Hi guys I have a blackstar series one 50 head, about a year old now with only home use. One of the 2 EL34 tubes has got a weird bright blue glow near the top of it. This seems to coincide with it making a constant crackle/hiss too. Does this equal tube gone. If so can anyone recommended the best replacement tubes for is head?

Thanks guys
Matthew

Valves can have a blue glow and not be in any way faulty but if you are getting a crackle (with master volume at zero?) then it looks like one of them is on the way out.

Surely the S1 50's are not 12 months old yet? The valves only carry 90days warranty but you would get them fitted, biased and the amp checked out for free if still under warranty.

I would not sweat the type of valve, I doubt than any of the "exotics" will make any discernable difference to the sound. They are probably TAD, maybe JJs but whatever you get will need biasing. The amp is very simple to bias for a tech with the right equipment, simply set for 50mV across the 1 Ohm cathode sense resistor.

Dave. Greg: kind offer but you have me at a disadvantage sir?

Thanks for the reply. Why do you say you doubt any of e exotics would make any difference ?

Quote Matthew Seed:

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Thanks for the reply. Why do you say you doubt any of e exotics would make any difference ?

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Because in 2 years with "The Men" there was never a suggestion that different brands of the same valve made a significant difference, some yes and it can be detected with a carefully rigged A/B test but in the sweat of a gig? Nah!

Then the Series ones are a very sophisticated circuit even if you leave out the power control there is a lot of voicing and tone shaping circuitry in them and the small change a valve would make would be largely swallowed up I suspect. Last of all the amps have global negative feedback from the output transformer and that tends to resist changes made by valves, i.e. small differences in characteristics or ageing.

But it's YOUR money!
BTW! If you decide to try different PREamp valves DO note that one of them is an ECC EIGHTY TWO and make a note of its position. No harm to amp if you get it wrong but you will probably fork an 83 and the amp will sound rubbish.

Dave.

Edited by ef37a (19/03/12 11:48 PM)

Can't sleep tonight
So I'll poke my oar in here

Sharply defined bright blue glow (usually in-line with slots/holes in the anode) is not a problem. A general pale blue haze can denote a 'soft' valve.

The bright sort of glow usually varies with any income signal, so can be quite pretty to watch. This would account for it seeming to coincide with your crackles, which could easily be caused by something quite external, like an intermittent jack plug.

As Dave asked, what happens if you turn the master volume down to zero?

--------------------
It wasn't me!
(Well, actually, it probably was)

Morning Will ("it" has got me up again) I had retired just before you poked your paddle in.

It is quite hard to explain to someone who has not seen it the difference between the two blue glows. I suspect however that the OP's glow is benign since a soft pentode in an output pair would hum like Stilton and the amps are normally very quiet.

Then there is the dreaded purple glow that exists for about 1 to 10 seconds and heralds the total demise of the valve in a most spectacular way, basically HT is dumped through the heater circuit. "We" suffered a fair few instances of this until better valves were sourced.
Some people said "why are you fitting crap valves anyway?!" The fact is you trust what you buy/have bought and tho' these are in many ways "boutique" amps they are at far from boutique prices and have to be fitted with standard valves. Two factors were in both Blackstars' and the punters' favour however.1) The valves failed very quickly, weeks, even just days and so were in warranty.
2, No consequential damage was caused to the amp circuitry save a fuse.

Dave.

Hi Matthew,

Should it turn out to be a faulty valve, I can heartily recommend TAD (Tube Amp Doctor), as I recently replaced all the valves (4xECC83/12AX7, 4xEL84) in my amp with a full set of their own brand, after being nudged in their direction by Dave and Will.

No regrets here: decent price, prompt delivery (from Germany!) and the new valves have perked up the tone on my amp (admittedly, there was probably nothing wrong with the quality of the old valves on my amp, they were probably just on the way out...).

Of course, I'd try out some of the checks that Dave and Will have suggested first, before splashing out on a new pair of EL34s (irrespective of how reasonably priced they may be!).

Mind you, I know Dave has his own thoughts about "matched" pairs/quads...

Cheers,
Si

Right Cap'm!

And if you MUST have a thermionic rectifier make it a TAD GZ34 since they seem to be virtualy indestructable.

