Blues Deluxe to ODS #183 Thread

[pompeiisneaks]

oh and guitar volume definitely impacts it/makes it go away (at 0 that is, even at really low levels it does go away but anything above 1 or 2 on the guitar volume and it happens). It only happens with single coils. Not humbuckers. It is, though, nasty and I'd assume that a single coil, although adding hum, shouldn't add nasty oscillations.

~Phil

[pdf64]

Rather than routing it away from, I suggest to twist the plate wire to its grid wire, at least as much as is feasible.
And likewise for the next stage at least.
Sometimes, contrary to normal good practice, it can help to have the grid stopper at the ‘other’ end of a screened cable run, rather than at the tube socket end
Is the layout somewhat topsy turvey, eg wouldn’t the ‘physical’ signal flow be better if the other triode section of the tube was used for the input stage?

[pompeiisneaks]

Rather than routing it away from, I suggest to twist the plate wire to its grid wire, at least as much as is feasible.
And likewise for the next stage at least.
Sometimes, contrary to normal good practice, it can help to have the grid stopper at the ‘other’ end of a screened cable run, rather than at the tube socket end
Is the layout somewhat topsy turvey, eg wouldn’t the ‘physical’ signal flow be better if the other triode section of the tube was used for the input stage?

I've tried putting a 33k at the jack side so I get 66k total, 33k at each end of the connection, just to try and cover bases. No luck.
I'm not sure about the layout being topsy turvy? I'm using the second half of the triode as the first input and the first half as the second gain stage. This is how the amp was designed and xtian has built one this way as well.

I've tried playing in two different places in my house but not another house. It's currently plugged into a furman floor style filtering power supply that is also plugged into a rack mount furman power conditioner, but that isn't necessarily a guarantee of clean power.

~Phil

[xtian]

I'm going to suggest that what we're hearing is not oscillation from the circuit, but high frequency RF noise picked up by the single coils. So I repeat my questions:

You say this is only with single coils? And does the noise vanish if you turn the Volume of the guitar OFF? If yes, do you get the same noise in other rooms of the house? Other houses?

[pompeiisneaks]

oh and guitar volume definitely impacts it/makes it go away (at 0 that is, even at really low levels it does go away but anything above 1 or 2 on the guitar volume and it happens). It only happens with single coils. Not humbuckers. It is, though, nasty and I'd assume that a single coil, although adding hum, shouldn't add nasty oscillations.

~Phil

and

I've tried playing in two different places in my house but not another house. It's currently plugged into a furman floor style filtering power supply that is also plugged into a rack mount furman power conditioner, but that isn't necessarily a guarantee of clean power.

~Phil

[pompeiisneaks]

Except I lied and now it's happening with nothing plugged into the input jack WTF.

I'm about to pull all of my hair out. It's happening with humbuckers as well.

~Phil

[pdf64]

It sounds like oscillation to me
I strongly suspect that the layout is contributing to this, and that swapping the input stage to the other triode section would be beneficial. And twisting the plate and grid wires.

[pompeiisneaks]

It sounds like oscillation to me
I strongly suspect that the layout is contributing to this, and that swapping the input stage to the other triode section would be beneficial. And twisting the plate and grid wires.

I'm assuming it is too, but I don't understand how. I did try pulling the grid and anode wires and somewhat 'spinning them around one another' to no change.

Why would using the first or second triode matter? the wires are physically closer to the second triode for the first half of the first stage on purpose, per the board design. So I'd be crossing the wires between stages to do that... is that wise?

Right now, the state of the OD is unusable for any guitar, I have the amp 'on' and can hear massive noise, and when I touch the tip of the input jack it goes more towards a normal 60 cycle hum, but no squeal anymore.

Do I have a bad input jack that's somehow microphonic and the more I'm messing with it, its' getting worse?

~Phil

[xtian]

Do I have a bad input jack that's somehow microphonic and the more I'm messing with it, its' getting worse?

In your photo, I can't see where the shield of the shielded input wire is grounded. And where is the input jack grounded? To the chassis? Where is the PCB's Preamp Ground grounded to the chassis? In theory, all three should be grounded to the same spot on the chassis, near the input jack. And the opposite end of your shielded cable should not be grounded.

[Charlie Wilson]

Yeah I'm also thinking some kind of grounding issue. Check and make sure that everything that is supposed to be grounded, is.
CW

[pompeiisneaks]

They all ground to the same grounding lug on the chassis right next to the input jack. You can see the black wire coming down from the jack in the picture I posted, and the bare wire coming from the shield as well, and the preamp ground, not visible in that pic, is also connected to that ground lug.

I did figure out why the jack is still 'acting odd' now, the switch seems to have gotten pushed up a bit with all the work I did, and I'm having a hell of a time getting the switch to set right so that when the jack isn't engaged, it's connected, but when it is, the tip actually touches the jack... both are a bit 'off' now. I'll fight that for a bit, and see, but it's likely not the problem,

The oscillation still is a problem, though.

~Phil

[xtian]

FWIW, I have finished populating my Rev B PCB, and will have a donor amp (Carvin XV-112) to put it in next week.

[pompeiisneaks]

FWIW, I have finished populating my Rev B PCB, and will have a donor amp (Carvin XV-112) to put it in next week.

I'm starting to be suspicious of the shielded cable. I'm tempted at this point to remove it completely and just jump in a regular wire as a test to see. (not that shielded wire is bad, just THIS is bad).

I gave up today as the frustration level was making me go mad.

I'll probably replace the jack as well, as I think I've buggered it up too bad at this point.

~Phil

[sluckey]

If you want to eliminate everything on the input, just put a ground clip directly on the tube grid pin.

I've had mixed results fixing bent switch contact on switchcraft jacks. It's usually easier and more reliable to just replace the jack.

[pompeiisneaks]

If you want to eliminate everything on the input, just put a ground clip directly on the tube grid pin.

I've had mixed results fixing bent switch contact on switchcraft jacks. It's usually easier and more reliable to just replace the jack.

yeah this one had a weird issue to start, where the switch was bent too much off the bat, and it was still engaged when I had a cable plugged in. I think I might have done something trying to fix that.

I agree it seems like too much of a PITA to try and fix it, I'm pretty sure I have spares, so I'll get a new one and put it in, and to rule out the shielded wire, I'll just connect a simple wire and make sure that's not doing the same thing. If it's still happening I'll replace the shielded wire.

~Phil