Teodorom,
A100452CD-ND is not found on Mouser because it is a Digi-Key part number. Also the part number is incorrect; it should be A100452CT-ND. Digi-Key has 305,721 in stock. I used Mouser part number 571-1217861-1-CT which is the same tab connector. Mouser has 2,800 in stock. These parts are suitable for all tab connectors on the board. There is no need to search RS Components for tab connectors.
652-3296W-1-102LF (10k Multiturn Trimmer) is not found on Mouser. Firstly, this part number is for a 1K trimmer, not 10K. Mouser does list both a 1K and a 10K trimmer, part numbers 652-3296W-1-102LF (5,597 in stock) and 652-3296W-1-103LF (3,798 in stock).
771-BC847CT115 is no longer available, replace with Mouser part number 621-BC847CT-7-F, 14,296 in stock.
A100452CD-ND is not found on Mouser because it is a Digi-Key part number. Also the part number is incorrect; it should be A100452CT-ND. Digi-Key has 305,721 in stock. I used Mouser part number 571-1217861-1-CT which is the same tab connector. Mouser has 2,800 in stock. These parts are suitable for all tab connectors on the board. There is no need to search RS Components for tab connectors.
652-3296W-1-102LF (10k Multiturn Trimmer) is not found on Mouser. Firstly, this part number is for a 1K trimmer, not 10K. Mouser does list both a 1K and a 10K trimmer, part numbers 652-3296W-1-102LF (5,597 in stock) and 652-3296W-1-103LF (3,798 in stock).
771-BC847CT115 is no longer available, replace with Mouser part number 621-BC847CT-7-F, 14,296 in stock.
blacknoz,
Item 5 quantity is three, just a typo.
504-HTC-210M is the correct Mouser part number for the fuse clips, 2,920 in stock.
Here is the explanation Bonsai provided regarding resistors R28, R29, R36, and R37. It is a fix for all NX, not just for the use of BC550/560.
Q8 and Q10 are high hFE BC5x7C type devices, while Q9 and Q11 are lower gain
range, higher Vce BC5X6B device types. Both the buffer and level shifter
stages were designed to run at 1mA on the original design. 15 mV degeneration
is applied via the 1mA flowing through the 15 Ohm resistors in the emitters
of the 4 diamond buffer transistors – R28, R28 and R36 and R37
After some investigation, the problem has been isolated to normal differences
in the spread of the Vbe’s of Q8-Q11.
The problem with the front end design as is that if the Vbe’s of the level
shifter devices Q9 and Q11 are greater than the front end buffer devices Q8
and Q10, they are starved of current, and in extreme cases can actually be
biased OFF, just as the one builder reported.
The standing offset across the degeneration resistors is 15mV and this is not
enough to cater for the worst case spreads in the Vbe’s between the
transistors - and matching hFE will not solve the problem either. The
modifications detailed below (which consist only of resistor value changes)
raise the degeneration voltages to 120-150mV, solving the problem.
If you have not assembled your boards yet, or you are having problems, make
the following changes:-
R36 and R37 become 150 Ohms
R28 and R29 become 110 Ohms
R1 becomes 4.7k (but first read note below)
If you leave R1 at 10k, you will have around +-500mV of offset adjustment. I
would suggest that you change R36/37 and R28/29 and then check the offset
adjustment. If you cannot dial out the offset, then change R1 to 4.7k.
Across each of the degeneration resistors R28 and R29, you will read 120mV
which is 8x to 9x the original value, while across R36 and R37, you will read
150mV.
The distortion, bandwidth and slew rate of the amplifier essentially remain
unchanged.
Item 5 quantity is three, just a typo.
504-HTC-210M is the correct Mouser part number for the fuse clips, 2,920 in stock.
Here is the explanation Bonsai provided regarding resistors R28, R29, R36, and R37. It is a fix for all NX, not just for the use of BC550/560.
Q8 and Q10 are high hFE BC5x7C type devices, while Q9 and Q11 are lower gain
range, higher Vce BC5X6B device types. Both the buffer and level shifter
stages were designed to run at 1mA on the original design. 15 mV degeneration
is applied via the 1mA flowing through the 15 Ohm resistors in the emitters
of the 4 diamond buffer transistors – R28, R28 and R36 and R37
After some investigation, the problem has been isolated to normal differences
in the spread of the Vbe’s of Q8-Q11.
The problem with the front end design as is that if the Vbe’s of the level
shifter devices Q9 and Q11 are greater than the front end buffer devices Q8
and Q10, they are starved of current, and in extreme cases can actually be
biased OFF, just as the one builder reported.
The standing offset across the degeneration resistors is 15mV and this is not
enough to cater for the worst case spreads in the Vbe’s between the
transistors - and matching hFE will not solve the problem either. The
modifications detailed below (which consist only of resistor value changes)
raise the degeneration voltages to 120-150mV, solving the problem.
If you have not assembled your boards yet, or you are having problems, make
the following changes:-
R36 and R37 become 150 Ohms
R28 and R29 become 110 Ohms
R1 becomes 4.7k (but first read note below)
If you leave R1 at 10k, you will have around +-500mV of offset adjustment. I
would suggest that you change R36/37 and R28/29 and then check the offset
adjustment. If you cannot dial out the offset, then change R1 to 4.7k.
Across each of the degeneration resistors R28 and R29, you will read 120mV
which is 8x to 9x the original value, while across R36 and R37, you will read
150mV.
The distortion, bandwidth and slew rate of the amplifier essentially remain
unchanged.
BOM / PSU errata
I'm moving forward and began to build the NX-Amp.
I'm currently doing the PSU and noted what maybe mistakes in the BOM we were working on. Can someone confirm that (PSU only at the moment):
- R15/R16 should be 100k and not 22k. They are 100k on the PCB and on hifisonix website and documentation but 22k in the BOM posted in this thread
- R21/R22 should be 5.6k and not 2.7k. They are 5.6k on the PCB and on hifisonix website but 2.7k in the BOM posted here
- R27 should be 10K. It's 10k on the PCB/hifisonix website and doc but 2.7k in the BOM posted here.
BTW, did anyone provide an implantation scheme for the SMD components to be soldered at the bottom of the PSU PCB. I think I was able to figure out which one should be soldered where and in which direction but I guess that would be helpful. If not, I'll also propose something for this part.
Thanks,
Raph
I'm moving forward and began to build the NX-Amp.
I'm currently doing the PSU and noted what maybe mistakes in the BOM we were working on. Can someone confirm that (PSU only at the moment):
- R15/R16 should be 100k and not 22k. They are 100k on the PCB and on hifisonix website and documentation but 22k in the BOM posted in this thread
- R21/R22 should be 5.6k and not 2.7k. They are 5.6k on the PCB and on hifisonix website but 2.7k in the BOM posted here
- R27 should be 10K. It's 10k on the PCB/hifisonix website and doc but 2.7k in the BOM posted here.
BTW, did anyone provide an implantation scheme for the SMD components to be soldered at the bottom of the PSU PCB. I think I was able to figure out which one should be soldered where and in which direction but I guess that would be helpful. If not, I'll also propose something for this part.
Thanks,
Raph
A few more question concerning the PSU (finishing it slowly
:
- C3 on the PSU BOM from this thread is 0.47uF 100V RAD0.2 but the documentation and PCB both refer to a 1uF Poly (the same as C2). Which one shall I use (I have two 1uF at my disposal and in fact I don't know if it makes a real difference to use one or another).
- Can I replace the two BC547C (Q6,Q7) by two BC550CG that I have in stock?
Best,
Raph
:- C3 on the PSU BOM from this thread is 0.47uF 100V RAD0.2 but the documentation and PCB both refer to a 1uF Poly (the same as C2). Which one shall I use (I have two 1uF at my disposal and in fact I don't know if it makes a real difference to use one or another).
- Can I replace the two BC547C (Q6,Q7) by two BC550CG that I have in stock?
Best,
Raph
Use 1uF for C3. It was changed from 0.47uF to allow for lower voltage transformers to work with the circuit. 1uF is the new value.
BC550 is a good substitute for BC547. However the collector to emitter breakdown rating for the BC547 is quite marginal in the circuit. I used a BC546C in my amplifier. Mouser has them in stock, their part number 512-BC546CTA.
BC550 is a good substitute for BC547. However the collector to emitter breakdown rating for the BC547 is quite marginal in the circuit. I used a BC546C in my amplifier. Mouser has them in stock, their part number 512-BC546CTA.
Sorry for my poor experience...
I tried to understand how the PSU behaves under load of the amplifier. My simulation tells me that when the nx amplifier (single channel) delivers 100W the PSU exhibits a ripple of 1.49Vpp. Good, bad? I don't know.
When I add to the PSU the "ripple eater" (no diode bridge, no 47mF capacitors) only the active part, the ripple reduces to 430mVpp.
So, the "ripple eater" is needed in the nx amplifier?
When I compare the "ripple eater" with the original nx PSU a lot of circuitry is missing, why?
Thanks
I tried to understand how the PSU behaves under load of the amplifier. My simulation tells me that when the nx amplifier (single channel) delivers 100W the PSU exhibits a ripple of 1.49Vpp. Good, bad? I don't know.
