Power Supplies: Linear vs. Switched Mode???

[E5RSY]

What's the rub, here? I know the standard is kinda shifting over to switched-mode units. But, high quality outfits like Walrus Audio still market linear supplies (not to mention the Vodoo Lab products are still selling well). Does it really matter all that much? I've heard lurid tales of linear supplies with their toroidal transformers introducing hum to a rig when tucked underneath a pedal board. Has Walrus Audio figured out a way to avoid this, or are they also due for a move to switched-mode units?

Thanks, in advance, for any education on the issue.

 

[E5RSY]

Nobody got nuthin' on this???

 

[redhouse_ca]

What's the rub, here? I know the standard is kinda shifting over to switched-mode units. But, high quality outfits like Walrus Audio still market linear supplies (not to mention the Vodoo Lab products are still selling well). Does it really matter all that much? I've heard lurid tales of linear supplies with their toroidal transformers introducing hum to a rig when tucked underneath a pedal board. Has Walrus Audio figured out a way to avoid this, or are they also due for a move to switched-mode units?

Thanks, in advance, for any education on the issue.

This is not guitar specific but I just read a posting by Benchmark (the audio company) about their change to switch mode for their hifi amp. I thought it was pretty interesting and their are clearly some interesting implications if done right (for hifi, at least). I make a pretty good opals based phono preamp (not as a business, I made one that my friends and I really like and they asked me to make one for them too. Im using a wall wart power supply intentionally, as it's far from the amp and I can clean up the DC with far fewer parts and regulate precisely for the op amps i am using. I don't think I'll ever build another power supply for a preamp.

Here's the link:

Audio Myth - "Switching Power Supplies are Noisy"

This Myth Goes Something Like This: "Switching supplies are noisy." "Linear power supplies are best for audio." We disagree!

benchmarkmedia.com

 

[guitar_paul1]

IMHO

Switchers are a lot more difficult to repair, lighter, and often cheaper. I can't tell any audible difference, at least in my limited amount of stuff.

If you are testing a switcher for output, some designs shut down without a load. Therefore you have to remember to test them under load.

I like (my) old stuff that's easy to fix, so that's my personal bias.

Any transformer can induce hum in a high gain circuit if it's too close to a signal line. A toroidal should do it less because the magnetic flux stays in the core better (no corners).

If everything is properly designed and shielded, volts is volts.

 

[24 track]

I dont know if this is relevant or not
but I made an ATX switching power supply ( from an old computer) into my+12, -12, +5 powersupply for my euro rack system , it gave +12V @16 amps, -12V @1 amp, +5V @ 22amps , ( maximum) with very little issue , and by using buck converters and/or 7809 (+) voltage regulators could be dropped to +9V using the +12V rail

tons of you tube videos on the subject , I havent tried this for a pedal supply , but there is a ton of current available to try this

I used the -12volt blue wire instead of the +3 volt orange wires, I placed a 8 ohm resistor from the 5 volt rail to ground to ensure there was a load on the supply ( just like in the diagram)
I also used 4 of each wires twisted together to ensure there was enough current to power my outputs with out taxing the supply

I hope this may help, but again it may not be what you are looking for BTW the +5 volt rail can power USB devices but wont transmit data.

 

[guitar_paul1]

8 ohm resistor seems like an awful lot of wasted power. W=E^2/R, so 3.125 Watts running all the time?
I'm thinking a 1k would be enough to get it to turn on if it's needed at all. I bet it's not even needed on that ATX.

 

[24 track]

8 ohm resistor seems like an awful lot of wasted power. W=E^2/R, so 3.125 Watts running all the time?
I'm thinking a 1k would be enough to get it to turn on if it's needed at all. I bet it's not even needed on that ATX.

I agree,
the conversion was for a bench supply so I followed that plan and tailored it to my needs , it works but 22 amps at 5 volts was not going to be an issue at all , the PCB I built for the euro rack used a 7805 regulator off the +12 volt rail so other than powering a few USB keyboards and a light the 5 volts from the supply is not being utilized at all , or more accurately barely at all.

it was recommended to put the 5 volts rail under load because depending on the year of the ATX some units had then internally some did not so in general it was a failsafe. and if used for a bench supply the draw could be hefty at some points.

 

[telemnemonics]

Almost like the tube vs SS debate, both work and each has pros & cons.
Transformer type needs to be kept away from certain pedals, plus is heavier.
Switching type has a rep for being cheap and disposable, not sure that is really true though?
Choose one and move on...

