Ampeg SVT-CL question
Hey, I have a question about my Ampeg
I have had my SVT-CL for quite a few years now and had all the power tubes replaced maybe 6 months ago and haven't played it too much since then.
The last few times I've played it semi loud, around 10-11 o'clock on the gain and maybe 2-3 o'clock on the main volume, I've noticed I am getting an over driven distortion sound. I am sure previously (before tubes were replaced), as long as the gain was low and volume up, I could go loud and stay clean, but now it is always sounding over driven. Now, this may have always been the case and I either didn't notice or I've forgotten, but I thought I could go loud & clean before.
From someone that has one or played a lot through one, is this normal, a typical SVT-CL sound, or should I be able to run loud and clean?
If it isn't normal, what could it be? The biased lights on the back run green & red at the same time which I think is how they should be.
Any info/help would be appreciated. Also, ask any questions if I have missed any important info.
Let's assume that you amp is not performing as it was before the tube change.
Tubes do not all perform the same way. Some sets will distort sooner than others. These will distort sooner and have less headroom. Other tube sets will have a later onset of distortion and more headroom. It could be that your new tubes fall into the first category. More info on this here.
It is also possible that one or both of the 12AU7 driver tubes in the power amp is weak. This would cause the amp to distort sooner.
Of course, there are always a number of other possibilities.
You're right on the verge where distortion usually starts in an SVT-CL, though this is dependent on how hot your bass is. But generally, right around that area is where it starts.
What kind of tubes did you get? It's possible that one or two are ka-flooey or low gain, so David's advice is right on and you might want to get your tubes tested, but to be honest, it sounds pretty much like business as usual to me.
the tubes are 6550VE tubes
I just went through the whole biasing testing and it did need some minor adjustments. I really hope this makes a difference as , as you know, the tubes for these puppies are not cheap.
Any other suggestions still welcome.
If after the adjustments there is no change, now I am unsure whether it is business as usual or I should take it in.
When doing the bias, make sure that the amp is well warmed up. Ampeg recommends 20 minutes in playing mode (standby off) but I find that it can take up to an hour for the bias setting to stabilize.
Also keep in mind that the line voltage affects the bias. If you set the bias at home and then go yo a venue where the wall voltage is higher or lower, it can depending on how much the voltage differs, affect the bias and other voltages in the amp. This will affect how it sounds.
VE? Very economical? Variable Emmission?. Vaguely effective?
When I buy tubes I buy guaranteed new old stock by known respected makes.
I have a healthy disrespect of new production tubes and Auto/LED based bias circuits are usually an utter disaster.
Get a decent matched set of JAN GE6550, They have a service life in excess of 10,000 hours.:bassist:
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