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Old 9th June 2006, 10:55 AM   #2931
SimontY is offline SimontY  United Kingdom
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Quote:
Originally posted by 6h5c

Hi guys,

That's all true, but......

there's also the low frequency group-delay that starts to act up when the signal frequency is at and below the -3dB point. I don't know how much harm that will do, because the low-end is less critical. But, just in case, to be sure, if you have some room to spare (and some bucks $$$) take a cap that's bigger.

How much bigger? I always like to calculate things . Well, you have to set some limits to determine the cap size. So I looked at the group-delay at 5kHz and though it would be nice to have a point in the low-end where the group delay would be no more than twice that value. Is that sane? I don't know. We're talking microseconds here at low frequencies. Maybe ten times that value? Or 1% of the frequency's period? Anyone?

To give you an idea how all this looks:
Both graphs are with 100k input impedance. The top graph is with 3u3 and the bottom one with a 10u output cap. The only problem is, at what frequency do we want this to happen??

Regards,

Ray.
Hi Ray,

That's an interesting graph but I for one won't be worrying about that tiny amount of delay. I'm sure my subwoofer is capable of causing problems 1000x more severe and audible. And then there are the crossovers.. Can't wait to hear your filter in action!

Simon
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Old 9th June 2006, 11:53 AM   #2932
disco is offline disco  Netherlands
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Quote:
Originally posted by SimontY
Well I rather like banana! I wait with bated breath.

Cheers,
Simon
Hi Simon,

Thanks for sharing this insight on your favourite meal...

My modification is inspired by Diva

After heavy modifications on my first CD63 I tried how far I could come with minimal parts. I got surprised.

Looking at the central 5 volt power supply it's obvious it has to deliver divers currents into divers loads, one affecting the other.
Safest remedy is to build separate supplies but I reasoned otherwise. Why not make use of small capacitances and two reservoirs? One at the beginning as usual near the regulator, and one at the end at the most remote part of the traces. This resulted in two benefits as inter capacitor load currents are kept small and the smaller caps fill up quicker than big ones.

So, what I did was replacing the 5V reservoir cap (C815, was 3300uF) with a Black Gate NX 1000uF and placing another in position C504 (HF LPF, was 220uF). I made a new ground connection to the central PSU ground and cut the original at U256. Furthermore I replaced every electrolyte with standard Black Gate 10uF/50V (unfortunately I had not enough, so I also used some 47uF general purpose Nichicon). Modern caps have very good HF decoupling property, so there's little need for bypass anymore.

As one can imagine a faster supply has impact on dynamics. As a result Music is more natural, vivid. The soundscape has become clearer. Bass has authority without the often heard boom.

Another field of progress lays in stopping resonance interfering with laser tracking. Looking at the flimsy case brings tears to your eyes. The effort put in the circuits is completely negligent in the housing. So, out it goes. I have build a wooden case of 9mm birch multiplex, two layers for the bottom, one layer for the sides. The transport was fitted on four pillars of foam (ca 5x5x5cm).
At the moment I am experimenting with damping. A weight of app 80 gram on top has big impact on the soundstage. Music is heard in 3D, the stage deepens. Voices sound softer yet better distinctive, now lacking the squeaking coloration.

I intended to give a elaborate list on components I have changed, but it comes down to HF-suppression (TNT-audio), coax and shielding of the XTAL. As time goes by my modifications will change because of the experiment, so I don't think it's wise to produce a list now. If someone is interested in the partnumbers for stripping the superfluous circuits, I'll happily supply.

Best regards, Jaap


My hifi is waiting sings Norah...
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Old 9th June 2006, 12:21 PM   #2933
SimontY is offline SimontY  United Kingdom
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Fascinating, Jaap.
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Old 9th June 2006, 01:51 PM   #2934
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I have had the discrete pcb running on a standard cd67. I am comparing the original output with the discrete.
The 67 HDAM and caps have been removed!!

The discrete pcb with bc550 transistors gave more air and a little more bass.
The FET version (matched 2SK170GR) sounds less open and has less low end bass than the original opamps.

I have 3.3uF caps

mmmm

At the moment I feel the transistor pcb is better.

Brent
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Old 9th June 2006, 01:59 PM   #2935
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Just to follow up my last post.

The discrete pcb is tagged onto r21 etc and 12v regs with crocodile clip leads and therefore not ideal.

I am switching between two inputs on amp (cd67 rca and discrete o/p).

Also I found the phase between the output of discrete and cdp was 180 deg out so I just swapped Ro/Ron and Lo/Lon around for the test

Brent
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Old 9th June 2006, 02:05 PM   #2936
awpagan is offline awpagan  Australia
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Quote:
Originally posted by rowemeister
I have had the discrete pcb running on a standard cd67. I am comparing the original output with the discrete.
The 67 HDAM and caps have been removed!!

The discrete pcb with bc550 transistors gave more air and a little more bass.
The FET version (matched 2SK170GR) sounds less open and has less low end bass than the original opamps.

I have 3.3uF caps

mmmm

At the moment I feel the transistor pcb is better.

Brent
Hi brent
very interesting
just finished layout for my fet version, except 2sk389 input
was going to etch pcb in morning, might wait at present

did you use all bc550's, including running as darlington on output?

i was thinking about the 2sk170 as driver on the output by itself!
and wondering if it was suitable.

allan
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Old 9th June 2006, 02:10 PM   #2937
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I had bc550 for first two and 2sk170 ripped from hdam for output.

I must say though I may have posted a little hastly!!!!!

Im just listening to Krall now and not to areas of the sound. The bass is defo less but when i flick over to opamps the bass feels overblown.

The Fets are a more natural sound, nothing over the top. mmmm

Im going to run them in before I fit to my 63

Brent
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Old 9th June 2006, 02:16 PM   #2938
awpagan is offline awpagan  Australia
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Quote:
Originally posted by rowemeister
I had bc550 for first two and 2sk170 ripped from hdam for output.

I must say though I may have posted a little hastly!!!!!

Im just listening to Krall now and not to areas of the sound. The bass is defo less but when i flick over to opamps the bass feels overblown.

The Fets are a more natural sound, nothing over the top. mmmm

Im going to run them in before I fit to my 63

Brent

might need time for caps to break in.

also for the caps
why didn't you use BG's for the output?

allan
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Old 9th June 2006, 02:23 PM   #2939
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Quote:
Originally posted by awpagan



might need time for caps to break in.

also for the caps
why didn't you use BG's for the output?

allan

I just got these to test. Not looked at BG yet.

mmmmm I will now.

PS Thanks for making me spend more money LOL

PPS Which ones are the best for this application the AC type (for crossovers)

Brent
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Old 10th June 2006, 07:36 AM   #2940
awpagan is offline awpagan  Australia
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Quote:
Originally posted by rowemeister



I just got these to test. Not looked at BG yet.

mmmmm I will now.

PS Thanks for making me spend more money LOL

PPS Which ones are the best for this application the AC type (for crossovers)

Brent
Hmmm
i think you would have more experince with BG's than me

Non polar

allan

ps about the fet/transistors
impedance input and output
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