One for the tube heads!

C

condyk

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I love my new Norh SE9 tube amp but have a number of basic questions, as a newbie tubie :-)

1. how will I know that the tubes need replacing ... does it just die, or kinda fizzle out slowly for a few days before hand?

2. How will I know exactly which tube to replace, or do I replace them all at once.

3. What's a good source of replacements?

4. Can tube be upgraded, i.e. are their better brands out there?

Thanks in advance. Sure the answers will help others as well as me :-)

Dave
 
ill do me best

1) they kinda glow dimmer,
2) see 1, some tubes you may want to replace in matched pairs, IE input stages where you have the same type in each channel
3) i use watford valves or tube-shop.com
4) yes, i can only speak for pre type tubes, most people trry a few different ones to see what they like (called tube rolling), i like a NOS mullard in the phono stage
 
cant resist....!

here's my go...



1. how will I know that the tubes need replacing ... does it just die, or kinda fizzle out slowly for a few days before hand?

as has been said they go dim. also the sound starts to go... tap them with a pen and you'll see which one is going. The sound will pop back to normal when you whack the right one. Output tubes go in about 1/4 of the time that pre-amp tubes do.

2. How will I know exactly which tube to replace, or do I replace them all at once.

I replace them all at the same time. But then I have EL34s, and I can get Mullards or Phillips for a tenner each..
You dont have to do that, but its better if you can.

NB You need to see if your amp has fixed/automatic biasing. Then you'll know if you can stuff them in or if it needs an engineer to replace the output tubes.

3. What's a good source of replacements?

Langrex supplies, wilson valves, watford valves, CVC. All in hifi world.

4. Can tube be upgraded, i.e. are their better brands out there?

They change the sound. My rough rule is british valves for warmth and body (like mullard), american valves for clarity (like phillips), russian/chinese valves for cheapness, military specification for reliability and length of life (and sometimes more power).

Hope that helped.
NB if your amp was new, youre ok for at least 18 months of v heavy use.
 
NB You need to see if your amp has fixed/automatic biasing. Then you'll know if you can stuff them in or if it needs an engineer to replace the output tubes.
Click to expand...

My amp has fixed biasing and therefore it is less straighforward to retube, however it may be worthwhile asking the manufacturer for some information, as it may be relatively easy to do it yourself.

Whan I asked, the nice man from Audio Research sent me instructions on how to retube taken from the service manual and also some circuit diagrams. It doesnt look too hard to do, as long as there is a multimeter handy.
 
I'm afraid you are wrong in saying that a tube goes dim when it needs replacing.

In most tubes the part that lights up is the heaters which run on a simple 5, 6.3 or 12v circuit. These will never go wrong unless you drop the thing from a great height, in which case it's bye bye amp anyway.

The only way of telling is by the sound. Things will get softer and less defined because there will be a lower flow of electrons between the anode and cathode. Often one channel will go before the other so you will notice an inbalance of sound.

EL34's last a long time as they are really a guitar tube and are therefore very well built. A long time in tube terms is usually about 4 years (having said that I have some Mullards from the 60's which still test strong)

As for make, if you forgo the expensive British made, the opinion at present is Svetlana EL34 or JJ E34L (no not a typo). Search around on www.AudioAsylum.com for more info. Or me as it looks like I may well be getting a quad of JJ's (and sell my Mullards for silly money to the Far East)

Nice amp BTW.
 
Thanks all round for good advice. For info., the Norh has:

2 Electro Harmonix EL34EH Power Tubes
2 Electro Harmonix 12AX7EH Drive Tubes
5AR4 rectifier tube

Thw two to four years life sound encouraging.

I have left the amp on since I bought it, but judging from the posts in the thread around whether it's better or not to turn it off when not in use, I may start to do just that. But I must say that it seems better to leave it on; feels like the on and off and warm and cold thing would put more strain on the tubes ... but what do I know!! Any thoughts!?

Dave
 
Dave,

Personally, I would strongly recommend turing it off after use and not leaving it on permanently, otherwise you are going to get through a lot of valves! For example, my AR amp power valve life is approximately 2000 hours (as recommended by AR). If I left my amp on permanently I would need a new set in 84 days! At $400 a set from AR, that is soon going to get expensive!
 
Hi

Lee is Im sure right about the dimness thing. It must be a pscho-visual thing for me, cos I thought they did, but Im sure I must be wrong.... you can definately hear it though, and as Lee said its usually one channel (because its usually only one valve thats going)... and you can tell which one by tapping it with something... it makes microphonic noises then, and comes louder again.

You've got EL34s like me then? - theyre great tubes, sound nice lots of power, and best of all cheap as chips when they go pop ! You could replace your entire complement of valves from, say £50-£75 no problem at all, and the EL34's will be anything from £3-£15 (or obviously more if you want to go daft).

IF you want advice on the different sounds you can get from different tubes, Wilson valves are very helpful, and Langrex are too - give them a bell when you need a new set... in 3 years !!... (or 18 months if you play it as much as me 6 hours a day ish..although thats obviously dependent on amp design and power too)
 
OK-do-kee [and bearing in mind I'm i/2 through the next bottle of "Deep South" {about £8.00 at Asda = Southern Comfort - maybe we should re-name it Northern comfort??}

As far as I remember [if I find it's wrong I'll post correction..]

Valves have their vacuum formed by igniting a reducing inflammable in the evacuated tube.

Since there is always left over of the "reactive stuff" left {my brain no longer holds the chemical info due to <welcome> alcohol damage..], then heating the tube should re-activate the remainder - restoring the high vacuum...
 
The way a valve works is nothing to do with obtaining a true vacuum. It all about how many electrons there are passing between the anode and cathode. The vacuum just means it is easier for the electrons to travel. Once the electrons have started to be used up then that is when a tube goes weak.

BTW
If you continue to run with weak tubes you run the likelyhood of damaging the amp as the tube will draw more and more current to try and generate electrons, and that is not good for the mains transformer.
 

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