Peavey Delta Blues

[Albert Kreuzer]

Albert, when you say "doubt its the chip though" can you expand on that? What comes to your mind?

I just wanted to say that I never had one of these go "hummy". In my experience they either work or they don't.
No idea what causes the hum, sorry.

Cheers,
Albert

[Dave Curtis, dB AudioTech]

So your saying if you turn the reverb down the hum is still there ? Try using the send out to another amp and see if the hum is still there or try another preamp into the return. Hum can be caused from preamp or power amp or bad tubes or badly mismatched power tubes.

Hum from bad tubes or badly mismatched power tubes is usually consistant, and not intermittant. They are, however the easiest thing to rule out, and should be 1st on the list. The power tubes are likely 6 years old and who knows how many hours are on them? Preamp tubes generally last a long time, but should be ruled out as a matter of course.

What does the DB have for tank connections? If they're RCA jacks/plugs, treat them with a Deoxit pen [1], although the problem sounds like it has something to do with the boost circuit.

[1]Radio Shack has Caig products; don't use Deoxit on tube pins, use ProGold.

[Steve A.]

Prob''y not, but the phrase 'half out of its socket' concerns me a bit.

Since the hum is more boost related than reverb ... if I read that right, then I'm probably look at the boost switching, the components that get switched and any rails that feed it.

The Delta Blues is not in my Peavey pile, so I'm working from generalities.

Hope this helps!

Don:

Here's the schematic and layout for the Delta Blues:

http://www.blueguitar.org/new/schem/...elta_blues.pdf

The boost circuit is the same as in the Classic 30: the treble cap is bypassed with a 0.047uF cap (which has a 220k resistor to ground).

One thought is that this boost circuit may have been altered by a previous owner- like maybe removing the 220k resistor for a bigger boost.

In any case I have always found the stock boost circuit in these amps to be way over the top. (The typical mid-boost circuit might use a cap ranging from 750pf to 2200pF but IMO 0.047uF is just too much.)

I do think that the IC must have been making a connection on all 8 pins or there would have been no reverb.

Since the IC is just a few bucks I think it wouldn't hurt to try swapping it out and seeing if that solves the problem. If it doesn't, well then we have a spare part in case we ever need one...

Steve Ahola

P.S. These Peavey amps are susceptible to a lot of hum, especially if you are using single coil pickups and are within a few feet of the amp. I don't see why having the reverb on would make a difference, though...

[pchilson]

I do use single coil guitars and I do sit within a few feet of the amp.
I picked up a TL082 but haven't had a chance to get back inside to change it out yet.
I have spoken with an aquiantence who had one a few years back and he said his would do the same hum from the reverb but it would just go away...I don't know if we were talking exactly the same thing, this was an over the phone conversation.
I need to get a fresh set of EL84s for it and eliminate bad tubes from the equation and see where it stands then.

Thanks for the help and if you think of something just holler...

[pchilson]

Ok, got the chance to change out the op amp, no change other than the reverb sounds better now, more pronounced so it was worth the change.

I have found that when the hum starts, as I stated earlier, it comes on when you add "boost" to the signal. The hum is consistant when not playing but if you strum the strings the hum subsides and then comes back when the strings stop vibrating. So you would never hear the hum if you are playing but stop and here it comes. Nothing affects the hum, it doesn't get louder or quieter with volume knob, only if you turn the reverb knob down or disengage the boost or hit the strings.
Again, I have not changed out the tubes but once I got rid of the nasty one the amp has behaved great with the exception of the reverb.
Also, the amp sounds great when playing.

Any thoughts on this?

Thanks

[Steve A.]

Ok, got the chance to change out the op amp, no change other than the reverb sounds better now, more pronounced so it was worth the change.

I have found that when the hum starts, as I stated earlier, it comes on when you add "boost" to the signal. The hum is consistant when not playing but if you strum the strings the hum subsides and then comes back when the strings stop vibrating. So you would never hear the hum if you are playing but stop and here it comes. Nothing affects the hum, it doesn't get louder or quieter with volume knob, only if you turn the reverb knob down or disengage the boost or hit the strings.
Again, I have not changed out the tubes but once I got rid of the nasty one the amp has behaved great with the exception of the reverb.
Also, the amp sounds great when playing.

Any thoughts on this?

Thanks

I've had tubes start humming when it was particularly loud on-stage- this was like a low A sharp note which kept feeding back. The bass player kept shouting "Key of A! Key of A!" I had to turn the amp (my Deluxe Reverb Reissue) off for a minute to get it to stop howling.

When you had the chassis out did it look like there had been any mods done? With the back of the printed circuit board presumably coated, it can be very noticeable if any parts were replaced.

You might want to check to see whether one or both of the cables going to the reverb pan have a good ground. (I think Enzo here would know if having both cables grounded could cause a ground loop.)

Steve Ahola

[tbatart]

Peavey Delta Blue 12ax7 issues

Does anyone know if the Delta Blue 12AX7's are wired in series or parrallel and what is their source of the power (AC or DC)?

The specs I read are not specific in this area.

Thanks!

[Steve A.]

Does anyone know if the Delta Blue 12AX7's are wired in series or parrallel and what is their source of the power (AC or DC)?

The specs I read are not specific in this area.

Thanks!

