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My_Ref Fremen Edition - Build thread and tutorial
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Old 17th July 2016, 08:18 PM   #2591
ggerla is offline ggerla  Italy
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Default Problem with one channel

Hi all
this evening I try to do some test on my new build with wave generator and oscilloscope.
One channel seems ok. Put 200mV at 1KHz and obtain 2V. There is a lot of noise but problably depends on connection...

The second channel doesn't work. If I put some wave in input I have a distorted output and often the led goes off. Probably he go in protection mode.

I welded both channel in parallel...
Can you help me?
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Old 17th July 2016, 09:35 PM   #2592
ggerla is offline ggerla  Italy
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Quote:
Originally Posted by ggerla View Post
Hi all
this evening I try to do some test on my new build with wave generator and oscilloscope.
One channel seems ok. Put 200mV at 1KHz and obtain 2V. There is a lot of noise but problably depends on connection...

The second channel doesn't work. If I put some wave in input I have a distorted output and often the led goes off. Probably he go in protection mode.

I welded both channel in parallel...
Can you help me?
It seems that there is a signal to high frequency with gigh voltage (more that 2V) at input of lm3886 (pin 10).
I'm not able to understand where this signal is genearted because when I put the probe on one pin (R12, C34, lm3886 pin 10) protection go on.
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Old 17th July 2016, 10:14 PM   #2593
ClaveFremen is offline ClaveFremen  Italy
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My_Ref Fremen Edition - Build thread and tutorial
Quote:
Originally Posted by ggerla View Post
The second channel doesn't work. If I put some wave in input I have a distorted output and often the led goes off. Probably he go in protection mode.

I welded both channel in parallel...
Can you help me?
Post some good quality pictures, please.

Let's see if there's something wrong.

Did you clean boards?

Did you take the indicated measures?
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Old 18th July 2016, 09:12 AM   #2594
xcj999 is offline xcj999  Austria
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troystg: yes plenty of space. Wanted to keep the option for 4 channels open. And the price difference for smaller cases is negliable anyway

dario: yeah, especially R12 since you put it up so high on the modding list *ggg* Ah, well ... first finish volume control and dac, then i have earned some more money for z-foil

rookie: well let me try. Its hard to do an AB comparison since I also modded my speaker crossover after building this amp. I used a yamaha ax-496 with Infinity RS 5000 speakers.
The first big difference i noticed was the soundstage. It really made it sound like the music was not coming from the speakers anymore. Very good separation and placement. Also, it definitely has this "tube-touch" not as extreme as with a normal tube amp, but to get an idea what it sounds like a very good picture. The voices now sound a lot more realistic to me. Now i sometimes hear a noise and only afterwarsd realize it was from the recorded music/movie *ggg* In my eyes a really worthwhile build with incredible bang for buck ( aaaand i went some 200 eur over budget since this was my first build and i needed to buy lots of tools and decided to go for some upgrades - so beware ;-) )


a general question - any of you has any experience with shielding? The amp is super robust and doesn't mind, but my dac seems to picks up EMI from lightbulbs(halogen) and the fridge. I do use a line filter before the psu, so i assume it comes from EMI, not over the power line. What materials would you suggest? mumetal?
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Old 18th July 2016, 09:18 AM   #2595
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by xcj999 View Post
........... my dac seems to picks up EMI from lightbulbs(halogen) and the fridge.
Sort the fridge first. Fit a mains snubber across the motor, or replace the faulty one. It is always better to sort interference at source. The regulations require source to be properly RF attenuated
Quote:
I do use a line filter before the psu, so i assume it comes from EMI, not over the power line. What materials would you suggest? mumetal?
Halogen lights are just resistors. They produce VERY little emi.
Your problem is more likely to be the SMPS used to convert mains 220/240Vac down to the 12V required by the resistive filament.
How many smps do you have? Is it worth replacing them with current emi compliant versions?
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Old 18th July 2016, 09:33 AM   #2596
xcj999 is offline xcj999  Austria
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Quote:
Sort the fridge first..
thanks for the quick reply. The problem is, that the fridge belongs to our landlord, so i shouldn't do any mods i can't make "invisible" in case something goes wrong with the fridge. Its pretty new and a solid brand, so I am surprised about the interference.

Quote:
Halogen lights are just resistors. They produce VERY little emi.
oh, good to know. It's only one SMPS. It seems to be built into the shelf with the lights. Have to check if I can access it.
The wierd thing is, when i first put the dac in the new case, the interferences stopped. But thinking of it, I did change the wire length of the dac psu to the dac. Could maybe 5cm more length of the dc power lines be the reason for this?
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Old 18th July 2016, 06:40 PM   #2597
ggerla is offline ggerla  Italy
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Quote:
Originally Posted by ClaveFremen View Post
Post some good quality pictures, please.

Let's see if there's something wrong.

Did you clean boards?

Did you take the indicated measures?
In attach photo. Let me know if it is enough...
Attached Images
File Type: jpg IMG_20160718_203331436.jpg (431.0 KB, 231 views)
File Type: jpg IMG_20160718_203229524.jpg (344.7 KB, 221 views)
File Type: jpg IMG_20160718_202113426.jpg (466.5 KB, 227 views)
File Type: jpg IMG_20160718_202025119.jpg (592.9 KB, 225 views)
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Old 18th July 2016, 07:52 PM   #2598
ggerla is offline ggerla  Italy
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Quote:
Originally Posted by ggerla View Post
In attach photo. Let me know if it is enough...
OK
probably I found the problem I have inverted db139 and bd 140...
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Old 18th July 2016, 10:09 PM   #2599
ClaveFremen is offline ClaveFremen  Italy
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I'm happy that you found the problem.

Replace also both zeners and it's not a bad idea to replace also the LM317s.

LM318 and LM3886 should not be affected.
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Old 22nd July 2016, 04:01 AM   #2600
ghiglie is offline ghiglie  Italy
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Join Date: Mar 2013
Location: Ancona but roaming in Rome, Milan and Turin.
My build will stop again, I'm being in Milan and Turin till next Wednesday. I managed to solder Amtrans on one side - too late for asking, but if C32 goes reversed, printed side of Amtrans' goes on same side, right? Wish I'd have taken a picture...
My soldering struggle is still on, seems my iron suffers working at high temperature and sometimes it "misses it", while the wire I'm using needs it really. Hope I haven't burnt the Amtrans...!
So, I'll order 50g of Oyaden, just found a cheap eBay seller from Spain.

Inviato dal mio D5803 utilizzando Tapatalk
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