on top of any other electronic device. Move it away

check if hum is still present. If it is still there, check if your outlets are properly installed and are grounded. 

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