I would of liked to have seen twisted wires for the inputs and the output but let's explore a little more. Do you have two other 100pf capacitors so that putting then in parallel would double the value?Here's a photo
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Also, is the preamp on to or near a digital source?
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I will try to add parallel capacitors. I am not clear what is going on. It sounds like the distortion is there when there is music, but silence durong the 'silent tracks'. Will see whether I can do it tomorrow or the day after. It's 11 pm now
And no - it is about a yard away from the dac
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The capacitors was actually 170pf. Adding another in parallel did not make any difference to the sound. I used an additional pot to check whether it is the current pot causing the issue - no change.
Did a check again on the resistors on the board and the joints - looks ok. Left two possibilities (besides RFI) - the diode, which will affect both channels, or the JFETs. What will be the typical voltage drop across the diode?
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Did a check again on the resistors on the board and the joints - looks ok. Left two possibilities (besides RFI) - the diode, which will affect both channels, or the JFETs. What will be the typical voltage drop across the diode?
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Is there a connection from Protective Earth to Chassis.Here's a photoAn externally hosted image should be here but it was not working when we last tested it.
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I see your green wire going into an insulated terminal block.
That's a weird way to install an untwisted pair !
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Thanks. I will switch the diode out to check. If that does not work, we are left only with the JFETs or RFI....
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Input impedance
Sorry I put the message in the wrong thread, now transferred to:
http://www.diyaudio.com/forums/pass-labs/124889-b1-buffer-preamp-427.html#post5074559
Sorry I put the message in the wrong thread, now transferred to:
http://www.diyaudio.com/forums/pass-labs/124889-b1-buffer-preamp-427.html#post5074559
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an output stage that can drive a >=10kOhms will be able to drive a 10k vol pot.
But is there a cable in between?
The more onerous requirement for the output is in driving the capacitance of the interconnect. 1Vpk into a 10k resistive load requires an output current of 0.1mApk
300pF of capacitance could require ten times that peak output current.
That's why the Pass B1 and Salas DCB1 use bl (or B) graded jFETs, to get adequate current driving capability.
It's the cable that your output stages need to drive.
And have you read the replies to your other questions?
But is there a cable in between?
The more onerous requirement for the output is in driving the capacitance of the interconnect. 1Vpk into a 10k resistive load requires an output current of 0.1mApk
300pF of capacitance could require ten times that peak output current.
That's why the Pass B1 and Salas DCB1 use bl (or B) graded jFETs, to get adequate current driving capability.
It's the cable that your output stages need to drive.
And have you read the replies to your other questions?
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Yes. Chassis is link directly to the Protected Earth. You cant see it from the photo
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