Here are a few errors I found:
1k resistors, the BOM says 2, 8 are needed
OPA 1641, BOM says 6, 4 are needed
LM4652, BOM says 3, 4 are needed
22uf 35V capacitors, BOM says 6, 4 are needed
BOM does not have the 120ohm, 110k ohm and 150k ohm resistors anywhere. The ones placed near the DIP switch, I don’t have the boards with me atm to check board reference.
1k resistors, the BOM says 2, 8 are needed
OPA 1641, BOM says 6, 4 are needed
LM4652, BOM says 3, 4 are needed
22uf 35V capacitors, BOM says 6, 4 are needed
BOM does not have the 120ohm, 110k ohm and 150k ohm resistors anywhere. The ones placed near the DIP switch, I don’t have the boards with me atm to check board reference.
I am really sorry about this. Something has happened between the first version I did a few weeks after publication, and the update in late 2023. I’ve set aside a few hours tomorrow to look into this And will come back to you with an update.
I have attached newly updated and checked BOM to the first post in this thread. I will leave this there until your builds are done so that if you have any further inputs, I can make those before putting the correct BOM up again on the audioXpress hosted website again, which will then be the master BOM moving forward.
Here is what I think happened with the BOM that has caused your grief. I had quite a few copies of the BOM on both my desktop and my laptop and in the Microsoft Office cloud storage service that I use. I think during the update late last year, multiple copies of the BOM were open across all three places and when I packed everything up into a zip file to send to aX, ended up somehow corrupting the BOM. I'm in the process of deleting all extraneous copies to avoid a repeat of this.
Again, my very sincere apologies for this. Any questions/input, please let me know.
Regards
Andrew
Here is what I think happened with the BOM that has caused your grief. I had quite a few copies of the BOM on both my desktop and my laptop and in the Microsoft Office cloud storage service that I use. I think during the update late last year, multiple copies of the BOM were open across all three places and when I packed everything up into a zip file to send to aX, ended up somehow corrupting the BOM. I'm in the process of deleting all extraneous copies to avoid a repeat of this.
Again, my very sincere apologies for this. Any questions/input, please let me know.
Regards
Andrew
Last edited:
Thank you for all your hard work, dedication and determination on this, Andrew. I know from personal experience how difficult it is keeping a BOM current (as things reach End of Life, Obsolete, etc.). And to complicate things further, your builders are from various countries and availability of some items can be different based on local suppliers.
The PCBs arrived today. I will probably begin my build in early October. All the items with a long lead or shipping times (like the Talema transformer and the ModuShop chassis) have been secured and are sitting on the bench along with all the necessary tools. A fresh batch of solder paste for the hot air gun for the SMDs is waiting for me in the refrigerator. And I finally figured out that "screened cable" (U.K.) is what I know to be "shielded cable" (U.S.). 😉
-Jon
The PCBs arrived today. I will probably begin my build in early October. All the items with a long lead or shipping times (like the Talema transformer and the ModuShop chassis) have been secured and are sitting on the bench along with all the necessary tools. A fresh batch of solder paste for the hot air gun for the SMDs is waiting for me in the refrigerator. And I finally figured out that "screened cable" (U.K.) is what I know to be "shielded cable" (U.S.). 😉
-Jon
Fantastic Jon - look forward to seeing your finished preamp and hope you like the sound! Thanks for your understanding on the BOM - I really learnt a good lesson on that one about having multiple copes open across different machines.
🙂
🙂
I've just checked the ax site - the downloads are mixed up between the ax-Amp and the X-Altra MC/MM. The download pack for this project has not been updated. So for now, please use the BOM on the first post of this thread.
Regarding the shielded cable to connect under the PCB, is coaxial prefered or should some other kind be used?
Hi Manuel, I just used 3mm diameter screened (aka shielded in the USA) 2 core cable from RS. The reason why I spec'd screened cable is to keep the loop areas small to reduce noise pickup.
In the "Final safety checks" section of the assembly instructions (page 5) it says "Fit the IEC inlet receptacle with a 50 mA slow blow (also known as a ‘T’) fuse." Is this a typo? Does anyone have a Mouser part number for the correct fuse?
Divide 180 uV by (40 + 3.25) Ohms = 4uA
This is a very low output cart in terms of output current so you will have to have all the MC gain switches in the OFF position and the system gain switches all ON.
This is a very low output cart in terms of output current so you will have to have all the MC gain switches in the OFF position and the system gain switches all ON.
Thanks for the calculation.
It is a great shame that there is no gain selection option on the switch.
It is a great shame that there is no gain selection option on the switch.