Hum trouble when connecting a Thorens TD 166 mk II turntable


Hello everyone ;)

First of all I want to send a big shout out from Denmark to the team that made Sprout happen - what a fantastic little box! For the past weeks I have enjoyed great sound from the bluetooth connection. Happy days!

However, since I am a novice in the world of hifi, I could really use a good advice or two from you guys: I recently became the proud owner of a beautiful 40-year-old Thorens TD 166 mkII turntable. But when I connect it to my Sprout I am having severe speaker hum problems.

Here's a rundown of the situation:

1. The turntable has been in my possession for only 4 months - I bought it from a well respected refurbisher in Denmark, who took it apart before the sale. The turntable should be in great order.

2. The Thorens I have is born without a grounding wire, so after reading some threads on the subject, I assume it is grounded through the RCA connectors.

3. All cables are of good quality and brand new.

4. Upon connecting everything, the speaker hum only occurs when input selection is set on Vinyl. No other devices are connected to the Sprout and bluetooth sounds perfect.

5. Hum is present from low volume and increases when volume is increased.

6. Vinyl music plays at a very low volume, compared to bluetooth level.

So, a novice question: Do I need to add in an additional preamp other than the one built into Sprout?

Can/should I ground the turntable in another way?

After googling around, I realize that hum can be a tricky thing to solve. But any advice is very much appreciated!

Thanks in advance!

Best regards,




What cartridge do you have in the Thorens? Assuming it is a moving magnet (MM) cartridge, you just connect it directly to the Sprout via the Phono inputs (as you have done). A turntable chassis isn’t grounded via the RCA shield lead. I’m betting you just need to run a ground wire. Just get a nice piece of insulated braided copper wire, connect a spade connector to each end, find a screw on the bottom of the turntable that connects to the metal chassis and connect the other end to Sprout. I would guess the hum will disappear.

Good luck



Yes, I believe Andy is correct. The metal parts of the turntable, in particular the arm, may be ungrounded. Sure sounds like it. You can test easily. Take a piece of wire. Connect one end of the wire to Sprout’s ground terminal. Then, with the volume turned up so you hear the hum, touch the other end of the wire to the turntable arm or other metal parts of the table to see if the hum goes away. I’ll bet it does.


Dear Andy and Paul,

You guys are the best… :)

I found a screw on the chassis and connected it to Sprouts ground terminal - the fix works like a charm! Tangerine Dream is now pouring out of the speakers beautifully…

Thanks guys, have a great Sunday!



Enjoy! Thanks for letting us know.