Salas hotrodded blue DCB1 build

I see. My plan was to use a 150VA transformer, but I may need a larger toroid. I've searched for a formula to calculate the required transformer power rating in order to have sufficient capacity for the 2 A version of the DCB1. Alternatively, is there anyone out there who has built the 2 A version, and would like to share details about toroid capacity?
 
a 150VA 15+15Vac transformer has a maximum continuous output current of 3Aac.

If you use that to feed a capacitor input filter you must de-rate the continuous output power. Usually the de-rating is around DF=0.70
The effective continuous output power is ~105W
The effective continuous DC output current is ~1.5Adc.
If you run any transformer continuously at maximum rating, it will run hot!
For long term reliability and for cooler internal chassis temperatures, it is advised to draw a continuous DC current that is less than the maximum rating.
I recommend around 50% of the maximum rating for cool operation, i.e. ~750mAdc.
 
a 150VA 15+15Vac transformer has a maximum continuous output current of 3Aac.

If you use that to feed a capacitor input filter you must de-rate the continuous output power. Usually the de-rating is around DF=0.70
The effective continuous output power is ~105W
The effective continuous DC output current is ~1.5Adc.
If you run any transformer continuously at maximum rating, it will run hot!
For long term reliability and for cooler internal chassis temperatures, it is advised to draw a continuous DC current that is less than the maximum rating.
I recommend around 50% of the maximum rating for cool operation, i.e. ~750mAdc.

That was clarifying, thank you AndrewT :).
 
I have a bit of a head scratcher here that I've not been able to find the cause of so far. I am rebuilding a Mesmerize DCB1 into a different case. It has worked faultlessly for around 3 years and the initial testing in the new case went OK. But now neither of the Vref LED chains light up and the regs are outputting 0.4v and -3v. The only change I have made is increased the CCS current to around 400mA, it was around 100mA in the old case. After rectification I have around +/-19V at the smoothing caps.

All LEDs test OK and the IRFP's have tested OK out of circuit and they have been replaced with new. All resistors measure OK. As it has been working for so long I don't have any polarity issues. Aside from the CCS resistor are there any other changes that need to be made when using 400mA and over? I didn't spot any. The CCS transistors are getting reasonably warm, all were bolted to a case with 2mm aluminium bottom and were getting only slightly warm when it was working.

As an aside, I had an identical issue with another Mesmerize board (but only on one of the regs) that I didn't find the cause of the issue for.
 
diyAudio Chief Moderator
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A way to have that is to stuff the PMOSFETS for NMOSFETS when rearranging. So recheck the types and sides closely.
Another is to have broken an Rset resistor by heat if small sized or it lost contact to some pad or trace due to rework. Perform continuity tests especially in reworked areas.
Also can break one or more DO-41 bridge diodes in the long term when operated above 250mA. This is constant current, no chance for them to breath. Mezmerize can be reliable up to 200mA CCS when constructed typically in spec. If its nothing of the above see that the BC transistors are healthy showing Vbe about 0.6V first. Then measure each JFET across for showing few tens of Ohms (when powered off) not open or short.
 
Ok, I can start building my B1 :) alle components arrived from Mouser.
I was waiting for it because I first wanted to know what voltage there is after rectification.
knowing that..I will start matching the Vref Ledstring.
Some helpfull guy from the netherlands donated me a really nice attentuator from a "Burmester". A ball beared beaty. You can feel the high quality of this. It is 10K....but no problem as my sources will be x10 lower in impedance. So I'm not worried at all.
An externally hosted image should be here but it was not working when we last tested it.

I hace 8 capacitors of 4700µF available..with a big ripple current. My plan is to hotrod @ 200mA.
rectifiers are MUR 860 and transfo cn give 3,3A per 15V rail. Any advise how much capacitors putting in parallel? or just use 4700µF per channel? Or going extreem with almost 20.000µF /channel for future hothothot rod.
 
