Building a symmetrical PSU B1 buffer

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Historic! One like this?
 

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diyAudio Chief Moderator
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That one is good to run as is at 60mA. No sinking. To make it symmetrical Vref for running it better at high mA you got to do this leg trick for that specific JFET only. Solder those two legs together and insert it as a two pin device. The original issue board connections will do the rest.
 

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I will attempt to use 2SK170V in the B1
Dissipation will be 10V*IDSS in DCB1. Type V has much IDSS. 15mA example will run at 150mW. Better don't run them unassisted like this. They may fail for longevity. There are TO-92 mini-sink hats to find in vendors. Or you may come up with a diy solution. High IDSS is good for DCB1 signal quad JFETs. THD and output current spec gets better. But those JFETS when beyond BL range should be running heat exchange assisted.
 
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The asymmetry I had embedded in that particular issue was in the Vrefs of the PSU to aid lesser matched signal JFETs offset and promote little more second harmonic because it was running low mA lest it would sound bit dry. It could be readily seen in the positive side 5X Leds cluster shining bit brighter than those on the opposite side. Positive is bottom side in #2742 post's picture.
In DCB1 there are only NJFET used so its not the same as with complementary pairs.
As for the PSU NMOS and PMOS power MOSFETS you don't need to match VGS in this.
 
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I have one on it's way by mail, and I have the original lighter note ldr kit as volume control, my problem is a small chassis with foot print of only 190 by 190 mm, psu might not fit, but have to be external, I guess that's also the optimum solution noise wice.
Have never listened to a b1 buffer so quite excited, ldr same deal. Hope combo is sweetspot.
 
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Luckily I had one such board and it measures 122mm by 68mm. It accepts five 100uF 5mm pitch 10mm max diameter electrolytic capacitors. Also two 7.5mm pitch 18mm max diameter 4700uF. Use no less than 25V spec for all electrolytics. Preferably 35V. For all resistors it allows 12mm leg to leg bend distance. It accepts four 1A rectification diodes at 10mm leg to leg. And one same dimensions flyback protection diode found next to the relay.
The Omron relay code printed on the PCB is not available anymore but you can alternatively use KEMET EA2-12NJ or NU.
There was a BOM indeed but not relevant for codes today. Still all component values are printed on the face of the board.
Its a single layer board with a couple of over-paths so don't forget to jumper over the two white lines end points. A long line at AC IN area and a short one next to two resistors near the output area. Also jumper the resistor with the NOTE word in it since the relay I suggested is a 12V type.

Hypno  Salas DCB1 2009 pcb version.jpg
 
Very good info you brought.. now I can start pick some parts. Board is a bit smaller than i imagined, but that is a good thing.
One question more, I mentioned external power supply, and I found this psu I build for some differential probes, and other measuring gear, it consists of two beta 22 psu low noise, one is dual other is single, both are getting dc from a ripple eater, and even under 1 amp load, ripple is but a few mv, could the dual beta22 power the dcb1 and the other single rail beta power the ldr volume control. . ? I'm unsure of power consumption of dcb1. Both supplys can regulate from 0 to 22 volt. I have some very nice multi chassis connectors male/female, I believe they are used is aero, and would use 1 meter cable with 1.5mm2.
Any issues with this? Or totally overkill? Also unaware of dcb1 pssr.
Hope this makes sense.
And once again thanks for taking time to help me make a great preamp.
Ps if the above approach is used I would off course not populate the rectifier sections of the boards.
 

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You can connect it as a symmetric pre-regulator directly to the 4700uF local reservoir capacitors. From there on its own 10V shunt type regulators take over and contribute much to its popular sound signature. DCB1 expands subjective traits over classic B1 a lot. That's not only about it deleted the coupling capacitors. Their PSRR is good enough for the circuit to deliver a measured 0.001% THD+N at 1VRMS signal output using just a transformer. With those 68R//68R board printed setting resistors values it will draw 50-60mA constant current per rail. Mosfets without sinks is still workable with that figure. With 18R//18R goes basic hot-rod at 180-200mA per rail and the Mosfets will need moderate sinks or direct to the box mounting for heat transfer. Insulation pads are needed in any situation that the Mosfet tabs will meet through a common conductive surface.
 
Okay, I believe I will use the shown psu, its build and ready to go, that's the nice thing with diy, you can go all in, overdoing stuff.
I can mount the mosfets to the bottom plate of chassis and boost the bias a bit, it's a steel chassis with aluminium front, but still I can absorb some heat.
So you think I should go all in using the shown psu? Pros/cons.
Attached photo is the leftover chassis mc tube preamp
 

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Pros is you get to utilize it and it maybe makes the whole thing a little bit better. Double regulated dual box hi-end configuration appeal and all that. Cons would be unnecessarily spending money and expanding to dual chassis for a an uncertain % of extra goodness vs just a small transformer in one same chassis if you didn't already have that PSU.
 
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By the way keep in mind that LDR is active attenuation in a way and brings second harmonic vs a basically well working series type potentiometer. How much depends on the specific type's photocell linearity and how its driven. It can be more likeable than most transparent I mean. You got to compare the two solutions on your own of course.
 
I will go ahead and build the darn thing, and return here with my impression. The ldr is a complete kit from Uriah dailey unassembled, but with measurement charts for all the ldr, can see it will require some fine tuning, to match source and amp. Each reg board has 5 trimmers .
Again thanks for taking your time for my project, have a pleasant day.
 
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