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Couple of questions on New Mini Torii (Read 2540 times)
seikosha
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Couple of questions on New Mini Torii
07/05/13 at 14:36:25
 
Just received a new Mini and have a couple of questions that I couldn't find answers to in the forums.

1.) The negative feedback controls.  I'm guessing that the default position is with them all the way turned to the left and as you turn them clockwise to the right you are actually increasing the negative feedback from a -6 value to a zero.  Is that correct?

2.) Hum - How much is normal?  I've seen various answers to this from absolutely none to some.  Right now I've got enough so it sounds as loud as a very very quiet equipment fan at the listening position when the ambient noise is low, like late at night.  I've tried moving stuff around, changing outlets and floating the ground but it stays identical.  For reference purposes, I'm in a semi nearfield set up with my ears about 6.5 feet away from the speaker driver.  I've never experienced hum in my system before.

If my hum levels aren't normal, any advice on reducing it?



Thanks in advance for anyone who can provide feedback.

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Fireblade
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Re: Couple of questions on New Mini Torii
Reply #1 - 07/05/13 at 17:02:57
 
I'm sorry about your humming issues. I've never experienced humming at any level with my Mini Torii, so I don't think it is normal or acceptable. This amp has a very low noise floor and is one of the most silent ones around.

There must be a ground loop or some similar interference.  It could also be a noisy tube, which may sometimes be confused for humming.

In any case, I cannot help other than encouraging you to systematically interchange tubes, try to isolate humming by channel, change accessories, etc., until you find the cause.

Good luck!
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seikosha
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Re: Couple of questions on New Mini Torii
Reply #2 - 07/05/13 at 17:27:15
 
Thanks Fireblade.  So I just want to confirm with certainty.  When your Mini is on with no music playing, even if you put your ear close to the speaker, you hear no noise or hum at all just complete absolute silence?

I tend to think mine is not a tube issue.  It's equal in both channels and if I touch for instance one of the speaker terminals on the amp, the hum level increases.
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Fireblade
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Re: Couple of questions on New Mini Torii
Reply #3 - 07/05/13 at 19:34:53
 
That's basically it. I don't experience the slightest hum, at all. I normally listen at about 8 Ft from the speakers (which is very close to near range) and I've never heard any noises.

In fact, I've tried with my ears right next to the speakers and no hum whatsoever. So, I insist there must be something there you'll need to identify and correct. Maybe loose connections, or some external interference you may be catching and channeling through the audio circuit.

Since I've not dealt with this particular issue, I'm not the person that can help you here, sorry. I just wanted you to know what you should expect from this great little amp. I'm sure other more informed forum members will give you better hints based on their personal experience.






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grinnell
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Re: Couple of questions on New Mini Torii
Reply #4 - 07/07/13 at 05:38:41
 
i have the MT with the ez81 rectifier and it is very quiet i can put my ear to my speakers De Capos (92db) and barely hear anything.
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seikosha
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Re: Couple of questions on New Mini Torii
Reply #5 - 07/07/13 at 21:04:30
 
Thanks for the help guys.  Grinnel, you may be close to where I am.  If I hook up a 90db speaker to the amp, I can barely barely barely hear any noise with my ear next to the driver.  My speakers are much more efficient than your 3A's, which incidentally, I'd love to hear on my amp, so maybe I'm in the ballpark of where I should be.

Also, can anyone out there confirm that the -6db feedback position is with the feedback controls turned all the way to the left?
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TubeNut
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Re: Couple of questions on New Mini Torii
Reply #6 - 10/18/13 at 22:43:18
 
I do believe that when the knobs are turned fully CCW(left) that that is no feedback.
As far as the hum issue, I would get an isolation transformer(filters and isolates the mains) and try that if you're certain it isn't caused by your equipment. My MT has no hum wwhatsoever.
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« Last Edit: 10/18/13 at 22:52:42 by TubeNut »  

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jorgen
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Re: Couple of questions on New Mini Torii
Reply #7 - 03/11/14 at 23:35:04
 
Seikosha;
Did you find a solution regarding the hum?
I recieved my MT yesterday and when I hooked it up with headphones there was a hum in them. Since I havent gotten my Omegas yet I decided to borrow some BW 686 speakers and hooked them up. With no volume from the amp there is a hum from the speakers, but i got to be real close to the speakers, same hum from both of them. The hum isnt noticable from a distance, but those speakers are 85 db, and Im worried that with 93 db speakers the hum will be more "present", correct? IF not necessary so I can easily live with noise IM having right now..
How can i check if grounding is ok?
What other things can I check?
If i assume the amp is OK, what options do i have?

Electric system in my house is pretty new, but not sure about the grounding though..
But can bad or missing grounding be the reason for a hum?
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« Last Edit: 03/12/14 at 00:14:59 by jorgen »  
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seikosha
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Re: Couple of questions on New Mini Torii
Reply #8 - 03/12/14 at 00:23:06
 
Hi jorgen,

I spoke to Steve about it and I think it's just the normal amount of hum from a Mini Torii.  I tried everything to see if I could reduce it and it's just inherent in the amp.  Obviously if I put in other speakers that are less sensitive the hum goes down.

