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#16 Re: why would changing transformers...

Posted: Thu Jun 08, 2017 4:49 pm
by karatestu
Does everyone know les ? I will surely say hello from you but I only know you as Nick.

I did want to join in with your get together near Doncaster but sadly family life has got in the way.

Stu

#17 Re: why would changing transformers...

Posted: Thu Jun 08, 2017 5:59 pm
by Nick
Just tell him Nick from Longdog Audio. Long hair, beard and confusion, he should know who you mean :-)

#18 Re: why would changing transformers...

Posted: Thu Jun 08, 2017 8:28 pm
by karatestu
Ok will do. I have just looked you up on google and i did not realise you were a designer and manufacturer. I can now put a face to the name. Thanks for your input here.

Stu

#19 Re: why would changing transformers...

Posted: Thu Jun 08, 2017 10:12 pm
by Greg
Yes, and of course you already know Nick, although you might not realise as Lurcher300b on HFS.

#20 Re: why would changing transformers...

Posted: Fri Jun 09, 2017 1:56 pm
by karatestu
Greg wrote: Thu Jun 08, 2017 10:12 pm Yes, and of course you already know Nick, although you might not realise as Lurcher300b on HFS.
Of course, silly me. I have only been there since January this year.

More messing about here with transformers. I decided for a laugh to put a couple (I have four!) of these Avondale EI transformers on the two tweeter dedicated monoblocs I have. They work a treat at the volume I am playing - sounds extremely good and not a hint of hum with them sitting in my power amps. At 36Vdc & 50VA per secondary (only using one at the moment) they would probably be no good for mid/bass duties but are doing an excellent job on the tweeters. :D

Anyway just proves to me that they don't like something about the way I have wired up my preamp. Probably the 0V arrangement? Some rewiring needed I should think.

Stu

#21 Re: why would changing transformers...

Posted: Fri Jun 09, 2017 3:59 pm
by karatestu
Nick - said hi to Les from you on the phone. He says hi back :D

Anyway mucking about with my 0V arrangement I have reduced the hum to a very small amount heard through the speakers. Instead of daisy chaining the 0V from caps to reg to preamp board to star earth I ran the reg 0V back to the caps and from there straight to the star earth in the preamp. Preamp boards have an independent 0V wire straight to the star earth. Does that make sense.

What I will try now is bringing the reg back as close to the smoothing caps as possible to reduce the length of it's 0V connection to the caps. See if that eliminates it altogether.

What I still can't understand is why the toroid was perfectly happy with the old 0V arrangement and the EI caused problems ?

Feel a bit happier now. Playing lovely music now with little EI's on preamp and the two high frequency monoblocs. I like it :D

Stu

#22 Re: why would changing transformers...

Posted: Fri Jun 09, 2017 5:00 pm
by Nick
karatestu wrote: Fri Jun 09, 2017 3:59 pm Does that make sense.
Yes, chaining anything to a star earth is generally a mistake unless you have a good reason to not do it, and good reasons are very rare.

Think in terms of the AC current that will be flowing in a wire and the effect that current will have generating a voltage across it.

#23 Re: why would changing transformers...

Posted: Sat Jun 10, 2017 10:18 am
by karatestu
Thanks Nick,

Thinking about it you are of course correct. Trouble is I do not have an extensive electronics knowledge. In fact I had non when I started dabbling in DIY audio 10 years ago. I have learned a lot in that time and made many mistakes which I have learned from. Read a lot on the internet but there is nothing like actually doing things and learning what is right and wrong. I don't own any measuring equipment except a DMM and so have to trust my ears - maybe that is what attracted me to HFS.

Thanks, Stu

#24 Re: why would changing transformers...

Posted: Sat Sep 23, 2017 2:55 pm
by karatestu
After speaking to Les W I changed the earthing arrangements in my preamp and most of the hum went away.

I then built some semi Omni doc mod speakers (see HFS) which meant I could remove the crossover inductors for my old speakers from near the power amps (sounded better that way :?: ) and the hum has completely disappeared.

Lessons learned - make sure earthing arrangements are optimal & don't put large speaker crossover inductors too near transformers and the like.

It must have been the stray field from the EI transformers that caused most of the problem. That is why when I changed the original toroid to an EI the hummmmmm appeared.

Oh well, more things learnt. :D Thanks for peoples input.

#25 Re: why would changing transformers...

Posted: Sat Sep 23, 2017 6:20 pm
by IslandPink
Useful info - good work !