Another one bites the dust!

[Big Dog RJ]

G'day maties, trust everyone is enjoying the music inspite of this crazy virus going on... corona whatever?

Purchased a few nice LPs from a great store, some very finely recorded music on Opus, Eric Bibb- just like love, LP album, superb!

Anyway, this was my only day off just before a long 6 day work week starting tomorrow, so I got ready for a second listen of this fine artist, and a small hiccup!

The right channel monoblock one of the 6922 / E88CC tubes had that infamous white flashes as if there was a mini thunderstorm going on in the tube... bad tube! So that one was replaced by a brand new spare of the exact same type- Genalex Gold Lion 6922 used as a driver phase inverter stage.

This one or pair as it was ordered wasn't even a year old! So now the new pair is from CJ and the much older pair, which are actually Sovtek are over 6 years old...go figure.
The Sovteks were the original in these monoblocks along with the Mullards m8080 that are still going, hasn't missed a beat.

I'm beginning to wonder whether the extra dollars spent on the fancy Genalex Gold Lions are worth... all I can confirm at this stage is that the Sovteks are far more reliable than these gold pins, perfectly matched and balanced sought after NOS types. The Sovteks also sound equally superb, so I'm not sure whether I'm going to order the Genalex again.

This is not the first time, I've made earlier posts where these 6922's went bad, and all the symptoms have been these white flashes ... Since Ive ordered 3 sets of these in pairs, around the same time I ordered the Sovteks from CJ, both sets of gold lions failed within a year or little over.

In summary it's good to note the failure symptoms that I've come across:

1. Input tubes - these would mainly cause sputtering noises, sudden burst like fire crackers, causing the output tubes LEDs to flicker having a hissy fit.

2. Driver / phase inverters- these would mainly have white flashes going on within the tube that is very bright and visible, like mini thunderstorms.

3. Output tube failure- well in most other tube amplifiers these tubes would just blow ... first with a very bright red along the entire grids of the tube from top to bottom. When output tubes are in normal operation, only the top / tip of tube and very end will glow orange/reddish that's normal. Leaving the middle portion grey in color which are the grids fitted along the length of the tube.

If at any given time these grids light up with a dark red hot color, that's a bad tube! Immediately off the amp and replace that tube. Thanks to CJ's clever use of highgrade output fuses, these protect the output transformer as well as the rest of the country side.

It is also good to know that many top end contenders also have protection fuses and steps in place to protect the country side, such as VTL, VAC, Manley Labs and so on. I remember back in the day, ARC didn't have protection fuses, and when an output tube went bad, it would blow along with the country side...and that was a pain in the capital butt to fix! I believe ARC has now incorporated output stage fuses, as well other measures to protect those big trannys.

CJ always used very high quality heavy duty ceramic fuses, and they do a fine job of protection. If an output tube is bad the fuss blows and an LED lights up. The only issue is finding the bad tube...After a little investigation it's pretty easy to identify the naughty tube.

Anyway, that's that. Just wanted to know if anyone else has had a not so good experience with the Genalex Gold Lions?
Don't get me wrong, they sound marvelous and do everything perfectly. It's just that I'm not too sure about their reliability factor...

Best, RJ

 

[Big Dog RJ]

Tube Bias, a few important things!

G'day maties,

Just got feedback from my tech, and yet again I've learned something new. So apparently, when biasing down your actually increasing current to the output tubes. Hence, if you turn the bias pots all the way down, you've actually provided the tube with maximum current, which in turn leads to Red plating. By turning up the bias (clockwise) you're actually reducing the current to the output tubes and setting the required idle current for the tube to operate. As volume increases, the amperage increases as well, and if monitored by a multi-meter, you can actually see these ratings rise and fall as levels are adjusted.

Now, who would have known that?! I always thought bias adjustment was the other way round; less bias = less current and more bias = more current but not the case, in fact just the opposite!

So, the lesson learned: when replacing output tubes with new ones, do not turn the bias pots all the way down. Instead, turn down just one slight turn and leave it. When new output tubes are installed, they would normally sit at a higher required current simply because they're new and not too weak or anything like older tubes. Once the new tubes are powered up, they would usually trigger off the bias circuits, lighting up the LEDs. Then all that's required at this stage is adjusting the bias for each tube and setting their idle current as closely as possible. That's about it!

This is mainly for those who own CJ gear and other tube amplifiers that are biased using trim pots. Multi-meter bias adjustment in milli amps, requires a slightly different skill, basically a steady hand! ARC requires matched tubes, simply because that's the way ARC gear is designed, hence if one or two tubes go off then you have to replace the full set. OTOH with CJ and VTL, they're individually biased and so matched is not required, although better to have for the amplifiers running optimally.

After so many years/ few decades in this audio field, what I had initially learned about tube bias was completely different to what the actual process is. Yet we cannot think we know it all... tube amplifiers and CJ in particular, are one of the most reputed and reliable brands money can buy. They're very well built and designed on such high standards, that if you don't know about tubes and not sure what you're doing, it's better to stick with SS. With tube amplifiers, it's always a learning curve, and more the experience, more the rewarding it is, especially when troubleshooting such areas that are common with tubes.

With careful adjustments, looking after the gear and no abuse, tube amplifiers will not only out-perform but will also out-last SS designs.
CJ is just one of those highend marquees that gets it right. Definitely worth the investment!

Speaking of CJ, they've come out with a full Class A monoblock design capable of 160w Class A, called the ART108A. Looks very similar to the ART27A but in monoblock version. Quite pricey though, something I'm seriously considering. Then again I've already got monoblocks that put out a solid 60w Class A and switches into AB with anything going over 80w well into 125w. It's not all about watts / power, means nothing. It's the current capacity that gets that extra grip, and is needed to fully control notorious impedence curves, such as full range stats or large planar ribbons. 60w of Class with an efficiency of 92dB is plenty!

So, keep an eye on that bias and those LED indicators and the amps should be running tops.

Cheers maties, and enjoy those fine tunes!
RJ