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Ever open up your wall wart? Mine was a surprise...
Old 3 weeks ago
  #1
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Ever open up your wall wart? Mine was a surprise...

I recently picked up a GAP 73 mkII to have something cheap in my apartment for spur of the moment song ideas, and recently read about someone upgrading the caps and such in their wall wart to improve the noise floor in their pre.

So, I decided to open mine up and found....a giant transformer. Nothing else, just huge iron, haha. By the way, this was an aftermarket power supply 'specifically' for this pre, no idea what an original one would be like.

Anyone else ever crack open their wall warts before and try and upgrade the components?

Also, it was quite warm when I went to unplug it, even though the unit hasn't been powered on in a day!

[IMG][/IMG]

Last edited by Carabinerx; 3 weeks ago at 12:10 AM..
Old 3 weeks ago
  #2
Lives for gear
The transformer is no surprise, since pretty much any PSU will have a transformer in it (unless it's a switch mode PSU)

There should be a rectifier in it though, are you sure it isn't hiding beneath the transformer? The text on the case is a bit too fuzzy to read, does it output DC or AC?

Also, be careful.
Old 3 weeks ago
  #3
Gear Nut
 

What else did you expect?
Old 3 weeks ago
  #4
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Matti's Avatar
It should be 24V. AC
Old 3 weeks ago
  #5
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JayTee4303's Avatar
Firefighter told me old wall warts start a lot of fires. Just one of many reasons my racks have master power switches which are shut off at the end of the day.
Old 3 weeks ago
  #6
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mbvoxx's Avatar
makes perfect sense...it transforms....
Old 3 weeks ago
  #7
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bitman's Avatar
That's perfectly normal. The rectifier bridge is on the GAP PCB and filter caps too - most likely anyway.
Old 3 weeks ago
  #8
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Quote:
Originally Posted by Carabinerx View Post
...

Anyone else ever crack open their wall warts before and try and upgrade the components?

Also, it was quite warm when I went to unplug it, even though the unit hasn't been powered on in a day!...
I had two GAP 73 preamps. They're among the few products that use an AC-only input, and do all the DC conversion work inside the red case. The original power supply is also simply a step-down transformer.

The primary current from the wall is always flowing in this transformer, so there's some power dissipated that you're detecting as warmth. The best answer is to use a power strip that has switches for each outlet. In that way, you can ensure that things are really "off" when you want them to be off. In addition, there's an increment of additional safety that's achieved.

Most wall warts are switching mode power supplies that supply DC volts. That's probably the type about which you were reading. I'm glad you stopped when you did. Power supplies are no longer simple linear devices that are easily modified, and of course, they're inherently dangerous when you're attempting to measure things with covers removed.
Old 3 weeks ago
  #9
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Gotcha, the transformer was no surprise but I did expect to see more — it sounds like it’s all internalized in the pre. I’m definitely going to take precautions about it continuing to draw power, the strip is a good suggestion (that’s what it’s using currently, I just wasn’t shutting it off before). I take it the more complex power supply I was expecting is generally found (more often) in tube pres...like I said this was a new thing for me, to investigate the wall wart on my recent gap purchase.
Old 3 weeks ago
  #10
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MarkF48's Avatar
Besides trying to avoid fitting a transformer into the box of the GAP73, keeping it outside the box reduces the chance that hum producing AC magnetic flux gets into the high gain circuitry and makes design somewhat easier.
My Warm Audio WA12 also uses an external transformer like the GAP73.
Old 3 weeks ago
  #11
It's warm because tranformer's primary side is fed all the time, even when your device is switched off.
Old 3 weeks ago
  #12
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12ax7's Avatar
 

Quote:
Originally Posted by MarkF48 View Post
Besides trying to avoid fitting a transformer into the box of the GAP73, keeping it outside the box reduces the chance that hum producing AC magnetic flux gets into the high gain circuitry and makes design somewhat easier.
My Warm Audio WA12 also uses an external transformer like the GAP73.
Well, yeah...

...But that's NOT the real reason why so many boxes are designed to use wall-warts and line-lumps:

The REAL reason is that (in most jurisdictions) if your box uses less than a certain voltage, it does not need to be certified by Underwriter's Laboratories in order to get insurance (against folks getting hurt by your box).

If they use an off-the-shelf (or OEM) external power supply, this cost has already been borne by the folks who made the wall-wart.

This is a MAJOR cost-cutting move (and nothing more).

What GAP did was to use nothing more than the (outsourced) transformer, then finish the job on their own (inside the box).

...Not really stupid at all!
Old 3 weeks ago
  #13
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MarkF48's Avatar
Quote:
Originally Posted by 12ax7 View Post
Well, yeah...

