Message started by kendoji on 08/14/13 at 14:58:44

Title: Hum
Post by kendoji on 08/14/13 at 14:58:44

So I just received my Taboo MKIII and it's a beautiful beast.  Everything seems to be working well, but I do have one issue which seems to be quite common among Taboo owners (we have a discussion going on about it over on head-fi), namely that of background hum.

What I, and seemingly quite a few others experience, is a constant low-level humming sound.  It's louder with new lucid mode engaged, but even with both lucid modes switched off it's there (and isn't affected by volume).

Obvious culprits would be power and tubes.  I've tried attaching mine directly the wall, which seemed to help a bit, but the noise is still there.  Us being the audio enthusiasts that we are, most of us would probably be content to spend tons of money on regenerators, conditioners, exotic power cables and new tubes to try to resolve the issue, but perhaps someone (from Decware?) can provide some advice?

I don't think the hum is 'normal', as at least one person on head-fi states that his Taboo is dead quiet.

One thing I'm wondering about is the transformer, which in my case hums quite loudly on its own i.e. with no music playing but the amp turned on, I can put my ear close to it and clearly hear it humming away.  Is that normal?

Any help would be appreciated!  :)

Title: Re: Hum
Post by kendoji on 08/14/13 at 16:47:07

So some more news from our thread on head-fi (argh I'm not allowed to post links yet, but it's in the Taboo MKIII appreciation thread).

It seems that the differentiating factor to whether you have the constant humming or not is whether there is that physical noise coming from the transformer.  Those with silent Taboos are reporting that they don't hear this sound.

I'm really hoping there's something we can do about this.

Title: Re: Hum
Post by thegrobe on 08/14/13 at 17:16:32

I have this same issue, and have posted on the Head-Fi thread as well.

I absolutely LOVE this amplifier, the sound is wonderful. I very much want a solution to this. I want this to work out. I am very interested to buy the CSP3+ to pair with my Taboo, my finger is hovering over the "button".  :D But I am unsure ... unless this is resolved.

Here is my experience:

- I get a hum noise through headphones (LCD-3) with both lucid modes off. The hum changes just a touch when old lucid is engaged. The hum gets quite louder and more intrusive with new lucid engaged.

- With both lucid modes "off" even I can hear the hum between songs or quiet passages of music.

- The hum does not change with volume knob position (in fact when volume maxed out and no music playing I get absolutely no hiss even with very sensitive IEM's plugged in) So I know the amp is otherwise quiet.

- The hum is present with or without inputs connected, either position of input switch

- Hum is present with SE or 4 pin XLR  or speaker output

- I have tried other tubes, a power filter, "lifting" the ground with a cheater plug, and turning off ALL of the breakers in my house except the one circuit feeding the amp. Tried other outlets, too. Still hums.

- With nothing connected to the amp other than power, I can hear the transformer physically humming. The amp itself makes noticeable noise with nothing plugged in.

- Many other Taboo III users report "silent" background and no physical noise coming from the transformer.

- Most users report a slight background "presence" when new lucid is engaged. That I may be okay with. What I am experiencing with no lucid modes engaged is an unacceptably high noise floor for any amplifier.

Please help find a solution. I have only had the amp for a little over a week and this is driving me nuts already.


Title: Re: Hum
Post by thegrobe on 08/14/13 at 17:21:26

I just got my 5 posts! YAY!

I can post the link to the Head-Fi thread. Page 72 is where I begin to discuss the issues I have. Thanks!

Title: Re: Hum
Post by thegrobe on 08/17/13 at 23:08:20

I had spoke with both DeVon and Steve about this the other day. Both were helpful. Steve had mentioned that one other thing to check would be the screws on the transformer. In rare instances, they can come loose creating a vibration.

I checked mine, that is not the problem however. I have a power conditioning device coming that I have ordered that is designed to remove "transformer hum" if there is DC on my power lines. If that turns out to be the problem, good. If not, they said to send it in for repair and it will be taken care of!

I will post after my power conditioner device arrives.

Title: Re: Hum
Post by seikosha on 08/18/13 at 00:36:08

One thing I can tell you is that some people also seem to be a lot more sensitive to the sound of hum than others.  I've got a slight hum in my Mini Torii.  I had a friend come over who said he thought he could hear it when his ear was against the speaker.  Wasn't even sure he was hearing it then.  I can actually hear it if there is zero ambient noise later at night with nothing playing in my listening chair 6 feet away.

He thought I was crazy and was imagining the noise.  We tried a test  with him turning the amp on and off without me being able to tell what state the amp was in while I was sitting in the chair.  I guessed when it was on every single time, he swore he couldn't hear a thing.  I wonder if some who say they hear nothing, really do have the same issue but just aren't sensitive to it.

Title: Re: Hum
Post by thegrobe on 08/18/13 at 04:50:08

Seikosha- Thanks for the reply. I have considered this, for sure. I do wonder if I am being overly sensitive so I am gathering input from other Taboo owners.

