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Old 25th October 2009, 12:00 AM   #71
audi0 is offline audi0  Australia
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Default Output filter modifications?

Re: output filter caps, the web research that I have done appears to show that very little improvement in sound quality can be made by replacing the filter caps, however it appears that some fine tuning can be done by optimizing the values of the C14/C15 and C18/C19 (nom. 220n) capacitors to the speakers impedance.
It appears to me that the Helder 2020 MkIII has been optimized for 6ohm speakers (Argen /Tubesteve, you can correct me if I am wrong)
From what I have read it appears by lowering the capacitors value to 120n better suits an 8ohm speaker or raising to 47n for 4ohm speakers
I would be interested if anyone has tried swapping these caps and/or the 100nF cap across the output and hear about the results, and have the modifications done been worthwhile?
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Old 25th October 2009, 01:54 AM   #72
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Default output filters

dear audiO,

each filter works correctly to its calculated impedances ( in / out ) . a speaker has not a constant impedance over the frequency range, and its resonant frequency shifts with a housing. and: speakers with a crossover network show even more complex behaviour. to be accurate, the filter in the output of the 2020 or others work best , but not perfect, for the calculated and then tested resistance and also type speaker.
therefore these filters and snubbers have a difficult task to fulfill, and any modification done, applies only for that load only, the modification has been done, to be correct. the filters in the amps must always be a compromise,
as also your speaker cable resistance, length changes the situation.
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Old 25th October 2009, 05:59 AM   #73
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Default Output filters

Hi Tubesteve,

I think from your response that you have basically agreed with my statement, maybe I should have added the word NOMINALLY before 6 ohm!
BTW have you guys tried other capacitor values / quality and noticed any difference to the sound reproduced?

Cheers.. Steve
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Old 25th October 2009, 11:02 AM   #74
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Default caps filters etc.

dear audio,

a you probably may guess, we are here inchina, shenzhen. i am here since 11 years. since this time i am are struggling with quality of products or with copied products or components ( = worse performance or failure ). so, as you may understand, its not easy to find reliable suppliers which not cheat, especially if the amount is low, lower than 1000000 pieces.... i am dealing everyday with this.
your 6 ohm story looks correct, its in the middle of 4 and 8 ohm. if you want change that, keep in mind that a speakers resistance in all cases increases with frequency until a certain point ( most over 20KHz). i am looking for the nobel price to invent an frequency flexible filter with constant impedance.
have a nice day!
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Old 25th October 2009, 07:52 PM   #75
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Default Filter caps

Thank's for your honesty, actually I think most of us knew that there was a quality problem with Chinese components!
I am unsure at the moment if I will change the filter, I am working from the other end at the moment replacing the input caps with Auricaps. I would like to know of other peoples experiences with filter changes before I jump in!
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Old 25th October 2009, 07:59 PM   #76
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Default Update

Audiosteve: I just read your latest post in the "Audiophiler Capacitor" forum;
"i again want to point out again, that the output snubber filter components, here in digital amplificationare for me much more imprortant bcc. they form together with the speakers EMF a complex load, which have more effect on the sound."

I think I have made up my mind with what I am going to do!
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Old 26th October 2009, 01:05 AM   #77
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Default filters

let me suggest one thing for that: the filter coils should have bigger wire diameter to improve the filter and efficiency. ofcourse same inductance at 1KHz. most problem is the space available on the pcb.
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Old 26th October 2009, 10:35 AM   #78
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Thumbs up filters

Quote:
Originally Posted by tubesteve View Post
let me suggest one thing for that: the filter coils should have bigger wire diameter to improve the filter and efficiency. ofcourse same inductance at 1KHz. most problem is the space available on the pcb.
Hi tubesteve,
I am looking at Autocostruire T-Induttanze-Litz, (Autocostruire il negozio degli autocostruttori) do you think these are a good choice?
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Old 26th October 2009, 12:07 PM   #79
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On another board (not 2020) I have replaced the standard yello 100nF caps with Siemens KP of the same value - result: a more natural sounding, a bit more warmth, to my ears an obvious 'Go'.
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Old 26th October 2009, 06:11 PM   #80
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Audio,
Sorry to get back to your question regarding input capacitor mods. I've been too busy to do anything.
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