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do an rCRC
the usual capacitance for normal output mains ripple is ~2mF per ampere. a bit more ripple to a bit lower ripple would be covered by the range 1mF to 5mF/A
You are asking for 0.2A. The most capacitance you will need for normal Pre and power amps is about 1mF.

Use your 4m7F that lowers your ripple to ~20% of the good standard.
The rCRC will lower it even more.
 
do an rCRC
the usual capacitance for normal output mains ripple is ~2mF per ampere. a bit more ripple to a bit lower ripple would be covered by the range 1mF to 5mF/A
You are asking for 0.2A. The most capacitance you will need for normal Pre and power amps is about 1mF.

Use your 4m7F that lowers your ripple to ~20% of the good standard.
The rCRC will lower it even more.

Dear AndrewT. what do you mean with rCRC in this case please?
On this moment I'm just using one 4700µF / channel...but I can raise this.
 
r = little resistance made up without adding any extra resistor.
It is the resistance of the transformer plus the resistance of the rectifier plus the resistance of the wiring.
R = added resistance between the first capacitor and the second.
C = the smoothing capacitors.

Is it nescessair for putting an R? I thought that it was only done when putting caps in serie....for giving them an equal voltage.
I don't like bleeding R's in this case.
 
Why waist all this time and money on a good designed supply but a stupid B1 ? A Burson Supreme opamp is is a factor 100 better.

The reason I went for the B1...is it design and simplicity. I'm not in need op an amplifer as you mention.
When the B1 is finische I can compare it with popular OPA's....I really like OPA's with JFET input.
But it is a totally different approach.

Thank you for you're feedback....nice word when talking about opamps. I also like the burson supreme opamp's...but it is something different.

Reason lot's of poeple went the way of B1....is impedance...when impedance wasn't an issue...we just went for an attenuator and nothing else.

In the case of a DCB....when well build...no waste of money to coupling caps.
 
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diyAudio Chief Moderator
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Care to clarify this answer? Have you done the test? I've tried my share of preamps and the DCB1 is in a league of its own when well built. Specs aren't the only thing here...

Do

If needing much current and very low output impedance in a system so to drive many meters of interconnect cable maybe, or a demanding low Zin & low gain amp, or multiple amp channels in parallel, there could be insufficient to use an IDSS biased small JFET source follower (that is what a B1 technically is). In general, the subjective feedback is overwhelmingly good in many years from (thousands?) of B1/DCB1 builders across a great range of audio systems. Phenomenally high positively agreeing subjective % for any type of audio gear as a matter of fact.
 
Then there are individuals that might need gain and is used to an amount of harmonic distorsion. Those will maybe not be satisfied. They simply built the wrong gear for their taste and/or need.


I need gain :) ....we all need....in the power amp ;):sing: My total cost of components for a DCB1 will be amount 160-150 euro's (including the case...270 euro's)...including a beautiful burmester attenuator....a helpfull enthousiast from the netherlands sponsored me. keeping it tha low cost is that I don't trow thing away..so I don't buy cable sleeves etc...all these will be disposable materials...also a lot of connectors etc...
I build a lot in the past...and I think a B1 buffer is the most beautifull and valuable thing to build.
As phono stage I will buil something better I have on this moment. Maybe I will step into tubes for this. There are clones available from big big brands....

For me....I like elektronics...And for me it is clear...poeple like Salas...andrew...all the rest. You guys help!
You all give me the chance for building something beautifull. thank you in advance.
 
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Is it nescessair for putting an R? I thought that it was only done when putting caps in serie....for giving them an equal voltage.
I don't like bleeding R's in this case.
I don't like "bleeding Rs" either.
When I see them recommended, I often say they are a waste of resources.
But they are worse than just that.
They increase the ripple on the supply rails and increase the heat inside the equipment and increase the cost of operating the equipment and...etc.

Don't use bleeders unless there is an absolute Safety Case for including them. BUT design this special safety case so that the bleeder does NOT bleed during "normal operation" and ONLY bleeds off the dangerous charge after shut down.