Ok the Zener sets (but not precisely) the current in Q9/Q11 but this current is then converted into voltage across R32/33 therefore these resistor values also sets the TIS current but is not related to the supply voltage (as you mentioned). I understand that you do not want to change the 1k resistor but a small difference of about 100 ohms (910 ohms or 1.1 k) may compensate for the other parameters variation such as the VBE of involved transistors, base current,....so the 25ma current target can always be reached instead of changing the TIS transistor emitter resistors value which changes possibly more the open loop gain of the whole amp....
Fab
This also matches with my findings on my built but I thought that you had obtained a different result on TIS current from your items # 3 and #5 of the doc to update.... Sorry if I misunderstood your items 3 and 5....
Fab
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OMG!
Today I have listened to Fab's nx Amp and I was blown away by the sound of this amp and believe me, I have built many amps!
I am now more motivated than ever to start my build.
The amp was connected to my Tubasson MK II speakers, the LDR3x attenuator from Tortuga Audio (a must have) and my modified TwistedPear Opus/IVY III combo which I also swapped the balse Opamp to OPA1642.
All I can say is this amp is in control! Bass is well defined and solid as we can expect from a bipolar transistors but where I was very surprised was the image depth which was like a bowling alley and had layers of instruments making it easy to locate them in space. the spaciality this amp project made it easy to distinguish each instruments and this even in complexe passages without masking others like many amps do in those moments.
This is to me a definitive must have/build amp!
Well done Bonsai! Now please correct your manual so we can build it!
Ciao!
Do
Today I have listened to Fab's nx Amp and I was blown away by the sound of this amp and believe me, I have built many amps!
I am now more motivated than ever to start my build.
The amp was connected to my Tubasson MK II speakers, the LDR3x attenuator from Tortuga Audio (a must have) and my modified TwistedPear Opus/IVY III combo which I also swapped the balse Opamp to OPA1642.
All I can say is this amp is in control! Bass is well defined and solid as we can expect from a bipolar transistors but where I was very surprised was the image depth which was like a bowling alley and had layers of instruments making it easy to locate them in space. the spaciality this amp project made it easy to distinguish each instruments and this even in complexe passages without masking others like many amps do in those moments.
This is to me a definitive must have/build amp!
Well done Bonsai! Now please correct your manual so we can build it!
Ciao!
Do
I had the same problem with nx psu. Seems that the switch-on delay circuit doesn't have enough energy to charge C10 to high enough level. Typo in the circuit? It did'nt work with Ltspice either.
Quick fix could be: add 22k resistor parallel to R6(330k), and >10uF cap parallel to C2(1uF).
You can solder them on bottom side of psu board. Works for me. Delay is 1-2s.
Real fix would be to rethink the component values of this delay circuit.
ps. first impressions of the sound
I had the same problem with nx psu. Seems that the switch-on delay circuit doesn't have enough energy to charge C10 to high enough level. Typo in the circuit? It did'nt work with Ltspice either.
Quick fix could be: add 22k resistor parallel to R6(330k), and >10uF cap parallel to C2(1uF).
You can solder them on bottom side of psu board. Works for me. Delay is 1-2s.
Real fix would be to rethink the component values of this delay circuit.
ps. first impressions of the sound
Hello Jpower, kindly let me know please if you use PDTA144ET or PDTA143ET in U2? in my case if R1 is remove SSLR is engaging but I cannot find any wrong value or incorrect parts in DC detect section. Temporarily I put a diode (cathode side to Gate of 2N7002) in series with R1.
I modified the Switch-on delay, it's a NOOB approach really
. I made the C3 1uF, if it's 0.47Uf I'm only getting 2.95VDC.With 1uf I have 3.95VDC at D17 (4.7V Zener diode) enough to trigger 2N7002.
I replaced 330K with 270K and 5.6K(R7) to 22K it's working but not the specs Andrew mentioned in the guide, my turn on delay is 10 seconds.
I'm very thankful with Andrew's assistance through PM's. I think I didn't make him sleep
, Sorry Sir!
I have updated the nx-Amp document and loaded it up to my website below. Please down load and take a look. Thre may be a few small issues to fix, but the big things have been addressed per the snag list.
I believe I've answered all the questions that have come up over the last few months on the builds.
The updated Gerbers will be loaded 15th October (I am very busy at work at the moment).
Hope to see many more of these things built!
I believe I've answered all the questions that have come up over the last few months on the builds.
The updated Gerbers will be loaded 15th October (I am very busy at work at the moment).
Hope to see many more of these things built!
For the amplifier board I found two conflicts between the schematic and bill of materials. R4 is not shown in the schematic but is listed in the bill of materials as 100K. I think the schematic is correct. R41 and R42 are shown as 33 Ohms in the schematic but 0 Ohms in the bill of materials. The schematic is wrong in this case.
Other issues in the amplifier board bill of materials:
There are two item 39 rows but no item 38. Items 39 and 40 should be combined, total quantity is two. R24-R27 listed as TUW5JR33E should be TWW5JR33E. U1 is listed as FODM3011 but is not available so FODM3012 is being used instead.
For the PSU board the schematic lists C3 as 1uF 100V but the bill of materials shows 0.47uF 100V. I think you changed this recently so the schematic is correct. R6 is 100K in the schematic but 330K in the bill of materials. Again the schematic is right. D1 and D7 are BZX84 12V in the schematic but BZX79-B12133 in the bill of materials. The BZX79 part has gone end of life but is still available at Mouser for now.