Valve amp electrical hum!!

[Amazoman]

Hi,
My Orange AD200 Mk 3, which is relatively new to me, has what I would describe as an annoying but not unbearable electrical hum. I am sure that at stage gigging volumes it wouldn't be a problem but for home practice it is!

I have tried all the usual, leads, ground problems etc and I am convinced that it is the actual amp. Never had problems with previous amps in the same place.

Can anyone explain why the electrical hum is more noticable/ louder when the master control is set half way round ie: between 10'oclock-2' oclock if it were a clockface but if I turn master all the way round to the loudest setting the humming dies down. ?
Similarly if I back the treble knob right to zero it quietens it?

I am consequently using the amp with master right round to max, no treble, and the gain at about 1
( ie 7'oclock )position.

What do people think is acceptable noise from a valve amp?

I have had the power valves renewed and biased, thanks to all who commented in my previous post. I went for KT100's but didn't do the preamp valves, it was a financial bridge too far!. Could renewing these pre amp valves sort the electrical noise issue?

[Beer of the Bass]

Hum in valve amps is often caused by capacitors in the power supply going leaky, this is less likely with a newer amp, though not impossible. If the treble control is quietening the hum, then most of the noise is coming from an earlier stage in the circuit. Does the gain control affect the hum too? You could try swapping a new ECC83 into both ECC83 positions in turn and see if one reduces the hum - it'd be cheaper than replacing both.
Valve amps can be very low in noise, but it depends on the design and layout, so some are better than others. It's worth talking to the tech who replaced the power valves. If he had it up and running through a speaker and didn't notice anything out of the ordinary, then it's probably the nature of the beast, although he may have just done a quick job using a dummy load.

Edited December 29, 2011 by Beer of the Bass

[Mr. Foxen]

Try just swapping about the pre valves, if one is a bit noisy, then moving it to a position with less gain after it will lessen the hum. Should be able to figure if one is duff, and which one that way, an know if you have to replace.

Since you had trouble with it before, might have partly cooked a capacitor that is being troublesome though.

[Dad3353]

A 200w valve amp is perhaps a tad 'overkill' as a home practice amp, and you may be expecting much to want stage power and bedroom use. I use a Hiwatt DR203 (200w PA amp, 4 x KT88...), which very quiet, but it takes little to produce hum from these monsters.
Was the hum there before changing the power tubes..? The KT100 seems a strange choice to me (I'm not [i]that [/i]clued up, however...); they have extra gain and power handling, but that would rather increase the problem, if it's in the pre-amp.
BB above has pointed the right way, however. Your amp tech should be made aware of the issue, and will doubtless suggest a solution. It may never be completely silent, of course, but it's rather a judgement call as to whether it's 'normal', or acceptable for that use.
Hope this helps...

[Amazoman]

Hi All,
Thanks for responding.
First - I like a creamy, bluesy tone rather than a gritty sound so the tech suggested a KT 100 ,which is a beefier version of the KT88, which is a recommnded change from the stock 6550 valves to get this sound. But like you, Dad 3353 ,I have to take advice from those with more experience and the KT100's were recommended to me by the tech to try and get the tone I wanted.

The gain control does have an effect on the hum BB but not as much as the master knob. What does this signify?

Mr Foxen- I will try swapping the valves about and will report on the effect to the pre amp stage.
I understand that it may be a 'tad overkill' for bedroom use but I simply wanted one!!!!!!!!! I have three solid state amps which are all OK but I needed to try a valve amp. I will probaby move it on as I now fancy a TC 750 but who knows!

[Beer of the Bass]

[quote name='Amazoman' timestamp='1325204640' post='1481050']

The gain control does have an effect on the hum BB but not as much as the master knob. What does this signify?

[/quote]

Figuring out which controls affect the noise is a simple way to identify which stage of the amp the noise might be coming from. If turning down a volume or gain control can silence the noise, it's reasonable to guess that the noise is happening at an earlier stage in the circuit. But the interaction between the gain and master volume controls suggests that there might be noise from more than one stage. Swapping preamp valves is about as far as you can safely go to diagnose a problem like this if you're not familiar with working on amps - if that doesn't help, it's a tech job. Chances are, if it's not a preamp valve, it'll be something small like a bad capacitor, or a ground connection needing re-soldering, so it probably won't be an expensive repair.
I think there are some other AD200 users on here - they could confirm whether some hum is normal, but I expect they're normally quieter than you describe, as most healthy amps are.

