JJ ecc803s in gainsection causing scratchy pot!!

[MikeD]

Well, like it says, I just replaced my gain-pre´s with JJ ecc803s and when I turn it on...scratchy pot?? switched between them, sovtek and the pps and when at least one of the JJ´s is in the mix, scratchy gain. It works great in the PI (really does work nice tone wise) but no can do in the prea amp section or even the Clean pre, cause I can hear it scratch there to!!.

On another note I noticed that both gain tubes were marked ECC83 whilst the Clean was marked E83CC. Anyone got any thoughts there??

[FleshOnGear]

I have a theory. The grids are drawing current, and that's causing a DC voltage at the wiper of the gain pot. Since most modern Oranges use dual ganged gain pots, with a section between 1st and 2nd stages, and 2nd and 3rd stages, it doesn't matter which position you put the ECC803 within the dirty channel. This isn't normal, of course. Do you think the seller would be kind enough to take them back?

[MikeD]

I have a theory. The grids are drawing current, and that's causing a DC voltage at the wiper of the gain pot. Since most modern Oranges use dual ganged gain pots, with a section between 1st and 2nd stages, and 2nd and 3rd stages, it doesn't matter which position you put the ECC803 within the dirty channel. This isn't normal, of course. Do you think the seller would be kind enough to take them back?

Yes he probably would, but it works great in the PI position so I'll just keep one as an extra. It's too bad cause they sounded great in the gain preamp section too

[Les Paul Lover]

Could it be that your valve is Microphonic?

I had a squealing at high volume ECC83 that caused mayhem in the preamp, but didn't cause any issue in the PI on my AD15 once.

[Valvelust]

Well, like it says, I just replaced my gain-pre´s with JJ ecc803s and when I turn it on...scratchy pot?? switched between them, sovtek and the pps and when at least one of the JJ´s is in the mix, scratchy gain. It works great in the PI (really does work nice tone wise) but no can do in the prea amp section or even the Clean pre, cause I can hear it scratch there to!!.

On another note I noticed that both gain tubes were marked ECC83 whilst the Clean was marked E83CC. Anyone got any thoughts there??

OR120 I just purchased the hz an khz pots are very scratchy, the khz when it's up past 2/3 it starts to squeal.
However I've got some pot cleaning and preamp tubes to play around with before evaluation further

[MikeD]

Could it be that your valve is Microphonic?

I had a squealing at high volume ECC83 that caused mayhem in the preamp, but didn't cause any issue in the PI on my AD15 once.

I had 2 that I tried, both seperatly in both gain sections and then together, and then in the clean. The result was the same. But it might just be 2 duds, but I dought this.

[MikeD]

I have a theory. The grids are drawing current, and that's causing a DC voltage at the wiper of the gain pot. Since most modern Oranges use dual ganged gain pots, with a section between 1st and 2nd stages, and 2nd and 3rd stages, it doesn't matter which position you put the ECC803 within the dirty channel. This isn't normal, of course. Do you think the seller would be kind enough to take them back?

Would this mean I got two duds or is it just that it's a different kind of 12ax7?

[Les Paul Lover]

I have a theory. The grids are drawing current, and that's causing a DC voltage at the wiper of the gain pot. Since most modern Oranges use dual ganged gain pots, with a section between 1st and 2nd stages, and 2nd and 3rd stages, it doesn't matter which position you put the ECC803 within the dirty channel. This isn't normal, of course. Do you think the seller would be kind enough to take them back?

Would this mean I got two duds or is it just that it's a different kind of 12ax7?

Very good question - can't answer it. The ECCxx valves are meant to be readily interchangeable, but it's possible that the ECC803 has a slightly different pin out / internal wiring that makes it unsuitable for your amp.

[a.hun]

I have a theory. The grids are drawing current, and that's causing a DC voltage at the wiper of the gain pot. Since most modern Oranges use dual ganged gain pots, with a section between 1st and 2nd stages, and 2nd and 3rd stages, it doesn't matter which position you put the ECC803 within the dirty channel. This isn't normal, of course. Do you think the seller would be kind enough to take them back?

It may or may not be that, but it is worth emphasising (again) that any DC voltages across pots will make them scratchy! So before replacing pots you want to be sure that there is no DC across them or you'll be solving nothing!


Andy.

