B1 Buffer Preamp

[kpsthakur]

Hi,

I am revisiting this post ~10 years after building my B1. I just wanted to encourage those thinking about building it to do it. It is quite a simple build and generally will not require troubleshooting. For fun I did my B1 in a point to point manner (no pcb) and put it in a simple enclosure.

My build is still working great with an 18v external laptop power supply after 10 years. I use it regularly in the garage coupled to a diy amp and mainly use a bluetooth receiver for input.

a few pics

Cheers

Ditto that, this pre still top’s any other thing I have built so far

 

[rob211264]

B1Buffer Volume Control

Can any one help
I have the Pass B1 board.
I'm not sure how to wire in a Alps27
The board has CW, W and CCW.
The pot of course has pins 1, 2, 3.
Thanks in advance.

 

[Soundhappy]

🙂

 

[rob211264]

Thanks that so easy that I can remember this next time. 🙂

 

[Abx74]

Hi,

I can't find post where Papa explain where to put weaker Idss Jfet in the circuit.
Help please...

Thanks

 

[Andersonix]

Put the lower Idss on the bottom.

 

[Abx74]

🙂 Ok thanks

 

[bjornje]

Hi guys - I got a stuffed B1 Buffer PCB (think 2008), seems to be well-soldered, high quality components and the correct JFets. It powers up, BUT there is a terrible distortion coming from somewhere in the circuit. Otherwise it is dead silent, no hum or anything (as expected). Only distortion when playing sound. I connect it to an amp camp which works just fine with my other gear, so no problem there. What could it possibly be? Bad cap? All parts seem to be in the right place and I have measured the resistor values as far as I can without ripping it apart completely.

 

[Zen Mod]

pics

 

[bjornje]

Here are some pics of the B1

 

[Zen Mod]

JFets in proper positions?

JFets of trusted origin?

vol pot properly connected ?

btw. those screw connections are not making your life easier ......... only less predictable

what's wrong with plan old soldering?

 

[bjornje]

JFets in proper positions, and yes they are trusted origin (from DIY audiostore). Have only tried one vol pot, but to my understanding it was properly connected. Even tried just connecting a resistor. My first try was to solder the connections directly to the board, but I wanted some flexibility so I attached to screw connections.

Question: What would happen if the polarity accidentally had been reversed (ground to positive and vice versa)? That was my first idea. Obviously, the polar caps could be damaged, so I exchanged them.

 

[Zen Mod]

post (or link) your reference schmtc and we'll tell what and where to measure

 

[bjornje]

Its the "original" schematic from Pass https://www.passdiy.com/pdf/B1 Buffer Preamp.pdf


PCB is also from DIY audiostore as far as I know.

 

[karajak]

b1 wiring


my b1

 

[zintolo]

Hi, what is the reason why it has been designed with single supply and coupling caps, instead of dual supply without coupling caps?

Thanks!

 

[Stanislav]

Simplicity.
Easy to build.
Easy to troubleshoot.
Same glorious, gorgeous sound!

 

[Zen Mod]

Its the "original" schematic from Pass https://www.passdiy.com/pdf/B1 Buffer Preamp.pdf


PCB is also from DIY audiostore as far as I know.

same distortion in both channels ?

 

[zintolo]

Thanks Stanislav,

any drawback in building a dual supplied version?

I have a device to blend different sources of audio in parallel (a DIY rack mixer) with 7815/7915 stabilized dual supply already there, I would like to buffer all I/Os and this seems a simple and very very effective solution.

Thanks

 

[Andersonix]

Hi, what is the reason why it has been designed with single supply and coupling caps, instead of dual supply without coupling caps?

Thanks!

There is also 'B1 R2' which uses one n-ch and one p-ch jfet with bipolar supply.