I solved this issue. It’s a design flaw with the PL Plus. The transformer that runs the rack lights is what is buzzing.
I unplugged the leads to it and it’s dead silent and the everything works perfectly, just the rack lights don’t work.
I emailed furman and have not heard back.
It seems like the power comes in, is stepped up to supply all the 9 outlets and then is reduced to power the lights. The reduction causes the hum/buzz. I read a lot of forums and everyone that owns the cheaper models of Furman’s say that their units are dead silent. What is the common denominator in those units? No rack lights.
James Perrett wrote:As others have said, humming US made gear is very common - and it isn't just the cheap stuff. My Eventide H3000 is one of the worst offenders. Mind you, I have a couple of UK made items that hum audibly too.
Yes, I sold my H3000 because of this hum, I tried everything, but you just can’t cure it. Totally unacceptable.
I’d get a European conditioner, but as others have said, is it really necessary?
As for the one button solution, is that a good idea? Having everything come on at the same time would worry me, there is a preferred switch on sequence, to avoid mains spikes.
Last edited by Arpangel on Mon Jul 13, 2020 7:10 am, edited 1 time in total.
James Perrett wrote:As others have said, humming US made gear is very common - and it isn't just the cheap stuff. My Eventide H3000 is one of the worst offenders. Mind you, I have a couple of UK made items that hum audibly too.
Yes, I sold my H3000 because of this hum, I tried everything, but you just can’t cure it. Totally unacceptable.
I’d get a European conditioner, but as others have said, is it really necessary?
As for the one button solution, is that a good idea? Having everything come on at the same time would worry me, there is a preferred switch on sequence, to avoid mains spikes.
As I mentioned (in 2017!) investigate wireless remote mains switches. I have one that can control 4 13A circuits individually but also has an 'all on' and 'all off' function. I have never had a problem banging all my, admittedly modest, rig on and off with just 2 switches on a 13A double outlet. You have to poke PCs anyway!
I could not see the waveforms Martin but in any case you have to be very careful not to display a signal that is the resultant of a transformer CURRENT. These are almost always distorted to some degree, especially those from small, crappy rats!
Hello gentlemen - I have read this full thread with much interest in 2021. My Furman PL-8C E makes a small noise, it's nothing major but enough to annoy me in a small studio, and contribute to background noise.
My question is this: I've been using the unit for a few years with the original main power cable which was supplied with a EU plug - plugged into the wall with one of those basic UK/EU adapters at the wall. I only just remembered/re-discovered this today as I was rewiring everything.
It got me thinking about how perhaps using a British plug would either a) be massively recommended anyway, and/or b) help to remove any humming noise?
I was encouraged to see some quite savvy people posting in the forum, so I signed up especially! Long time lurker, first time poster
It's easy enough to try, but probably won't help if the hum is mechanical (which I'm assuming it is as a power conditioner doesn't pass any audio signal itself).
And a warm welcome from me!
I assume the conditioner is securely screwed into a rack unit? If so I would look at ways to 'decouple' it from the rack. Cobble up some form of compliant fixing using grommets. There might even be a commercial product available?
If the hum does become unacceptable you could try bypassing it and when you found out that in all probability, here in UK, it is doing Fanny Adams, flog it!
ef37a wrote: ↑Fri Mar 11, 2022 5:18 pm
I assume the conditioner is securely screwed into a rack unit? If so I would look at ways to 'decouple' it from the rack. Cobble up some form of compliant fixing using grommets. There might even be a commercial product available?
Hi djpchem, and welcome to the SOS Forums from me too as well
I agree with ef37a about decoupling. Such buzzes are often due to vibrating transformer cores, which can often be largely silenced by decoupling them from the rest of the case, or even inserting a piece of neoprene/felt or similar between the offending transformer and the case lid to damp down the vibration.
