Building a symmetrical psu B1 buffer

[crt]

Originally posted by thanh1973
I just noticed right and left channel input share the same ground point.
Is this the preferred way of doing things?

sorry, i'm i have several pre-amp before (use ground like that) and all is quite.
is there any suggestion about ground ?
so maybe i can fix the layout next time.

Originally posted by Salas


If you print it out at 124X62mm the Mosfets and Transistors / JFETs pitches look right. I did and compared with the actual semiconductors. The filter caps pitch looks smaller than 4700uF snap in that I compared. But there is pad space to drill wider. Maybe Crt used straight long pin filter caps. I emailed him to give us the intended dimensions. If you want the high resolution files and Eagle files, email me. Jean Paul wants something arranged differently, don't know about that. Me I find the current one practical enough.

the dimension is 116,3 mm x 62,3 mm.
directly print my PDF files with A-4 paper.
about the Caps 4700uF/35V diameter, i will check it again.
any prefer diameterand pitch for those caps ?

Originally posted by Salas


I can see that Crt likes System Of A Down. Plus Malakian's short lived assortment ''Scars On Broadway''. About the snail, he is the one to tell us the symbolism if he likes.

sorry, i forgot to remove that "thing".
i will remove the SOAD/SOB letter in next layout.

Regards
La Ode

[Melon Head]

If you look at nelsons layout there is ground point for each channel input. I am not sure if this is the preferred way, but if Nelson does this it definitely isn't wrong.

[tinitus]

Originally posted by Salas


The filter caps pitch looks smaller than 4700uF snap in that I compared.

Do you use snap-in caps?

Those are high ripple caps for poweramps, I suppose

Why not use better ones like Elna Silmic, or similar, when it seems possible

But maybe cap quality matters less with the reg?

Input ground
If common ground is ok, at least make room for two pins
Some use small ground lift resistor?

I prefer a common ground for all connection, and not before that
Not even for supply, which needs double bridge to do that
I suppose thats what "star ground" is about
I like mono, but dont know really
Some claim a common supply is better

Is this shunt reg maybe similar to what Thel calls "electronic choke"?

[Salas]

Depends on what quality/value I got. I just checked with typical snap in and I saw that a wider pitch is needed to accommodate such. Panasonic FC 4700uF 25V and a 50VA 2X12V trafo are great for this project, and the lead spacing is correct on pcb as it is. Having a bunch of 4700uF/35V snap in I would just drill at 10mm instead of 7.5mm wide. The filter cap quality is still audible but little with the constant current shunts and particular constant current buffer. Silmic II is a good choice as well. Personally I prefer the FC or TS-HA.

I think that the ground is not problematic in the particular PCB. Remember that this is a tested PCB grounding by Crt which is silent when driving his Symasym, DX, and JLH amps.

Common supply with very low output impedance in PCB incorporated shunts, leaves very little to desire towards double mono shunts. B1 draws constant current as well. So no appreciable mixing between channels on the rails.

No, gyrators are constant voltage load sources. Have made and used such as anode loads on my tube preamp experiments.

These shunts are very low noise voltage referenced constant current sources, controlled for voltage stability, by a counteracting parallel circuit.

You can imagine many configurations, like a double trafo/bridge, 4 shunt, star grounded double mono with on board volume pot and switched input relays plus mute for a luxury full preamp version.

As a basic functional block/part of a larger free configurable scheme, I find Crt's PCB a good compact module.

For more, as SOAD would say, BYOB.

[tinitus]

Thank you, its clear now

Issue of possible failure have been raised from start
Though, I have never had a supply failure ever
But is there any component that could be suspect in the long run

Like say, if its left powered on forever, which component is likely to fail first
Like say, are those light diodes 100% reliable and what happens if just one fails or drift, or whatever

Well, they probably wont fail in my lifetime
But is there anything in such a supply design that could make it more sensible to failure than any other ordinary supply

[Salas]

I would only expect a Mosfet to fail if anything would ever fail. I have a shunt like that but at 230mA on for 6 months now 24/7, no problem yet. If you use 68R//68R=R1=34R and your LEDs are 1.8V Vf then just 60mA will run. I would not be afraid of 0.43W on the shunt TO-240 Mosfet. You can use rudimentary sinks on all Mosfets if in a hot environment and always on. If your amp has an input capacitor, then there is no problem anyway even if one rail fails and DC appears on B1's output. Actually, a non capacitor coupled B1 is NOT recommended for driving amplifiers that lack input capacitor or DC protection. This is a disclaimer.

[tinitus]

Originally posted by Salas


Actually, a non capacitor coupled B1 is NOT recommended for driving amplifiers that lack input capacitor or DC protection. This is a disclaimer.

Sorry for being slow, but wheres the advantage of a no cap output, if the cap is needed on poweramp input instead, Im confused

In which case I dont see the advantage over a "single end" B1, say with your Salas positive shunt reg
Transistor matching have been said to be a non issue anyway

Please, whats this about, how does this affect sound quality
We have heard some like something better
But I still have no clew what its about
What can we expect if doing this

btw, are specs the same as B1, output impedance etc

[Salas]

2 coupling caps less than in a similar case of driving an amp with an input capacitor and using a cap coupled B1. No line input no line output capacitor. Also if a DC coupled amplifier has reliable DC fault output protection system, then no capacitors at all. I just can't give a general recommendation of a capacitor-less B1 being used just on any amp because its a safety risk for the speakers just in case something fails.

Crt has made normal B1, symmetric series supply no caps B1, symmetric shunt supply no caps B1. He can tell you which one has audible advantages to his ears or not.

Output impedance is less than with normal B1 due to 220R series resistor instead of 1k. And of course lower anyway towards DC.

[jean-paul]

Tinitus, please send me a PM. I made a drawing with the differences.

[crt]

@ Jean paul
i will aborted to build the PCB layout include the pot.
sorry JP, i have little tried to put the Pot. onboard
do some routed parts, but i can not find a good wiev of PCB layout.

@Salas
about caps i use elna re-3 4700uF/35V (wrote in the body)
have diameter 18 mm with 7,62 mm pitch.

about sound of caps,until now i can not tell the differencei have tried Pan FC and Rubycon and this elna too. but sound same in my ears
sorry i have very limited ear bandwith.

maybe on saturday, i will try to reduce the R (from 3X 68 to 2x 68)
try to match the supply reg too.
and check it maybe sound will change or not.

YAP. SOAD RULES!