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Old 15th January 2012, 01:40 PM   #11
system7 is offline system7  United Kingdom
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Quote:
Originally Posted by Bonsai View Post
No, DC on the mains depends on whether or not the quipment causing the problem is turned on or not - so it will be an on-off problem.

Can you tell us what speakers you are using and something about your cables?

If you disconnect your speakers, do you still get this problem?
Ooh, CAREFUL, Bonsai. These tubey type amps and preamps often don't like driving open-circuit...

They can blow up. Valve folks always remember this. The same can go for low-feedback solid-state designs.
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Old 15th January 2012, 01:49 PM   #12
seebert is offline seebert  United States
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Thanks again to everyone.

My gear includes:

Classe DR-5 preamp
Musical Fidelity Pre24 CD
Threshold S/500 II
Threshold SA/3
Muse 160 power amp
Nothing special component interconnects - Monster M1000 MKII and DIY weave into RCA (waiting for balanced XLR's to arrive)
Bog standard 14G OFC speaker cabling into (well soldered) bananas
Speakers: ADS 1230's and IMF TLS 80 MK II's
(even tried ADS520's from the shed)

MF Pre24 CD alone into amp - sound is too bright/shrill/other similar words.

MF Pre24 CD via fixed tape outs into the Classe DR-5 and on into amps - much better music.

I'll be changing out the units for a simple CD into the Classe - I like the sound of that pre into the Threshold's particularly and it's also good with the Muse.

Hope all this tells a story - I know the system isn't great or well balanced but it can sound good and it's a work in progress - but isn't it always.

Thanks, Mike.

BTWmeasured DC offset on the Muse and it's not too good - varying figure from 2.5mV to 32mV on the 'hot channel and also varying on the L channel - anything from 8mV up to 52mV - it does not stabilize.

Last edited by seebert; 15th January 2012 at 01:54 PM. Reason: Added DC offset info.
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Old 15th January 2012, 02:04 PM   #13
seebert is offline seebert  United States
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Sorry I didn't mention : I have tried the Muse with nothing connected to it (haven't tried the Threshold's yet) and the noise remains the same. Wish I could describe the noise - it's not a hum or an 'even' buzzing - more a very very fast 'rattling' type of sound that can be heard easily two meters away.
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Old 15th January 2012, 02:05 PM   #14
Bonsai is offline Bonsai  Taiwan
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Threshold is a SS amp IIRC System7. Of course with a tube amp, you should not run it without a lad.
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Old 15th January 2012, 02:09 PM   #15
seebert is offline seebert  United States
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Bonsai:
Quote:
Threshold is a SS amp IIRC
Yes it's SS as is the Muse (an underrated amp IMHO). I learned a long time ago (much to my cost) not to run a valve amp without a load

(Great website you have there Bonsai - I've bookmarked it to go back later)

Best regards, Mike.
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Old 15th January 2012, 02:11 PM   #16
AndrewT is offline AndrewT  Scotland
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I can hear my transformer grumble due to bad mains waveform.
It constantly varies almost second by second from inaudible to quite loud on the worst occasions and/or most susceptible transformers.
The DC blocker cures the audible transformer noise/grumble problem.
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Old 15th January 2012, 02:23 PM   #17
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First and Foremost - As the Doctor says. Cure the problem and NOT the symptoms.

Identify the problem then act accordingly.

IF and ONLY IF, the ONLY solution is to cure the symptoms then you have to go that route.

I am not saying don't fit a DC blocker. Just make sure that that is the problem first.

A simple trial might be to borrow a 110V generator to see if the transformers still BUZZ.
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Old 15th January 2012, 02:34 PM   #18
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I'm having the same issues here. It's DC in the Mains.

With some of my vintage amps, the humming/buzzing from the transformers are so loud that even 10 ft away I can hear them. It's so annoying that I eventually unplugged them.

Only a month back, I plugged in a humidifier in another wall socket. It took the hum/buzz to a new level. Unplugged the humidifier and it went back to the previous hum level. It appears that the two wall sockets are simply in parallel.
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Old 15th January 2012, 02:37 PM   #19
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In a normal domestic installation, all the sockets are in parallel. At least they are here in the UK.

Load sharing of the transformer phases is usually an industrial issue.
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Old 15th January 2012, 02:38 PM   #20
system7 is offline system7  United Kingdom
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Quote:
Originally Posted by seebert View Post
Nothing special component interconnects - Monster M1000 MKII and DIY weave into RCA (waiting for balanced XLR's to arrive)
Ooh! WTH is that? Some sort of homemade twisted bellwire instead of proper coax cables?

Sounds like it could be RF interference problems to me. But awful US mains is always a possibility. Seems your stuff all blows up at the merest whiff of lightning storms.

(FWIW, I did wonder if this was some sort of current feedback Nelson Pass design. Not bad, but TRICKY with open load, no?)
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