Building a symmetrical PSU B1 buffer

I suggest that you get a second opinion before you order, because it is always a lot safer when somebody else error checks a new part suggestion.

That said, this one should work:

551-UA2-12NU [Mouser Part #]

http://www.worldproducts.com/pdfs/ua2ub2.pdf [manufacturer data sheet]

They're not cheap, but they also have "silver alloy with gold overlay contacts".

Mouser has many other relays that fit the bill. Just look for relays with the same specs as this one and/or the TQ2-12V.

Forget all the above. Mouser has the TQ2-12V in stock. That is what I use. Same specs and much cheaper than the NEC. Buy those and you'll be happy.

769-TQ2-12V [Mouser Part #]



any other mouser relays that would work? they are on back order.

edit - they have the 5v in.
 
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any other mouser relays that would work? they are on back order.

edit - they have the 5v in.

That is why we found a way around 5V relays on those boards too, so to have alternatives. Isn't there another make with compatible datasheet and pins order / connection on Mouser?. What comes up when you search for 12V relays?

Can this be good for instance? Please check thoroughly.
 
The relay that you are pointing to is of the "latching" variety. I'm not so sure that that is good.

Mouser does have TQ2-12V in stock. So he should be good to go!



That is why we found a way around 5V relays on those boards too, so to have alternatives. Isn't there another make with compatible datasheet and pins order / connection on Mouser?. What comes up when you search for 12V relays?

Can this be good for instance? Please check thoroughly.
 
Can't give you any warranties that your build ain't going to collapse at a point and drive DC to a de facto direct coupled and not output protected amp like the F5. Or that you will not never ever have a faulty source connected. On the other hand nobody says that the amp will never fail itself for instance. If you use just one capacitor in the chain, and that will be between buffer and F5, you will be safeguarded though. Using a shunt over a normal B1, I don't know if it matches this one, never tried. Uses 2 caps BTW.

Cheers.



I will go with the normal b1 then. It seems easy enough to build it, and after I have some more insight I can always build the one with the shunt powersupplies.
Perhaps the normal b1 is challenging enough for me. ;-)
 
2SK170 swap out for Shunt PS ??

Salas,

Any thoughts or considerations for swapping out the 2SK170's in the Shunt regulators with other JFET devices ? If so, do you think that either of these choices might work;

2N5245 <http://www.fairchildsemi.com/ds/2N/2N5245.pdf>

J210 <http://www.fairchildsemi.com/ds/MM/MMBFJ210.pdf>

The Idss range and Power dissipation are close to the 2SK170BL grade and the Yfs fall within the substitution range Nelson Pass originally identified for the B1 buffer.

Thanks,

David
 
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Vgs(OFF) is high, especially with the 210. Pins are incompatible with the boards too. The one under the leds could be J201 which has adequate pinch off, then again the 1.8Vf leds would not reach desired Vout with just 1mA max it can offer. In another board with one more led maybe, still pins are different. For the B1 audio part pinch off isn't a consideration. Its another thing there.
 
Salas,

Thanks for looking at it. :)

I didn't think that the pin outs would be that big a deal with the 2SK170 use in the earlier Shunt PS drawings showing the Gate and Source pins shorted ( J210 could still be inserted the same manner, 2N5245 would have to "face" the opposite direction of the board layout).

But with the other adjustments you touched upon, it may not be worth the tweaking at this point.

David
 
I did a bit more work on the compiled "build guide" the other day, a few additions and a fair bit of trimming. Any suggestions for improvements/alterations are welcome. Maybe it could be combined with the wonderful BOM, maybe not... Hope it helps...
 

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Salas,

Thanks for looking at it. :)

I didn't think that the pin outs would be that big a deal with the 2SK170 use in the earlier Shunt PS drawings showing the Gate and Source pins shorted ( J210 could still be inserted the same manner, 2N5245 would have to "face" the opposite direction of the board layout).

But with the other adjustments you touched upon, it may not be worth the tweaking at this point.

David

You can use alternatives in the led ccs and bjt collector ccs positions if you don't mind the pins hassle and figuring it out personally. Also you can see what j201 can do with what resistor as figured in my hypnotize as a psu only guide and get your desired voltages. But this is beyond the GB boards thing, its no practical alternative for general guiding and will create immense confusion in the threads. I.e. You are on your own if you fancy to modify. Those jfets are noisier than 2SKs non the less.
 
The one thing I've seen that ends up causing lots of grief for no good reason is missing jumpers. My build guide would start like this:

'Make sure you install all jumpers first.

In any build using 12V relays you need to install three jumpers. Install one jumper at "AC IN". Then find the white line right next to the two 220R resistors on the left output and insert a jumper across the two solder pads. Finally insert a jumper across the resistor pad marked "Note" in the 12 volt power supply for the relays.

In any build using 5V relays you need to install two jumpers. Install one jumper at "AC IN". Then find the white line right next to the two 220R resistors on the left output and insert a jumper across the two solder pads.'
 
Hi Grufti,

Good point...it is difficult to know how much detail to put in, or what the experience level of all the builders will be. Usually I build with an overlay and a schematic, and enough info to know any special requirements, e.g. in this case there are component matching requirements. That's what I was aiming to fulfill with the brief build guide, just enough info and links to get the job done.

If you want to go into more detail, for sure, go ahead, and from the 2 paragraphs you wrote above it looks like you have a real talent for this! Feel free to write a more detailed guide if you wish, I'm sure it will be appreciated.
 
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Hi Salas,

Sorry if this has been asked before, but I'm wondering why the swap of the 1M and 220K compared to the original B1. ie the original has a 1M shunt resistor on input and 221K on output, but the schematic at the begining of this thread (not the hand drawn one) has 220K on input and 1M on output.

I was also curious about the power supply caps. Is the shunt reg so low in ripple you can get away with only 100uf in the supply and nothing locally on the B1? It's a dramatic difference to Nelson's brute force approach with 2 X 15,000 uF ;)

Tony.
 
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Has to do with my suggested log pot value and the way I want to subtly help its balance between channels. 1:10 //.

Yes its very low in ripple. Bigger caps across its Vout just ''slow'' it down. Of course there is enough rectification filtering at 4700uF.

Its interesting when you listen side by side to two so basically same designs but differently executed as a whole. There are so many PCB's given on the GB, that we will possibly get feedback by people having original B1s also. Will be educating on how people perceive or not little stuff in the grand scheme of things.
 
The Pass PSU is simply an RC filter.
The Cap is sized appropriately to the value of the R used. It is not brute force.
The regulated supply starts from a completely different specification, but ultimately tries to achieve as little noise as possible, much the same as the RC filter tried to do.