B1 Buffer Preamp

[sangeet2]

I still dont know what is wrong. My input cap is a Solen 1uf. I can put in a higher cap and report back

 

[KatieandDad]

1uF should be fine. Are you sure its 1uF and not a fake - incorrectly labelled. If the cap is good and the pot is correctly wired you might have an impedance mismatch with your source. IE the frequency attenuation might be being caused by the volume control interacting with the output cap of your source.

 

[sangeet2]

The Solen is from a very good seller Tubetown. Also I measured it before...

 

[KatieandDad]

What is the output impedance of your source ?

 

[sangeet2]

My test setup is this:
Macbook-Apogee One-Rotel HiFi amp.
I also tried it with a CD player as source...

 

[sangeet2]

What is the output impedance of your source ?

Apogee One is 30 Ohm

 

[KatieandDad]

If everything is OK then it might be down to the rest of the set-up. The B1 is pretty transparent so wont affect the frequency response of the rest of the set-up. Try taking the B1 out of the system by simply connecting the wiper of the volume pot to the power amplifier.

 

[sangeet2]

Hmm, if I dont put the B1 inbetween everything is good. In the Rotel I am using the Input for tuner...

 

[KatieandDad]

In my B1 I used DIY boards derived from the PCB layouts on the Pass DIY site. Even then I found discrepancies. I would check your boards very carefully by reverse engineering the schematics. Also check VERY carefully for hairline whiskers of copper or solder.

 

[sangeet2]

Try taking the B1 out of the system by simply connecting the wiper of the volume pot to the power amplifier.

Ok will do this

 

[sangeet2]

In my B1 I used DIY boards derived from the PCB layouts on the Pass DIY site. Even then I found discrepancies. I would check your boards very carefully by reverse engineering the schematics.

Did this already but will do it again,

 

[sangeet2]

If everything is OK then it might be down to the rest of the set-up. The B1 is pretty transparent so wont affect the frequency response of the rest of the set-up. Try taking the B1 out of the system by simply connecting the wiper of the volume pot to the power amplifier.

Without the B1 pot is working fine

 

[KatieandDad]

Reverse engineer the board. I suspect that there is an error somewhere.

 

[sangeet2]

Ok, it looks like I found a msitake on this PCB from the other forum. There is one cap with 0,1uF called C4. This one is not in the original B1…
If I take this off my pot behaves normal

Thanks alot for your input!

An externally hosted image should be here but it was not working when we last tested it.

 

[KatieandDad]

That'll be the same one that I found.

 

[sangeet2]

In yours?

 

[sangeet2]

But its funny anyeay, cause the guy from the other forum shows a pic where this
caps are also installed…

http://diyaudioprojects.com/Forum/download/file.php?id=4027&mode=view

But he didnt put in a pot...

 

[KatieandDad]

As I said before, try reverse engineering the board. I suspect that there is something wrong somewhere. It's a simple enough circuit to check. The problem that I had was that there an incorrect connection to the 0V top plane.

 

[Rixsta]

Hi, I have a 18 V, 5.0 W Zener Diode Voltage Regulator
I presume with just a simple circuit and this Diode i can have a nice steady 18v PSU.
Do i just attach the diode over the Rectifier outputs or ?

Ill search for some diagrams

 

[udailey]

It needs a series resistor to limit current or it'll burn instantly.