The thing is I use the unit primarily for headphones, and it being a headphone specific amp, hum would naturally be more noticeable than on speakers. The noise floor seems very high, can't be right. Anyway, still troubleshooting, and gathering input from others as well.

The worst case scenario is that I send it in to have it checked by Decware and the stellar customer service will check it out! No worries!

Title: Re: Hum
Post by clowkoy on 08/18/13 at 19:11:16

Have you tried measuring the hum in your amp?
You need an AC voltmeter that has millivolt range. Just measure the voltage across the speaker or headphone terminals. You should get a reading of less than 1 mv.

Title: Re: Hum
Post by thegrobe on 08/18/13 at 20:58:13

Clowkoy- thank you, this is a great suggestion. I haven't checked yet because my multimeter (a real cheapie) does not have AC millivolt range. I'll be certain to pick one up and test it according to Steve's paper on hum:

Really the most foolproof and scientific way. If the reading falls below spec, I know that I am just overly sensitive. If it's over spec, I know to send it in for service. Thanks!

Title: Re: Hum
Post by kendoji on 08/19/13 at 16:09:25

I don't think I'm being overly sensitive to the hum coming from my Taboo, though I do have somewhat mixed feelings.  Reading that paper that Steve wrote, my hum is definitely of the type that you hear when music isn't playing.  It's not really noticeable or annoying when music is playing, apart from in occasional very quiet passages.  I could probably live with it, but it doesn't seem right when Steve says that the Taboo is supposed to have a low noise floor and that others experience exactly that.  I'd always be haunted by the niggling feeling that something is 'wrong' with my precious Taboo.  The high noise floor is a stark contrast to my beautiful Violectric stack and its infinitely black silent background - I'd like to think that the Decware amp can achieve something similar.

I don't have a multimeter type thing so I can't measure the hum myself.  I'm basically going to wait to see if thegrobe fixes his issue with that conditioning device and will then maybe consider doing something similar.  

Title: Re: Hum
Post by seikosha on 08/19/13 at 19:25:29

FWIW on conditioners and hum.... I've got my Mini Torii hooked up to a PS Audio P3 conditioner/regenerator and it does nothing for the hum.

Title: Re: Hum
Post by deucekazoo on 08/19/13 at 22:06:47

Just to let you know I don't have a taboo but would love to get one in the future. I read through this thread and have some ideas to try. I am not an expert but these are ideas I would try. To me it seems that the transfomer it humming to the point you can hear it physicaly and not throught headphones or speakers. Is it possible that the hum is getting transfered through the chassis into the tubes? I know on my other amps, if I tap the the top I can hear it through the speakers. I would say for the fun of it get sme Dynamatt and put some on the metal chassis and see if that helps any. Dynamatt is suppose to help stop vibrations. Also you can try rubber washers under the transformer or those tube dampners. Try that and report back.

Title: Re: Hum
Post by clowkoy on 08/20/13 at 19:25:55

Hearing hum on the LCD 2 on the Taboo is unacceptable.
I have a 45 amp that is AC-heated and I can't hear any hum on my LCD 2.
I could hear a faint hum on my Grado though.

Title: Re: Hum
Post by thegrobe on 11/24/13 at 20:13:22

Okay, here's a weird one...

Of course you folks following this thread remember my comments about background hum I can faintly hear it with LCD-3, and very much with IEM's, pretty much makes the amp not useable for me with CIEM's. I sent the amp back to have it checked out, everything was normal, warranty was transferred so it wasn't a wasted trip at least.  

So I continue to fool around with this, Trying power conditioning, etc. as I REALLY want my Taboo background silent so I can use my CIEM's. The CSP3 background is dead quiet, the CIEM's work well with that side of the pair, but not on the Taboo side.

Well the Taboo is most certainly sensitive a sensitive instrument.

Check this out. I have the Taboo next to the CSP3, naturally. I plugged my CIEM into the Taboo, with the Taboo TURNED OFF. But the CSP3 was turned on. I could hear the background hum.... with the Taboo turned OFF. Weird. So I figure something is coming through the cables maybe? I disconnect the speaker wires, the RCA interconnect, event the power cable feeding the Taboo. Nothing hooked up to it.

I turn the CSP3 on, plug my CIEM into the Taboo and guess what? Background hum. The same noise I'm hearing when the Taboo is on by itself. This is crazy. I pick the Taboo up and move it about two feet away and the noise stops. Something inside the Taboo is acting as an antenna and picking up "hum" from the transformer. Either the transformer of the CSP sitting beside it, or naturally it would pick up the hum from it's own parts as well. So this explains why it hums.

Soooo...should I send it back again? Or does anyone have an idea of why this is happening and a possible fix? I feel that this info may be helpful in troubleshooting, that the hum is present when it's fully disconnected, turned off, but even SITS next to another amp! I LOVE this amp but this one thing bugs me and would like it not hum. Totally weird that it can be fully disconnected and have a background hum by just sitting next to another amp.

