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post #1906 of 2101
Lars, how loud is the hum? can give some comparison?
post #1907 of 2101

The majority of the hum is coming from the output transformers mounted to close to the power/mains transformer.

A choke is not going to get rid of this the only thing is to put the power transformer in a separate box.

Or replace it with a high quality C core transformer.  Both of these would be quite a undertaking for the average person.

If the transformer was replaced with a Lundahl C core transformer no more hum. The Lundahl transformers do not

make a large magnetic field like cheep E-I core transformers.

post #1908 of 2101
Quote:
Originally Posted by RedBull View Post

Lars, how loud is the hum? can give some comparison?

Difficult to say, but not loud as such, just audible in a silent room when no music is playing, in quiet passages or with solo instruments playing. With most rythmical music it's not audible except when music fades in or out. With classical music it can be audible in some passages as mentioned.

post #1909 of 2101
Quote:
Originally Posted by 2359glenn View Post

The majority of the hum is coming from the output transformers mounted to close to the power/mains transformer.

A choke is not going to get rid of this the only thing is to put the power transformer in a separate box.

Or replace it with a high quality C core transformer.  Both of these would be quite a undertaking for the average person.

If the transformer was replaced with a Lundahl C core transformer no more hum. The Lundahl transformers do not

make a large magnetic field like cheep E-I core transformers.


Since I have the choke in I hear no hum anymore.

post #1910 of 2101
Quote:
Originally Posted by 2359glenn View Post

The majority of the hum is coming from the output transformers mounted to close to the power/mains transformer.

A choke is not going to get rid of this the only thing is to put the power transformer in a separate box.

Or replace it with a high quality C core transformer.  Both of these would be quite a undertaking for the average person.

If the transformer was replaced with a Lundahl C core transformer no more hum. The Lundahl transformers do not

make a large magnetic field like cheep E-I core transformers.

I am afraid you are right, but I hope not ...

So - it's the mains/power trafo that I should consider replacing with a Lundahl C core trafo? It should be Lundahl's LL1649 then?

 

Actually I don't know what to think, since Raaf says he got rid of humming after putting in that choke. blink.gif

post #1911 of 2101
Quote:
Originally Posted by LarsHP View Post

Difficult to say, but not loud as such, just audible in a silent room when no music is playing, in quiet passages or with solo instruments playing. With most rythmical music it's not audible except when music fades in or out. With classical music it can be audible in some passages as mentioned.

Hmm, ok, thanks, sorry, can't help much. I don't know much about electronic.
post #1912 of 2101
Quote:
Originally Posted by LarsHP View Post
Actually I don't know what to think, since Raaf says he got rid of humming after putting in that choke. blink.gif

 

Perhaps the powertransformer is not as bad as Glenn assumes

post #1913 of 2101
Leben amps were actually highly acclaimed for the custom wound transformers, although they were mostly the output transformers that were the "big deal".
post #1914 of 2101
I am not saying the transformer is bad any E-I transformer will have a strong 50 or 60 Hz magnetic field that will be picked up by the output transformers. If you take a output transformer hook a headphone to the secondary nothing to the primary and put it next to a E-I power transformer you will here hum. I built amps and hum drove me crazy couldn't figure what I was doing wrong until I turned the amp on with no tubes in the amp. Guess what HUM from the power transformer to the output transformers.
post #1915 of 2101
I see what you are saying, and that makes sense, Glenn, thanks. There isn't a lot of space inside the Leben's chassis...so the transformers are indeed quite close together.
post #1916 of 2101

I'm getting your point Glenn, and I assume you are right that the power transformer will influence the right- and perhaps even the left- output transformer.

Now I can only speak for myself, but taking out the EL84's to hear if there's any hum goes beyond the level of what I want to achhieve with this amp.

I think it's better to sell it in original state and get a good price for it and buy a better one rather than to do a complete power transformer switch.

Anyway,I always listen to my amp with the EL84's in wich is now silent with the choke.

Some day when I have some more time I would like to build a tube amp from scratch and I will definitely try to build that as good as possible, meanwhile I enjoy the Leben alltough not being perfect.

 

 

 

*edit style and typo's


Edited by Raaf - 8/21/13 at 3:21am
post #1917 of 2101
Quote:
Originally Posted by Raaf View Post

I'm getting your point Glenn, and I assume you are right that the power transformer will influence the right- and perhaps even the left- output transformer.

Now I can only speak for myself, but taking out the EL84's to hear if there's any hum goes beyond the level of what I want to achhieve with this amp.

I think it's better to sell it in original state and get a good price for it and buy a better one rather than to do a complete power transformer switch.

Anyway,I always listen to my amp with the EL84's in wich is now silent with the choke.

Some day when I have some more time I would like to build a tube amp from scratch and I will definitely try to build that as good as possible, meanwhile I enjoy the Leben alltough not being perfect.

 

 

 

*edit style and typo's


A choke in the power supply will get rid of a little ripple in the B+ voltage. It is much better then just a resistor.

I took the output tubes out just as a test to prove to myself what was going on when I still had hum on the output.

This is why some amps have a separate power supplies.   But this does not mean these amps sound better

If you want a total black background with no input and the volume turned all the way up best go with SS.

And here is a question if you can here a little hum when there is no music playing what difference does it make???

What is important is the amp sounds good with the music playing.  I don't understand this total black background

thing most SS amps don't even achieve this.

post #1918 of 2101
Quote:
Originally Posted by 2359glenn View Post

And here is a question if you can here a little hum when there is no music playing what difference does it make???

What is important is the amp sounds good with the music playing.  I don't understand this total black background

thing most SS amps don't even achieve this.

 

Good question, but I don't know the answer

I personally like to have things as distortion free as possible, because in the end noise will start to annoy me and I get tired of listening.

Its like my pc that is on now, it makes noise, not a lot and I sort of ignore it but if I turn it off I become aware of how present the noise was.

However there is a point where the technical measures you take in music equipment can kill the music as I posted earlier:

 

"Before I placed the choke I tried all sorts of improvements like net-filters and even a net decoupling transformer for my dac and amp , but although that gave a very clean sound it also cleaned out the soul of the music."

 

Finding the right balance is the trick but I think what is acceptable is different for each person.

You have people that listen to opamps and UCD amplifiers and enjoy that

And there are people that are horrified by the thought alone.wink_face.gif


Edited by Raaf - 8/21/13 at 6:41am
post #1919 of 2101

A choke will get rid of high frequency noise coming in from the power line as well as other noise

I don't understand a amp with this price tag just uses cheep resistors in the filtering of the power supply crazy.

post #1920 of 2101
Quote:

For the HE-6 and LCD-2 it might be better to use the speaker outputs with a resistor in parallel. I have asked Leben how high impedance they recommend as maximum (with 8 Ohm setting on the selector). This will give me an idea how much power the headphones will be able to receive. It should be able to handle more than 8 Ohms, I expect, but how much, I don't know.

 

Did you get an answer from Leben?

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