New valve(s) needed?

Dr_Necessiter

Dear All,

I recently bought a Mesa Boogie Stiletto Ace. It has been fine up to now but has started making some crackling noises when I hit certain notes. It isn't constant but does seem dependent on resonant frequencies. It has a set of Mesa tubes, well at least the front ones being the rectifier and power amp valves so I'm guessing that there's a decent chance that they are the orignal ones. Before I lash out on a new set of tubes can I please pick your brains as to the cause of the noise and the likelihood of it being valve-related? So far I have done the following:

-Swapped guitar;

-Swapped cable;

-Plugged in the the return jack on the effects loop to cut out the pre-amp and played through that;

-Checked and swapped the speaker - I was going to do this anyway so it made sense to do so whilst I had the back off;

-Tapped the front valves with a pencil with the amp on which generated some crackling similar to what I'm getting whilst playing.

None of this made a difference to the crackling.

Is this suggestive of a power amp valve about to let go or possibly something requiring a trip to a technician? I'd be grateful for any thoughts please. Also, there doesn't appear to be a lot of room to remove and insert valves, do I need to take the chassis out to do this and am I likely to encounter any high voltages by doing so?

Thank you!

ecc83

AFAICT the amp uses EL34s and I have had them go microphonic and crackly. I doubt anything will fail with dire results but ICBM is THE Mesa Man and will I am sure be along directly?

Dave.

ICBM

It is likely to be the power valves - or more likely just one of them.

If you bypass the valve rectifier (set the switches to Diode) you can eliminate that as the cause.

If it's not the rectifier, its probably a power valve. It's possible that tapping either will make the other one crackle since the vibration can be passed via the chassis, so it's best to lightly hold the other one with a cloth while you tap one.

If you identify it as one valve, replace both with a matched pair and keep the good one as a spare. You don't need to open the chassis to change valves on a Mesa - the bias isn't adjustable. It's easiest to use Mesa-branded valves since they are tested to be in the middle of the bias range. They do them in several 'colours' - if you want the exact same sound and to make best use of the spare (if you ever need it) get the same 'colour'.

The existing valves aren't necessarily the originals since this may have already been done.

Dr_Necessiter

Thank you gentlemen! New Mesa EL34s duly ordered from:https://sickamps.com/

I've not used them before so I'll post again to update on the experience.

Alex2678

Oddly I had this exact problem with my DR yesterday 

Kittyfrisk

Holy Shit!
Mesa really have sewn up the 'exorbitant premium plus prices for branded consumable items that they don't actually make' market, FFS

:-O

Dr_Necessiter

Yeah, https://www.ampvalves.co.uk/ has two kinds of JJ EL34s that come in matched pairs and which are checked to make sure that they fit the tolerance for this amp at about half the cost but I like the tone I'm getting from my Ace now I've swapped the speaker so I wanted to keep it similar. 

Being a bit of a tinkerman, it is slightly tempting to go chasing the tone dragon by swapping out different brands of valves though...

ecc83

Dr_Necessiter said:

Yeah, https://www.ampvalves.co.uk/ has two kinds of JJ EL34s that come in matched pairs and which are checked to make sure that they fit the tolerance for this amp at about half the cost but I like the tone I'm getting from my Ace now I've swapped the speaker so I wanted to keep it similar. 

Being a bit of a tinkerman, it is slightly tempting to go chasing the tone dragon by swapping out different brands of valves though...

I may get shot down but I doubt you will find much tonal variation between EL34s especially since they have to meet the bias requirement.

IF you could alter the bias and found a pair of valves several volts apart for the same Ia then, because the valves must have a different mu (g1 to g2) they stand chance of sounding a bit different from a pair that need a higher or lower bias voltage.

From reading Frets and other forums and a bit of personal larnin', I find the general view on valve amp OD tone is that 70-80% is from the preamp 18% from the output stage (when driving the nuts off it!) and 2% unknown factors. This applies it seems EVEN if you swap 34s for 6L6s?

Now...Speakers! Different animals altogether!

Dave.

Dr_Necessiter

Ah thanks Dave! That's interesting, I hadn't taken my googling much past the power amp valve stage. The pre-amp valves look to be a pain to reach in the Ace as they are set behind the power amp and rectifier valves and so I'm tempted to leave this alone for the time being.

ecc83

Dr_Necessiter said:

Ah thanks Dave! That's interesting, I hadn't taken my googling much past the power amp valve stage. The pre-amp valves look to be a pain to reach in the Ace as they are set behind the power amp and rectifier valves and so I'm tempted to leave this alone for the time being.

Ah, I did not mean to suggest that you swap about with pre amp valves either! Just that messing with output valves is very expensive and IMHO will make very little difference.

It is of course a very big, subjective area but I would say the circuit configuration can make changing even pre amp valves a bit pointless in some cases.

I am sure ICBM can suggest the 'best fit' but even that depends I think on the sound you want to emulate?

Dave.

Dr_Necessiter

OK, noted. I'm actually quite happy with it now I've changed the speaker - I've put a Tone Tubby 40/40 green hempcone in it which seems to have warmed the tone up nicely - it was a little glacial before. The problem is I am the kind of guy who lets perfect get in the way of good enough...