Also anyone else with a CSP pre and a Taboo that has a little background hum, see if you can recreate this?



Title: Re: Hum
Post by Robertiii on 03/22/14 at 10:37:50

Just bought a Taboo III and using with Sennheiser HD-800s (110dB at a volt) and still on RCA jacks though not for long - absolutely no hum, my Denon AVR headphone jack  :P has audible hiss when maxed through these cans, they are so sensitive.

Did you get it fixed/find the problem?

Cheers / Robertiii

Title: Re: Hum
Post by alper_yilmaz on 01/13/15 at 10:55:18

It has been quite some time that this thread has not been attended...

I recently bought a TABOO as well, which is a great amp.  I also hear the hum on my LCD-2 and after tracing the source of the hum I figured out that it is the transformer.  I have not had a chance yet to measure the noise (that will be the next), but do we have any solutions for the transformer hum apart from checking the screws, bolts and nuts, etc?

The hum is not in the way of the music, so it should be acceptable, but with such an amazing sound quality, one wants everything to be perfect (if there is such a thing!).



Title: Re: Hum
Post by Archie on 01/13/15 at 17:27:17

FWIW, I have had audible transformer hum from my ZP3 and CSP3.  Steve mentioned that transformer hum can be caused by a "noisy" rectifier tube.  Recently I replaced both rectifiers and the mechanical hum seems to have gone away or been significantly reduced.

My ZP3 and CSP3 sit side by side but I don't find any influence from one to the other.  Of course, a Taboo might be an entirely different animal.

Title: Re: Hum
Post by alper_yilmaz on 01/14/15 at 12:43:39

I actually tried four different rectifier tubes with the TABOO so far.  In terms of the hum, they did not make any change.  

I also measured the AC voltage at the speaker outputs yesterday and it reads 0.4-0.5 mV which is significantly below the threshold Steve has mentioned before in his white paper from 2003.  

Maybe, I should stop being obsessive compulsive about this next to negligible hum!  :)

Title: Re: Hum
Post by alper_yilmaz on 01/14/15 at 12:50:30

By the way, I also asked Steve a question regarding swapping transformers between the TABOO and my SE34I.2+ which is dead silent.  Since I am not using the SE34 any more, such a swap (if possible) should be fine as I won't sell the SE34 anyway.

My gut feeling is that the two amps might require different transformers as one is based on EL84s and the other on EL34s, despite the fact that they use pretty much the same rectifier and input tubes.

I have not heard from Steve yet though.  Any ideas?

Title: Re: Hum
Post by alper_yilmaz on 01/16/15 at 14:07:38

Steve just got back to me mentioning that the transformers on the TABOO and SE34I.2+ are the same...

Title: Re: Hum
Post by Archie on 01/17/15 at 17:49:11

I live with a hum that comes through my vinyl channel.  At the higher listening levels that I use I can clearly hear it when nothing is playing.  However, it seems to be entirely masked once the needle is on the record.  Does it color the music?  Probably.  Can I tell?  Not as far as I know.

At times I have to remind myself to just let go and enjoy the music.  It's the end that really matters and not the means.

Title: Re: Hum
Post by alper_yilmaz on 01/19/15 at 08:47:46

Over the weekend, I tried a BlackNoise Extreme filter on the mains, and it reduced the hum, just by a tad though.  Along with a friend who has an audiophile store and who is very experienced in the field (he designs and builds his own tube amps), we listened to the amp with different AC filters and our conclusion was not touching the amp at all, as it sounds so good already and any change would not be worth the attempt.  So I think I will live with the little hum!  :)

Title: Re: Hum
Post by funch on 02/10/15 at 00:16:04

I thought I would share my experience with hum. I have a CSP2+ which drives a TabooII. I listen to HD800's from the CSP and LCD3's from the Taboo. DAC is W4S DAC2. Power comes from a PS Audio Power Plant Premier regenerator.

Here's what I did to solve the hum:

Disconnected everything.

Plugged the CSP directly into the wall with no inputs: no hum.

Did the same with the Taboo: same result as above.

Reconnected both to Power Plant and reconnected IC's between CSP
and Taboo: no hum.

Connected DAC2 to CSP: Bingo!! Hum.

Disconnected ground wire on DIY power cord from DAC. Hum gone!

Cause? Ground loop. Now, everything is dead quiet. Yah, I know, not a
safe practice to disconnect the ground connection, but ....... .


Title: Re: Hum
Post by Rivieraranch on 02/10/15 at 13:12:38

The causes of hum can be incredibly benign. I noticed a hum from one of the channels of the Zen CKC I have at my office, a loud 60hz hum from the right speaker. I changed the rectifier - no difference. Then I swapped the power tubes around and voila! Hum gone! It appears that the right power tube was simply not making proper contact in the socket.

Title: Re: Hum
Post by funch on 02/10/15 at 17:52:35

Of course, sometimes it is the equipment. I recently had a loud
hum show up in my CSP2+, along with an unusual smell. Turned out
that a PS cap died.

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