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Old 9th December 2011, 07:21 PM   #351
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Quote:
Originally Posted by terranigma View Post
@powerflux:
15R and 56R on bottom are reversed on silkscreen. Also, you can push them a bit front side due to opening room for driver heatsinks. You can flip 1R and 0.5R in safe. There is enough room.

Bottom side decoupling capacitor's pads different. Upper ones seem good.

You can avoid first bypass cap each side (most left ones) and you can use their pin as supply pad. If you go with this, current will flow through these caps in optimal way. I have modified pdf in this manner. I will post some pics soon.
you are correct, my apologies. i've swapped those values on silkscreen and i've also moved the resistors to give the BD's more space for future revisions. you can now put one sheet of +/- 1.5mm aluminium across the board and mount both BD's to it. they're "in-line" i've got the feeling there will be more recommendations so i won't attach this subversion at the moment, only a screenshot.

Click the image to open in full size.

just make shure to first mount BD's and "cooling-sheet" before surrounding components.

however, i don't understand what you mean by different pads. negative pin is octagon, positive is round.

Last edited by powerflux; 9th December 2011 at 07:50 PM.
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Old 9th December 2011, 08:29 PM   #352
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Quote:
Originally Posted by powerflux View Post
you are correct, my apologies. Swapped values on silkscreen and i've also moved the resistors to give the BD's more space for future revisions.
i've got the feeling there will be more recommendations so i won't attach this subversion at the moment.

however, i don't understand what you mean by different pads. negative pin is octagon, positive is round.
I expected each side pin as same. If there is a design rule, then it's not a big of deal. But my recommendation regarding using first caps as supply pad should be a good improvement.

EDIT: I depicted on last last revision. Also, wire jumper's pads too small for etch and drill.

@Elvee
Dc-offset is under 1mV now..It seems putting volume pot after input cap causing varying input impedance thus producing weird offset readings. My bad.
Attached Images
File Type: jpg suggested-pad.jpg (43.2 KB, 482 views)

Last edited by terranigma; 9th December 2011 at 08:58 PM.
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Old 10th December 2011, 02:16 PM   #353
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Quote:
Originally Posted by terranigma View Post
@Elvee
Dc-offset is under 1mV now..It seems putting volume pot after input cap causing varying input impedance thus producing weird offset readings. My bad.
You are really lucky this time: getting less than one mV spread on two randomly chosen discrete transistors is rather unusual.

I didn't get better than 5mV on any my Circlophones, but of course, to play the game fairly, I duly constrained myself to use only suffix-less, unsorted, unmatched BC's.

The input filter has been carefully designed to offer an equal impedance to the bias currents, and when you disturb all that, it is normal to see things deviate.
Anyway, it is always a bad idea to rely on the wiper of a potentiometer to conduct a bias current. At the very least, you risk unpleasant noises when you manoeuvre it.
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Old 10th December 2011, 04:57 PM   #354
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Originally Posted by Elvee View Post
You are really lucky this time: getting less than one mV spread on two randomly chosen discrete transistors is rather unusual.

I didn't get better than 5mV on any my Circlophones, but of course, to play the game fairly, I duly constrained myself to use only suffix-less, unsorted, unmatched BC's.

The input filter has been carefully designed to offer an equal impedance to the bias currents, and when you disturb all that, it is normal to see things deviate.
Anyway, it is always a bad idea to rely on the wiper of a potentiometer to conduct a bias current. At the very least, you risk unpleasant noises when you manoeuvre it.
After putting potentiometer in right place, offset dropped into this unexpected level. I got this value with pair of exact hfe match 2sa970's (hfe=353) and matched 470R's and 10K's and other symmetrical things as well. I'm not bothering to measure things before populate. BD140's are even same. Actually, I wasn't aiming minimum offset while populating, it was just a habit of symmetry. I think that the matter is topology of Circlophone. Everything is symmetrical from input to output.

Last edited by terranigma; 10th December 2011 at 05:24 PM.
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Old 11th December 2011, 08:18 AM   #355
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Originally Posted by terranigma View Post
I got this value with pair of exact hfe match 2sa970's (hfe=353)
That's cheating!!!
It eliminates the offset current, and the Vbe-Hfe correlation does the rest.
It is no surprise you end up with 1mV.
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Old 15th December 2011, 12:45 PM   #356
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Originally Posted by Elvee View Post
That's cheating!!!
It eliminates the offset current, and the Vbe-Hfe correlation does the rest.
It is no surprise you end up with 1mV.
Actually it is far below of 1mV

BTW, I'm trying to figure out why new PCBs didn't operate as silent as previous wakibaki's.. wakibaki's has performed freaking dead silent without any extra effort. Could wider ground plane be the reason?

Last edited by terranigma; 15th December 2011 at 12:56 PM.
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Old 15th December 2011, 04:50 PM   #357
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Originally Posted by terranigma View Post
BTW, I'm trying to figure out why new PCBs didn't operate as silent as previous wakibaki's.. wakibaki's has performed freaking dead silent without any extra effort. Could wider ground plane be the reason?
What kind of noise do you hear?
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Old 15th December 2011, 05:09 PM   #358
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What kind of noise do you hear?
It is not a typical hiss. Looks like some environmental HF noise interfering my gear. If I disconnect my source (linear supplied soundcard) I can hear a very distorted radio channel which is a known issue due to big antennas near my house. If source connected, noise level is quite gentle but audible nearby speakers. My speakers are 100db.

Last edited by terranigma; 15th December 2011 at 05:16 PM.
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Old 15th December 2011, 05:48 PM   #359
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Is the input filter R19 C5 properly implemented, on board?

Did you try with the input shorted?

Does the board serve as relay point for various grounds?

Did you try to disconnect everything that has a common ground with the amp?

Try disconnecting the speaker, and replace it with headphones having minimal wiring length. (no signal obviously, and be very careful not to blow your eardrum with a sudden bad contact or similar).

Does the hiss change when you move your hand near the board?
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Old 17th December 2011, 08:04 AM   #360
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Originally Posted by Elvee View Post
Is the input filter R19 C5 properly implemented, on board?
I respected pcb as is. It seems pcb layout and schematic a bit different if we concern about input signal current. C5 is behind of R19 in pcb but, C5 is the most close one to input pair in original schematic. Please take a look there.

I didn't use C5 in wakibaki's pcb. I couldn't have opportunity for re-setup wakibaki's pcb yet. It seems things will be clear if I do same setup again for a fair comparison.

Quote:
Did you try with the input shorted?
Yes, it is worst as like as input disconnected.

Quote:
Does the board serve as relay point for various grounds?
It seems No.

Quote:
Did you try to disconnect everything that has a common ground with the amp?
Yes, it is no effect.

Quote:
Try disconnecting the speaker, and replace it with headphones having minimal wiring length. (no signal obviously, and be very careful not to blow your eardrum with a sudden bad contact or similar).

Does the hiss change when you move your hand near the board?
My speakers are very are close to setup and I did it without headphone. No effect. If I grab and move input and speaker cable, noise and radio signal raises somewhere that what looks like playing with an antenna. I used bigger polystyrene type cap at zobel (C7) in previous pcb but small mkp type in latest pcb. I haven't altered it yet.

Last edited by terranigma; 17th December 2011 at 08:13 AM.
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