2. amps-preamps
  3. 182155-130193

can you please help me around how to use my first tube amp?

Hi, I picked up on a whim an older tube amp, first I have ever had that is non automatic biasing and outside of that really no nothing about tube amps

Its a used 10 year old or so Rogue Audio Atlas Magnum power amp with KT 120 power tubes

the pre amp/dac will be RME adi-2 and speakers are Sonus Faber Lumina V's (4ohm)

I was thinking I would also also try it without preamp from a bluesound node

I believe the stock setting is 8ohm on the amp and you need to crack the lid to adjust down to 4

nervous about installing and biasing the tubes

can anybody advise what happens if I run the amp without the tubes being biased correctly?

also, can I run this from the 8ohm default so I dont have to open it up?

finally, how do I know when i need new power tubes and pre tubes?

any other advice will be appreciated

 

 

 

 

 

 

 

 

 

audiocanada
russ69's avatar
russ69
3,360 posts
 

I just want to say, get the meter you need to bias the amp. It's not very hard at all and I'm a total dummy on electrical stuff. I'm sure the manual tells you how to do it. It's not something to be feared it's just something new to learn. You got this. 

mazian's avatar
mazian
361 posts
 

You've got a great amp. You can probably still get a manual online which gives all the instructions you need.

dmk_calgary
93 posts
 

you will probably also need a cheap digital voltmeter - you can get them online - not sure of cost in Canada. Easy to bias the tubes, as the other posters have given great instructions. You can probably get the manual online and download and print it. And call them if you have questions.

mulveling's avatar
mulveling
1,774 posts
 

Guys - Rogue amps have the bias meter built in lol. He doesn’t need to run out for a multimeter.

kingsleuy's avatar
kingsleuy
175 posts
 

Probably too late now.  The first thing I would do is to Open It Up.  Check for over heated resistors, leaking capacitors, burnt wires, dead roaches...  And while you are in there change the output ohms tap.  10 years.  Might start thinking of recapping the unit.

Test the Tubes.  Find someone who has a Tube Tester.  Or buy one.  Mutual Conductance Tube Tester. You're getting into tubes.  Mind as well start getting the tools to support your hobby. Write down the values of each tube.  Check them every 6 months to a year.  See if the values are deteriorating.

If it has been sitting or stored for a while, I would do a slow power up without the tubes.  But you probably don't have a variac.  Remove the tubes.  I usually put in a smaller rated fuse in but eh, lets chance some excitement. Plug it in, get ready to jump away and flip the switch on.  No pop, sparks or flames you doing good.  Put the tubes back in.

Checking the Capacitors.  I would have done this when doing the internal inspection with a cap tester.  Hook up the speakers, turn it on and listen for a 60/120hz hum or buzz as the tubes warm up.  Should be dead silent.  If you hear anything, probably the filter capacitor.  It can get destructively loud.  If you see the plates inside the power tubes start glowing cherry red, shut it down.  Probably a shorted coupling capacitor or internal short and can damage the tube.

Bias the tubes per the manual.

Good Listening

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