Can you lessen it by putting your hand on it? Is it a physical hum or electrical hum?

I'm just curious really, I don't have any solutions for you.

Electrical hum is usually dealt with in the design stage. If the layout of the transformers is good, you shouldn't hear that fluorescent ballast buzzing. That's Amp Building 101, layout of the transformers, and I'm sure Steve has that down. So unless there is an issue with the transformer it shouldn't be a problem.

Now, you could still have physical vibration simply from the current flowing through those parts. If you put your hand on it and can make the noise go away, something simple like a physical damper for the transformers is an option. Something like the Herbie's SuperSonic Stabilizer can help. http://herbiesaudiolab.net/stable.htm

Once you know more and can accurately describe the problem, call Steve, I'm sure he's got things you can check to possibly solve this.

In guitar amps I've had failing tubes or other parts cause an electrical imbalance that makes transformers resonate, so don't put it off as it could be a small issue that could turn into a bigger one.

I agree, you shouldn't have to; that's why I feel once you narrow it down a bit more and feel you can describe it, give Steve a call. There are so many things that can cause transformers to make noise...I'm betting even bad power (harmonics in the 120v line) could cause noise in the transformers! That's not something an amp builder would be responsible for (as an example)

As with all issues, divide and conquer till you narrow down what the issue is.

I have discovered that the hum is not coming just from one side.  It is cumulative.  I was confused because of the power up sequence.  I always turn on the right channel first, then the left.  When I tried doing it in reverse order now the right channel seems to add the hum.  Reality is that both are generating some noise and it just gets louder when I turn on the second channel.

I do need to talk to Steve.  Maybe some further line treatment is needed.  I don't put the amp through any conditioner.  I have a PS Audio Quintet which is super for my sources and preamp, but I have always read to not use one for the amp.  I go straight into the wall.  Odd however that this seems to have just started a couple of weeks ago.

Putting my palm on the transformers had no effect.  This is internal electrical hum.

Yeah, not all power filters/conditioners/regenerators are the same.

The first point is that the device first needs to be able to handle the constant current of your amp, but the key point is that it need to be able to handle the amps sudden current demands, and do so without being sluggish about delivering that inrush of current. That's where the power device can and will effect the sound.

PS Audio seems to have a grasp of this, and it can't hurt to try it assuming the device can handle the constant current. It would also let you see if that filters out the problem!

I know you'll update us. . . .

I played around with different power outlet options last night.  Good news and bad news.  The bad news is I couldn't eliminate the hum.  It would likely not be noticable or less so in a larger room, but my space is small and very quiet.  

The good news is I now have the amp plugged into the amp outlet on my Quintet.  That helped the sound quite a bit.  I didn't think the degree of transparency could rise any more but it has.  The bass has also tightened noticably.  One advantage of this problem is I never would have tried the conditioner based on my prior thinking.  Nice lift.

I was listening to John Mayer's Gravity on his live Where the Light Is 4 LP set.  This is a super engineered recording, heavily center focused on many of the numbers.  Simply amazing realism and I highly recommend this if you like Mayer's music.  The set was $80 for the 4 180 gram LPs, but worth it.  I was guilty of audiophile focusing on the sound more so than to the music.  So clean, clear, and in the room, it was scary.  I could live with the hum I guess, but I know its there.  Talking to Steve will be the next step.  

Quote:


You just earned plus two in cool factor with me. Thinking of our ZMA amps first, and coming up with a cool and diabolical company name!


J- I'm starting to wonder if maybe your just hearing the inherent tube noise that comes with tube amps...they aren't dead quiet, and if your room is super quiet, you can actually hear that slight buzz of the current going through the tubes come out of the speakers. My 2 watt, 15 year old Zen amp used to have a lot of that, but is much, much quieter with new tubes and Steve's circuit mods (I had a big tune up done on the old amp). If that's what it is, I personally feel it's just nature of the beast with very transparent, single ended tubes.

