omsoc-
I realize I didn't answer your question as well as I could; There will be a version of this circuit/PCB in the store in the future. There will almost assuredly not be another run of these little pink boards if for no other reason than there's no mounting holes on them...
This will be a project supported in the store and on the site, it's a great circuit and this is just the very beginning of what will come.
I realize I didn't answer your question as well as I could; There will be a version of this circuit/PCB in the store in the future. There will almost assuredly not be another run of these little pink boards if for no other reason than there's no mounting holes on them...
This will be a project supported in the store and on the site, it's a great circuit and this is just the very beginning of what will come.
Members listed in post #68, please check your Email.
Hi 6L6, no email received yet...
Hello,
i have a problem with the preamp.
After soldering i checked some voltages and found no voltag drop on R12 (Drop = 0V). The voltage drop on R7/13 is 1,45V, that should be okay. On R15 it is 39V, representing the 0,36mA figure, so this should be fine, too (rails are at +/-21,5V). At the moment the feedback resistor (R16) is not in the circuit, because i adjusted P1. Voltage drop on R6 and R14 are both 1,5V.
With the feedback resistor (R16) installed i found a voltage drop on R11 = 1,2mV, R12 still 0V. But something else changed: the drop on R2 became 26mV, befor it was 15mV, same value as on R1.
After that i checked the base voltages on the transistors: Q7/8/14 in the range of +20V, Q11/9 at -20V; but Q10 at about +16,6V. I expected it to be -20V or so. Can someone give me an hint? Thank you!
Best regards,
Michael
i have a problem with the preamp.
After soldering i checked some voltages and found no voltag drop on R12 (Drop = 0V). The voltage drop on R7/13 is 1,45V, that should be okay. On R15 it is 39V, representing the 0,36mA figure, so this should be fine, too (rails are at +/-21,5V). At the moment the feedback resistor (R16) is not in the circuit, because i adjusted P1. Voltage drop on R6 and R14 are both 1,5V.
With the feedback resistor (R16) installed i found a voltage drop on R11 = 1,2mV, R12 still 0V. But something else changed: the drop on R2 became 26mV, befor it was 15mV, same value as on R1.
After that i checked the base voltages on the transistors: Q7/8/14 in the range of +20V, Q11/9 at -20V; but Q10 at about +16,6V. I expected it to be -20V or so. Can someone give me an hint? Thank you!
Best regards,
Michael
Hello,
first of all i want to thank you for your input! After changing Q10 the circuit works as expected. I can now measure an voltage drop over R11/12 of 0,33V, over the diode its 1,85V. Q10 and Q8 are getting quite hot, so i will lower the rails a little.
Best regards,
Michael
first of all i want to thank you for your input! After changing Q10 the circuit works as expected. I can now measure an voltage drop over R11/12 of 0,33V, over the diode its 1,85V. Q10 and Q8 are getting quite hot, so i will lower the rails a little.
Best regards,
Michael
No, I did not matching. Neither transistors, nor resistors. I wanted to build the circuit as fast as possible to have a basis to experiment with an balanced solution... By the way: I measured a gain of 12db. Can somebody confirm? Because Mr. Colburn says in the BAF video, gain should be 15db.
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