Salas hotrodded blue DCB1 build

Balanced DCB1

I’ve managed to do some listening to my balanced dcb1 I must say that I’m really impressed. I’ve only hooked it up between a Buffalo32 dac and a balanced headphone amp. No hum of noise problems to speak of. The fact I cannot tell that it’s in the signal is saying something :D

nycavsr2000 attached is an updated diagram that is working for me, well as least its sounding good so far.

Thanks Salas for a great project!
Some final pics for entertainment :snare:

*Wiring diagram updated to match that of post 1333 as requested. :captain:
 

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Your welcome Tea-Bag.

FYI the signal return on both boards are connected to ground chassis via a ground loop breaker as follows;

The ground loop breaker is a 10Ω 5W resistor in parallel with a 0.1µF capacitor rated at least 250VAC. For safety this capacitor should be rated for class X or Y (good for across-the-line use) with flame retardant casing.
 
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Hi John,
What do you use for volume on your balanced DCB1 configuration?

Volume is controlled via a volumite controller at the DAC. It’s a simple I2C/SPI device available from Twisted Pair Audio.

Nice looking build John.

If I recall correctly, you were running a stage 2 at 600ma. Are the mosfets staying cool enough?

Thanks Mike, yes 600ma, after a couple of hours I measure 35°C, comfortably warm.
 
the signal return on both boards are connected to ground chassis via a ground loop breaker as follows;

The ground loop breaker is a 10Ω 5W resistor in parallel with a 0.1µF capacitor rated at least 250VAC. For safety this capacitor should be rated for class X or Y (good for across-the-line use) with flame retardant casing.
I recommend a pair of diode connected inverse parallel in parallel to your Disconnecting Network (loop breaker).

This limits the voltage difference between chassis and audio ground to <700mVpk during normal operations and ~<=2Vpk during fault to earth operation. A pair of 1n4002 would do nicely.
 
Many of the earlier implimentations of the impedance between the Safety Earth on the chassis and the Audio ground were referred to as Disconnecting Network. I adopted this phrase because I could see that it avoided the misleading use of earth "loop breaker".
Many interpret that phrase as breaking the connection from Audio Ground to Safety Earth.
Some commercial gear even have a switch to allow this to be selected.
Some commercial gear have two connections from Audio Ground. One direct to chassis and the other via a resistor, labeled "hum reducer".
I'll stick with "Disconnecting Network" to avoid those ambiguities.

Join two traces with a diode. Now connect a second diode in parallel. There are two ways to add that second parallel diode. True parallel or inverse parallel.
Inverse parallel allows AC and DC current to pass in both directions with a maximum voltage drop (Vdrop) of Vf for the diode. This is usually given in the datasheet and can vary from 400mV to a couple of volts depending on the current passing.

If one uses a CL60 as the sole component in the Disconnecting Network, then try to determine Vdrop when Fault Current passes from Audio Ground to PE.
I don't know how to test that a CL60 is safe for all fault conditions.
I have tested inverse parallel diodes and know they are safe. See my report from a couple of years ago.
 
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Hi

Can somebody validate the balanced wiring on Tea bag's blog. It appears to be different from the one posted in #1321. It seems to be missing a wire on the left channel input. Furthermore, it indicates both boards as being for the left channel.

regards.

necplusultra thank you!

This is now corrected see attached;

Tea-Bag please update the diagram to the attached.
 

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I reckon from the transformer Manufacturers' data that an 50VA 15+15Vac transformer has a maximum continuous DC output current of ~830mAdc.

Running a 50VA transformer continuously at ~72% of maximum rating is asking a lot. It will work, it will run warm and even warmer if Ta is high.

I prefer to recommend that continuous DC current be <=50% of maximum continuous rating.
 
I reckon from the transformer Manufacturers' data that an 50VA 15+15Vac transformer has a maximum continuous DC output current of ~830mAdc.

Running a 50VA transformer continuously at ~72% of maximum rating is asking a lot. It will work, it will run warm and even warmer if Ta is high.

I prefer to recommend that continuous DC current be <=50% of maximum continuous rating.

Hi Andrew,
It will be better to use one with 100VA and run cooler.

Thanks
 
I reckon from the transformer Manufacturers' data that an 50VA 15+15Vac transformer has a maximum continuous DC output current of ~830mAdc.

Running a 50VA transformer continuously at ~72% of maximum rating is asking a lot. It will work, it will run warm and even warmer if Ta is high.

I prefer to recommend that continuous DC current be <=50% of maximum continuous rating.

Andrew for typical 50VA single secondary 15V winding ~1.6A, does one typically half that value to calculate continuous DC output current for ~830mAdc?