...But that's NOT the real reason why so many boxes are designed to use wall-warts and line-lumps:

The REAL reason is that (in most jurisdictions) if your box uses less than a certain voltage, it does not need to be certified by Underwriter's Laboratories in order to get insurance (against folks getting hurt by your box).

If they use an off-the-shelf (or OEM) external power supply, this cost has already been borne by the folks who made the wall-wart.

This is a MAJOR cost-cutting move (and nothing more).

What GAP did was to use nothing more than the (outsourced) transformer, then finish the job on their own (inside the box).

...Not really stupid at all!
Yup... that's another reason as well
Old 3 weeks ago
  #14
Lives for gear
Quote:
Originally Posted by 12ax7 View Post
Well, yeah...

...But that's NOT the real reason why so many boxes are designed to use wall-warts and line-lumps:

The REAL reason is that (in most jurisdictions) if your box uses less than a certain voltage, it does not need to be certified by Underwriter's Laboratories in order to get insurance (against folks getting hurt by your box).

If they use an off-the-shelf (or OEM) external power supply, this cost has already been borne by the folks who made the wall-wart.

This is a MAJOR cost-cutting move (and nothing more).

What GAP did was to use nothing more than the (outsourced) transformer, then finish the job on their own (inside the box).

...Not really stupid at all!
It actually makes a lot of sense from a manufacturing and design point of view. Lower the volatage with an of the shelf transformer wall wart and do all the bridge anf filer design in the box. Also, that transfo would likely turn the pre into a 2u box.
Old 3 weeks ago
  #15
Quote:
Originally Posted by j.frad View Post
What else did you expect?
A Decepticon?
Old 3 weeks ago
  #16
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Brian M. Boykin's Avatar
I use these and have them plugged into a power conditioner. They work great if the wart is not inline with the cable. I’d suggest only one of these per conditioner. You can also mount this away from other equipment and prevent potential hum.
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Ever open up your wall wart? Mine was a surprise...-e2bbb069-4566-4fb6-aed2-2ef0d9389d55.jpg  
Old 3 weeks ago
  #17
Manufacturers use these wall wort supplies to avoid expensive safety certification which can run into $10,000 or more per product. The wall worts are already safety certified so then they can avoid the entire thing.
Old 3 weeks ago
  #18
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12ax7's Avatar
 

Quote:
Originally Posted by Jim Williams View Post
Manufacturers use these wall wort supplies to avoid expensive safety certification which can run into $10,000 or more per product. The wall worts are already safety certified so then they can avoid the entire thing.
Yep...

...And you said that in a whole lot fewer words than I did back at Post #12!
.
Old 3 weeks ago
  #19
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MarkF48's Avatar
Rane's spin on use of external transformers which is generally echoed by other manufacturers as well and what I was familiar with when I was in electronics development and manufacturing years ago.....

https://www.rane.com/rap.html
"Reasons To Use External Power Supplies

Better Audio Performance. Removes the hum source, i.e. the AC line transformer and all primary circuits resulting in quieter noise performance, without the usual (and annoying) 50/60 Hz and 150/180 Hz hum components.
Increased Safety. Remove the AC primary circuits from the unit and you remove the shock hazard. Remove the shock hazard and you remove the requirement for safety agency compliance. All RAP units qualify worldwide as Safety Extra Low Voltage (SELV) units, i.e., no shock hazard.
Agency Compliance Exemption. By using remote power supplies and sizing them correctly all products powered by them become as exempt as possible from safety agency compliance - only the power supply itself must comply with each safety agency.
Quicker Product Development Time. Eliminates the (considerable) time required to develop a separate power supply for each new product. Getting a transformer correctly sized and located is much more of an art form than a science. Each solution is unique and requires much trial and error - a very time consuming task. Making a product work is much easier than making it work without hum in the noise floor. A tedious thankless job. Rane could not have developed as many products as it has without external power supplies.
Faster Product Manufacturing. Eliminates the time spent on issuing, prepping, installing and testing transformers, line cords, grommets, brackets, hardware, fuses, holders, insulation, hum barriers and shields for each product built. Rane could not build all the units it does each month without external supplies."
Old 3 weeks ago
  #20
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Brian M. Boykin's Avatar
I have 16 channels of Symetrix SX202 which require a 16vac wallwart per 2 channels. I’m using them for a mobile recording rig. I’m currently looking for a power One module I can put in a 1u or 2u 19” rack case and create a distribution block to power all 8 boxes. I’ve had zero luck but I’ve been half heartedly trying. Another possible solution if you hate wallwarts that much. I could easily pull the transformers out of their enclosures and rack them I guess. It’s mostly for space savings and cleanliness.
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