If your Source can drive the 10k vol pot and the cable, then use this lower value.
rubbish , in exact context .
stop showing overwhelming knowledge and help solving particular problem .
context is preamp
so , dispute Pass's logic in B1 , where pot is on input and impedance matching/gain stage afterwards , as best compromise .
you can do the same for myriad commercially made gain blocks , from 1920 and afterwards
Ah, i got your point, the port and cable will became load for previous stage. and this stage normally not "strong" enough to driver that load.
Thanks,
Could you describe this bus? I dont recall seeing it in the photos?
Thanks for any help.
Russellc
Post 490
https://www.dropbox.com/s/lm2oieahi8n4apv/Preamp inside.jpg
It just the manner the ground tabs are all connected together.
https://www.dropbox.com/s/k559fou2l00fjmz/BA3preb.jpg?dl=0
https://www.dropbox.com/s/ccrbz6f6srchz68/Preamp.jpg?dl=0
rotate second picture and you can see ground and components. Left side is power supply. Pcb is made for 3 kinds of power supply, LM317-337, zener diode with transistor, and cap multiplier. Left and right channel have the same ground in star ground. This is if you want to make balanced BA3. In that case you need two pcb.
On the right side of pcb is relay selector with 5 inputs, step attenuator with 7 relays and one relay for mute. Step attenuator with relay is connected with relays in shunt and when is no input preamp is in minimal volume. Loosing one connection on relays contact volume increase only for this resistor value, not on high loud, like on other shunt types of attenuators. Pcb for preamp can be used for BA3 or another preamp with several thousand pages on this forum.
If you use pot that can be connected as a classic pot or as a shunt. I use as a shunt with z-foil in series
This is case for preamp. I made it for my friend nmiro. He has a picture of F3 which i made on this forum http://www.diyaudio.com/forums/pass-labs/166784-pictures-your-diy-pass-amplifier-291.html
https://www.dropbox.com/s/9lym93w0aewwpta/komplet2.jpg?dl=0
https://www.dropbox.com/s/05dhiykr37uck68/kople1.jpg?dl=0
https://www.dropbox.com/s/ccrbz6f6srchz68/Preamp.jpg?dl=0
rotate second picture and you can see ground and components. Left side is power supply. Pcb is made for 3 kinds of power supply, LM317-337, zener diode with transistor, and cap multiplier. Left and right channel have the same ground in star ground. This is if you want to make balanced BA3. In that case you need two pcb.
On the right side of pcb is relay selector with 5 inputs, step attenuator with 7 relays and one relay for mute. Step attenuator with relay is connected with relays in shunt and when is no input preamp is in minimal volume. Loosing one connection on relays contact volume increase only for this resistor value, not on high loud, like on other shunt types of attenuators. Pcb for preamp can be used for BA3 or another preamp with several thousand pages on this forum.
If you use pot that can be connected as a classic pot or as a shunt. I use as a shunt with z-foil in series
This is case for preamp. I made it for my friend nmiro. He has a picture of F3 which i made on this forum http://www.diyaudio.com/forums/pass-labs/166784-pictures-your-diy-pass-amplifier-291.html
https://www.dropbox.com/s/9lym93w0aewwpta/komplet2.jpg?dl=0
https://www.dropbox.com/s/05dhiykr37uck68/kople1.jpg?dl=0
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OK, getting very close. need to solder pots in. The P3 are put in, set "in the middle" of the range. I see reference to set the P1 and P2 pots "to zero"...
Question 1: Where do you measure on the BA-3 board for setting P1 and P2
to zero?
Question 2: I have the parts on hand to make P1 and P2 1K, or the stock
500.
Does it matter if I use 1K? (as suggested for BA-3 Power amp)
I am using Toshiba mosfets.
Question 3: There are only 2 "G" pads (per channel)on the BA-3 board, yet
for BA-3 as pre I think I need 3, one for signal in, one for
signal out, and one for power supply ground. Is there a
problem with linking the 2 G pads and hanging all 3 off of that?
Otherwise I can solder the signal IN ground to the leg of R2?
Or am I missing how they should be hooked up?
Thanks,
Russellc
Question 1: Where do you measure on the BA-3 board for setting P1 and P2
to zero?
Question 2: I have the parts on hand to make P1 and P2 1K, or the stock
500.
Does it matter if I use 1K? (as suggested for BA-3 Power amp)
I am using Toshiba mosfets.
Question 3: There are only 2 "G" pads (per channel)on the BA-3 board, yet
for BA-3 as pre I think I need 3, one for signal in, one for
signal out, and one for power supply ground. Is there a
problem with linking the 2 G pads and hanging all 3 off of that?
Otherwise I can solder the signal IN ground to the leg of R2?
Or am I missing how they should be hooked up?
Thanks,
Russellc
Nice F3. Those heatsinks are very nice, as is faceplate. Excellent job!
Thanks for the pics, very well thought out and executed.
Russellc
Nice job, I misunderstood which grounds you were talking about, my mistake. I thought you were talking about the grounds on the FE BA-3 board. I have decided to loop the two G pads together ( on each channel, not loop both channels together!) and connect the IN grounds, the Out grounds as well as the power supply grounds to that loop on each side, like very short "bus" to solve the problem of only two ground pads.
So my question 3. from post #769 is answered, I think I have the answer to setting the pots to their "Zero", only wondering about if 1K pot (like suggested for BA-3 power amp) would be OK for the BA-3 as pre in place of 500K. Since I havent read about anyone experiencing difficulty in either of the BA-3 as pre amp threads with alternative mosfets, I am assuming 500R pots dont cause a problem with the "as Pre" version, just with Power amp. I am using Toshiba mosfets anyway. I just hate unsoldering boards if I can help it!
Russellc
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Now if the delay board and the F-4 boards would get here too!
Thanks !
But your 2nd circuit seems to still have a gain of about 7 to 10 or so...
Have you also reduced the output loading resistor and run simulation again?
Fab
It is strange since according to papa article the original components preamp has a gain of about 30 and yours have only about 10....
Or maybe I have missed something....
Fab
Oh, that is your problem…
I remember we all had only gain about 10x.
Nobody got 30dB…. maybe the balanced version and with less load.
It is the only time that I could not get the data Papa said…..
there were long tries in the thread to calculate the real gain with mathematics…….
sometimes with different results… was funny.
with the changing of the 100R going to ground you can vary the gain easily….
I remember we all had only gain about 10x.
Nobody got 30dB…. maybe the balanced version and with less load.
It is the only time that I could not get the data Papa said…..
there were long tries in the thread to calculate the real gain with mathematics…….
sometimes with different results… was funny.
with the changing of the 100R going to ground you can vary the gain easily….