Burning Smell?

If the tubes are old and have been pushed a lot they can crack or weaken. If they're the original tubes then you prob just need some new tubes. And like John said, use a speaker cable if you're not already doing so

Ah right, beyond my "expertise" I'm afraid!

*cough* pictures *cough*

Ban Him...

It wasn't me! wrote:

no worries. It turned out to be a non-problem. I gave the brother the task of putting the tubes in while I sorted the documentation, assuming he couldn't possibly get it wrong, and, well, he didn't quite put in one of the ECC83's, resulting in it falling out in my hand when I removed its casing, him receiving a glare, and the amp being easily fixed, with no current perceptible burning smell, and the tube filaments glow with a nice red hue, so we're sorted kiddies. She sounds like an absolute monster, for those who care.

Hmm, I can't think of a reason why a loose valve would cause a burning smell. If the pins on one of the ECC83s weren't making contact, the amp wouldn't work at all.

When you say nice red hue... you mean a nice yellow hue, right?

Did you get the valves with it, or buy new ones yourself? If the 6550s are bit old, it might explain the burning odour. It also wouldn't hurt to clean out the amp, if you haven't already.

Hmm, red does not sound right at all tbh. The filaments should be yellowish orange under pretty much all circumstances, afaik. Maybe we just have different ideas about where orange ends and red begins. If the idle current is too high there is sometimes a reddish tinge to the plate. This would be a bad thing also, but quite correctable.

As for replacing teh valves... Valves don't really fail in a reliable or predictable way. Sometimes they blow out and short, usually taking out a fuse, occasionally burning out a screen resistor, and - just once in a while - blowing the output transformer. For that reason they're generally replaced at the first sign of something amiss. I would say blackened valves alone, even ignoring the smell of burning, would be cause enough to replace them without delay.

Just clean the inside around the valves with a cloth. I can only imagine what happens to all the dust and greasy fudge when it starts to heat up. No need to go inside the actual amp, it's probably fine in there, and not safe to go poking besides.

You'll get a retube from bob for about €55 shipped, i did

I just got a straight swap for whatever was in the ENGL, premium graded matched JJ's. Took about 30mins for the email reply, on a sunday

Well, the Marshall "sound" really comes from EL34s. KT88s have more clean headroom, and are supposed to sound more linear. I have yet to try some myself.

Yeah, biasing is simple enough if you have a multimeter and a bias probe. If you don't have a bias probe you'll need some 1 ohm resistors and a soldering iron.

It wasn't me! wrote:

Where would I acquire those tools?

Go a-googling. If you have none of those things I would suggest something like the Weber Bias Rite.

http://www.amp-head.com/ also has all of the tools required. If you're getting a multimeter, don't skimp anyway. The cheap ones just won't have the accuracy. And I would strongly recommend the plate voltage probe as well, unless you feel pretty confident in holding the multimeter probes while measuring it. Plate voltage is usually around 400-500 volts.

That sounds plausible. The Pumkpins sound was always preamp distortion.

Should probably add, while "modding" has been brought up, that putting KT88s into a JCM800 or 1959 does usually require that the bias resistor be changed to the get the bias into range.

I'd switch to EL34s.

Define "heavier"? Afaik, 6550 has a slightly higher gain factor, which means they have more clean headroom - they will distort less at the same volume as an EL34. For this reason, 6550s are more commonly used in bass amps than EL34s. EL34 is the valve that a JCM800 or Super Lead was designed to use. To be honest, it's less relevent in a JCM800 than it is in a Super Lead - for the most part you're probably not getting close to distorting the powerstage unless your master volume is at 10 anyway.

6550s originally appeared in Marshalls when 1959s were first exported to the US. The amps were shipped without valves, and 6550s were a cheaper domestic US alternative. Most US players later modded their amps back to EL34 spec.

"Deeper" I can only imagine is a reference to it having an extended bass frequency response. I haven't heard much of this about 6550s. I know KT66s and KT88 definitely do, but, to be entirely honest, your cab is the bottleneck in the low frequency response of your rig anyway. You'd have to put in some 15s or get a larger enclosure before you'd start really noticing the difference.

EL34 are where you should start anyway, imo. Until you've heard them with your ears, I wouldn't put too much into anything anyone tells you. They define the "British" rock sound, and most people would consider them more aggressive sounding than most other valves given that they're less "mid-scooped". But, more to the point, they're what the amp was designed for - so start at the beginning.

Just my take on it.