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JJ preamp tubes - repeated problems

I purchased an amplifier that came with stock tubes made by JJ.  There were problems with the amplifier so I replaced some tubes and then figured out it was the pre-amplifier tubes and small tubes. The manufacturer in this case who is McIntosh did send me replacement tubes and they worked for a month or so and then began to crackle. Now I have to figure out which of the six small tubes is creating a problem. 

I'm curious to know if manufacturers test the tubes that they use in the amplifiers before they ship them out? Maybe they test fine and then go bad within a month. I'm very suspicious they don't bother testing their tubes.

Judging by the process to test individual tubes and when you have 24 tubes on an amplifier I can understand them not giving them much attention during the manufacturing process. Maybe they expect people to replace all the tubes just like the power cords they send out.

 .Many replace the stock tubes immediately with gold lions which seems like an easy choice. Maybe manufactures do test their tubes and they're just using a poor manufacturer. 

Do others have tube problems with McIntosh amplifiers?

emergingsoul
yoyoyaya's avatar
yoyoyaya
737 posts
 

There's nothing particularly bad about JJs - they are extensively used in the front end of guitar amplifiers that get a much harder life than hi fi. It's relatively unusual for small signal tubes to fail early in their life, but it does occasionally happen.

@OP - it's not guaranteed that it's the tubes that are at fault. It could be a dry joint on a tube base, for example.

dinov's avatar
dinov
833 posts
 

Yes they do test them but current tubes aren’t what they used to be quality wise. McIntosh is very easy on tubes, so the problem is definitely the JJs. That’s why I use NOS. I use Amprex Medical 12 ax7 s in my C2300 and have well over 10000 hours. I would look into those or NOS Telefunkens. I think you’d be very happy both quality wise and sonically.

thecarpathian
4,350 posts
 

JJ's are mediocre tubes at best. For best sound and reliability, get some nos from a reputable dealer.

elliottbnewcombjr
5,330 posts
 

Repeated problem: I am highly suspicious of the AMP, not the tubes.

TUBES: A simple tube tester puts you in control, without one, it’s a confusing mess.

test single and matched sets you buy, test periodically, test when problems occur.

Have Spares, but they should last many thousands of hours.

Many are on eBay etc.

Keep your eye out for a decent tester that seller says works, and accepts returns.

I have the smaller model 157, I would get this model 257 if I did not have one. I got a 257 for a friend, he loves it.

seller: 100% positive rating: 30 day returns:

read full description and ’watch video’

 

moonwatcher
443 posts
 

Until you get your amp checked out by a reputable technician, all these comments are guesses at best. Blaming the JJ tubes might be correct, or not.  As many have noted, poor shipping, handling, and such can damage any tube, even NOS. 

JJ tubes are treated roughly in guitar amps and don't fail very quickly. I have used them in a Schiit headphone amp to good effect (6922). Sure, NOS might sound better, but if we want this hobby to continue with vacuum tubes or "valves" as they are called in Europe, then we have to be looking at new production tubes because the supply of vintage tubes will run out one day. What do you do then, move to Class D with Hypex or PuriFi chips? 

Perhaps replace the JJ tubes with something else and see if they too get fried. If not, then you'll sort of know it might have been "something unquantifiable" with the JJ. But if they too get fried early on, then you definitely should get the amp looked at. Nothing made by humans is 100% perfect or as intended 100% of the time. Just the reality of manufactured goods. 

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