a question of noise!

[the_doc735]

That sound file doesn't sound like transformer buzz at all to me - it sounds like humming coming from the speakers. A hum in the signal can have many causes but in this instance I suspect power supply ripple. I could be wrong about that though.
Of course, hearing the humming in isolation doesn't give any indication of the signal-to-noise ratio. That hum could be at a very low level or a very high level, there's no way to tell. Also, no indication of whether or not the hum goes up/down with the volume control.

Anyway, it doesn't sound like transformer buzz and isn't caused by DC on the mains.

The microphone was 1cm from the OPT on one of the sophia's, but they are both same anyway. The speakers are about 4 foot away from the amps - to either side. There is a very very small hum from the speakers too that is almost inaudible unless you jam you ear right on the speaker itself! The amps can JUST be heard when sat about 5 feet away and can easily be masked when there is talking on a TV set for example. THe noise level doesn't vary and these are like power amps with NO volume controls at all; all there is - is a on/off switch on each monoblock.
Also, when I switch on my REL Stampede sub woofer the deep bass hum through the speakers increases (say) 'six fold' and can almost be heard on quiet passages of music! Not good for amps costing $4999!
Before these amps I had a puresound 2A3 and a Lyric Ti 60. BOTH of these were completely silent WITH THE EXACT SAME SYSTEM (i.e. only the amps changed, nothing else)! So, I can't really blame the speakers, mains, DAC, laptop, interconnects, home plugs, pure AC sign wave generator, APC EMI/RFI blocker etc. etc.

Many thanks - hope this helps?

[the_doc735]

You may have a problem with DC on your mains?
http://sound.whsites.net/articles/xfmr-dc.htm
Are you using any of those home plugs for networking they work on the earth network so could be a source of noise
Alan

unplugging the 'home plugs' make no difference.

[Arkless Electronics]

The DC, if there is any... won't make it past your step-down transformer... ( I guess theoretically it could be causing an asymmetrical magnetic loading on the step-down transformer, such that it distorts the mains and passes on this distorted mains, causing the less good quality transformers in the amps to buzz.. clutching at straws here though!) Some transformers do buzz a bit and from what you describe I reckon yours are thus...

Sometimes transformers intended for 60Hz mains will buzz rather on UK 50Hz mains if money has been kept tight on the spec.. it often is!. Nowt you can do about that... unless your "pure sine wave generator" is a mains re conditioner with the option to output 60Hz of course... 50Hz transformers in other kit should be fine running on that.

It is true that gear intended for 220V mains is often exported to the UK and our 240V mains can give hum in some cases, but if this is 120V and being powered by a 240v to 120 v step down transformer all should be well... unless your step-down transformer is nowhere near up to the job and is itself saturating and passing the distortion on to the amps' mains transformers.... If so I would expect your step-down transformer to be running rather hot and probably buzzing itself. Beware when judging "rather hot" that 50-60C or so can be a normal running temp after several hours use for lower specced transformers.

I have come across plenty of UK gear with audible mains transformer hum as well though so this is something that can just be intrinsic to some amps.
If you can see the nuts and bolts holding the transformer laminations together it's worth checking they are not loose as this can be the cause...

The hum issue with the sub is probably unrelated.

[RothwellAudio]

The sound file I heard (Paul sent me an email with the file attached) did not have the usual buzzing sound that transformers with rattling (or at least under tightened) laminations make.
I would suggest that the HT voltage should be measured to check if it's what it's supposed to be. Also check the output valves' bias current to see if it's what it should be. Of course, that will require a circuit diagram or a service manual or an email to the manufacturers. However, it should be the first thing to check before anything more drastic is contemplated.

[the_doc735]

The sophia Electric 91-01 300B has been returned as it did not work correctly on the UK mains power grid.

[Barry]

Sometimes the transformers used in US gear are optimised for the 60Hz mains frequency. I have heard of cases when such equipment is used in the UK (where the mains frequency is 50Hz) the transformer laminations can vibrate and buzz. If there was a problem with DC on the mains, the 'buzz' would be at 100Hz.

[the_doc735]

Sometimes the transformers used in US gear are optimised for the 60Hz mains frequency. I have heard of cases when such equipment is used in the UK (where the mains frequency is 50Hz) the transformer laminations can vibrate and buzz. If there was a problem with DC on the mains, the 'buzz' would be at 100Hz.

thank you, yes true, I heard that too, now I have hands on experience of it.

[the_doc735]

http://www.pinkfishmedia.net/forum/s...d.php?t=146788

...going to get a JOHN WOOD 6L6 AMP.

http://www.retrosellers.com/features577.htm

http://jwoodaudio.com/

J WOOD 6L6 .jpg

[the_doc735]

Well, got the 6L6 by John Wood:

What can I say:

Gob smacked! Speechless! There simply aren't enough superlatives in the dictionary to describe it!

This is completely inaccurate:

http://theartofsound.net/forum/showt...-a-tale-of-woe

The guy is really really good and the amp is amazing!

In his defense: John said:

"Well you all ways get one and he found out you can try and get your money back and keep the goods and I am not the only one he as tried it with .I have more than 1000 bits of audio out there and as you can see my second hand price is one of the highest in the world so what does that tell you ?.He is just a thief and A liar.
John"

Grab one now BEFORE 'the word' gets out! These will take off in the future, no doubt about it! They are incredibly good value at the moment, I.M.H.O they could be sold in the same price range as Audio Research, McIntosh & Ayon etc. NO JOKE!

In fact I would like to hear Audio Research, McIntosh & Ayon amps in my setup to compare ~ ANY OFFERS? (bake-off).

PS: John has offered to give my 6L6 a FREE health check and transformer dip, so that it will be as good as new! Can't say fairer than that - can you? Good bloke?

[the_doc735]

http://www.pinkfishmedia.net/forum/s...d.php?t=146788

...going to get a JOHN WOOD 6L6 AMP.

http://www.retrosellers.com/features577.htm

http://jwoodaudio.com/

J WOOD 6L6 .jpg

https://hifiwigwam.com/forum/topic/5...ohn-wood-amps/