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Old 27th September 2004, 09:06 AM   #1
foxyb is offline foxyb  United Kingdom
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Default Affect of Power Supply on Soundstage Width

Apart from some interesting information on Aspen's and Mark Levinson's website, I have not found much information that talks about the effect of the power supply on stereo separation in power amplifiers.

Are there any general improvements I should make to improve the soundtage width? (The depth of soundstage seems to be fine).

What improvements would you expect on imaging/ soundstage and minimising crosstalk from the following changes made to the JLH 80w Mosfet amp:

1) Having a rectifier per channel for the voltage amplication stage, but the high current stage still will use a high quality shared supply (fast diodes, soft recovery witha full bridge per voltage line, and Elna Cerafine 10,000 muF pre line)
2)Having a shared transformer, bridge, capacitor, but both channels having a seperate rectifiiers for both the voltage and current gain stages (cheaper than new transformers, caps and diodes);
3) The whole hog: seperate power supplies per channel.

Additionally, if I go for option 3) - what is the recommended replacement for the 80V, 10,000muF Elna Cerafines in the other channel?

Many thanks for any information you may be able to provide.

Regards,

John
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Old 27th September 2004, 10:52 AM   #2
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Default Yes, i heard four times, good people as you told, that this makes difference.

I could not "feel" that till today, but i am collecting informations to have the chance to hear that difference.

Those people guaranteed that make difference, and those people i trust.

regards,

Carlos
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Power supply; ripple, filter, noise, stability and the use of capacitance multiplier... Portuguese and English; https://www.youtube.com/watch?v=sSm0ku1eIgg
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Old 27th September 2004, 11:42 AM   #3
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You know a lot of turntables image better than CDs?

Crosstalk on a typical phono cartridge is 20dB at 1Khz, dropping to 15dB or less at the frequency extremes.

Are we barking up the wrong tree?

I have seen amplifiers with a common high voltage supply for the front end have better than 80dB crosstalk at 1Khz.

If I was building a no feedback amplifier with poor PSRR I would do up as good a supply as possible.
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Old 5th October 2004, 05:50 AM   #4
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Hi,

The effect on the sound stage is huge, depending which capacitors you use. Elna Cerafines are good, but soundstage can be improved dramatically if you cut the noise floor even further! The best way to do this is by using bypass capacitors. Many people use film capacitors at DIFERENT points. These points are important and can be defined only by experiment for the given power supply. I have tried many bypass caps, and the best one for me is Black Gate 0.1 uF / 50V non polar NX. If you need higher voltage, use two 0.47uF / 50 V non-polar NX caps in series "super E" configuration. Now, where to put them:

Try straight after the bridge rectifier (use only soft recovery, fast switching diodes, TWO IN PARALEL if you could afford it - but it's worth it!).
The other point to install these caps would be as close to the pre-amp section of your amp as possible. Avoid placing them in parallel with Elna Cerafines!!! - experiment a little and you'll notice a huge difference.

Let me know what you found!

Regards,
Nick
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Old 5th October 2004, 09:47 AM   #5
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"The effect on the sound stage is huge, depending which capacitors you use."

Total agreement here.

Be careful when using values less than 1F very close to the output stages, oscillation can occur. You may need to add a small series resistor to the cap, say 5 ohms ~ 10 ohms. Ideally the bypass caps should be grounded at where the high current returns. This is many times just not possible. In these cases you just have to find a ground where you can, and the oscillation caused by the inductance of the extra trace length is damped by the resistor in series with the cap.

Many times I take what improvement I get from adding 22F~47F to the main supply caps and just move on from there (look at coupling/feedback caps and diode snubbers).
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Old 10th December 2005, 10:33 AM   #6
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Default larification Please

Quote:
Originally posted by Extreme_Boky
Try straight after the bridge rectifier (use only soft recovery, fast switching diodes, TWO IN PARALEL if you could afford it - but it's worth it!).
Nick,

Could you clafify if "TWO IN PARALEL if you could afford it - but it's worth it!" is two bridge rectifiers or two capacitors?


