Power supply problems ??

[mickeyb]

Hi There,
Could anyone tell me if expensive mic pre-amps (AMEK) are in some way more sensitive to power fluctuations than everything else in my studio ?
Probably to vague a question. It's been sugested that I have a power problem .. but only the Amek is effected???

[rob]

more information required.
but...unlikely
Australian mains power is a loose cannon, i've seen vary from 200V to 265V. And some gear is affect by these sort of extremes, but what are your symptoms?

[Howard Jones]

I had a client make an Amek pre-amp specific enquiry along exactly these lines in early December. He's out of town, so it was hard to diagnose over the phone. He seemed to think that his Amek was more inclined to overheating/power supply issues than any of his other equipment.

[mickeyb]

Twice there has been a crack ... that smell ... second time sparks!!

[JulienG]

If you have a good quality UPS they usually output the input voltage and frequency, if you have the ability you could graph the result and see how stable your power is.

If you don't have one and you rely on a computer in your studio you really should go and buy one.

[wez]

i have an online UPS and it is a beautiful thing... i bought it to clean up AC and keep it in the right shape, the battery backup is a bonus. make sure you go for 'online' (or double conversion i think it's also called), that way you get fully cleaned up AC, not just 'spike' protection.

i just run computers and sensitive digital stuff off it, make sure you get one big enough for the job (700 - 1000 VA is enough, unless you want to backup everything, amps and all).

[rob]

" a crack, a smell and sparks" .... sounds to me like the unit is faulty

[rick]

there could well be a problem if you have the newish ( last 5 -7 years) amek stuff ( with the little lights on the rack ears)

they have a switch mode power supply built in on the circuit board.

when i first saw this it scared me because my thought was as soon as these things get a bit older and run into our normal australian 220-265 power fluctuations the parts in the switch mode supply will more then likely explode !
this happens with switchmodes regularly, and there are ways to insure it doesnt ( like designing the thing properly) retrofitting the supply with higher tolerence parts and as suggested using a ups.

at the time these things came out the dealer for amek yelled at me for casting aspertions on this type of design, "everything uses switchmode supplies nowadays " he said
but i argued the amek supply is on the same board as the audio so if it blows you have to replace the entire unit !
"no problem he said if that happens amek will replace it !"
but people can keep mic pres for 20- 30 years ! i countered

its a few years down the track and i have been waiting patiently to be proven wrong (or right)

every thing would be more secure if amek we still in business making them
the thing is they are not ! ( as of last year)

put a ups on it, try and get a tech to upgrade the parts, sell it or just cross you fingers .

[mickeyb]

Hi Rick,
Im the one with the problem AMEK DMCL power supply.
Frank Hinton has just repaired it for me and now I need to get a UPS to solve this problem.
I phoned one place and the guy said a UPS wont regulate the power .. its only for battery backup when there is a power failure ... as you can see I know nothing of these matters.
My question is should I just protect my most critical devices and is a UPS what I need (Dick Smith sells one POWERWARE USB Uninterruptible Power Supply 700VA for $186.00)
A Dave Peach device was mentioned to me by John Prior .This is I'm sure a complete drag on your time and energy however any advice would be greatly appreciated by this electrical ninny.

Regards
Michael Bartolomei

hi michael
heres the thing a cheap ups will not regulate the power , an expensive one will , a very expensive one.
heres what you need to do

get a tech to add up the amount of amps all the units in your studio need to run
or have a look at your fuse box and if your fuse is ten amps or less ( it probably is) assume that is the figure.
start chasing a regulated 240 v supply something that will clamp down the over voltages and raise the undervoltages that will handle the amps you pull, the more amps the more expensive , something like the american made furman devices would suit
expect to spend between 5 and 350 thousand dollars

or except that some things blow up in australia with the high voltages we have ( mine moves from 210 - 261volts !) , plan in power supply rebuilds ($350-700) into everything you buy for the one time every two years that something fries....

you can get peachys power box and it will help some devices but it wont help switch mode supplies computers etc ( well it might actually..?)

that amek box..? will if frank has "fixed it" ( hes a good guy ) it should be fine right...?
was there actually a fault...?

if it makes you feel any better i have choosen not to buy ups or regulated supplies and i just accept the power supply limitations of my devices and repair or buy my equipment wisely

i have worked that way for 20years , and so has every studio i have ever worked in or poked around in, so regulated supplies might look like the current solution, but the problem is not worth the expense of solving it untill regulated supplies drop to a affordable price.

the arguement is how can you afford not to ...? well a bet on a repair every two years or so is my method - its a calculated gamble it seems to work
- i hope this helps
Rick

[Chris H]

So the Amec Dual Mic Pre i purchased 2 years ago has a switch mode power supply?

I have been under the impression that they are not an option in good quality recording gear, that they were prone to introducing noise etc.

[rick]

i do not want to get into any kind of arguement about wether the amek range sound good, work well or are a good device to have, and i do not know if the power supply issues that i haved suspected them of will actually ever be a problem, but yes the last series of amex outboard gear has switchmode supplies, and so does nearly everything currently made.

switch modes are cheap, efficient and easy to source, however they dont seem to last anyway near as long as a good linear supply,
and thats now problem for most gear because its designed to be obsolete by the time the switchmode gives in.

i have never thought a mic preamp should be obsolete in 5 years

the fact that the importer can fix them after they are no longer made speaks volumes about his service and custumer care (thumbs up frank !)
but still says nothing about the design

i think its a dumb idea to put switch modes in audio devices
the only reason to do it is cost cutting

[Howard Jones]

No manufacturer assembles a custom switchmode power supply (SMPS) to use in a piece of audio equipment. In other words, the SMPS is bought from a high-volume OEM manufacturer of such devices and is simply bolted into the back right hand corner of the audio device enclosure. This relieves the manufacturer of having to design a multi-rail power supply, assemble the individual components and thereby probably deal with at least a couple of extra suppliers e.g. transformer manufacturer etc.

All-in-all then, a quick and pretty cheap solution for the audio manufacturer. As has been pointed out, such SMPS will not last very long

[norm]

Quality power supplies can be obtained very cheaply thru Australian Ebay. However not all USPS are equal. learn which suppliers build them with a regulated supply side. I have found these in the computer section of Ebay. That is wher I have obtained mine.

[rick]

howard the rub with the newish amek stuff is they HAVE built a custom switchmode supply AND its is on the same and only board as the mic pre and eq .
so replacing it means replacing the whole board or a component swap for the charred bits ( if you can get the same size replacement bits in 5 years)

amek are not the only manufacturers to do this BSS and several more of the harmon kardon companies think this is the way of the future.


this is why i am harping on about this
if audio professionals do not tell manufacturers that this is dumb practice how will they ever know...?

quotes of mine about from this (the old ) forum have put me on the amek pure path homepage... and seeing they are no longer in business...
geez.. i just wanted them to fix the supplies :)

[Howard Jones]

Allen & Heath use custom-designed switchmode power supplies in the MixWizard series also. It's not desirable. These supplies are invariably designed around a highly individual switching transistor and I have grave doubts about the availability of those sort of parts in 5 or 10 years time.

I'm also completely unenthusiastic about integrating power supply circuits on to the same PCB that accommodates the audio circuits. At least the separate-box SMPS improve on that. I wonder why Amek went down this path?

I'm reminded of a NAD consumer amplifier from about 10 years ago that came in for repair. It used a type of output device that we just couldn't source. Turned out that Philips were having a runout of these devices and NAD bought several thousand and used them in these amps. Hard luck for NAD owners once the Philips device blew.