When I add to the PSU the "ripple eater" (no diode bridge, no 47mF capacitors) only the active part, the ripple reduces to 430mVpp.
So, the "ripple eater" is needed in the nx amplifier?
When I compare the "ripple eater" with the original nx PSU a lot of circuitry is missing, why?
Thanks
So, why not use another regulator? Something like this:
Ripple is less that 2.1mVpp and it keeps the Vcc very stable under (even heavy) current requests.
Thanks
An externally hosted image should be here but it was not working when we last tested it.
Ripple is less that 2.1mVpp and it keeps the Vcc very stable under (even heavy) current requests.
Thanks
Dear Bill, dear all,
hope you are fine and my best wishes for 2020.
I'm currently testing the AMP boards and I'm facing a situation I'm not sure I fully understand and which maybe related to you previous answer quoted below:
In the test sequence indicated on page 41, we have this:
14. Next, connect your meter between the output and 0 V. Set the meter initially to the 2 V range.
15. You should get a reading of between +-0.5 V, although in some cases it can be lower than this. If you are
reading more than +-1 V, you have a problem.
16. Adjust R3, the OFF ADJ potentiometer for a reading of +-5 mV
Does this mean that I should have 0.5v at +-5mv between output and 0V (which I was able to get on my board with R1=10k and adjustment on R3) or does this mean that I should end up with 0-5mv between output and 0V after adjustment on R3 and that if I'm not able to get it I should modify R1 to 4.7k?
Thanks,
Raph
hope you are fine and my best wishes for 2020.
I'm currently testing the AMP boards and I'm facing a situation I'm not sure I fully understand and which maybe related to you previous answer quoted below:
In the test sequence indicated on page 41, we have this:
14. Next, connect your meter between the output and 0 V. Set the meter initially to the 2 V range.
15. You should get a reading of between +-0.5 V, although in some cases it can be lower than this. If you are
reading more than +-1 V, you have a problem.
16. Adjust R3, the OFF ADJ potentiometer for a reading of +-5 mV
Does this mean that I should have 0.5v at +-5mv between output and 0V (which I was able to get on my board with R1=10k and adjustment on R3) or does this mean that I should end up with 0-5mv between output and 0V after adjustment on R3 and that if I'm not able to get it I should modify R1 to 4.7k?
Thanks,
Raph
Many thanks, my min voltage was around 120mv when R1 was at 10k, switching it to 4.7k per you suggestion fixed it and I was able to adjust to 0VDC +-5mv.
Another question, once adjusted if I switch off the amplifier, wait for a while and switch it on back again, the DC Voltage between output and 0V PSU is around 100mv and goes down slowly (I'd say that it takes about 15-30s) to the point of 0V DC +-5mv. It then "oscillate" between -6mv and +6mv. Is it something I should consider as normal or is it a sign I did something wrong?
Best,
Raph
Thank you so much
Thank you Andrew for your support and for the whole thing. I've been able to listen to the amp this week end, although it was still on it's temporary heatsink and totally opened, I must say that I personally never heard my previous speakers sound like this! I'm _really_ impressed by the sound, thank you so much for this.
BTW, I'm still facing issues (the main one being me creating a shortcut on R30, just like you said in your testing guide but I'll try to figure them out by myself in a first place before boring people further
To all people here (special mention to Bill_P), I must say that I'm really impressed by the kindness and the sharing mindset. I have a quite good idea, as a free software guy, of how much it can cost to help others and I'm glad I could find people like you to begin with this audio/electronic adventure.
Raph
Hi Raph, this is quite normal - your offset adjust is correct. Once you box it up in the enclosure it will probably settle to a slightly tighter tolerance.
Thank you Andrew for your support and for the whole thing. I've been able to listen to the amp this week end, although it was still on it's temporary heatsink and totally opened, I must say that I personally never heard my previous speakers sound like this! I'm _really_ impressed by the sound, thank you so much for this.
BTW, I'm still facing issues (the main one being me creating a shortcut on R30, just like you said in your testing guide
but I'll try to figure them out by myself in a first place before boring people further To all people here (special mention to Bill_P), I must say that I'm really impressed by the kindness and the sharing mindset. I have a quite good idea, as a free software guy, of how much it can cost to help others and I'm glad I could find people like you to begin with this audio/electronic adventure.
Raph
Salas DCG3!
A set of full range speakers too.
Fane 12-250TC.
Mine SX still under construction....
Attachments
Where i can find pcb for that salas DCG3 pre amp?Salas DCG3!
A set of full range speakers too.
Fane 12-250TC.
Mine SX still under construction....