As an ex service tech, can I caution you Martin about suggesting 'damping materials' ? There are strict rules on what you can and cannot put in mains powered gear. For instance, we had a lot of bother with an inductor (called a transductor) screaming at 15,625 Hz line frequency, it was the more irritating because its level changed with beam current i.e. picture content.
The fix was to coat the component in some form of sealer but the only one that met fire safety regs was PVA glue.
Sometimes transformers can be silenced by tightening the fixing bolts. I would bet the one in that Furman is of the 'clamp' form of construction and a good squeeze in a big vice often sorted them.
Sometimes the hum is due to a loose lamination inside the stack and there is nothing to be done with it. Toroids tend to be much quieter but are of course more expensive, va to va.
ef37a wrote: ↑Sat Mar 12, 2022 9:21 am
As an ex service tech, can I caution you Martin about suggesting 'damping materials' ? There are strict rules on what you can and cannot put in mains powered gear.
Good point Dave - it's all very well performing DIY fixes on your own gear, but where fire safety regulations are involved you really do need to stick to sensible rules
ef37a wrote: ↑Sat Mar 12, 2022 9:21 am
As an ex service tech, can I caution you Martin about suggesting 'damping materials' ? There are strict rules on what you can and cannot put in mains powered gear.
Good point Dave - it's all very well performing DIY fixes on your own gear, but where fire safety regulations are involved you really do need to stick to sensible rules
Thanks Martin, I do admit the point is a bit pedantic/academic but you know how insurance companies can wriggle!
Changing the plug makes no difference. I would strongly consider removing the Furman altogether. Replace it with a UPS that incorporates a filter. These are around €120. As with the Furman you’ll need to calculate total current draw, and the power draw if you want to utilise the uninterruptible bit.
Much better value than a Furman.
Or put a medical grade mains filter in a project box. About €40 from Farnell. Requires electrical skill though. https://ethanwiner.com/dimmers.html
I have this in my studio to eliminate switching noise from a water pump on the same circuit as the studio (don’t ask!).
Thomas, I thought incandescent lamp dimmers had to be 'zero crossing switching ' now and for a long time since? ZCSing generates very little crap.
Watch out! Old bugger about to drone on...
Rank Bush Murphy produced an all solid state CTV with a clever (they thought!) SCR (not Triac) regulated power supply producing about 80V direct from the mains. Basically a half wave lamp dimmer with a reference supply. They did not care where the negative half cycle went. The electricity companies bloody did!
Cause all sorts of interference in the area of the TVs.
There was a mod, a socking great 1/2kg toroid that we had to bolt into the tellies.
Later designs from Philips e.g. used full wave rectifiers and then a pair of SCRs to regulate the DC. Still had the chassis connected to neutral mind...You hoped!
Just a word of caution about electrical power advice from the USA. Some things they do and get away with there can be lethal in Europe because our mains system operates at double the voltage. So always seek professional qualified advice.
Technical Editor, Sound On Sound...
(But generally posting my own personal views and not necessarily those of SOS, the company or the magazine!)
In my world, things get less strange when I read the manual...
ef37a wrote: ↑Sun Mar 13, 2022 11:16 am
Thomas, I thought incandescent lamp dimmers had to be 'zero crossing switching ' now and for a long time since? ZCSing generates very little crap.
Where did the h come from Dave? I love these stories from your old days! That's scary stuff. No company could afford to send that many techs out into the field these days, not to mind the cost of a trafo now.
Sorry, that link was only meant to show how to put the mains filter in a box. It's not fancy modern HTML so I can't link directly to the relevant paragraph. In fairness I said nothing about dimmers in my post. Although the article is a good general primer on mains-borne noise.
I'll remember to put the disclaimer for regional mains voltages the next time
60Hz transformers should not be used on 50Hz supplies. Core saturation and overheating may occur. Vendors selling equipment not rated for UK standards should be aware of the potential safety issues and liability issues that might arise. Personally I would return the unit for a full refund and find something designed form European power systems.
Hope the wound wasn't deep. 