But you really cannot trust any amplifying valves from anyone these days. If you buy a set fit them as soon as they arrive and drive the living hell out of them for as long as you can, 2 hours minimum and at the first sign of a crackle bounce them back.

Dave.

Hi Guys, thank you all for this info. Just turned down the master volume and the hiss goes away (of course) but there is still a continuous crackle, sounds a bit like static on a TV. I have posted before that i live near some massive MOD ariels that interfere sometime with my amp, that normally comes and goes which drives me insane but this has been constant for about 2 weeks now. Not sure if it 100% coincides with the blue glow but certainly in that ball park. The blue/purple-eee glow is just on one valve and about an inch from the top just where the first metal plate in there is.....sorry i am not that knowledgable about all things valve.

I was thinking of replacing all the valves in there just to see what happens anyway. So any advice on which are the best to get would be much appreciated.....it's all a bit of a minefield isn't it ?

Matthew

Hi Matthew,

As I said above, I went with TAD, without any regrets.

Don't bother going for any fancy "cryo", "premium" or "NOS\vintage" type values: TAD's own brand items seem just fine.

The only exception to that is that the first pre-amp valve is normally specced to be a "high-grade" or "premium" valve as this reduces the amount of noise getting amplified at the start of the signal chain, thus making the whole amp quieter. Check your amp's schematic/manual to be sure.

Of course, with your particular circumstances, it could be worth trying high-grade valves throughout your amp to see if it helps block out interference, but it probably won't be worth the extra expense to experiment.

One other thing to note is that the naming convention for valves might not quite be what you expect: most of us know that an ECC83 and a 12AX7 are essentially the same thing, but TAD also use 7025 (IIRC) for the same thing - techincally, I think that's a somewhat higher spec version of the same valve type.

Let us know how you get on.

Si

morning Si,

There is no great cause to worry about a super low noise/low m'phonics valve for any of the Blackstar range save the Artisans and the "fussiest" of these is the A30. The regulated DC heater supply on the other amps also helps ensure a longer life.

Re the 7025. Just to further confuse everyone there are two marks of this! The 7025 and the 7025 "high grade". The latter is supposed to be lower in hum and microphonics but don't bet on it! It IS true that for the price the 7025( of either mark) is generally a better valve than bog standard ECC83/12AX7s but it is still a bit of a lottery. Mind you, I was getting valves in 50piece lots to test. One would hope that a supplier of one or two to Joe Pub' would select out the rubbish?

My advice always is. Try the valves as soon as you get them and in the case of output valves, thrash the bits off them for a couple of hours. The odd click or spit is acceptable in the first few minutes of operation but any problems after that, bounce 'em back!

Dave.

Hi Dave & Gang

I have decided to buy a full set of TAD Valves for my Blackstar Series One 50 head and see how i get on with my tone in general but mainly my weird crackle, glowing valves and Radio interference. Now i know they may solve none of the above but hey its worth a stab. Could i just ask one last bit of advice as i'm getting confused with how these tubes are named. TAD seem to make the following : EL34 B-STR is that right for my amp ? And on the preamp valves they make : TAD7025/E83CC Highgrade Premium Selected & also TAD7025s/12AX7, Mullard Style Premium Selected. But i can't seem to see an 82 anywhere ?

Any advice would be great
Matthew

Hi Matthew,
My advice would be to save your money!
I very much doubt that a change of valves will bring about any audible change, let alone improvement in the tone of the amplfier. Due to the nature of the pre amp design especially, Series one amps are not really valve "sensitive", you would have to find a real dog for example to give rise to any microphonic problems and regulated, DC heating means even crap cathode insulation is no big deal, ie. no hum.
But it is your money: The TAD EL34B-STR is indeed a good valve as is the 7025 (the high grade has lower noise and microphony,useful in an old amp design front end, wasted in an S1!)TAD do do an ECC82, PT# RT005 14.95ees. Should be a good value choice for those building the Gyraf mic pre amp but YOU don't need one. Note also than NO valve switcheroony is going to make the slightest difference to the RFI problem.

Lastly Matt' if you really want a different tone pallette try a pair of 6L6s. Of course any new op valves will need to be biased and balanced.

Dave.