Well, I solved the problem the audiophile way.  After talking to Steve and hearing that the faint sound was inherent, I decided to take the only sensible path left.  Upgrade to the ZMA!  Steve and I worked out how that will happen.  Don't worry, I'm at the back of the list.

This actually solved another dilemma that was eating at me.  I've been holding on to a monster SS amp as an insurance policy if the MK IV proves too weak when I get a bigger listening room.  Selling the SS amp will more than cover the cost of the upgrade and I will have an amp with enough power for any room.

I should have pulled this trigger as soon as the ZMA was announced, but the MK IV sounds so damned good I was nervous.  I will now have visions of meters and big ass caps dancing in my dreams during the cold months ahead.

Scott

It's interesting about the hum of Scott's MKIV.

I had hum issues from time to time with my MK II and III.  Once I started using a Running  Springs Audio Haley (latest version) on my MK III, it became dead silent. I was previously using a a PS Audio Quintet, and before that, PS Audio Power Plant Premiers (one of the first 100 built and a later replacement, both self-destructed).  

Now that I've converted my MK III to a MKIV, it's still dead silent.  No transformer hum. I can hear the rectifier tubes if I put my ears close to them, but that's it for amp noise.

Mike in Seattle area

ps  I should mention I'm using a PS Audio Duet in my second system (ZSM's with Jupiter caps), and they are dead silent.

I want to be clear about what I was hearing so anyone reading this thread isn't confused.  The sound through my speakers is dead quiet.  Steve's design is great.  What I hear is a very faint electrical hum from the transformer's windings.  I know enough about electricity to know that current running through wires will generate this sound.  You can hear power lines as well if you are close enough.  Experimenting with my power conditioner was beneficial and yielded better and cleaner sound through the speakers, but physics still prevail with the transformers.  I had a hard time believing this noise was in the signal path.  A number of designers use covers over their transformers if not not the whole amp, and if not this issue would likely be discussed more.  I like the open design however.

Steve in fact told me (no surprise) that all transformers have this inherent hum.  I really expect that the ZMA may also give me similar behavior and if so that won't be part of the "mystery".  Sorry for the pun.  I really believe in a more open room this will all become moot.  Today the easiest remedy is lowering the stylus on to the record.

Scott  

For my Torii MK4, the closest I ever get to my amp is when I have to change the volume.

At that close distance, I still can't hear any external transformer hum emanating from my unit.

Hi LR,

Yes, I agree with you and Scott.

My listening area is semi-open rather than a "man cave ".
So maybe the natural transformer hum is more pronounced in dedicated listening rooms.

The power lines in my residential area are also very clean.
I've never had any Hum issues with audio equipment both Decware or otherwise.

On a side note, I'm using an Oppo-95.
I belong to the religious (*) category of audiophiles who believes in using the max output volume of the DAC, hence I don't mind the "extra" exercise involved in changing the volume manually.


(*) I suppose this make me a Puritan then

LR,

I could not resist testing my equipment, must be a carry over of my tube rolling OCD.

Late at night with minimal ambient noise, I turned on my MK4 and put my ears literally next to the transformers.
There was completely no hum nor any noise at all!
If it weren't for the fact that my tubes were glowing, I might have thought that the MK4 was turned off.

As for the Oppo's digital volume control , my settings are normally

Oppo 95 : MAX 100 Fixed volume
MK4: 9 turns volume

I then tested it with
OPPO 95 : Variable Volume 90-95
MK4: 11 turns volume

In my audio chain, with variable volume, there was something missing from my music.
I can't say for sure, I admit that it might even be Psychologically induced, but I felt less drawn by the music.

For this reason, I'll stick to my normal Oppo 95 settings and change the mk4 volume manually.
I'm using pure silver interconnects and speaker cables so my audio chain is really sensitive to the minutest changes made.
This could be the reason why the adverse effects of using an extra volume control are more pronounced in my audio chain.