Regards,

John L. Males
Willowdale, Ontario
Canada
10 December 2005 06:33
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Old 10th December 2005, 04:31 PM   #7
lineup is offline lineup  Sweden
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Quote:
Affect of Power Supply on Soundstage Width

Apart from some interesting information on Aspen's and Mark Levinson's website, I have not found much information that talks about the effect of the power supply on stereo separation in power amplifiers.

Are there any general improvements I should make to improve the soundtage width? (The depth of soundstage seems to be fine).
I think dept and width of sound should depend on the size of your room.
If too wide and/or deep, the whole stage will not fit inside your listening space.

For minimum power supply impact on stereo separation,
wouldnt totally separate left/right amplifiers as well as loudspeakers
be good?
Preferable both amplifiers should be placed as far as possible from eachother.
You also should use two different AC mains wall outlets for minimum ground connection interference.


Just my simple thoughts, but I am no expert, so I am not sure how this would work compared to traditional setup.
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Old 10th December 2005, 09:52 PM   #8
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Quote:
Could you clarify if "TWO IN PARALEL if you could afford it - but it's worth it!" is two bridge rectifiers or two capacitors?
Two diodes in parallel making "one diode". That's 8 diodes in total for a full wave bridge rectifier.
I saw this approach in some Japanese high end gear and tried it myself. It is definitely better, more relaxed and natural with better details retrieval.


Extreme_Boky
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Old 10th December 2005, 11:06 PM   #9
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Hi foxyb,

Firstly, if ML are spruiking this on their website you can bet, London to a brick, that it's because they use elaborately regulated power supplies on their amplifiers - approaching the complexity of the amplifier module itself and there's the #1 commercial reason. Many manufacturers don't do this so they're trying to make a + out of it.

What they don't tell you is why they do this. I can tell you because I spent 4 months as a consultant to this company. The answer is they have found the only way THEY KNOW to improve their amps sound is to do this. So they're flogging it as necessary.

However, if they knew more about the finer aspects of amplifier design, they would design an intrinsically high PSRR topology AND they would design their PCB's and wiring looms and chassis layouts to minimise interactions of modulated Vs tracks and wiring with sensitive early/high impedance stages. It takes a very enlightened designer to do this and they invariably like to be paid for their work, accordingly.

That's too hard for many to get their heads around let alone do, so the easy, very expensive approach is to have lots of seperately regulated high and low power supply lines, to achieve an end result that could be achieved at very low cost of intrinsic design. And they've lost the advantage of power supply headroom and efficiency.

Not only that, it doesn't solve the problem of interactions as there are still track to track and wiring loom interactions not related to PS artefacts, like the naive running of high current driver tracks in proximity of the input stage causing high distortion (0.5% cf 0.03%), or the loud em-radiated traffo hum that had resulted in my re-working of one existing model after complaints by their Japanese agents that the hum was LOUD!

A more wholistic approach could use unregulated supplies for full dynamic headroom, better PCB and lead dress for lower THD and noise and a far better and cheaper amp.

But of course designing amps is a Black Art they're privvy to.

And here's an example of the cr@%^ that's on supply lines in AB amps at only 5W output. Imagine that all around your PCB near sensitive current sources.

Cheers,
Greg
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Old 11th December 2005, 12:06 AM   #10
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Now,
With soundstage size (height,width,depth) the information is contained in low level mostly HF directional detail so anything that reduces the miasma of artefacts from power supplies, grounding irregularities or bad PCB layout or lead dress is going to allow through more detail.
Soundstage size in particular relates to what spatial information comes out of well seperated speakers - that shouldn't. This is often measured as crosstalk and can be due to a shared power supply or grounding or proximity interactions. Often crosstalk is considered only as 'pure tone' while measurement techniques read 'residue + noise" or everything that comes out of one channel when the other is stimulated with a swept pure tone. This will include the miasma of harmonics,IM products and noise.

Where to put a capacitor to make it right?

Cheers,
Greg
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