 

[Blrfl]

Switching type has a rep for being cheap and disposable, not sure that is really true though?

This isn't directed at you specifically, but it grinds my gears when people say things like that. Linear and switching are designs. What makes a power supply cheap and/or disposable (or noisy or unstable or a long list of other things) is the implementation. The cheap, disposable wall warts we've had for decades are linear designs and I've never heard anybody say that linear supplies have a reputation for being cheap and disposable.

Anybody own a Strymon Zuma? Trutone CS12? Voodoo Labs PP2+? Fender Engine Room? Friedman Power Grid? Priced at $200 or more, none of those products is cheap and I dare say not disposable. Only one is linear.

 

[telemnemonics]

This isn't directed at you specifically, but it grinds my gears when people say things like that. Linear and switching are designs. What makes a power supply cheap and/or disposable (or noisy or unstable or a long list of other things) is the implementation. The cheap, disposable wall warts we've had for decades are linear designs and I've never heard anybody say that linear supplies have a reputation for being cheap and disposable.

Anybody own a Strymon Zuma? Trutone CS12? Voodoo Labs PP2+? Fender Engine Room? Friedman Power Grid? Priced at $200 or more, none of those products is cheap and I dare say not disposable. Only one is linear.

Right, which is why I said the transformer AKA linear vs swiching debate is similar to the tubes vs SS debate, where we have a long history of attitiudes and association from a time when SS was cheap and disposable, yet long after that truism became false we still have the old attitudes.

I know you said you were not directing this at me, not arguing, just agreeing.

 

[telemnemonics]

I would say buy high quality and buy what suits your board, not what tech seems more popular.
I was down to the CS12 vs the Voodoo 4x4 and chose the latter for size, voltage options and price.
Could have gone the other way with no worries.

 

[redhouse_ca]

I dont know if this is relevant or not
but I made an ATX switching power supply ( from an old computer) into my+12, -12, +5 powersupply for my euro rack system , it gave +12V @16 amps, -12V @1 amp, +5V @ 22amps , ( maximum) with very little issue , and by using buck converters and/or 7809 (+) voltage regulators could be dropped to +9V using the +12V rail

tons of you tube videos on the subject , I havent tried this for a pedal supply , but there is a ton of current available to try this

I used the -12volt blue wire instead of the +3 volt orange wires, I placed a 8 ohm resistor from the 5 volt rail to ground to ensure there was a load on the supply ( just like in the diagram)
I also used 4 of each wires twisted together to ensure there was enough current to power my outputs with out taxing the supply

I hope this may help, but again it may not be what you are looking for BTW the +5 volt rail can power USB devices but wont transmit data.

View attachment 1078588View attachment 1078587

Cool. I use the behringer PS from an old mixed all the time to power stuff. I thinks it's the same as their Eurorack supply's and it's great, +/18v AC, with I think off hand 2A. With regulators and a few resisters just adjust for what I need.

But like a lot of people, I got a box full of old power supply's from all sorts of electric stuff I've acquired over the years. I have a couple female power connectors that I wire up to peddle and other stuff I build and again, I don't think I'll ever build another PS. In fact I think I'm gonna tear apart the one I used to use for parts.

 

[redhouse_ca]

Right, which is why I said the transformer AKA linear vs swiching debate is similar to the tubes vs SS debate, where we have a long history of attitiudes and association from a time when SS was cheap and disposable, yet long after that truism became false we still have the old attitudes.

I know you said you were not directing this at me, not arguing, just agreeing.

I agree. In hifi, I really think the linear is better philosophy (with massive toroidal transformers and banks if caps) persists because you can't sell a wall wart, maybe couple of caps and a $2 regulator for $5000.

That said, I don't use digita effects on guitar amps (or peddles really) and I stick with the old stuff in my guitar signal chain (to the DAC if I'm recording digitally). I don't have an opinion on linear vs switched in analog guitar signal chain.

 

[24 track]

Cool. I use the behringer PS from an old mixed all the time to power stuff. I thinks it's the same as their Eurorack supply's and it's great, +/18v AC, with I think off hand 2A. With regulators and a few resisters just adjust for what I need.

