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performingchimp
Copper Member
United Kingdom
10 Posts |
 Posted - 07/04/2008 : 17:40:04
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Hello all,
I have a DD7, the new Boss delay. It is great, but has added a faint but annoying hum to my chain. The frequency suggests it is mains hum, so I am assuming there's some earthing issue. Also, the cable that connects to the input is very loud and crackly if I move it. Really banging.
I've isolated the problem to my LS-2 line selector. The hum and loud cable crackle does not occur unless the LS2 is connected in my chain. It immediately precedes the DD-7. SO the problem is either the DD7's input, the LS2's output or more likely neither is actually faulty, its just that they hate each other.
Oddly, this problem never occurred with my DD5, so there is some reason why the LS2 and DD7 do not get along.
I think the loud cable crackle could be an earth connection banging about as it connects and disconnects willy nilly as I waggle the cable.
Any ideas of a solution? Is there some way I can disconnect the ground from the LS2's output socket (ideally without risking future death)? Or use an unshielded patch cable?
I am at a loss.
Jon
P.S. For those interested: The LS-2's job in my chain is to blend two signals. I have two pickups in my guitar running at the same time - they both go through their own EQ pedal, then one pickup runs into a couple of effects (OD, Octave), then these two EQd/effected signals go into the LS-2, where they are blended into a single mono signal, which goes into the DD-7 (then into a Verbzilla reverb in stereo).
I also use the DD7 as a mute pedal, for when unplugging my guitar, etc.
http://www.jongomm.com/images/Jons_pedal_board_big.jpg
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bossarea
Forum Admin
United Kingdom
3652 Posts |
Posted - 07/04/2008 : 20:35:34
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What power supply are you using? Boss pedals are notoriously fuzzy about the quality of the adapter and it wouldn't surprise me if the DD-7 is even worse than the older ones. If there's a tiny bit of hum early on in the chain it will get amplified up as the signal goes through the different pedals. Sometimes it's easy to give a pedal the blame while it really takes the whole chain for the hum to become audible.
I would borrow a different power supply and test that out first. |
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performingchimp
Copper Member
United Kingdom
10 Posts |
Posted - 07/04/2008 : 20:58:03
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I've tried it on batteries with nothing before it in the chain. It's not an amplified sound, it's a new sound.
I think it might be the input connector. I'm gonna return it as it's under warranty. |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 07/05/2008 : 03:37:16
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Hi performingchimp
Like a lot of the newer COSM digital Boss Pedals.
The DD-7 needs to have it's own dedicated power supply.
And preferably not a switch mode one.
See if it still happens with an old transformer based power adapter.
Same goes for the other newer pedals.
It has something to do with the mixing & interference of the internal Analog signal ground, & the Digital round.
Or it might be the intermodulation, that is created by the frequency of the switch mode power supply & the frequency of the On-board digital clock/s, that run the pedal.
You didn't say if the noise is still there when you run it off a battery.
BTW, they DD-7 has a very high current consumption, & I wouldn't be surprised if the battery last less than 15 mins.
Regards Dr. Bob |
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performingchimp
Copper Member
United Kingdom
10 Posts |
Posted - 07/06/2008 : 15:10:27
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Yes the hum is still there from a battery.
There's no reason I can see why the reasons you describe for using a dedicated PSU should reslut in extra ground hum, though! There's no reason why analog/digital issues or clocking should have any relation to earthing!
They tell you everything needs its own PSU these days, not just Boss, but other manufacturers too. Mostly I believe they say it to avoid complaints. There can be issues between pedals, for sure, but they can be fixed mostly I think with some modification to the cables or PSU.
I suspect the input jack socket is not shielded because something is loose. Boss use very crappy connectors anyway. |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 07/06/2008 : 15:27:49
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quote:
Originally posted by Dr. Bob
Hi performingchimp
Like a lot of the newer COSM digital Boss Pedals.
The DD-7 needs to have it's own dedicated power supply.
This is certainly optimal... but I have my DD-7 at the end of my chain supplied by my home-built linear supply that is runnning 12 pedals (containing every type of electronics from a DM-2 to the DD-7) - with no issues. It is completely transparent and just "does it's job".
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 07/06/2008 : 15:44:51
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Hi Laurie
quote:
my home-built linear supply
I've seen your power supply, and I'm telling you it looks more like the:
Linear Accelerator
Out of Star Trek. 
That's one awesome bit of gear you built.
even if it is about 22 feet long.... (just kidding).
Regards Dr. Bob
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Edited by - Dr. Bob on 07/06/2008 15:45:47 |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 07/06/2008 : 15:53:12
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Hi performingchimp!
quote:
Originally posted by performingchimp
There's no reason I can see why the reasons you describe for using a dedicated PSU should reslut in extra ground hum, though! There's no reason why analog/digital issues or clocking should have any relation to earthing!
Analogue and digital grounds exist uneasily together. If precautions aren't taken, digital noise will always leak to the audio - usually over the ground rail. When digital circuits change state, there is an instant of theoretical infinite current. This never happens in reality of course, but there are always high frequency small spikes on the power supply from the digital circuits "doing their thing". Analogue circuits by their very nature simply don't do that, and more importantly, any noise on the power supply will be amplified by the analogue circuit.
Often all that is required is an inductor between the digital and analogue ground points (inside the device). Even when the digital noise has been sorted inside a given device by the manufacturer, noise can leak across to other devices on the +ive supply rail - it would require a power supply with "infinite" current capability to ensure that doesn't happen - instead the conventional wisdom is to only have one pedal per supply so the digital noise can't leak between pedals.
Sometimes you can get lucky - in my post above I noted that the 12 pedals I have on one linear supply all coexist happily. It should be noted that I have been painstakingly careful with the grounding and spike handling capability of the supply (it's not just any old store bought supply).
quote:
Originally posted by performingchimp
I suspect the input jack socket is not shielded because something is loose.
If you can feel/hear something loose, then it's defective for sure! Problem solved - get them to swap it for another one
quote:
Originally posted by performingchimp
Boss use very crappy connectors anyway.
I have a different opinion - I've done maintenance on HEAPS of pedals and have found the Boss connectors to be fairly robust. They tend to get dirty and noisy fairly easily, but a touch of contact cleaner fixes them every time.
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Edited by - Laurie on 07/06/2008 16:01:37 |
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performingchimp
Copper Member
United Kingdom
10 Posts |
Posted - 07/08/2008 : 02:44:06
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Thanks for the great reply, Laurie! I don't know, maybe I have bad luck with the connectors!
I'm convinced this one is faulty now and have sent it back! Hopefully that'll sort out my humming problem too. We shall see.... |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 07/16/2008 : 15:09:13
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| Hi performingchimp! Did you get the DD-7 swapped for a new one? Did it fix the problem? |
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Topic |
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DD-7 woes.....
