General Background Noise / Noise Floor Questions

[thekak]

Hello--

I've had my crack for about 7 months. Am completely in love with it. Equipped with the speedball, Solen film caps, audionote volume pot, Chatham 6AS7G, and a JAN RCA 6SN7.

My question has to do with background noise.

Recent diagnosed interference in the output wiring due to poor braiding and proximity to the heater cables. Addressed that only you realize that a second problem existed with the heater cabling and the 9-pin socket. Apparently I elected to ignore the photo in the manual and route it along the far side of the socket as opposed to the inside. Not a fun fix after everything has been assembled, but I did it.

Fired the headphone amp back up, removed input connections, and now have a dead-quiet right channel but an aggressive buzz in the left starting at about 65% volume. This is about at the limit of what I comfortably listen to, and is much improved above the buzz I would hear in both channels near 40% before.

When I connect the Crack to my Seduction, I don't hear that buzz sound at all, even at maximum volume. What I do hear is a hum that seems pretty close to 60 hz hum videos you can find on YouTube.

Why is the buzz sound gone when connected to the Seduction?

So if I wanted to attack this hum further, what are my options? Choke on the seduction? Choke on the crack? Input power transformer? Running with battery power?

One thing I will definitely do is inspect my Seduction for any obvious problems. That was my first-ever kit over 10 years ago and I now have the Crack and an Audio Note DAC under my belt, so I ought to revisit it.

Thank you for your time.

[Paul Birkeland]

With nothing connected to the Crack and the volume pot all the way down, do you hear hum?

Hook up your Seduction and listen to a record at a normal level, then lift the needle.  Do you hear hum?

If you turn the volume pot on the Crack all the way up, you may hear noise.  This isn't abnormal or really indicative of anything, as you'd never listen that loudly anyway.  This is especially true when you turn the pot up with nothing plugged into the Crack, and also if you turn the volume pot all the way up when you have a Seduction feeding the input. 

[thekak]

There's nothing until about 10 o'clock on the dial when connected to my Seduction. My audio note DAC is even quieter.

I've read several posts here where people will say their setup is "dead quiet" up to 90% volume. Though this isn't a speaker amplifier, I've read plenty of online discussions and reviews where low wattage amplifiers are connected to ~100dB sensitivity speakers and, cranking the volume, they hear next to nothing.

I was under the impression that this would be attainable with most gear, especially gear which allows for easy modification.

If I could get rid of that hum on my turntable setup, it would be great.

I realize that my home situation likely contributes to this sort of noise, as I live in an older home where some of the wiring is "knob and cloth."

Just curious as to what other folks here have achieved as far as noise floor goes. I should have mentioned I use Sennheiser HD 600s.

[Paul Birkeland]

There's nothing until about 10 o'clock on the dial when connected to my Seduction. My audio note DAC is even quieter.

OK, if you put the needle down at this level, is that a comfortable listening level?  Is there any hum with the DAC?

I've read several posts here where people will say their setup is "dead quiet" up to 90% volume. Though this isn't a speaker amplifier, I've read plenty of online discussions and reviews where low wattage amplifiers are connected to ~100dB sensitivity speakers and, cranking the volume, they hear next to nothing.

Again, there isn't anything meaningful here.  Are these analog setups?  Zero feedback setups?

If I could get rid of that hum on my turntable setup, it would be great.

I realize that my home situation likely contributes to this sort of noise, as I live in an older home where some of the wiring is "knob and cloth."

Do you have a good earth ground on the outlet you're using?  That could definitely bring up some noise issues.

[Deke609]

It might also be worth checking the routing of your interconnects from source all the way to the Crack.  If they are unshielded (most are, I believe) and sit against mains power wiring (power cords, power bars, etc.) or strong magnetics, you might end up with 60Hz hum on your signal wiring -- and once the hum is part of the signal, there's no filtering it out.

cheers, Derek

[thekak]

Hi Paul--

I realize the anecdotes I am quoting are without context. I'm not trying to troubleshoot a specific issue. I've consulted this forum in the months since I assembled the crack to attempt to minimize hum and have been successful in mitigating it. I intended for this thread to get a sampling of just how low of a noise floor others have achieved with their Crack (and accompanying setups).

This isn't a "please help me diagnose and solve this hum" post. I was interested in understanding electronically why I would hear a sort of buzz without any components plugged in vs a hum when the phono stage was plugged in.

 That said, there is no "hum" with the DAC but there is a sort of background "static" at high levels.

My turntable setup is in the basement and is extremely close to my home's input water pipe. The breaker box's bare copper grounding wire is clamped to it. If I attach a ground from the Seduction to that, it is quite noisy. I believe this is because the grounding wire runs 30+ feet along knob and cloth / Romex wiring, often parallel, occasionally crossing at right angles. So I don't necessarily have a great way to ground the phono stage.

I don't want to waste anyone's time with troubleshooting here and apologize for giving that impression.

[Paul Birkeland]

That said, there is no "hum" with the DAC but there is a sort of background "static" at high levels.

That's a good reference.  A little background static with the pot all the way up would be considered completely normal, as you'd be amplifying the low noise floor of the DAC.

My turntable setup is in the basement and is extremely close to my home's input water pipe. The breaker box's bare copper grounding wire is clamped to it. If I attach a ground from the Seduction to that, it is quite noisy.

That's quite interesting!
That's a good reference.  A little background static with the pot all the way up would be considered completely normal, as you'd be amplifying the low noise floor of the DAC.

I believe this is because the grounding wire runs 30+ feet along knob and cloth / Romex wiring, often parallel, occasionally crossing at right angles. So I don't necessarily have a great way to ground the phono stage.

What is the DC resistance between the water pipe and the ground post on your Seduction when it is plugged into the wall?

[thekak]

I measured 1.1 Ohm.

Noticed that there's some patina to the copper wire.

[Paul Birkeland]

Well, at least your outlets are well grounded. 

Another step you could take would be to unplug the cables from the TT to the Seduction, then short the inputs of the Seduction.  That will give you an idea of the noise floor of the Seduction and the Crack.  If the nature of the noise changes substantially, then you would want to focus in on the TT/arm/cart.