My se84 is significantly more quiet than the mini Torii.  You'll have to decide if you can live with it.   I've noticed that some people are much more sensitive to hum than others.  I had a friend over and he could barely detect the hum even though it was very easy to hear for me.
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Fireblade
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Re: Couple of questions on New Mini Torii
Reply #9 - 03/12/14 at 02:27:50
 
I hate to disagree with the idea of an acceptable hum, sorry. IME the M-T does not present this issue and it has one of the blackest backgrounds I've heard. This trait is part of the merit of Steve's designs.

I would not settle for any hum and would look for possible causes. Is not easy, I guess, but people in this situation have successfully found a way to eliminate the hum.

You can see my modest signature and confirm that without anything fancy although quite resolving, and listening at almost near field, it is normal not to hear any hum.

BTW, my hearing is still quite good.
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seikosha
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Re: Couple of questions on New Mini Torii
Reply #10 - 03/12/14 at 11:45:41
 
Hi Fireblade,

My MT measures normal for hum according to the specs Steve lists.  I've  tried every suggestion out there and if you search through the archives you'll see there are examples of others with hum issues who have even sent amps back to Steve who confirmed that their amps measured within spec.  A huge factor is going to be the speakers you pair them with. I can get rid of the hum by putting in a different speaker, but that's not a direction I wanted to go.  It's quite possible I could put your speakers in my system and the problem would disappear or you could put mine in yours and it would appear.

Here's an example of a hum issue in a Decware amp that measured within spec, but still hummed:

http://www.decware.com/cgi-bin/yabb22/YaBB.pl?num=1362932039

Interestingly enough, this person is running Omegas too and postulates that single driver speakers are more susceptible to revealing hum.  One thing to realize is that if a speaker is down 2db in a hum region where another is up 2 db in the same area, even though the speakers would have identical sensitivity ratings, one would reveal hum very easily whereas the other could sound almost silent.  4db is a big swing, so there is more to sensitivity ratings and predicting hum levels than just sensitivity ratings.
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« Last Edit: 03/12/14 at 12:06:30 by seikosha »  

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Fireblade
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Re: Couple of questions on New Mini Torii
Reply #11 - 03/12/14 at 12:46:23
 
I understand and you may be right, I've just been lucky so far in this regard. What puzzles me, though, is one of the traits in any good tube amp is the low floor noise requirements. The success of these amps depend in part precisely on achieving this black background, which would be inconsistent with an 'acceptable level of hum'.

I also have not seen many complaints/comments about it among M-T owners in this forum, so it looks as if it comes up with a certain kind of single-driver speakers only, which would be important to identify, and evaluate if the tradeoffs with those speakers' other features is still positive.

Thanks for the heads up.
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jorgen
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Re: Couple of questions on New Mini Torii
Reply #12 - 03/13/14 at 00:37:03
 
hi all
Im not reallty sure what to think in this matter. Im waiting for the omegas to arrive, maybe in a week or so, but if/since the hum is increased by more efficient speakers that will be a bummer, as I said on a 85dB speaker I can hear it when close to the speaker (4-6 inches) , with the Omegas (93dB) im afraid the hum will be present even several feets away from the speakers.  I know I have issues with ground, getting that fixed tomorrow hopefully, and I have an option with adding a power conditioner, but thats a lot of money....
What other options can you guys suggest to isolate and terminate what causes this issue? And would you assume that a Power conditioner would take care of the problem if it isnt the amp in itself?

as mentioned before Im confident there isnt a problem with the amp, its tested at decware, and I dont think they would/could have missed hearing it. If course I might be wrong, but since im living in Norway there is a bit of a problem shipping it back and forth...so im leaving that for a last option

BTW; the known ground issue I have: Ground is connected to the "water pipe supply"  to my house, my house is really old so for a couple of years ago I had to change waterpipe, they took away the old metal pipe and reconnected the "pipe"" with a PVC pipe.,, so from what i understand I have no grounding at all.... I have never notiiced anything.., the odd thing is that I have changed el-wiring (professionaly) and the electicians ever noticed anything... But if no ground at all, would you guys suspect a hum as a result??


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seikosha
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Re: Couple of questions on New Mini Torii
Reply #13 - 03/13/14 at 02:50:55
 
Hi Jorgen,

one thing I did to help my troubleshooting was to try my system in different houses.  If the problem follows the amp in different locations then you know that you probably won't be able to fix it by reworking the electrical systems in your house.

I have a PS Audio P3 power plant and using it has no effect on the hum, so keep that in mind before you go out and spend money on power conditioners.

Once you get the speakers, you'll have a better feeling for how it affects your enjoyment of the amp.

Good luck and let us know how it works out.
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jorgen
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Re: Couple of questions on New Mini Torii
Reply #14 - 03/13/14 at 11:42:55
 
Is there a difference between power conditioners and power filters? And if so, what difference is there?
If a con.doesnt help, will a filter likely make a difference either?

Is I wrote, im using some BW speakers now, and allready im in love with the amp. To describe sound in words in a foreign language is challenging.
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« Last Edit: 03/13/14 at 13:09:00 by jorgen »  
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