New-building of my B1 buffer

[AndrewT]

Refer to my last schematic.

and ask yourself one question;
why are the voltage at x3 different from the voltage at x6?

 

[AndrewT]

The tail current through R10 is (16.57V-8.49V)/2K7 = 3mA.

that is the current through R10, not the tail current of the LTP. A large proportion of the current through R10 goes out the base of Q3. The remainder is what is conventionally called tail current.

In most LTPs the base currents are so small that we can ignore the it and look at either emitter current or collector current to see if the difference amplifier is balanced and th see the operating current that each transistor should be selected for.
Your schematic values are so skewed, that convention does not hold any longer.

 

[Babowana]

that is the current through R10, not the tail current of the LTP. A large proportion of the current through R10 goes out the base of Q3. The remainder is what is conventionally called tail current.

Objection!
Tail current is tail current. Whole current flowing through the tail.

In most LTPs the base currents are so small that we can ignore the it and look at either emitter current or collector current to see if the difference amplifier is balanced and th see the operating current that each transistor should be selected for.

Yes, most diff pair is balanced, having the same character and seeing the same base voltage with respect to the dc current.

Your schematic values are so skewed, that convention does not hold any longer.

Absurd . . .
I have built and measured all


><

 

[AndrewT]

ask your self that question re. x3 x6

 

[Babowana]

and ask yourself one question;
why are the voltage at x3 different from the voltage at x6?

ask your self that question re. x3 x6

I have already talked about it in my post #279. Read again.
Please don't send me private E-mail. I feel like receiving kind of a blackmail . . .

 

[Leeuwarden]

Hi everyone!

I have built a B1 like Babowana's. Used his lay-out from page 1 of this thread (thanks Babowana for publishing!). I got the left channel working and from what I hear it sounds like it would be nice to hear the right channel too...

One way or another I can't get the right channel working... Is gives a light humming sound and very faint in the distance I hear some music. I checked the wiring but maybe I'm going blind or something... I don't see a mistake...

Since I'm only doing this as a "kit-builder" I'm afraid I need some help...
The underside of my "fröbel-work-pcb" looks like this (Two wires on the topside is the LED):

(Edit: picture too small,I'll post a bigger one)

 

[Leeuwarden]

Bigger picture of the underside...

 

[AndrewT]

I cannot identify the two channels from that underside pic.
There are too few similarities to allow me to recognise which components are wired identically.

 

[Leeuwarden]

Maybe this helps?

 

[AndrewT]

right in the middle of the board, looking at underside.
The 10uF to the jFET looks like it goes to the wrong leg of the FET. It should connect to the top leg not the middle leg. The middle should be connected to the bottom, because that's your FET CCS

 

[Leeuwarden]

Thanks Andrew! I must have been checking for at least 5 times or more. Did not see it. I just wired it correctley and I have two channels playing.

First impression is I can put my Blue Velvet pre-amp aside for this buffer...

 

[sandyhooker]

Yes, I will build Type A first.


>><<

Did I miss something??Why such heavy duty mosfets??Why not 9610??

 

[sandyhooker]

Sorry!!Reference is to Babo's regulator!!!

 

[Babowana]

Did I miss something??Why such heavy duty mosfets??Why not 9610??

Simply because of availability . . . no other reason . . .
Sure that 9610 will also work.

 

[ruudjoo]

I bought Leeuwarden's B1 (see just above here) and it works fine but I only use the first quarter of the pot, and because I am not (NOT) an electrowizzard I want to know what value I should choose; I use a 10KOhm now; would 100KOhm be better? And should I use linear or algo something type?
Ruudjoo

 

[ruudjoo]

reply doesn't work for me?

 

[AndrewT]

B1 ..... and it works fine but I only use the first quarter of the pot,

the B1 is a buffer.
It has a gain of one times (+0dB).
Your source and your amplifier gain and your speaker sensitivity determine the maximum SPL.

 

[ruudjoo]

Sorry, but I don't know what SPL is. Thanks anyway.
Ruudjoo

 

[Johnloudb]

That's just the sound level. The value of the potentiometer value won't affect the maximum output (sound) level of your system. A 10k pot is fine, I don't remember what value Pass used ....

 

[Beftus]

Sorry, but I don't know what SPL is. Thanks anyway.
Ruudjoo

Sound Pressure Level.