[Dad3353]

[quote name='Amazoman' timestamp='1325204640' post='1481050']
...a creamy, bluesy tone rather than a gritty sound so the tech suggested a KT 100 ,which is a beefier version of the KT88, which is a recommnded change from the stock 6550 valves to get this sound...[/quote]
Slightly off topic here, but this still seems very strange, so I'll pursue slightly, if I may. I am open to correction, but for my money, a decent KT88 design would be about as 'transparent' as one could get, most especially if not 'pushed'. The term 'gritty', or even 'creamy'/'bluesy', seem out of place somehow. These valves don't 'break up' easily at all, until concrete-grinding volumes are reached. They are used especially for those requiring 'headroom' for just that reason (I don't want break-up with my bass, only headroom...). The KT100 has a slightly higher break point still (some 3db, depending on circuitry...), or roughly double the volume. If that's where you're looking for your 'creamy' sound, then heaven help your FOH sound engineer, and bring on the masons for rebuilding the stadium..! The 'tone' comes from the pre-amp and tone stack; the power section takes that to a higher power with as much transparency as possible, until driven hard enough to contribute it's own tonal characteristics. That point is pretty damned high for these valves, and even when reached, is far from 'gritty'. That's a term that I would more easily associate with a choice of pre-amp valve (selection of ECC83, for instance, between Mullard and Electro-Harmonix , NOS versus new, etc...)
In general (few exceptions...) a good valve amp with a 'tone' is a small(ish...) amp cranked. If you want creamy/bluesy for a guitar, a Pignose does better than a Marshall stack most of the time. I can't recommend much for 'creamy' bass tone, as I look rather for clean headroom, but I'm pretty certain you won't find it in a powerful amp at anything under high volume (or very heavily attenuated, perhaps..?).
Just my tuppence worth; there may be other elements not covered that I've missed, in which case; apologies.
Hope this helps.

[umph]

kt100 is basicaly a tougher version of kt88, it's still pretty similar though.

Best way to troubleshoot the noise would be to pull valves starting with the input valve until the noise goes then do some valve swapping till you find a quiet one.

[Amazoman]

I am an absolute novice with regard to valve amps and the characteristics of the different valves. The stock valves that come with the AD200 are 6550's. From what I have read they do start to break up and give that gritty driven sound quite early on when driving the gain when compared to KT88's.
When I spoke to the amp tech about this and that I was after a smoother tone, and as I was having it revalved anyway, he suggested KT100's. His reasoning was that they are very similar to a KT88 but in his terms a little beefier I assume he meant more robust,
The tone that I am getting from them is just what I was looking for but I'm not driving them hard as I said in a previous post I am only using the amp in the bedroom currently so I certainly don't want any masonary falling down.

Just a final question in the pre amp stage the amp takes two ECC83 and one ECC81. I can get the ECC83's locally and save on posting but not the 81. Could I put 3 ECC 83's in as their characteristics look to be the same when I've searched the internet. The 83 are high gain the 81 medium gain thats the only difference I can find.

[umph]

[quote name='Amazoman' timestamp='1325265493' post='1481543']
I am an absolute novice with regard to valve amps and the characteristics of the different valves. The stock valves that come with the AD200 are 6550's. From what I have read they do start to break up and give that gritty driven sound quite early on when driving the gain when compared to KT88's.
When I spoke to the amp tech about this and that I was after a smoother tone, and as I was having it revalved anyway, he suggested KT100's. His reasoning was that they are very similar to a KT88 but in his terms a little beefier I assume he meant more robust,
The tone that I am getting from them is just what I was looking for but I'm not driving them hard as I said in a previous post I am only using the amp in the bedroom currently so I certainly don't want any masonary falling down.

Just a final question in the pre amp stage the amp takes two ECC83 and one ECC81. I can get the ECC83's locally and save on posting but not the 81. Could I put 3 ECC 83's in as their characteristics look to be the same when I've searched the internet. The 83 are high gain the 81 medium gain thats the only difference I can find.
[/quote]

81's can push more current than 83's. You may find the drive will suffer on your amp. An 83 is at its limit driving a quad of kt88's.

In other words grab a nice NOS 81 off ebay

[Anders]

[quote name='Amazoman' timestamp='1325265493' post='1481543']
I am an absolute novice with regard to valve amps and the characteristics of the different valves. The stock valves that come with the AD200 are 6550's. From what I have read they do start to break up and give that gritty driven sound quite early on when driving the gain when compared to KT88's.
When I spoke to the amp tech about this and that I was after a smoother tone, and as I was having it revalved anyway, he suggested KT100's. His reasoning was that they are very similar to a KT88 but in his terms a little beefier I assume he meant more robust,
The tone that I am getting from them is just what I was looking for but I'm not driving them hard as I said in a previous post I am only using the amp in the bedroom currently so I certainly don't want any masonary falling down.

