All kits currently spoken for.
There may be some spare PCB remaining, once everything is packed, if there are I will happily distribute them to interested people. Don't contact me about that yet, I'll send out a call at the appropriate time.
There may be some spare PCB remaining, once everything is packed, if there are I will happily distribute them to interested people. Don't contact me about that yet, I'll send out a call at the appropriate time.
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.
@6L6, did you try the board edge mounting kit in post #26? Are you including them in the kits? (Given the price of the kits, I’m guessing not).
I haven’t actually mounted the PCB to a chassis with them, but yes, they fit.
They are not included in the parts kit.
They are not included in the parts kit.
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
Check you didn't swap Q9 & Q10. Q9 = 1845 Q10 = 992. Also check polarity of D1. Does D1 light?
TJ
TJ
I checked the transistors several times. No mistakes here. The led in on, working correct. Maybe i should change the 992 in the output stage, maybe its damaged...
What's the voltage drop on the LED? Should be close to 2 volts. Also what is the Vbe on the output Transistors.
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
Did you select Idss for the Jfet CCS or just used what you had on hand? Your voltages were right in line with Wayne's.
BDP
BDP
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.