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Powering (problems?)
MUFF WIGGLER Forum Index -> 5U Format Modules  
Author Powering (problems?)
Dob
Hi all!!

I seem to have troubles with powering. But I'm not sure.
I'd like to know how to find out what the problem is.

I've got a 66 space system, with a dotcom QPS1, which is advertised as being able to power up to 66 modules.
Still, any digital module I add (after removing an analog one) seems to be troubled. Now I've added a Waveplane oscillator that doesn't track v/oct well, it will go off within an octave. Paula acknowledged that bad powering could cause this.

The questions I have is; dotcom modules are probably mainly analog, does that mean that if Roger says it will power 66 spaces, he means "of analog (dotcom) modules"? Do digitaal modules ask more power? I've got quite a few of them now, an env by SSL, 2 Mutable Instruments (Clouds and Rings) , a Morphing Terrarium, not sure about the 2 Moon Modular trigger modules!?

Also, how would I know for sure there's a power problem?
daveholiday
I would recommend building your system on modulargrid to see get some ballpark numbers regarding your system as a whole. Compare those to the output specs of the QPS1. It is a easy way to see if you are close to your limit.
daveholiday
So I went back and read my spec sheet, I too use a QPS1, looks like 1500ma on the 15 volt rails, 6000ma on the 5v. Rogers description reads will power 66 "spaces" not modules. So I would put all your modules into modulargrid and just see where you are in terms of consumption.
daveholiday
The other thing I might suggest is with a decent test meter, monitor each of your rails while you are powered up. That might show you if something funky is going on. If your digital modules are giving you fits I would look closely at the 5v rail.

I am not a modular power expert...but I did stay at a Holiday Inn Express last night.....
levelhead3
Dob wrote:
The questions I have is; dotcom modules are probably mainly analog, does that mean that if Roger says it will power 66 spaces, he means "of analog (dotcom) modules"?


I think so, and even in the analog realm my sense is that dotcom modules tend to be fairly efficient power usage-wise.

I was running a single QSP5 (same internals as the QSP1) on a (very) mixed manufacturer 48u system, thinking I had plenty of overhead. All but maybe one or two of my modules are analog, and none have LED displays or anything like that.

Then I checked my system's current draw using Modulargrid and quickly discovered how wrong that assumption was - I was already well over 1.5A on the +15v rail.

So take the "66 space" rating only as a rough guide, especially if you're using modules from multiple manufacturers.
Dob
OK. So it's going to be a check at modulargrid for starters...
Dob
Finally got to setting up my stuff on modular grid.

https://www.modulargrid.net/d/racks/view/1068775

It seems I have 10 modules with no known power consumption on modular grid... so I guess I will have to go and find out?!
Dob
Does seem that it might be more efficient to get some sort of power consumption measurement going on?
Anyone have experiences with that?

Or should I just go and buy the "biggest" dotcom powering there is and safe the hassle...?
Can someone peek at my system and... give it their gut feeling?
https://www.modulargrid.net/d/racks/view/1068775
Ockeghem
Do you have a 44-space and a 22-space, or three 22-space cabinets?
How are your power interfaces and/or control modules set up?
My gut feeling is that the digital modules may be part of the problem, but it’s a lot of unknown variables right now.
Just me
I run a power supply in every other cabinet. I no longer have issues related to power.
Ockeghem
Hmm, you have three interfaces. If you have a 44 and a 22 you only need the q137 on the 44 connected to one power interface on the 22.
If, as I suspect, you've three 22s, then I’m not really sure you can daisy chain the interfaces. Roger's example setups on his page don't seem to do that.
Ockeghem
I too tend to use just me's rule and it works...
Three cabs, minimum two power supplies.
hsosdrum
My system (below) has a QPS-1 powering the 44U cab and a second QPS-1 powering the two 22U cabs, and I have no power problems (and no ground loop problems between the 2 supplies either).



Recommended rule: 1 x QPS-1 for every 44U (spaces, not modules).
levelhead3
hsosdrum wrote:
Recommended rule: 1 x QPS-1 for every 44U (spaces, not modules).


This is a good rule!

Also remember, current reserves never hurt. Other than financial, there is no reason not to over-spec your power supply.

And once you factor in all your time & the headache of dealing with these maybe-power-related gremlins, in my eyes it's a no-brainer to just over-spec from the get-go.

Because then if you still have problems you know for SURE it's not related to current-starved modules, and you can narrow down the actual problem that much easier.
Dob
Ah.... thanks everybody.

I've got 2 22-space cabs, and 1 home-brew cab with 25-ish spaces (mixed MU/MOTM format), all daisy chained to 1 power supply.

I think I've pinpointed the problem then.... I've searched in my emails and found out I'm powering everything with 1 QPS1. Somehow in the back of my head I thought I invested in the QPS3... but no I didn't.

Wouldn't it be wiser to have 1 QPS3, instead of a second QPS1, to avoid ground loops?

Ockeghem
QPS1 = 66 space capacity
22 + 22 + 25 = 69
69 > 66
That looks like the problem then smile
Quote:
Wouldn't it be wiser to have 1 QPS3

That should also work, and allow for expansion.
hsosdrum
Dob wrote:
Ah.... thanks everybody.

I've got 2 22-space cabs, and 1 home-brew cab with 25-ish spaces (mixed MU/MOTM format), all daisy chained to 1 power supply.

I think I've pinpointed the problem then.... I've searched in my emails and found out I'm powering everything with 1 QPS1. Somehow in the back of my head I thought I invested in the QPS3... but no I didn't.

Wouldn't it be wiser to have 1 QPS3, instead of a second QPS1, to avoid ground loops?


If you plug both QPS-1s into the same power strip you shouldn't have any ground loop problems between them. Ground loop problems can arise when they're plugged into different outlets or AC power circuits.

If you do decide to use a single QPS-3, bear in mind that Dotcom states that it's too large to fit into a Dotcom portable cabinet or a 22U studio cabinet. it's 15-1/8" x 5" x 5", and you'll need room beyond that for the harness.
Dob
Yeah I see the QPS3 is big... It would get tricky even in my deeper bottom cab.
But hey, getting a second QPS1 would allow me to take 1 or 2 cabs out elsewhere, and be self contained/powered...
I see advantages there.
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