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> Reducing Power Output Via Removing Power Tubes: Safe?
Ajmurrell
post Dec 23 2008, 12:50 AM
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While I'm awaiting enough money to purchase an attenuator, I was wondering if it's safe to remove one of the two powertubes that are in my Dr Z 18 W tube amp?

I ask because I know that a few people have talked about removing power tubes from other tube amps to remove wattage (MikeM with his switchblade I seem to recall being an example) and wanted to know if you can do this on any amp is ok?

If it's ok to do so, should I remove a particular one in the Tube chain? And as there are two, can I assume it will half the wattage? Or is it more complicated than this?

Thanks for your help smile.gif Always first class responses smile.gif

This post has been edited by Ajmurrell: Dec 23 2008, 12:51 AM


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Andrew Cockburn
post Dec 23 2008, 12:56 AM
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Not necessarily a good idea.

It depends on the circuit, but it is most likely a push pull output, and removing one of the 2 power tubes will at best sound awful and and worse could cause damage.

Micke can do it because he has 4 tubes - that's 2 pairs. They work in pairs and removing a pair is ok, but removing half of your only pair is not going to work.

Unless of course this is class A with a paralell driver stage but that is rather unusual.


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Ajmurrell
post Dec 23 2008, 01:00 AM
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Ah that does make a lot of sense when I think about it! I believe it's not actually classed strictly as a class A as it has *insert technical word here* (thing that automatically bias's replacement tubes!). Not sure if that makes any difference?



QUOTE (Andrew Cockburn @ Dec 22 2008, 11:56 PM) *
Not necessarily a good idea.

It depends on the circuit, but it is most likely a push pull output, and removing one of the 2 power tubes will at best sound awful and and worse could cause damage.

Micke can do it because he has 4 tubes - that's 2 pairs. They work in pairs and removing a pair is ok, but removing half of your only pair is not going to work.

Unless of course this is class A with a paralell driver stage but that is rather unusual.



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MickeM
post Dec 23 2008, 01:03 AM
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QUOTE (Andrew Cockburn @ Dec 23 2008, 12:56 AM) *
Micke can do it because he has 4 tubes - that's 2 pairs. They work in pairs and removing a pair is ok, but removing half of your only pair is not going to work.

Yes, works fine here. The rule I have to stick with is to remove either the outer or the inner pair, but at all times leave a pair.

I would not pull one tube in the DrZ. Better just wait for the attenuator.


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Ajmurrell
post Dec 23 2008, 01:08 AM
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Thanks guys smile.gif Waiting it is!

The DR Z attenuator is a good recommendation apparently if anyones interested in buying one, cause it works on any Ohm output for tube amps upto a 100W, with a maximum reduction down to 1W.

Apparently he's bringing out a mini Air Brake, for lower wattage amps in the new year. Might wait for it.



QUOTE (MickeM @ Dec 23 2008, 12:03 AM) *
Yes, works fine here. The rule I have to stick with is to remove either the outer or the inner pair, but at all times leave a pair.

I would not pull one tube in the DrZ. Better just wait for the attenuator.



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Andrew Cockburn
post Dec 23 2008, 01:09 AM
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QUOTE (Ajmurrell @ Dec 22 2008, 07:00 PM) *
Not sure if that makes any difference?


Neither am I! I would play safe and wait ...


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Ivan Milenkovic
post Dec 23 2008, 11:54 AM
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QUOTE (Andrew Cockburn @ Dec 23 2008, 12:56 AM) *
Not necessarily a good idea.

It depends on the circuit, but it is most likely a push pull output, and removing one of the 2 power tubes will at best sound awful and and worse could cause damage.

Micke can do it because he has 4 tubes - that's 2 pairs. They work in pairs and removing a pair is ok, but removing half of your only pair is not going to work.

Unless of course this is class A with a paralell driver stage but that is rather unusual.



You can almost feel the experience of Andrew when he starts with this kind of tech talk cool.gif


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Andrew Cockburn
post Dec 23 2008, 02:30 PM
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QUOTE (Ivan Milenkovic @ Dec 23 2008, 05:54 AM) *
You can almost feel the experience of Andrew when he starts with this kind of tech talk cool.gif


smile.gif


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