The Delta Blues, like the Classic 30, uses DC for the preamp tubes and AC for the power tubes. Each string is wired up in series so if you remove one tube, the other filaments will not light up.

It's all in the schematic (specs and sales blurbs are often wrong or misleading).

steeve

P.S. I never use the Boost switch but the fact that the hum is also there when a stomp box is used does concern me. I think it would be a good idea to put in a matching set of output tubes, and also try swapping out the preamp tubes one at a time. No sense going crazy trying to fix a problem with a tube amp until you have first confirmed that the problem is not with the tubes!

[Enzo]

OK, so it is not "hum" we are fixing, it is a reverb pan feeding back.

Take the screws out and move the reverb pan and its bag outside of the amp cabinet. Let it sit on the table outside for now. Does that help?

The reverb pan is feeding back acoustically. Sometimes just moving it helps. SOmetimes flipping it over helps. If there is not one, cut out a piece of stiff cardboard to cover the open bottim of the pan and tape it in place, then all back into the bag.

Inside the reverb pan itself, are all four short corner springs intact?

The wide flat top surface of the reverb pan can ring. If there is not one there, stick a long strip of adhesive-backed foam weatherstripiing along the centerline. Car makers use this trick on the inside of large body panels on cars - it stops then from making sheet metal sounds.

And sometimes the only cure is a new pan.

[pchilson]

OK, so it is not "hum" we are fixing, it is a reverb pan feeding back.

Take the screws out and move the reverb pan and its bag outside of the amp cabinet. Let it sit on the table outside for now. Does that help?

The reverb pan is feeding back acoustically. Sometimes just moving it helps. SOmetimes flipping it over helps. If there is not one, cut out a piece of stiff cardboard to cover the open bottim of the pan and tape it in place, then all back into the bag.

Inside the reverb pan itself, are all four short corner springs intact?

The wide flat top surface of the reverb pan can ring. If there is not one there, stick a long strip of adhesive-backed foam weatherstripiing along the centerline. Car makers use this trick on the inside of large body panels on cars - it stops then from making sheet metal sounds.

And sometimes the only cure is a new pan.

Enzo, you are smack dab in the center of the bullseye
If you don't do this for a living, you should.
It absolutely was the pan feeding back. I moved it outside the cabinet as you suggested and it was quiet as a mouse. I wrapped the pan and the cardboard with double sided tape, put it back in the bag then back in the cabinet. Not a peep and the reverb sounds so much better with the new TL082 installed. Thank you so very much!

Now on to tubes. I realize its subjective but if I could ask for preferences for this amp on what power tubes to try even if its Sovteks. What have you used and like in the DB and why? What didn't you like in this amp? I need to pick up a quad and I will need to order them so whats your favorites? What should I try? Who from?

You guys on this forum are an invaluable resource and I thank you for sharing.

[Enzo]

There are only so many brands of EL84 to choose from, and they don't tend to last all that long in guitar amps anyway. I suggest you just try the several brands and see if you have a preference. I have no complaint about the Sovteks or the JJs, they are good tubes. They sound different. But just because I like one better doesn't mean you will.

[Don Moose]

Don:

Here's the schematic and layout for the Delta Blues:

http://www.blueguitar.org/new/schem/...elta_blues.pdf

P.S. These Peavey amps are susceptible to a lot of hum, especially if you are using single coil pickups and are within a few feet of the amp. I don't see why having the reverb on would make a difference, though...

Much obliged, Mr A.

I could see the reverb making it bigger if the source is before the reverb drive, but I haven't looked at the schemo yet.

I was thinking that a loose ground or other poor solder could the source - especially if there's a connector or cable the signal has to go through in boost mode - even more especially if it does so for boost and not for normal.

IIRC, in general the Peavey interboard wiring leaves a bit to be desired in the execution/durability area.

-- hey, just to be sure we're talking about the same thing - when you say 'boost' do you mean the boost switch that's part of the tone stack, or do you mean the OD section? I'll re-read the thread to see if that's already clarified, but if not ...

Hope I get to spend some time on this issue this evening. (suddenly fostering a 14-yo golden retriever in addition to the usual menage)

[Don Moose]

You might want to check to see whether one or both of the cables going to the reverb pan have a good ground. (I think Enzo here would know if having both cables grounded could cause a ground loop.)

Steve Ahola

You have 2 cables with 4 ends. I think the trick is to ground 3 of the shield ends and move that ungrounded end around among the 4 possible positions until you find the least hummy - I'd suggest starting with putting the ungrounded end at the receiving/recovery amp input.

My thinking goes:
- The drive end needs a good ground return to get the spring motor wiggling, so I'd think you need a solid ground there.

- The receive/recover end just needs a shield, it's a very sensitive input with tiny currents that shouldn't be bothered by having to go the long way 'round.

Reality may not agree with me, and neither may Enzo, so proceed in a way you can reverse what I suggested.

Hope this helps!

[pchilson]

Wow, thanks for the input guys. I really appreciate the help and ideas but read post 24 and 25. Enzo nailed this coffin shut. This amp is dead quiet now, hum wise that is...hehe

[CharlieP]

I would say a good re-tubing is in order anyway. If it still hums go from there but, tearing into the chassis before you rule tubes out doesn't make sense to me. You have an amp that is 8 years old and probably many of the original tubes are still in it. It has a right to hum with those old tubes.