B1 Buffer Preamp

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#1,561
b-1

digi-key and mouser are probably the best choices- remember its the value and rating that are the most important then its the choice of manufacturer-
if you are a newbie stick with what is recommended- ie read the articles and posts carefully, make notes and you will find your sources.
hope that helps
rob
 
#1,562
Re: Re: New B-1 build

timothyshields said:



I am a new builder and am trying to construct the B-1 as my first serious audio project. I have read the Pass materials but am having trouble find the PN55D resistors and the capacitors referenced in the DIY article. Might anyone have a suggestion on a source?

Thanks for your help.
Click to expand...


This is the .25W resistor series I used from Mouser.
R2

here is the link to theAxon Capacitors from the article

If you want my excel order sheet send me an email
jim
 
#1,563
I have more or less read all the posts in this topic, but apparently I've missed something :smash:

Does anyone know the approximately output impedance of the b1 buffer? I think it said 2k ohm somewhere, but I'm not sure at all. If anyone can please correct me (or maybe confirm that the 2k ohm is right) it would be just great.

Thanks a lot!
 
#1,565
Re: Re: Re: New B-1 build

max426 said:



This is the .25W resistor series I used from Mouser.
R2

here is the link to theAxon Capacitors from the article

If you want my excel order sheet send me an email
jim
Click to expand...

Jim, Thank you for your offer for the excel sheet, but I cannot send you an email via the board until after a certain 'grace' period as per the forum mechanics.

I did see the Axons online, but saw the specifications where sparse the numbers had 'T' appended (10T) to them while I expected to see the unit uF (10 uf). Also, I noticed some vendors are backordered on the 1 uF capacity at 62VDC until mid-year. Might the Axon 1T at 250 VDC be compatible?

Timothy
 
#1,566
Theeagle said:
Does anyone know the approximately output impedance of the b1 buffer?
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Babowana said:
I believe it is about 1.045K . . .
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I have not measured the B1 output impedance (yet) but that 1045r figure will be made up from the 1k0 resistor on the output and 45r due to the actual output impedance of the buffer.
If you change the output resistor from 1000r to 510r the impedance seen by the next stage ~555r
 
#1,570
audiok said:
B1 I have been build, but my power amplifier is not Av gain enough.

Is anyone have an idea to build B1 with Av gain ?
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You could use a trafo attenuator with 6db gain, they are available
Dont know whether the buffer makes sense then

Would really like a response to the issue whether a buffer makes any sense at all with a TVC/autoformer
Or whether it only makes sense with say a tube gainstage

Or THEL in Germany sells small linegain trafos fore passive preamps
Dont know whether such are available from other sources
 
#1,575
In looking at the picture of the interior of the b1 I notice that
the singnal and ground wires from the circuite board to the
input and output jacks are not twisted. In the past wasn't
it universal practice to twist these wires? Why was this
practice changed?
 
#1,576
woody said:
In looking at the picture of the interior of the b1 I notice that
the singnal and ground wires from the circuite board to the
input and output jacks are not twisted. In the past wasn't
it universal practice to twist these wires? Why was this
practice changed?
Click to expand...


Papa was lazy that evening :clown:

do not overestimate some things ........ especially when signal is in line level range ...
 
#1,577
Sorry if this is a stupid question.
Why isn't coax cable used internally from the chassis mount rca to the pcb?

I suppose the output signal will be more sensitive to noise than the input (eg 2V in, 0.5V out).

Can anyone give some general advice (or a link) on signal wiring for the B1
 
#1,578
thanh1973 said:


Why isn't coax cable used internally from the chassis mount rca to the pcb?
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Havent used shielded cables fore many years, neither inside amps or as interconnects between amps
Just ordinary thin solid core wire

What matters is sensible layout
If it only works with shielded cables, then amp layout is less than optimal

But I have just heard about a radiostation transmitting with such powerful signal that all users located near by even need shielded mains cables

A good simple trick you can do is to mount noise filter on your computer mains
 
#1,579
thanh1973 said:
Why isn't coax cable used internally from the chassis mount rca to the pcb?
Click to expand...

The wiring is short and inside a box already.
Coaxial is not as easy to solder to an RCA, the last 1/2" is not shielded due to having to split the wire, why bother if the connection spans only a couple of inches anyway.

In a preamplifier with several long interconnecting wires it makes sense to use a shielded/coaxial variety.
Example is the Blowtorch preamp ; Twisted wire from RCA to phono board, Single short pieces between XLR and RCA at the output, All other wires are long and would be better off being coaxial.
In the Blowtorch, all single silver signal wires are spread out like a big leaf to prevent them from interacting.
The last inches of signal wire at the XLR output are sleeved to keep them separated, and also keep the right channel output wires clear from powersupply lines.
 
#1,580
thanh1973 said:

Why isn't coax cable used internally from the chassis mount rca to the pcb?
Click to expand...

Coax is *needed* at RF and Microwave frequencies for a constant impedance transmission line. For audio, shielded and balanced cable is best for noise immunity. But usually only needed in long runs, i.e. in a studio.

I mostly use single solid conductor twisted pair for wiring inside the chassis. Usually CAT5 or some other tefl0n insulated solid core wire. You can also get fancy and used 3 or 4 wire braids.
You can choose to ground only one end, or both ends, of the ground wire twisted (or braided) around the signal wire depending on how you are doing the grounding overall. This gives one shielding action in a much easier to implement (solder) solution than coax, which is a mess. Works for me.
Bob
 
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