I got a new record player (TEAC TN-300. (Kids: records are like giant CDs except they break easier and sound worse.))
Anyway, there is a noticeable constant hum with this thing. I don’t think it’s a ground loop problem, since the player and receiver and amps and stuff are all plugged into the same surge protector. The player itself is powered by a 12v DC wall wart which does not have a ground pin. Unlike older players there is no screw terminal to connect to a receiver’s ground.
I know the hum is definitely coming from the record player since other audio sources don’t have any hum. And the hum changes in volume as I adjust the volume on the receiver. It’s there whether or not a record is currently playing.
Any ideas what it could be, or how to fix it? Other things I should investigate?
Could be a crummy wall wart.
Does the hum change when your hands are near the tonearm? That implies hum pickup, and better grounding will help.
How about when you unplug the power supply? If the hum stops instantly when you do, it’s lousy filtering, if it tapers off, then it’s a shielding / grounding issue.
Phono-level. (Well there’s only one RCA output; the built-in phono preamp has a bypass switch, which is currently in bypass mode.)
I haven’t tried the USB output yet.
Here’s the results of further testing:
No change when attempting to play the tone arm like a theramin.
I did find that the current RCA cables (cheapo ones that came with the player) made quite a lot of noise when jostling them around, so I replaced them with a spare and that seemed to help, but the buzz was still there, just quieter.
Interestingly, disconnecting the power supply barrel connector from the turntable seemed to have no effect. I haven’t tried unplugging the wall wart at the other end yet because I have to move a big heavy thing to get back there.
Unplugging and re-plugging the RCAs seems to cause the noise to go away for a couple seconds and come back. So I suspect there is a grounding problem somehow, or perhaps a problem with my receiver’s phono preamp stage.
I will have to try switching the turntable to a non-phono input and using its built-in preamp stage to see if that makes any difference.
I suspect that the (CHEAPO) output wires are picking up noise from some switching power supply - likely a wall wart or computer. If these connecting wires are just parallel line zip cords they can be be good antennas feeding into your main amp. You may need coaxial wires or do some unplugging of devices to find the noise source.
“…disconnecting the power supply barrel connector from the turntable seemed to have no effect.” Seems like the noise is coming from the wires, not from anything generated in the turntable.
The first thing I’d try is switching to line-level output. Phono level is pretty low, requiring a lot of amplification. Any small amount of hum coming through the cables gets this amount of amplification along with the signal.
If you want to use phono output, I’d suggest using shielded cables.
Another thing you could try is reversing the amplifier’s power plug.
There is no ground wire? Turntables USED to have one to prevent this exact hum. It usually was attached to a specific terminal on the back of the amplifier.
I have no idea what they do now with technology. But my 80s table requires one to be used.
Trouble with this turntable is that is is a teensy bit more complex than a conventional one. SO there are lots more possibilities.
Hum or buzz? Both words have been used. It can matter which. Pure mains hum, or is there a buzz on top - ie harmonics.
Very unlikely to the the power supply, as they typically run at many kilohertz. Unless it is faulty and there is a leakage path inside.
Given there is an internal RIAA pre-amp there are a lot of possibilities with signal and ground paths. Even when bypassed we don’t know what residual connectivity there is in place. I would bet the grounds remain common.
Trying the inbuilt pre-amp is clearly needed.
Proper hum loops can be rotten things to find and fix. It isn’t just the power supplies coming from the same place or not. Any loop in the system can and will have an induced current, and wherever there is sufficient voltage drop, there you find hum. Separate ground wires were just a way of trying to manage these currents and voltage drops.
Note: You can make your own ground connection from the metal parts on the turntable to your amp. And also use “shielded” wire from the turntable to the amp. RCA cables may be cheap junk allowing in “outside electrical noise”. You can get a coax to RCA adapter, then use a good quality coax cable which will shield out all outside noise…
If the player and receiver are connected to the ground at the surge protector, and there is also a ground connection between the player and receiver (which there would be, through the RCA cable shields), then that’s a ground loop. If this is the problem, you could eliminate the loop by using a 2-prong power adapter for the receiver.
(Disclaimer: I don’t know anything about audio equipment, I’m extrapolating from my experience with low-noise scientific instruments.)
The turntable uses a wall wart - a DC power supply plugged into a 110 volt outlet. This isolates it from the neutral, so it’s unlikely that this is the source of a ground loop.
If the wall wart is a switched mode PSU, you might be getting noise from that. A “ground loop isolator” is recommended - not because of a ground loop but because the phono “ground” is noisy. The isolator uses coupling to transfer the signal without any direct electronic connection.
As long as the wall wart doesn’t have a ground pin that connects to the turntable chassis or signal ground, then I agree that’s probably not the cause.
Well, I tried switching on the record player’s internal pre-amp and using a line-level input on the receiver. And it sounds perfect. No buzz or hum, and absolutely silent when no record is playing.
