B1 Buffer Preamp

using a res as a ccs is the simple solution ("poor man's ccs" ).
imho a fet ccs has an "output res" in the 100k region............if you want to substitute the fet ccs with a res you should use 100k or better - but this does not fit into most schematics (exept some tube amps or sowhat).
have a look into the textbooks.........
 
mjf,

Thank you for your response. Currently I am using the ARRL handbook as a reference. I also have a couple of Douglas Self's books, and Bob Cordell's book. Approx 14 years ago I was taught some of this stuff in school, but haven't used it in years, and didn't get very deep into it at that time.

Now I am trying to recover the knowledge I had, and add to it :). I like to understand how all the components interact and create the finished product.

- Tim
 
I was using bad models in spice. I found better ones, and now I can simulate the same output for I-R1 or I-R3 using an 833.33 ohm resistor.
 

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So assuming that the output signal of the above two circuits(post 4493) behaves the same with JFET 2, or R9(~830k) installed; would it be correct to say that the both have different output impedances? Do you think it would be safe(won't damage anything) to build both and compare? This is completely a thought experiment for me at this point, so that I can better understand Nelson's choices in this design. Thanks.
 
I managed to put my B1 together!

I am now a proud owner of a working B1!
No critical listening just two hours testing that it works hooked up to an old amp and it does!

This is my first build ever, and this thread has been a great help. Thanks to everyone!

It is the kit from Jim`s audio.

For C100/C200 1,5 uF caps were supplied. Normally these are 1uF. Should I change those to 1 uF?
 

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I'm curious why you would buy a B1 kit from someone in China (did he steal the design?) instead of buying a pcb and matched jfets from PassDiy. Even more curious is why you would then post on the Pass thread asking for advice. Why don't you ask Jim about the values for C100/C200? :confused:
 
I am now a proud owner of a working B1!
No critical listening just two hours testing that it works hooked up to an old amp and it does!

This is my first build ever, and this thread has been a great help. Thanks to everyone!

nilsW - Well done on your first build. Those caps will be fine.

WBS - have mercy. This is nilsW's first ever build. He obviously wanted to start with a kit. The diyAudio store does not have the B1 in a kit, only the Mezmerize board and that is sold out currently. The B1 schematic is available for all anyway.
 
2cents, your point about a first build is understandable. And yes, the schematic is published for personal use, not for commercial exploitation by "Jim".

I only commented because some of us are bothered by intellectual property theft for profit.

Oh btw, it is an impressive 1st build. :)
 
The diyaudiostore doesn't have it but passdiy does PassDiy.
It isn't a full kit though.

Although the schematic is available for all I believe it is only for personal use not commercial and buying knock off boards is supporting those that choose to violate that.

I would guess that nilsW didn't realize any of that but it is good to put the info out there for anyone reading this thread that it is best to avoid encouraging those that rip off designs. Because even though imitation is the sincerest form of flattery it can make anyone who designs anything like this less likely to release the schematics and it could even make some less likely to come up with original designs in the future.
 
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are we breathing around ?

:clown:

everyone tried that

see Iron Pre and Iron Pumpkin as examples from Mighty Moi

that's one of rare occasions where I'm content with non fully differential treatment of balanced signal, speaking of buffers - hard to make it both purest and differential in same time

I believe its better to use a input transformer for the application.
 
Voltage and grounding questions... anyone?

I posted this a couple of days ago on a different B1 thread, but no one replied so I thought I'd try here:

I'm powering my B1 with a Meanwell 24VDC wall wart. What's weird is that by itself it measures 24VDC at the plug, but when I plug it into the B1, the power only reads 9VDC at the input pads!

Also, this morning when I turned it on, and before playing music, I could hear a faint 60 Hz hum on both channels. The pcb is isolated from the chassis by nylon stand offs. So I'm wondering how I should ground the pcb in order to eliminate it.

The only mistake I've discovered was wiring the linear pots backwards! I just copied the pics I saw of the commercial B1.:eek: