About to buy MA-1 monos- how long do the tubes last and how easy are replacements to source?

Nuforce

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Since these were just shipped, more than likely you simply had a power tube fail rather than the amp itself. During the first week or two after installation is when we encounter the most problems with power tubes.

It the amp simply stopped playing, its likely the fuse by the power cord blew; this fuse can blow if a power tube arcs. Usually its a simple matter to replace the fuse and locate the arcing tube by simply knocking on the tops of the tubes.

the fuses are fine, i was experiencing major crackling in the speaker on one side once switched to full power, damn near blew the very expensive ribbon tweeter on my magnepan 20.1!
 

Atmasphere

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the fuses are fine, i was experiencing major crackling in the speaker on one side once switched to full power, damn near blew the very expensive ribbon tweeter on my magnepan 20.1!
The crackling is a bad power tube, and unless your Maggies have a bad crossover, your ribbon was perfectly safe. We'd not have stayed in busness nearly 50 years if a power tube failure was damaging speakers like that!
 

Nuforce

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The crackling is a bad power tube, and unless your Maggies have a bad crossover, your ribbon was perfectly safe. We'd not have stayed in busness nearly 50 years if a power tube failure was damaging speakers like that!
Ok thanks, and apologies, it is just that I am very partial to my Magnepans and possibly overreacted!
 

DetroitVinylRob

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Atmasphere

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Ok thanks, and apologies, it is just that I am very partial to my Magnepans and possibly overreacted!
No Worries! That fuse by the power cord is solely for the B+ of the power tubes; if the amp attempts to make more power than its rated for, that fuse will blow. When a tube arcs its primarily a low frequency event so unless you are using a speaker with low power handling its no concern. If you are using a speaker that does not handle much power, a series fuse is prudent simply because a careless switching of inputs or the volume control position could cause the amp to damage the speaker without any sort of failure otherwise. IOW if you are using a 140 Watt amp with a speaker that only handles 10 Watts some common sense is in order :)
 

Nuforce

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Ralph do you think GE 6as7ga tubes would be ok for the MA-1s?

A very well respected UK dealer (Langrex) had a vast qty of them.
 

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ACHiPo

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Ralph do you think GE 6as7ga tubes would be ok for the MA-1s?

A very well respected UK dealer (Langrex) had a vast qty of them.
As I recall Ralph has told me they are not recommended as they do not have as good power handling capability as the GT (I think?). That being said I have used them and they sound fine. I did lose about 30% of them during burn in, likely because of the lower power rating.
 

Nuforce

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Little update on my MA-1 amps. After a few issues with worn out power and signal tubes I have them singing beautifully. I have a trio of CV181 treasures that I am breaking in.

I also discovered after popping the lid that these amps already have the v-cap upgrade!

Hats off Ralph, what rich and textured amps. So much more enjoyable than my Pentode amps. PXL_20220611_102512800.jpg PXL_20220611_140245293.jpg
 

ACHiPo

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They are pretty magical! Glad you've got them sorted. They are pretty bullet proof once you get them sorted as well.
 

Nuforce

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Magical is the right word for sure. Mated to the equally magical Magnepan 20.1 ribbon tweeter the experience is pretty awesome.
 
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