[megalithic]

I have a theory. The grids are drawing current, and that's causing a DC voltage at the wiper of the gain pot. Since most modern Oranges use dual ganged gain pots, with a section between 1st and 2nd stages, and 2nd and 3rd stages, it doesn't matter which position you put the ECC803 within the dirty channel. This isn't normal, of course. Do you think the seller would be kind enough to take them back?

Would this mean I got two duds or is it just that it's a different kind of 12ax7?

Possibly you got two which are a bit off spec, or simply they don't work that well in that amp.

It is quite possible that they sound awesome in one amp and rubbish in another. I love the ECC803 in the Micro Terror, but I don't like the stock ECC83 in there. I do love the JJ ECC83s in another amp.

[FleshOnGear]

I have a theory. The grids are drawing current, and that's causing a DC voltage at the wiper of the gain pot. Since most modern Oranges use dual ganged gain pots, with a section between 1st and 2nd stages, and 2nd and 3rd stages, it doesn't matter which position you put the ECC803 within the dirty channel. This isn't normal, of course. Do you think the seller would be kind enough to take them back?

Would this mean I got two duds or is it just that it's a different kind of 12ax7?

The pinout on the ECC803 is the same as the usual ECC83/12AX7. There shouldn't be any issues with using that tube. Yes, it's possible you have two duds. It seems pretty unusual for two new tubes to arrive with the same fault, but I have no other explanation for why they would cause your amp to have scratchy pots. Well, maybe these tubes are more "detailed" and your hearing the scratchiness better than when other tubes are in it? Seems like a stretch...

[FleshOnGear]

I have a theory. The grids are drawing current, and that's causing a DC voltage at the wiper of the gain pot. Since most modern Oranges use dual ganged gain pots, with a section between 1st and 2nd stages, and 2nd and 3rd stages, it doesn't matter which position you put the ECC803 within the dirty channel. This isn't normal, of course. Do you think the seller would be kind enough to take them back?

It may or may not be that, but it is worth emphasising (again) that any DC voltages across pots will make them scratchy! So before replacing pots you want to be sure that there is no DC across them or you'll be solving nothing!


Andy.

Andy, you're totally right about that. I just wanted to be clear that I wasn't advocating replacing the pots. I was just saying that a faulty tube could put DC onto the pots.

[MikeD]

Many interesting answers leading of course to more questions. The tech I bought them from was questioning what I heard as well. There is no doubt that the scratchy came from the tubes.. the pots do not scratch at all with the originals or sovteks in place... dead quiet.

He's getting in a new batch of preamps next week and I'm planning on taking my amp there and testing them on sight... hopefully he will have a new shipment of the 803's so I can test them too and see if it really is a case of dud tubes.

[MikeD]

Ok, time for an update,

I took the amp to my tech (where I purchased it 2 years ago) and I made him listen so he didn´t think I was crazy. We then put in fresh 403s`s and then tried JJec83 and the same scratchiness occurred. Tried a sovtek and switched the PM;s around and no scratchypots.

His thoughts were soldering in a capacitor and he believes this would do the trick. I´m not technical enough to tell you exactly how that would work and seeing that we have a few gigs coming up I told him I´d get back to him on that.

After taking it home I´ve swapped through all the tubes and realized the problem is in the 1&2 gain pre-amp section. I can have a 403s in the PI and the 3-4th preamp slots and no scratchiness from the pot whatsoever.

So any new thoughts or words of advice from you guys?

[Les Paul Lover]

Ok, time for an update,

I took the amp to my tech (where I purchased it 2 years ago) and I made him listen so he didn´t think I was crazy. We then put in fresh 403s`s and then tried JJec83 and the same scratchiness occurred. Tried a sovtek and switched the PM;s around and no scratchypots.

His thoughts were soldering in a capacitor and he believes this would do the trick. I´m not technical enough to tell you exactly how that would work and seeing that we have a few gigs coming up I told him I´d get back to him on that.

After taking it home I´ve swapped through all the tubes and realized the problem is in the 1&2 gain pre-amp section. I can have a 403s in the PI and the 3-4th preamp slots and no scratchiness from the pot whatsoever.

So any new thoughts or words of advice from you guys?

If I read you correctly, sovtek and Pm valves didn't cause the pots to be scratchy and solved the problem?

If it is that, that would be my solution. Ditch the problematic valves....