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Old 27th November 2009, 04:23 AM   #541
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Quote:
Originally Posted by Salas View Post
Never used one with the DCB1, don't know what it can do for it. If you use one let us know of any possible pros or cons you will find against a straight IEC connector's mains feed please.
Yes, please let us know.
In the Blowtorch thread quite some time ago designer John Curl wrote against such a mains filter advocating a single large 8 uF capacitor across mains as a better solution. (If trying, remember to use a dedicated capacitor for such use.)


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Old 27th November 2009, 09:02 AM   #542
MRupp is offline MRupp  Germany
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Default line filters

FWIW: Normal line filters contain Ls and Cs that “might” cause additional ringing with the mains transformer though I have not seen any conclusive information on whether that really causes an issue. However, at least for a preamp with it’s low supply current draw, an RC or CRC type filter may actually be a good alternative to a standard line filter. Additional snubbers on secondary (should be used anyway) but also on the primary of the power transformer might also help, actually a CRC filter on the primary would act both as a line filter and snubber circuit. I would put two Rs both in the live and the neutral wire, and calculate it such that you have a reasonably small voltage drop (say 1 – 2 Volts primary).

A frequent claim is that a normal line filtet “kills” the dynamics especially of power amps (not the subject here, I know) but again it is not clear to me whether this is because of a negative impact on the power supply, say by reducing peak current, or whether it is just subjective because some high frequency hash has now been filtered out and the sound is “less dynamic”.

Lastly, Charles Hansen of Ayre states that any component that can be magnetised, e.g. ferrites, are bad and should be avoided even in the power supply. Hence he is using his own type of line filter that he says contains no magnetic materials. My “guess” is that he is using some conductive material and is inducing eddy currents in the material, thus damping high frequencies.
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Old 27th November 2009, 10:00 AM   #543
AndrewT is offline AndrewT  Scotland
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Originally Posted by MRupp View Post
Lastly, Charles Hansen of Ayre states that any component that can be magnetised, e.g. ferrites, are bad and should be avoided even in the power supply. Hence he is using his own type of line filter that he says contains no magnetic materials. My “guess” is that he is using some conductive material and is inducing eddy currents in the material, thus damping high frequencies.
could it simply be small air cored inductors in the mains side CLC filters?
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Old 27th November 2009, 10:25 AM   #544
MRupp is offline MRupp  Germany
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Hard to say, one would have to talk to the horse's mouth, presuming it wanted to talk in the first place. However, just a few windings would have very low inductance, and I believe I read something about a "patent pending" which would lead me to assume there must be more "in it" ... plus I gleaned some details from a photo showing the entrails of a Ayre USB Dac with an onboard HF filter, again something in the coils ...
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Last edited by MRupp; 27th November 2009 at 10:29 AM.
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Old 27th November 2009, 11:09 AM   #545
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I had another listen to mine last night. There is a little bit of sibilance in it, though its settled down a fair bit. Sounds very good though apart from that, and definitely better than the regular b1. And thats with the stepped pot in palce which was inferior to the lightspeed in the regular B1. Bass definitely bigger with more dynamics - I wonder is this because the stepped pot is 50k?

So tonight I hope to add in a 560k resistor across the inputs to match teh 50k pot a bit better. That sibilance might just go. Also I know the wiring of inputs needs to be tidied up a bit.

Would anyone have a link fo rhow to simply measure input impedance? I have a signal generator, old scope and a decent DMM that can measure frequency etc.

Fran
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Old 27th November 2009, 11:17 AM   #546
Salas is offline Salas  Greece
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Characteristically sibilance free is my experience with it in several systems.

1. Change to 560k. 2. What resistors are on your pot? 3. What resistors are your 220R in the audio part? 3. Still you need more secondary voltage.
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Old 27th November 2009, 11:24 AM   #547
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1. will do

2. SMD - its the cheapo stepped pot DACT-like from ebay. Its ok in use, and works fine, better than an alps blue, but not as good as the lightspeed.

3. xicon metal film 1%50ppm from mouser: 273-220-RC (nothing special I know, and deinfitely not kiwame or takman!!)

Voltage, I know, I know!!!


Fran
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Old 27th November 2009, 11:27 AM   #548
Salas is offline Salas  Greece
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Input Z

You can set the generator at say 1kHz 100mV and insert 1k in series when it drives DCB1. Measure the drop across 1k, derive some current I=V/R and then divide that 100mV by it.
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Old 27th November 2009, 11:30 AM   #549
Salas is offline Salas  Greece
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Quote:
Originally Posted by woodturner-fran View Post
1. will do

2. SMD - its the cheapo stepped pot DACT-like from ebay. Its ok in use, and works fine, better than an alps blue, but not as good as the lightspeed.

3. xicon metal film 1%50ppm from mouser: 273-220-RC (nothing special I know, and deinfitely not kiwame or takman!!)

Voltage, I know, I know!!!


Fran
Hmm...Its a whole system and a family of parts special to your rig as anyone's. You will see what will smooth it out step by step. The base is that you should know there is smoother high range heard with that circuit.
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Old 27th November 2009, 03:05 PM   #550
udailey is offline udailey  United States
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I am not sure what you mean by sibilance. Sorry for my ignorance, but could you explain how sibilance sounds?
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