Salas hotrodded blue DCB1 build - Page 65 - diyAudio
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Old 27th November 2010, 07:12 AM   #641
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No problem. All shunt´s in my DAC project run´s with the 10R for months without a problem.
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Old 27th November 2010, 01:13 PM   #642
Marra is offline Marra  United Kingdom
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I look forward to hearing your findings Oliver.
I altered the resistor on mine to 5ohms but went back to the 10R; the sound seemed to take on an edge; became very hifi so your opinions will be very interesting.
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Old 28th November 2010, 09:50 AM   #643
qusp is offline qusp  Australia
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where are the LEDs on your LED volume control Oliver ? well i've started building up mine, in the new place now and its about 6-7m to the monitors so thought id try them out. I too have ordered some mills, great resistors, love them and they have that really cool looking hand made chic look too. i'm going to see about getting some from isabellahnute (sp?) for this position also. the boards are going together nicely and quickly, well specced project guys. using TO220 zero recover diodes for the rectifiers at the moment, but considering cutting the trace and using a discrete rectifier stage with a couple of big *** rifa supply caps and suplying DC to the buffers. output resistors are just 1/2W PRP for now

Last edited by qusp; 28th November 2010 at 09:55 AM.
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Old 28th November 2010, 02:09 PM   #644
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Originally Posted by Marra View Post
I look forward to hearing your findings Oliver.
I altered the resistor on mine to 5ohms but went back to the 10R; the sound seemed to take on an edge; became very hifi so your opinions will be very interesting.
Yes dvb-projekt,

Your input on the 600mA current setting is much appreciated. I want to really know if going from 200mA (10 ohm) to 600mA (3.3 ohm) is worth it sonically, or if we are already pretty far ahead already.

Best,
Anand.
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Old 29th November 2010, 03:18 PM   #645
qusp is offline qusp  Australia
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decided to get some 7.5R mills as well as the 10R to just try a bit more current (~266ma) first up and I will parallel another pair for 3.75 to find subjective improvements. what size caps for bypassing the LED refs are people using? is 0.22 a median number have people found improvement by going up to 1uf or higher films here?
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Old 29th November 2010, 10:53 PM   #646
TerryC is offline TerryC  United States
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I finally completed installing all the components in the regulator section, and fired it up. All the LED's lit up. Output voltage measured at +10.58/-10.56. Waited a few minutes...... then I notice a bit of smoke rising!

I shut it down immediately and tried to spot which component was smoking, but no visible evidence. I also noticed that the heatsinks on the postive rail MOSFETS were substantially warmer than those on the negative rail.

I then proceeded to power it back up for a few seconds at a time, and take some quick voltage measurements. What I found was that the total voltage across the three current setting LEDs on the positive rail was 7.6v, and should be slightly under 6v. This would explain why the MOSFETS are running hotter, probably closer to 400ma than 200ma (using 10R current setting resistor).

So it appears that the current being drawn from these LEDs is much too high. Could it be that I have a bad JFET between the LEDS and the 100R resistor that is causing the extra current draw?
The regulator section of my build is now working after replacing all of the components in the current source section of the positive rail. I'm not sure which component was the culprit, but apparently the bad component caused others to fail as well.

It has become apparent to me that managing the heat from the MOSFETs is important considering their proximity to the Vref LED string. At 10R, using Aavid "Big Chief" heatsinks, my build is running a tad hotter than I'd like. Using the 5 second touch test, I can go 5 seconds but not much more. What's more concerning however, is that the Vout drops 2-3 tenths after having run for ~ 5 minutes. I suspect that the heat coming from the "Big Chiefs" is effecting the Vref LED string.

AAVID THERMALLOY|ML524-30-B|HEAT SINK BIG CHIEF TO247/218 | Farnell United Kingdom

At this point I just want to get this project done, so I think I'm going to go with a 15R Iref resistor rather than change heatsinks. However, you guys who used the massive blocks facing away from the Vref LEDs did the smart thing. Live and learn.
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Old 30th November 2010, 01:55 AM   #647
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Can anyone suggest a case for the buffer?
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Old 30th November 2010, 10:04 AM   #648
Marra is offline Marra  United Kingdom
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Originally Posted by TerryC View Post
The regulator section of my build is now working after replacing all of the components in the current source section of the positive rail. I'm not sure which component was the culprit, but apparently the bad component caused others to fail as well.

It has become apparent to me that managing the heat from the MOSFETs is important considering their proximity to the Vref LED string. At 10R, using Aavid "Big Chief" heatsinks, my build is running a tad hotter than I'd like. Using the 5 second touch test, I can go 5 seconds but not much more. What's more concerning however, is that the Vout drops 2-3 tenths after having run for ~ 5 minutes. I suspect that the heat coming from the "Big Chiefs" is effecting the Vref LED string.

AAVID THERMALLOY|ML524-30-B|HEAT SINK BIG CHIEF TO247/218 | Farnell United Kingdom

At this point I just want to get this project done, so I think I'm going to go with a 15R Iref resistor rather than change heatsinks. However, you guys who used the massive blocks facing away from the Vref LEDs did the smart thing. Live and learn.
I did as Salas suggested and fastened mine to the chassis floor; keeps the heat away from everything.
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Old 30th November 2010, 10:44 AM   #649
Atilla is offline Atilla  Norway
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Can anyone suggest a case for the buffer?
I know the DCB1 fits in the case described here: Good Case for simple chip-amps
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Old 30th November 2010, 02:56 PM   #650
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Finally got this thing built now. It's taken longer than I thought what with work and waiting for Texas resistors.

The only real deviation from normal is that I will be using a separate power supply. BC components 3300uF caps in CLCRC. I just happened to have these spare and wanted to use them rather than buying new ones. Transformer will be 50VA R-core 15-0-15V.

Hopefully get it up and running this week. I am slightly concerned with Terry's reports of excessive heat with the Big Chief heatsinks as I will also be using 10R Caddock MP930 resistors. we will see what happens. I have these in the basket just in case:

AAVID THERMALLOY|OS512-100-B|HEAT SINK MAX CLIP - STANDARD | Farnell United Kingdom


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