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Old 1st November 2010, 05:13 PM   #111
Spev is offline Spev  United Kingdom
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Maybe it's the tinnitus , but definitely sounds like someone's taken the cotton wool from in front of the speakers
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Old 1st November 2010, 05:30 PM   #112
needsp is offline needsp  United Kingdom
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Hi Spev

There you go! Removing the filter's like cleaning a window, isn't it?

Paul
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Old 1st November 2010, 05:38 PM   #113
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Removed the filter caps as well but sounded a bit "glassy" to me. On FFT there was a spray of high freq spikes and the fundamentals were also higher in level. When I tried 1.8nf polystyrene caps it looked a lot cleaner on measurement but sounds almost as dynamic and crisp.
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Old 1st November 2010, 05:59 PM   #114
needsp is offline needsp  United Kingdom
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Hi vanwykca

What kind of amp are you using?

I'm a big fan of polystyrene caps. Did the 1n8 caps alleviate the perceived glassiness in your system?

Paul
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Old 1st November 2010, 06:19 PM   #115
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Hi Paul

Krell KAV400ix via NAC A5 into PMC OB1:-). I know the combination is intrinsically bright but I heard the same via KT88 triode valve amp in my man cave system. Yes, it tames the glassiness but sounds as dynamic/open as without the caps.

I have one of the Legato 2.0.0 boards with Takman metal film IV resistors, Charcroft for 4.7k and 1k resistors, Blackgate N 100uF bypassed with Vishay/Roederstein MKP1837 100nF as DC blocking caps. Panasonic FM for powersupply decoupling caps. Balanced to unbalanced conversion with metal can LME49720HA.

The powersupply uses Hexfreds to Nichicon Superthrough 4700uF and 0.47R CRC to Placids. When using the Krell the connection is balanced and unbalanced to valve amp.

As you can see I've pushed this board a bit, but it responds brilliantly to component upgrades. I use PC based audio analysis software via a EMU 0404 soundcard to check that I don't mess up:-0.

Cornelius
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Old 1st November 2010, 06:45 PM   #116
needsp is offline needsp  United Kingdom
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Hi Cornelius

My I/V resistors are also 1W Takman metal films, and the op amp a metal can LME49720HA- snap! (I've also done some other mods and use Paul Hynes series regs- but not TP approved)

When using the Bal/SE stage, try bypassing the output caps- you should find the dc offset between the Legato's output pairs is small enough (a few mV) for this

I use valve amps with only local series feedback- very different to your solid state system, and even your KT88 amp will have some global feedback. Which may explain our somwhat different experiences. My treble is the sweetest it's ever been!

Paul
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Old 1st November 2010, 06:48 PM   #117
avr300 is offline avr300  Denmark
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Are you guys bats or what ?

With 1n8 you have -3db at 590kHz

What are we aiming for here. What frequencies do we need to filter ?


I really like the procedure:

Quote:
...to check that I don't mess up..
That's the way to go
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Old 1st November 2010, 07:25 PM   #118
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I can't explain it, but have a look a some FFT's

Picasa Web Albums - Cornelius van Wyk - Legato Filtering
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Old 1st November 2010, 09:19 PM   #119
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Default That...

Quote:
Originally Posted by vanwykca View Post
I can't explain it, but have a look a some FFT's

Picasa Web Albums - Cornelius van Wyk - Legato Filtering
Does not seem right at all? Can anyone explain what we are looking at here? Are we looking at the output of the Legato alone, or the output of another component being fed the Legato's signal?
Why would a filter effective about 500 kHz have any effect here?
I am considering going 10nF REL polystyrene here, with R1-4 at 180R.
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Old 1st November 2010, 10:36 PM   #120
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I'm pretty sure my method of measuring is ok but electronics is just a hobby, so I might be completely off base. PC - 27" iMac Quad core 2.66GHz, 8Gb ram running Win7 in bootcamp with Virtins Multi-Instrument 3.2. Emu 0404 usb external sound card. Signal to DUT via Emu 0404 and M2Tech Hiface using ASIO and MME drivers with similar results. Sampling at 24bit and 96kHz using Flattop and Blackman Harris windowing also with repeatable results. The test signal(SPDIF) was at 24/96 but I get similar results with 16/44.1.

Using Audiotester software in Windows and Mac the Scope in OSX I also get repeatable results with numerous devices including Cambridge Audio DacMagic(latest), DIY 1541aS2 DAC, Musical Fidelity TriVista DAC and Devilsound V2 DAC, so I'm fairly confident about the results even though they baffle me. There is quite a few reports online about the accuracy of the Emu 0404 as measurement device. It's quite tricky to get Windows to not interfere with sample rate conversion and you can see obvious jitter sidebands when you've got it wrong

What's been encouraging is that when ever I've heard something that bothers me after a mod/"upgrade", it was obvious when I measure that something is wrong. Also I noticed that I like some low order distortion and seem to be sensitive to phase and pre-ringing with impulse response testing. I can only postulate that there is some phase/timing changes with the filtering that's minimised with 1.8nf whilst higher order distortion is decreased enough not to bother me any more as with no filtering.

This is a interesting hobby, as it is pretty obvious that we all have a unique taste in sound and DIY allows us to tune equipment to our liking

Cornelius
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