Speaker Hum

[ecc83]

Hi Tyrone,

Well, the few minutes I had on an audio test rig with them showed frequency response to be amazingly extended and flat and the waveform was pure but 'scopes do not give a very good indication of distortion, still, used at "domestic" levels, especially at virtually zero power (10kload) I think they are fine. My only concern is the HF peak at 60kHz but I am sure I can tame that. While we are having this happy little chat about hum, earths, isolators and suchwhich can I get very serious for a moment?

There is it seems to me to be a certain amount of confusion concerning earth loops and "isolating" transformers ( often sloppily called DI boxes).

It is IMPERATIVE to realize that NO audio transformer is usually tested for or meant as a MAINS VOLTAGE ISOLATOR. That is to say, just because a box, like the one I am making, breaks an earth path between two bits of kit FOR AUDIO signals it does NOT mean that if one piece of gear became live the box would protect you. Good quality trannies, like OEP's probably would but THEY don't say so! (except for special products). The £3 a piece or so jobs I would not trust in America let alone in 240volt land!

So chaps(&ess's) Cardinal rule, everything must have its own mains earth and boxes just keep things quiet. That's ALL they do.

Dave.

[sureno]

i just want to see if any hum can be removed i dont want my mains volted to a tranny isolator

[ecc83]

Don't worry S!

The warning was mainly aimed at folks who use tranny boxes on live shows and a few posts at other sites have given me the impression that sometimes peeps think they can do more than they are designed to do.

Your app' is typical and non lethal I assure you!

Dave.

[sureno]

Originally Posted by ecc83

Don't worry S!

The warning was mainly aimed at folks who use tranny boxes on live shows and a few posts at other sites have given me the impression that sometimes peeps think they can do more than they are designed to do.

Your app' is typical and non lethal I assure you!

Dave.

cool looking forward to the box of tricks

[tyronehowe]

Originally Posted by ecc83

There is it seems to me to be a certain amount of confusion concerning earth loops and "isolating" transformers ( often sloppily called DI boxes).

It is IMPERATIVE to realize that NO audio transformer is usually tested for or meant as a MAINS VOLTAGE ISOLATOR. That is to say, just because a box, like the one I am making, breaks an earth path between two bits of kit FOR AUDIO signals it does NOT mean that if one piece of gear became live the box would protect you. Good quality trannies, like OEP's probably would but THEY don't say so! (except for special products). The £3 a piece or so jobs I would not trust in America let alone in 240volt land!

So chaps(&ess's) Cardinal rule, everything must have its own mains earth and boxes just keep things quiet. That's ALL they do.

Dave.

Thank you very much for explaining that Dave – appreciated.

I was oblivious to the entire “earth loop” problem UNTIL I purchased a Mac (a white MacBook to be precise). I plugged it into my normal amplifier and there were all sorts of horrible sounds (and that was BEFORE I pressed play in Logic ).

After looking at forums and asking questions someone mentioned about an “earth loop” or “ground loop” so I looked up that gadget in Maplin and thought for a tenner it was worth a try. Bingo – instant success.

I was worried that it might affect the HF, so I A/B tested a number of times (by ear) and I couldn’t tell any difference (apart from the cleaner signal with the unit in place).

Oddly enough when I later bought a MacPro I had the same problem. So my unit is now hidden away behind the audio interface (Edirol UA-25) and everything is clean.

[ecc83]

Sorry chaps, been away, blood in pee sat night.

All sorted now but no lifting.

Sureno, I have all the bits for your box and will fabricate a soon as I can.

Dave.

[sureno]

Originally Posted by ecc83

Sorry chaps, been away, blood in pee sat night.

All sorted now but no lifting.

Sureno, I have all the bits for your box and will fabricate a soon as I can.

Dave.

oooh that doesn't sound too good, least it wasn't burning when you pee'd
seriously hope all's well and no rush

[saxman]

Originally Posted by sureno

oooh that doesn't sound too good, least it wasn't burning when you pee'd
seriously hope all's well

True. True.
http://www.youtube.com/watch?v=3Cb7inx4BLA

[Monarch]

[quote=ecc83;21719]

Sorry chaps, been away, blood in pee sat night.

All sorted now but no lifting.

Best wishes for your health. Thankfully you got it sorted.

[ecc83]

Number one channel blocked again! Waiting for taxi to A&E.

Maybe in the New Year Sur'!

Dave.

[modz1]

Speedy recovery Dave..

[sureno]

Originally Posted by ecc83

Number one channel blocked again! Waiting for taxi to A&E.

Maybe in the New Year Sur'!

Dave.

good luck Dave, stop putting it in iffy places

[Monarch]

Originally Posted by modz1

Speedy recovery Dave..

Yes. I hope and pray your health improves.

[ecc83]

In case any of you want to know,

I'm out of H again, had an op', they said they removed a "rather large" tumour in the bladder. I won't know if it is a good or bad guy for a week or so.

Still sore but much, much better.

Dave.

[sureno]

Damn!!!
i really hope it all works out for you Dave!!!