@tomiiv,
Good Move.
There are plenty of great amplifier designers out there that you can choose from.
Especially at that price point.
Bob |
It's a story as old as the hills.
A company spends decades establishing a really good name.
A conglomerate swoops in and buys it up--and they're buying the name much more than the factory or the know-how. They proceed to try and squeeze every last drop of profit out of it--and then they'll throw away the dry husk when they're done.
The attitude you've gotten--it's your problem, we really don't want to take it back (=we've already made our profit off of you)--is a classic demonstration of this.
|
@twoleftears ,
Exactly.
I bought a 2016 TTS that has a B&O sound system.
It sounds like crap. My previous TTS had a Bose system that sounded leaps and bounds above the B&O-and that is saying something.
B&O had some really interesting gear in the day, but now that they have been acquired by another company, they are just resting on the name recognition.
Too bad for me, Audi trusted them- but, hey, it all comes down to money.
B |
Food for thought. Quote from an Audio Circle audio forum thread about DC offset on the AC mains.
HAL
- Industry Contributor
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- Posts: 4101
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Re: DC offset on AC line
« Reply #8 on: 30 Nov 2007, 03:51 am »
If you have access to a Fluke
43B power line analyzer, you can check the harmonic distortion on the
AC line. Had a similar problem with lots of audio gear in the house.
Turned out the the AC line harmonic distortion was running about 6%.
The
local power company did some investigation. Found out the meter base
contacts had corrosion. After clean up, the AC line distortion runs
about 2%. No more power transformer hum.
https://www.audiocircle.com/index.php?topic=47973.0. |
https://www.diyaudio.com/forums/solid-state/2080-dc-filter-6.html#post331815
22nd February 2004, 08:09 PM
#57
Eva
diyAudio Member
Join Date: Oct 2003
Location: Near the sea
I've done some measurements that show what's really hapening when you connect a transformer to mains
Using a lowpass filter [100k + 47uF] I have measured about 50mV average over time of DC on my mains supply
I also have an old electric heater that in half-power mode uses a diode
in series with the heat element to pass only half of the mains waveform.
When I plug this heater in half-power mode I get an additional 1V of
offset on mains supply
To test the need and the efficiency of DC filtering, I've done some
measuremens of the current through the primary of a 750VA toroidal
transformer
This oscillogram shows what happens when I connect the transformer to mains and let it deal with the 50mV DC offset
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Blue trace is mains waveform at 100V/div [230V AC], it looks more like a
clipped triangle wave instead a sine wave due to the line inductance
limiting the slew rate and all the rectifiying applications consuming
all the current only during the peaks [30% of total time]
Red trace is the current through the primary at 200mA/div. Transformer
saturation towards the negative side is evident, reaching 350mA peak of
leakage current. The transformer buzzs slightly due to the saturation
The noise present in the current waveform is common mode and was
suppressed in further measurements adding a common mode filter between
mains and measurement point
The second oscillogram shows what happens when I plug the electric heater in half-power mode
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Red trace this time is in 2A/div so the leakage peak current exceeds 6A.
The transformer is heavily saturated towards the upper side and buzzs
loudly.
The third oscillogram shows what happened when I placed a DC filter
consisting of two 1000uF 16V and some diodes in series with the primary
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This time, red trace is 20mA/div and shows the small leakage current due
to both the magnetizing inductance and the parasitistic capacitance
between adjacent turns. The transformer is no longer saturated and
performs silently
the fourth oscillogram shows the induced voltage in a loop of wire of
10cm diameter placed vertically, paralell and 1cm away from the
transformer [placed horizontally] obtained when the transformer was
saturating with more than 6A peak [with the electric heater plugged]
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The red trace is 2mV div and shows the induced voltage in the loop of wire
That measurement demonstrates that when a 50-60Hz transformer is
saturating, it produces electro-magnetic-interferences that induce noise
voltages on everything in the nearhood
Actually, I think that +-5mV of low frequencies induced in a loop of
wire of 10cm diameter near the transformer is a serious thing since this
EMI is at audio frequencies, it's not RF so it's 100% audible and it
may be happening in all your transformers
In the other hand, all the tests were performed with open secondaries
but if we add load so that primary current has peaks of 6A, then the EMI
radiated would be the same or higher
With load, the EMI is produced due to flux in the leakage inductance,
resonances due to parasitistic inter-turn capacitance, RF ringing due to
diode turn-off characteristics and the fact that the peak current
through the transformer is 3 times or more the average DC current after
rectification
In conclusion : Rectifiying the output of 50-60Hz transformers produces
EMI as any SMPS does and this phenomena gets aggravated when the
transformer is saturating due to direct connection to mains without a DC
filter
50-60Hz transformers are nothing but big, bulky and crappy antennas
https://www.diyaudio.com/forums/solid-state/2080-dc-filter-6.html#post331815.
22nd May 2004, 05:20 PM
#71
Eva
diyAudio Member
Join Date: Oct 2003
Location: Near the sea
Bricolo :
DC levels on mains cannot be measured by directly connecting the
multimeter to the line. You have to place a low-pass filter between the
line and the DMM. I use a first order filter made of a 100K 1W resistor
and a 22uF non-polar capacitor for that purpose
Non-gapped transformers must be operated on 'pure AC'. Even 50mV of DC may be enough to see signs of saturation on toroids
. |
