[Anders]

Quote:

It's not an amp I would modify.  If you want a tube amp to modify, buy a vintage Scott, Fisher, or Dyna.

 
I think this is a very wise statement. Replacing the output transformers of a tube amp is not far from building a new amp. The only thing that my tube technician (with long-time experience of high-end tube equipment) regarded worth changing was the coupling capacitors, and you should not do that at random.

 

[Skylab]

Exactly. The whole point of the Leben is the quality of its custom made, hand wound transformers. It would be simply wasting money to buy a Leben and the try to "improve" it with different output transformers. The only reason to buy the Leben in the first place is the transformers.

 

[vert]

Hi Anders, which Dueland capacitor model did you have installed?

 

[Anders]

Quote:

Hi Anders, which Dueland capacitor model did you have installed?

 
It is Duelund VSF Cu (copper foil). I am not sure about the exact specification, I think it is 0.47 uF. There also seems to be different versions for speaker filters and electronics. I think my are speced for 400V but am not sure and there could be different versions for AC and DC. They cost about 150 Euro each and you need four. There is also a bigger model named Cast that costs about the double. It may not fit in CS300 because of physical size.
 
I didn't do it myself, they were selected and mounted by an expert on tube electronics. He suggested the modification and I just searched around about Duelund capacitors before I decided. Duelund has a very good reputation as high class and neutral capacitors. There are probably also other possible choices but not many of the same quality. I think the Duelund modification enhances the sound without changing the basic signature of CS300. I think you should know exactly what you do (and should do) before trying this modification, or leave it to an expert.

 

[zeluiz]

Hello Anders, 
Please, what kind of problem caused the accident during the tube rolling?
Thanks!

 

[vert]

Thanks Anders. Sounds like the Dueland upgrade would be worth doing. You seemed to have inadvertently arrived at your own CS300XS special edition. 

 

[Anders]

Quote:

Hello Anders, 
Please, what kind of problem caused the accident during the tube rolling?
Thanks!

I used a tube that is electrically equivalent with EL84 but not pin compatible, a way to get NOS tubes very cheap. I bought the tubes with adapters from a reputable tube company but it seems that the pinout is different from the standard on CS300. They have changed the description after that, but when I bought the tubes it looked like a drop in replacement with the adapters. When I turned on the amp, it began to smoke. I turned it off directly and the damage was limited, a resistor burned and an inexpensive capacitor was slightly damaged and replaced. As a compensation I got a quad of NOS Mullard EL84 from the tube company, so when all was cleared up it was a rather nice experience.
 
With all the talk about humming Lebens, I sometimes wonder how many that could have been damaged by tube rolling? Obviously, an incompatible tube need not burn a component in the amp, it could instead result in a more subtle damage. Nowadays, I only use 12AX7, 5751, EL84 or close substitutes.

 

[zeluiz]

Thanks,
My CS300XS uses now a full set of Gold Lion´s. I also have some NOS EL84 quads here and many 12AX7/5751 pairs to try, but with little time to make the changes and experiment the results...
They all came from reputable dealers, anyway  I´m always afraid to change them, only tried once a pair of NOS 12AX7 from Miniwatt (Philips/Ibrape) but changed back to the Gold Lion´s due to sound quality.
I really miss a reliable tube tester here, since in my region nobody deals with tubes anymore!
So I must trust on the concept of "matched" pair or quad from the dealers who sold them to me...

 

[RedBull]

Leben is a self bias, it doesn't have to be match pair, isn't it?

 

[bigdish]

My initial choices of capacitors are V Cap TFTF or REL AudioCap RT Polystyrene Film & Tin Foil. Duelund is simply out of my reach.  
  
Shall I get 0.33uF 600V or 0.47uF 600V to replace the four coupling capacitors of my Leben CS3000?  

 

[RedBull]

I'm very sure what you meant was CS300 

 

[bigdish]

Oh yes. A typo.

 

[Anders]

Quote:

Leben is a self bias, it doesn't have to be match pair, isn't it?

The preamp section is self-biasing so tubes need not to be matched there. The power amp has a push-pull design and tubes work in tandem and should be as similar as possible in pairs. So the best is two matched pairs of EL84, a matched quad is of course good too but not necessary. The caveat is that it is doubtful if "matched tubes" really are matched. Sometimes sellers only seem to mean that they are of the same brand and look similar, in other cases they have matched them carefully on at least one parameter. Still there is question if they have been matched on the properties that are most essential for the circuit in the Leben amp. I think that it is best to find reasonably matched pairs in the power section. However, tubes bought as unmatched can be similar enough and work well.

 

[Anders]

Quote:

My initial choices of capacitors are V Cap TFTF or REL AudioCap RT Polystyrene Film & Tin Foil. Duelund is simply out of my reach.  
  
Shall I get 0.33uF 600V or 0.47uF 600V to replace the four coupling capacitors of my Leben CS3000?  

Your question makes me wonder it you really have the know-how to to this? It can also affect the resale value negatively. That can also apply to my modified amp but I will keep it and and don't bother.

 

[log0]

I've had some time to spend with my new toy, the CS300 big brother. Unfortunately I had to sell my LCD2s in order to fund these, but boy do they make music. Currently using the 6p3se tubes and Devore Nines speakers. Long time coming, glad to finally see this beauty in my home! When I can afford a pair of headphones I'll post my impressions.