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Mezmerize DCB1 Building Thread
Mezmerize DCB1 Building Thread
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Old 16th May 2016, 06:40 PM   #1671
Salas is offline Salas  Greece
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Mezmerize DCB1 Building Thread
Quote:
Originally Posted by Liliya View Post
Salas: To be sure that I do not misunderstand: The Fairchield PF5102 are subsitutes for the SK170 in the PSU section only? The SK170 BL that are noticed to be matched, should they still be the "real thing" or is there some subsitutes to be used for them as well.
I still have some of my "old" and real SK170 BL left, but since I am building as much as four(4) Mezmerize, I will be in shorts of SK170 BL. I will use this four Mezmerize as buffers before the amplifiers in my 4-way active speakers.

Eivind S
Yes, substitutes for the PSU area only. Going along well given you will also perform that specific simple mod I attached. Don't worry when you will see in the datasheet that they are not pin compatible, because due to the way they are connected in the specific circuit positions the G-S or S-G pin order amounts to the same result. The audio signal path "JFET quartet" should be the real thing or the Linear Systems clone. LSKs are on the diyaA Store but graded not matched. Andrew used to have some LSK matches I think, not sure if anymore, ask him. There is also one ebay guy "alweit" from Israel that people say has genuine matched pairs. I don't know if Tea-Bag could also help you out, ask him.
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Old 17th May 2016, 02:03 PM   #1672
redjr is offline redjr  United States
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Quote:
Originally Posted by dodog View Post
...SjoerdSmits- Are you talking about taking three strands out of CAT7 and braiding them together? I was thinking of doing that but thought that, for some reason, people frown on a two-signal/one return braid vs. two twisted-pairs. A braid would make it easier to mount three wires in the PCB...
Despite Andrew's warning of using a braid, I've done so very successfully with no ill affects in my Light-Dependent Resistance (LDR) volume control here. Remember, for very short runs of signal wires this will usually work with fine results. For more critical application, or longer internal runs, I prefer very small coaxial cable.

Years ago I was building a project that called for some RG-174/U. I bought a roll and since I've started building audio projects, it seems to work very well where I need better shielding for longer runs of signal wire. It may be overkill for audio, but I have lots of it! It is super small diameter (1/8"), very flexible (26AWG) so it can be tucked away in tight spaces very easily.

Rick
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Old 19th May 2016, 04:27 PM   #1673
aradan is offline aradan  Singapore
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Hi All,

Thanks everyone who helped me to troubleshoot my dcb1 build. I have finally had a chance to test it with a power amplifier directly and it has shown no oscillation.

So the problem was when using line in input of audiolab only.

Thanks everyone for the help and all suggestions

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Old 19th May 2016, 05:11 PM   #1674
Salas is offline Salas  Greece
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Mezmerize DCB1 Building Thread
Good news. It maybe had seen some extra capacitance or something to that specific input. Don't mod it with higher output resistor than 220R if its not you must often pair it with the audiolab. Much resistance damping is not helping the SQ except where strictly necessary for good working order.
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Old 30th May 2016, 11:06 AM   #1675
soldersober is offline soldersober  Hong Kong
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Here is my first message on this board, troubleshooting the Mez.. I've seen similar questions before, but still don't get what to do

The 5 LED's on the plus side barely glow. Measurements:

Board voltage -10.5V / +8.9V
Across 2x68R: 3.55V om each side
Across 10R: 0.15V / 0 (zero)
DC offset 0.1mV / 0

Mosfets are equally hot on both sides. The amp does play music, although I did not get to judge how good it is yet
I did not match the LED's initially. Should I take them all out and resort? I have some spares to shuffle around if needed

Thanks for any help in advance
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Old 30th May 2016, 11:26 AM   #1676
Salas is offline Salas  Greece
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Mezmerize DCB1 Building Thread
Welcome to the forums. Make sure that the 10 Ohm resistor on (+) side is 10 Ohm indeed first and not higher by mistake. Change the FET next to that 10 Ohm resistor if she is right.
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Old 30th May 2016, 11:43 AM   #1677
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by soldersober View Post
Here is my first message on this board, troubleshooting the Mez.. I've seen similar questions before, but still don't get what to do

The 5 LED's on the plus side barely glow. Measurements:

Board voltage -10.5V / +8.9V
Across 2x68R: 3.55V om each side
Across 10R: 0.15V / 0 (zero)
DC offset 0.1mV / 0

Mosfets are equally hot on both sides. The amp does play music, although I did not get to judge how good it is yet
I did not match the LED's initially. Should I take them all out and resort? I have some spares to shuffle around if needed

Thanks for any help in advance
You don't need to match the LEDs
They each just drop some voltage and the string of LEDs drops a bigger voltage.

What voltages do you have at the AC input and at the DC input?
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Old 30th May 2016, 01:31 PM   #1678
soldersober is offline soldersober  Hong Kong
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Quote:
Originally Posted by Salas View Post
Welcome to the forums. Make sure that the 10 Ohm resistor on (+) side is 10 Ohm indeed first and not higher by mistake. Change the FET next to that 10 Ohm resistor if she is right.


It is 10 Ohm. I'll look for a replacement FET, thanks


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Old 30th May 2016, 01:35 PM   #1679
soldersober is offline soldersober  Hong Kong
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Quote:
Originally Posted by AndrewT View Post
You don't need to match the LEDs

They each just drop some voltage and the string of LEDs drops a bigger voltage.



What voltages do you have at the AC input and at the DC input?


AC inputs are close to 12V, DC is around 17V

Voltage drop measured across the 5 LED strings on the board is 9.9V on negative side and 8.6V on plus side


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Old 30th May 2016, 03:38 PM   #1680
AndrewT is offline AndrewT  Scotland
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You have been a bit unlucky to have that much spread between your 10 LEDs
Find the highest LED on the high side and find the lowest LED on the low side and swap them.
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