Speaker Hum

[sureno]

Originally Posted by ecc83

Well I have one,
Bigger than I thought 75mm x 40mm but not as heavy as I would like, not a lot of iron in there!

I have tried to get it apart but don't have the kit to hand here, I shall go in early tomorrow and crack it at work. I also have a dB test rig and 'scope there to do some tests.

Sureno, I did try to get Oxford Electronics Products interseted in marketing a rival to the ART CleanBox 2. OEP make some fine transformers at very reasonable prices I use their type A262A7E as a output balancing transformer from amy 2496 cards. They very nicely sent me a pair of high grade 10k10k input trannies as samples and they are ensconced it a nice diecaste box close to the pc and unbalance (and earth break) the signals back from a variety of kit some 4mtrs of cable across the room. Their type OEP1200 is useful at low levels -10dBV, for isolating all sort of kit and are only about a fiver.

Well! What would you know? In sitting here fiddling with the Map thing I have just popped the can! Reveals two decent sized trannies mounted on a pcb but in the tranny world, size definately is not everything!

If these spec out ok I shall put them in a civilized tin, fit some proper connectors and put it on Ebay! Nah! 1stCFS, it's yours if you want it S!

OEP? You had your chance!! (actually I might send them one.)

Dave.

Well tbh most of your post made no sense to me Dave
but if you put together a nice anti hum box with balanced jack ins and outs il snap it up immediately and run it right after my a/i outs and before my mackie big knob

[ecc83]

Sureno,

Do you have a hum loop problem then? If so the Mackie has balanced inputs and outputs (unless you are being perverse and using the RCA's!)

If you are feeding active monitors you can just disconnect the pin 1 earth in left and right XLR's or TRS's at one end, monitor end prob' best.

If you go to www.rane.com they have a list of all the possible cable combinations to connect virtually anything and avoid earth loops.

Oh! And sorry for the waffle!

Dave.

[sureno]

no nothing serious, on my Mackie active 350's there is a hum thats noticeable on powering and my other monitors there is a very quiet hum hardly noticeable but just enough to be able to tell the monitor is on, i was thinking i would just plug one in to eliminate anything i could to see if i can get an even tiny improvement, iv heard severe ground looping and i have nothing of this nature

when it comes to wiring i really have little knowledge or confidence in the field

[ecc83]

Fekking valves! Valves are *&^^te!!!

Two of Fridays repairs bounced because of FEKKING VALVES!

So, (composing oneself...) I did not get as much time on the tranny box as I would have liked, but. It is bloody good! Going into the females from 600R source and into 1M. 0dB loss! @1kHz -2dB @10, yes T E N Hz! Sails up to 20K no sweat and hits a peak at 60kHz.

At +17dBV into 10k @1Khz no visible distortion
At +13dBV " " " 20Hz just " "

A 1K load did not increase distortion but dropped level but then the oscillator drooped as well.

I did not have time to "turn it around" the resistances differ so the other way must give a loss me thinks. Yes, these look ok I shall box them up, work up a Zobel network to tame the HF lift and fit an earth lift switch.

Dave.

[ecc83]

my spacing got screwed by dv247's puter. 10k load, 20 Hz input.

Dave.

[sureno]

...................

[ecc83]

Ha! Ha!

Sureno, all you need to know is they are bloody good for a tenner and a total steal for a blue 'un!

Dave.

[sureno]

Originally Posted by ecc83

Ha! Ha!

Sureno, all you need to know is they are bloody good for a tenner and a total steal for a blue 'un!

Dave.

now your talking my language, so we are talking about the first lesser priced unit correct Dave?

[ecc83]

Er? No,

I have tested the Maplin unit at £9.99.

The mailorder jobby looks the very same, one way to tell would be to measure the resistance of each set of windings. If they are the same as mine it would be most unlikely that the transformers are different. I am sure any telly repair shop would do that for you if you smiled sweetly!

Dave.

[sureno]

Originally Posted by ecc83

Er? No,

I have tested the Maplin unit at £9.99.

The mailorder jobby looks the very same, one way to tell would be to measure the resistance of each set of windings. If they are the same as mine it would be most unlikely that the transformers are different. I am sure any telly repair shop would do that for you if you smiled sweetly!

Dave.

ah so you rate the maplin one at £9.99, do you think you will be making a jacked box?

[ecc83]

" do you think you will be making a jacked box?"

Yes! Yes! Ok! I will put it in a posh tin for you!

Dave.

[sureno]

Originally Posted by ecc83

" do you think you will be making a jacked box?"

Yes! Yes! Ok! I will put it in a posh tin for you!

Dave.

PM me how you want payment

[ecc83]

Right,

Give me a week or so to can it up and re check the spec. I want to be sure it is ok.

Won't be a lot ( for THIS ONE!).

Dave.

[sureno]

Originally Posted by ecc83

Right,

Give me a week or so to can it up and re check the spec. I want to be sure it is ok.

Won't be a lot ( for THIS ONE!).

Dave.

No worries just give me a PM or post here, which ever is easier

[tyronehowe]

So if I understand this correctly, Dave, you are saying that the awful looking £10 designed-for-car-audio job is pretty good?