But like a lot of people, I got a box full of old power supply's from all sorts of electric stuff I've acquired over the years. I have a couple female power connectors that I wire up to peddle and other stuff I build and again, I don't think I'll ever build another PS. In fact I think I'm gonna tear apart the one I used to use for parts.

just be careful lif the power supply outputs A/C then you need to convert that to D/C to power pedals , that will involve a bridge rectifier of sorts , and some caps to smooth out the ripple the A/C powersupplies
this is what i used , and is the ATX PS , most people can get these for a dollor or two at a second hand store or have one in their storage , the small lap top units will not have enough current to power very many pedals , they will have the voltage but at 2-5 amps may cause issues,

go on you tube and see if any one has doe this before , I may be wrong here ,best of

 

[redhouse_ca]

just be careful lif the power supply outputs A/C then you need to convert that to D/C to power pedals , that will involve a bridge rectifier of sorts , and some caps to smooth out the ripple the ATX powersupplies
this is what i used , and is the ATX PS , most people can get these for a dollor or two at a second hand store or have one in their storage , the small lap top units will not have enough current to power very many pedals , they will have the voltage but at 2-5 amps may cause issues,

go on you tube and see if any one has doe this before , I may be wrong here ,best of

View attachment 1078820

Yeah, for sure, and I should have def said that for safety sake. Thanks for the call out. what is great, tho, and what I was trying to say is that after the rectifier, it's a darn clean PS. I have a bunch of cheap regulators I use to get the voltage and current I need, but it's so much nicer than building a bunch of filters and lining up a bunch of caps to get a clean power. I really don't understand why anyone would do that, except to learn why you don't need to do that.

 

[24 track]

Yeah, for sure, and I should have def said that for safety sake. Thanks for the call out. what is great, tho, and what I was trying to say is that after the rectifier, it's a darn clean PS. I have a bunch of cheap regulators I use to get the voltage and current I need, but it's so much nicer than building a bunch of filters and lining up a bunch of caps to get a clean power. I really don't understand why anyone would do that, except to learn why you don't need to do that.

these are the eurorack modules I am powering from the ATX PS

this is the full system

so there are no bad ideas , just what works for you!

 

[Nogoodnamesleft]

Linear - less efficient (very much so) but cleaner. Heavier generally due to the larger transformers to accommodate said efficiency. Easier to service and tweak.

Switching - more efficient (very much so) but not quite as clean (in most cases) and significantly more complex. But light, small, etc.

Edit: I see my post here is redundant. Pls ignore.

 

[aging_rocker]

It all comes down to how 'clean' the DC supply is after it's been rectified, regulated and smoothed. How that's achieved is almost irrelevant.

When I worked in the weird & whacky world of hifi, we spent a lot of effort getting the DC supply rails for devices (particularly for anything like a pre-amp or a DAC) as smooth as possible, and it certainly made an audible and measurable difference.

Massive transformers and multiple smoothing caps the size of baked bean cans are not essential, but as mentioned above, are lucrative, and a lot of hifi purchasers just 'expect' them.

The 'mains' ripple noise on cheap 'n' nasty DC power supplies (el cheapo wall-warts particularly) is often horrendous. You can see it (with a scope) still there in the audio signal coming out of whatever it is you are powering.

Not the end of the world for a distortion pedal, but not so good on any sound reproducing equipment.

But yeah, whatever works is good. I've got several old 'modified' ATX power supplies in the shed, always handy.

 

[Blrfl]

I agree. In hifi, I really think the linear is better philosophy (with massive toroidal transformers and banks if caps) persists because you can't sell a wall wart, maybe couple of caps and a $2 regulator for $5000.

If Silver Rock can sell a wooden volume knob with magic lacquer on it for $500, I'm pretty sure I could find the right ad copy to sell a $5,000 wall wart. There's one born every minute...

I think you, me and @telemnemonics are in violent agreement about all of this.

@aging_rocker hit on what makes me grit my teeth about this stuff: it's measurement. For the moment, I make my living developing measurement systems and am big on the idea that if you can't quantify it, you can't say it's a problem. DC power supplies have three important parameters: voltage, how much current it can deliver while maintaining that voltage and how much ripple is on the output. A product that needs DC power will have requirements for all three and any supply will meet those requirements or it won't. All of that is determined by measurement.

 

[24 track]

Linear - less efficient (very much so) but cleaner. Heavier generally due to the larger transformers to accommodate said efficiency. Easier to service and tweak.

Switching - more efficient (very much so) but not quite as clean (in most cases) and significantly more complex. But light, small, etc.

Edit: I see my post here is redundant. Pls ignore.

not at all, its apositive confirmation , thats a good thing!