Hum/buzz after finished new Eros 2 assembly...

[mediumgrade]

I just (finally) finished my new Eros 2 build. I am running it on a Dual 1218 with a Hana EH cart. It's only barely breaking in and I am already really liking it (more on that later).

My only issue seems to be a hum/buzz sound. It's relatively low and I generally don't hear it when music plays (except for quiet passages). It seems to be more dominant in the left channel, but I am not 100% sure on that. Any ideas as to how to best troubleshoot or where I should look first?

 

[mediumgrade]

Correction: I think the buzz is the same in both channels. There is a slight channel imbalance on my amp at low volumes.

 

[Doc B]

The EH is a comparatively low output cartridge so there will be a little more likelihood of hum coming thru. That said, the place to start is to disconnect the tonearm cables from the Eros and see if the hum changes level or character. It's best to short the inputs otherwise you might pick up a lot of noise from the open input. You can do this by jumpering the center pin of the the input RCA jacks to the ground tab of the jacks. Doing this eliminates any external interference from getting into the input.

With a lower output cartridge you will sometimes notice a soft 60Hz hum from the Eros. This is typically due to pickup from nearby power transformers. But if the noise is buzzy (as I think you are describing) it is most likely a grounding issue with your turntable setup. Be sure you have a snug connection of any ground wires from your tonearm cables to the ground post on the Eros. 

 

[mediumgrade]

The EH is a comparatively low output cartridge so there will be a little more likelihood of hum coming thru. That said, the place to start is to disconnect the tonearm cables from the Eros and see if the hum changes level or character. It's best to short the inputs otherwise you might pick up a lot of noise from the open input. You can do this by jumpering the center pin of the the input RCA jacks to the ground tab of the jacks. Doing this eliminates any external interference from getting into the input.

With a lower output cartridge you will sometimes notice a soft 60Hz hum from the Eros. This is typically due to pickup from nearby power transformers. But if the noise is buzzy (as I think you are describing) it is most likely a grounding issue with your turntable setup. Be sure you have a snug connection of any ground wires from your tonearm cables to the ground post on the Eros.

Thank you for your response. The Hana EH is a high output moving coil with an output voltage of about 2.5mV. My previous phono stage was set to 50db and that sounded about right which is exactly why I selected the Eros 2 for this cart.

Otherwise, I will perform the troubleshooting steps you suggested. It is more a bit "buzzy" to my ears. I will also check my solder connections. Thanks!

 

[Paul Birkeland]

A pair of Sowter 1090s would bump the cartridge level up to be more compatible with the Eros if that ends up being the issue. 

 

[Doc B]

I'm reading 2mV nominal output on the Hana website. That would be a hair on the low side even for a HOMC. And compared to the typical 3.5 to 5mV from a MM or a LOMC with a step up it works out to being a little bit lower than average. All this aside, if it's buzz rather than soft hum that you are hearing it's most likely a grounding/ground loop issue or possibly a cold solder joint.

 

[mediumgrade]

Thank you all for your input.

I took it home for lunch, re-soldered the main ground plug, one or two other suspicious joints, brought it back to my office, made sure all of my RCA cables were nice and secure and the buzz seems to have gone away. more on this as it develops.

As for the sound, all I know is that my previous phono stage (an op-amp-based one) was set to 50db and that sounded about right to me. Maybe it could be a bit more authoritative, but I am happy for now. I know the suggested load for my Hana EH is 47K, so if I were to step up the gain a bit, I need to make sure that the load will still work well with in input impedance of the Eros (forgive me if what I said doesn't make sense).

 

[Paul Birkeland]

I suspect the EH would be happy with any load over about 1300 ohms.  The suggested load impedance of 47K is likely to suggest that you can just plug this cartridge into a MM phono preamp without modifications.

 

[Doc B]

The only reason I mention the output level of the cartridge is that the lower it is the more the signal to noise ratio will be affected. If the gain chain of your overall system is typical then 50dB of gain is probably fine for the 2mV cart. I have even used a .9 mV cartridge with the Eros. Basically if you can turn it up too loud then you have enough gain. The noise floor will be higher as the nominal cartridge output decreases, and at some point around a 1mV nominal output cartridge I find that background noise can start to intrude a little on the music. As PB says, most HOMCs are designed to run into a 47K load since they are generally intended to be replacements for a MM cart. So that is the best starting point for loading.

But this nominal preamp noise floor discussion is irrelevant if the noise you were getting is the buzzy kind from cold joints or ground loops. Noise floor from a properly functioning Eros really only has to do with any residual noise from the power supply - which is very low in the Eros, and 1/f noise in the tubes - which is not buzzy but rather like faint pink noise. If you have the buzzy stuff resolved then you can start to do some serious evaluation. If you find you desire a different presentation in terms of tone or dynamics you might want to roll some EF86s and 6922s to season the stew.

 

[mediumgrade]

A pair of Sowter 1090s would bump the cartridge level up to be more compatible with the Eros if that ends up being the issue.

Tell me more about that transformer. How hard is it to install?

 

[Paul Birkeland]

If you order them with the threaded grommet option, they fill the holes in the chassis plate that are now plugged by those black plastic plugs. 

You'd have to post a pic of the 1090 datasheet if you ordered them, as there isn't one available on the Sowter website.  I would expect there to be about 5 wires, and these would install similarly to the step-up sticky here:
https://forum.bottlehead.com/index.php?topic=11097.0