Just to make sure I wasn’t going crazy, I switched it back to the PHONO input and turned off the pre-amp, and the buzz was back. So I assume there is either some kind of problem with my receiver’s phono pre-amp, or I’m just getting amplified induced current from nearby power cables, but at line level it’s too small to hear.
(There’s a lot of power cables back there, not to mention a million RCA, HDMI, XLR, Cat5, etc. Reorganizing all my cable crap is a future endeavor.)
Anyway, I guess I’m content to use the record player’s internal pre-amp for now. Though it annoys me that I now have my record player connected to my “VCR” input. (I mean, one day I might want to watch one of those old VHSes in my mom’s attic, right?! (I’m just kidding. (Mostly.)))
Your amp is probably OK, but if you want to check then disconnect the leads to the phono inputs at the amp end - you might get a small amount of hum with the volume cranked up, but that’s fairly normal. Don’t leave the leads in the amp and disconnect at the deck end, that’ll hum like crazy.
I reckon you’ve got screening issues with the deck when the amp is plumbed straight into the cartridge, probably caused by the tone arm/chassis not being electrically connected to the signal ground. If you haven’t got a multimeter to check continuity then you can check for a floating tone arm by setting up the deck for a direct connection to from amp to cartridge and if the hum increases when you touch the tone arm then it’s probably floating. A wire from the amp chassis to deck chassis should cure this (no guarantees though - noise pickup can be tricksy).
A standard moving magnet cartridge has quite a high impedance (about 47,000 ohms) and this makes the cabling very susceptible to noise pickup. Having an RIAA phono preamp/equaliser close to the deck (or in this case, built into the deck) can reduce the source impedance to the sub-ohm level, which will massively reduce the noise pickup on the cabling between deck and amp.
Decent cables are important too. Quality cables will have better shielding and will be less prone to the microphonic effects you were noticing with the cheap cables. It’s not just the crackling when the cables are being manipulated that’s an issue - the same microphonic effects will pick up vibrations from the speakers and make for a muddier sound. It also pays to keep the cables as short as possible as they will be less prone to noise pickup, and the high capacitance of long cable runs can adversely affect the stability of any driving preamp stage.
Well, I did some more experimenting today and was able to isolate the cause of the problem. It was <drumroll>
The cable TV.
I didn’t expect that since the CATV coax is plugged into my TiVo which is connected to the receiver via HDMI. But of course the HDMI has a ground pin connected to the cable shielding, so there you go.
I suspect that the potential difference between my power supply’s ground and the CATV ground was so small that it was simply not audible on my line-level analog sources, but came through on the phono level. (I haven’t measured it since I can’t find my multimeter at the moment.)
I stopped by the local Worst Buy and picked up an extra length of coax so I could connect the incoming CATV to through my surge protector and thence to the TiVo. The surge protector advertises a ground-isolated coax pass-through for this exact purpose, and it worked perfectly! Buzz killed.
I also got some better-quality RCA cables with beefier shielding for the record player just to help isolate any interference from nearby power cables.
Anyway, my small vinyl collection now sounds fantastic. Thanks for all the suggestions.
The Teac TN300E is an outstanding entry level turntable that gets little respect. It has one of the best looks of any turntable in its price class (especially the Mahogany wood grain with silver aluminum tonearm and controls). The stock AT cartridge is one of the best stock cartridges available. It has a couple of drawbacks that are very easily fixed and just makes this turntable better and better.
It could use a better power supply. The very basic wall wart, ungrounded transformer should be replaced. I found a company online that sells only power supplies and purchased a heavy toroidal transformer and wired a ground to the chassis next to one of the RCA pots. This takes care of the “hum” and speed fluctuations some complain about. I also upgraded the cartridge to something a little more high output and rigged the Ortofon Red to the tone arm. To overcome the lighter weight of the tonearm counterweight, I made 2 wraps of lead tape (1/4 gm per inch) used on tennis rackets around the counterweight to allow for the heavier cartridge.
These small upgrades (inexpensive except for the Ortofon, which will be upgraded again to the Blue cart) address all of the negative feedback given the Teac TN300E, and elevate this turntable equal to many in the 500 to 1000.00 price class.
I will assume your turntable doesn’t have a built in pre-amp. This is what you require. It will eliminate the hum. $50 - $100 will get you a passable one. You connect the turntable to the pre-amp and the pre-amp to your amplifier. You may now find that rather than connecting the pre-amp to the turntable (phono) connection on your amplifier, you will need to connect it to another of your inputs. Hopefully you have spare inputs. This would be where you have your CD player connected. Most amplifiers will have extra inputs. Connect the pre-amp to one of these and now when you play a record you’ll have to select Input 2 or 3 (for example) as opposed to selecting Phono as you’ve done in the past. It may also change your volume setting to what you’re accustomed to. You may need to turn it up higher. But the hum will be gone.
Alligator clip between turntable gnd and amp gnd has solved this hum many times for me. Despite the fact that it should not be a ground leak, it’s well worth testing to see if that’s the problem. Phono output signal is very small.
