I have a pendant and mine hums as well, and seems to be about as much as what you described. on high z the VC picks up quite a bit of noise. the Atticus and HD650 not nearly as much. i think this amp is just very prone to interference. i’ve noticed changing tubes has helped quite a bit.
i swapped out the Sovtek EL84 tubes it came with, with some JJ new production backups, and those helped. I ditched the JJ 12AT7 input tube for a Baldwin Organ rebrand 12AU7 (Japanese manufacturer, but can’t identify who), and that lowered the noise floor considerably. now trying to decide if i want to bother with the rectifier too.
i did notice placement was important for me. i have mine at work (while not under covid lockdown), and in that metal frame building with all the computer equipment, it would hum and pop like crazy in certain spots. i relocated my desk to the middle of the room away from the walls/window, and that helped. but it still hums no matter what. it drove me insane the first few weeks with it, but now, i don’t even notice or care. i just had to get used to it.
when playing music i can’t hear it at all, and i love the sound of it so much overall, i’ve just accepted the hum. i am going to pick up that power cord @ProfFalkin mentioned, as my unit was 2nd hand and had a beat up cord packed with it. hopefully that will help. i also tried all the suggestions others have made to no avail.
Noise and hum are things I specifically listen/check for when evaluating tube amplifiers. In fact, I have a dedicated section on it in my Pendant review.
I got no audible hum with the Pendant I had for review, even in a quiet room (<30 dBA), with nothing playing, and with headphones more sensitive than the ZMF models. And that was regardless of the position of the volume pot.
Hum (as opposed to hiss or other noises) is almost always either a ground-loop or some other power-related side issue (be it a transformer problem or rectifier tube problem on the amp, actual line-noise, a bad ground or DC offset on your AC line). And even if a device is the ONLY thing on a circuit, that doesn’t mean there is no other noise on that circuit (power cables act like antenna, just like any other wiring).
If all else fails, try lifting the ground to the amp temporarily … and if that helps, an EbTech Hum X will likely sort you out. If not, get the line checked for DC-offset (in which case a CMX-2 would likely fix it).
Also, surge-protectors are a bad idea for reducing noise or hum. They’re intended to surpress big transients, and if they don’t specifically have noise/power filtering on them, they’ll likely cause it … especially those with little neon bulbs in them …
It’s not connected to a surge protector currently.
I’m just as a loss to understand where the ground loop is with no input connected.
I’d have thought physically re positioning the powercord (horizontal vs vertical) would change the hum if it were the power cord acting as an antena, and I’ve tried that.
The only valve I have not changed is the rectifier, I don’t have one lying around, but in my extremely limited experience with rectifier tube failures, they tend to just die, or if one half fails make a terrible noise.
It’s very obviously power noise, or possibly the transformer, there is no question in my mind on that. I can hear amplified mains hum come in over the top of the persistent hum if I wind the volume way up.
I’m not sure I understand what your asking me to try here.
It’s not the power cord that’ll act as the antenna (it will, but probably not at a frequency that’d be something typically described as hum). I was actually referring to the main AC wiring.
Lifting the ground means disconnecting it. I am NOT asking you to try that. Just saying that it is one way to eliminate ground issues. It’s something you do at your own risk and If you don’t know what you’re doing, or what the implications of it are, just try a Hum X instead.
I find with very efficient headphones if I put them on the High Z channel with no-input past 4 O’clock I can get some noise. But when playing music I never even get close to that level of Volume Gain
Last night i swapped out my NOS RFT rectifier for the JJ new production tube the amp ships with, and the noise level for mine went down noticeably. all i have now is the slightest of buzzes from the high z jack with my VC. i don’t really like the sound of the JJ, so i’ll be searching for a new rectifier, but at least i know now the main issue was the tube.
This noise is different to that, I can hear obvious mains hum at those volumes, but given I can’t get past 7 ot 8 o’clock in normal listening that’s not an issue.
This is a consistent volume invariant hum, I’d guess either 60 or possibly 120Hz that is always present regardless of volume level even swapping out the 12AU7 for a 12AX7 which has dramatically more gain makes no real difference to it’s volume, which implies it’s not going through the the signal chain.
I have a socket in our house in my office that has an issue with 60 Cycle hum. But I also get AM radio when I use certain Gain pedals with my Guitars in that room.
One thing checks your RCA cables from the DAC to AMP as well. I had one DAC driving White noise even with Suvara into the amp above, but it absolutely black-out of the Schilt Audio Bifrost 2 via some 20-year-old monster RCA cables to the amp at full volume on High-Z. Make sure they have shielding.
No hum on mine, mild tube pops upon initial warm up, usually gone within the first 5 minutes. Mine is great though at letting me know when my cell phones are about to go off. I’m getting roughly a 2-4 second warning every time I’m about to get a text, Call, email dump, or any other message. I find that 5-6ft away is minimum distance i need to minimize the interference. Some of the low impedance HP’s and IEM’s i own have a mild hiss at no or low volume. Otherwise my Pendant is extremely quite, and noise free.
Hey everyone I am new here. Super happy to find this thread with all of the great model specific info. I have a special build ZMF Pendant/Leeloo. Which has a couple of factory upgrades including the upgraded power supply and solid state rectifier from the Leeloo. I have used 12ax7, 12ay7, 12at7 and 12 au7. Has anyone successfully used the 12AV7? So far with my ZMF Eikon I really like the lower gain tubes, 12at7 and 12au7. I asked @ampsandsound and they had actually never heard of the 12AV7 and thusly would not recommend for or against it. Thank you
Here are the Spec sheets. I don’t have a ZMF Pendant, but the 12AV7 and 12AY7 have similar amplification factors, with the 12AV7 being a bit less than the 12AY7. Other spec differ somewhat. One is low level amplification. You can use 12A_7 series tubes with an adapter to substitute for 12SL7 in the Kenzie line, although I think octal 2C52 is an excellent octal tube sub on the Kenzies.
The 6201 is a good substitute for the 12AT7. The 6201 tube was used in HP computers.