Just a final question in the pre amp stage the amp takes two ECC83 and one ECC81. I can get the ECC83's locally and save on posting but not the 81. Could I put 3 ECC 83's in as their characteristics look to be the same when I've searched the internet. The 83 are high gain the 81 medium gain thats the only difference I can find.
[/quote]
Just thought I would add,I haven't heard any Orange AD 200MK3 owners say there is a hum in their amps.So probarbly something wrong with,hopefully a preampvalve,as said.Did the humming start right after you had it at the tech?Not to critisise him,but is he a well known,experienced with valve amps?Either you had just bad luck with the preamptube or whatever broke right after he had it,or he might have done not a pefect job.Otherwise he would have heard it.
Again,I'm just asking,not blaming the tech.

[Amazoman]

The tech is a top man, highly recommended. It was John Chambers from Champ Electronics in Nottingham. I did have a problem originally with the power tubes which was caused by a cracked tube and air getting inside. This had the effect of taking a second tube out as apparently they work in pairs.
When those tubes were replaced and biased John found a small black line of (I can't remember what he called it!!) material that was linking two of the power tube bases together on the board and causing one tube to discharge all of its volts into another. This he cleaned off and everything power wise was fine. All of this was checked using an oscilloscope and meters. There was no need to look at the preamp stage for any of this repair. He said it looked like the amp had been worked on before and this material should have been cleaned away and was the root cause of my original problem.
He did this work as I waited and watched, absolutely fascinating. He kept inviting me to look through his workbench magnifier to see exactly what he was talking about.
With regard to 'was this hum there before he worked on it' I expect so but I don't actually know because the amp developed the problem with the power tubes within half an hour of me taking ownership of the amp. (See previous post).

[Anders]

[quote name='Amazoman' timestamp='1325284286' post='1481870']
The tech is a top man, highly recommended. It was John Chambers from Champ Electronics in Nottingham. I did have a problem originally with the power tubes which was caused by a cracked tube and air getting inside. This had the effect of taking a second tube out as apparently they work in pairs.
When those tubes were replaced and biased John found a small black line of (I can't remember what he called it!!) material that was linking two of the power tube bases together on the board and causing one tube to discharge all of its volts into another. This he cleaned off and everything power wise was fine. All of this was checked using an oscilloscope and meters. There was no need to look at the preamp stage for any of this repair. He said it looked like the amp had been worked on before and this material should have been cleaned away and was the root cause of my original problem.
He did this work as I waited and watched, absolutely fascinating. He kept inviting me to look through his workbench magnifier to see exactly what he was talking about.
With regard to 'was this hum there before he worked on it' I expect so but I don't actually know because the amp developed the problem with the power tubes within half an hour of me taking ownership of the amp. (See previous post).
[/quote]
OK,the tech seems to be a great guy.I guess as said by others here ,see if it's the preamptubes.If not,I would call the tech and ask if he could help you again.
I've not been very helpful here,sorry.Im' not very good at the technical stuff,if I were maybe I could help.Hope it works out well for you.

[Mr. Foxen]

[quote name='Amazoman' timestamp='1325284286' post='1481870']
When those tubes were replaced and biased John found a small black line of (I can't remember what he called it!!) material that was linking two of the power tube bases together on the board and causing one tube to discharge all of its volts into another.
[/quote]

That would be soot/carbon. A spark goes across, leaves a bit of soot where it burns stuff, slightly more conductive path, so sparks easier, until a solid strip of soot builds up and shorts it.

[umph]

[quote name='Amazoman' timestamp='1325284286' post='1481870']
The tech is a top man, highly recommended. It was John Chambers from Champ Electronics in Nottingham. I did have a problem originally with the power tubes which was caused by a cracked tube and air getting inside. This had the effect of taking a second tube out as apparently they work in pairs.
When those tubes were replaced and biased John found a small black line of (I can't remember what he called it!!) material that was linking two of the power tube bases together on the board and causing one tube to discharge all of its volts into another. This he cleaned off and everything power wise was fine. All of this was checked using an oscilloscope and meters. There was no need to look at the preamp stage for any of this repair. He said it looked like the amp had been worked on before and this material should have been cleaned away and was the root cause of my original problem.
He did this work as I waited and watched, absolutely fascinating. He kept inviting me to look through his workbench magnifier to see exactly what he was talking about.
With regard to 'was this hum there before he worked on it' I expect so but I don't actually know because the amp developed the problem with the power tubes within half an hour of me taking ownership of the amp. (See previous post).
[/quote]

John is my mentor and a top amp tech, i thought it might've been him when you said he suggested kt100's! He's loving the shuguang atm