If I put my notes here, I might be able to find them again later!
Standard Resistor Values for RJM Audio Projects
From now on every effort will be made to consolidate to the following values, 1/4W metal film:
1, 4.75, 10, 47.5, 100, 150, 221, 475, 1000, 1500, 2210, 4750, 10000, 22100, 47500, and 100000.
Also, the 1/4W 47 ohm and 68k carbon comp. resistor is widely used as damping and bleeder functions, respectively.
Exceptions will be made for the RIAA eq. of the Phonoclone and VSPS circuits, and the business end of the X-reg, where specific, non-standard resistance values are required.
*****
On resistor selection-
I honestly don't know if one resistor sounds better than another. I do know, however, that one resistor can be more expensive than another. At Mouser your basic 1/4W metal film resistor can run between 5 cents and 2 dollars in 100 unit quantities. Setting aside sound quality, it's not at all clear that you are getting any kind of material benefit at all by getting the expensive parts. Instead, it really just seems to be the whim of Mouser's inventory management. The standard line items are going to be relatively cheap. Non-standard values or low volume part numbers are going to cost you.
Here at RJM Audio I've always used Vishay CMF55, but lately the prices - and the inconsistency of the pricing - has been getting out of hand. If you want to use these throughout, you'll perhaps find 70% of the resistors you need at a reasonable price, and then find the remaining ones cost 10x as much. Also, there's about a half dozen obscure variations of each part, tolerance, tempco, and packaging ... sometimes 100 ppm/C bulk KHEK will be cheaper, sometimes 50 ppm/C tape FKEB will. I was having to re-optimize my BOM line by line each time I ordered, which is hugely time consuming.
Cut to the chase, I'm throwing CMF55 under the bus and moving to KOA Speer MF 1% 100 ppm/C metal film resistors. Updated BOMs for all projects will be propagated shortly. It's cheaper, but more importantly it's consistent - every value I need is available within the model range, and apart from tape vs. bulk packaging, there are no variations.
I briefly considered Vishay RN60, which Mouser also seems to keep a large stock of. Most of the values are available and the prices are reasonable. The problem is these resistors are actually CMF60 in military uniform, it's a larger 1/2W body de-rated for military use and won't fit comfortably in my boards, which are 0207 packages for the most part.
Finally if you just want to stick with standard values the CMF55 KHEK are still reasonably priced if you really want to go Vishay. Just be aware that the available values are somewhat limited and if you need anything off that range the price goes up exponentially.
1, 4.75, 10, 47.5, 100, 150, 221, 475, 1000, 1500, 2210, 4750, 10000, 22100, 47500, and 100000.
Also, the 1/4W 47 ohm and 68k carbon comp. resistor is widely used as damping and bleeder functions, respectively.
Exceptions will be made for the RIAA eq. of the Phonoclone and VSPS circuits, and the business end of the X-reg, where specific, non-standard resistance values are required.
*****
On resistor selection-
I honestly don't know if one resistor sounds better than another. I do know, however, that one resistor can be more expensive than another. At Mouser your basic 1/4W metal film resistor can run between 5 cents and 2 dollars in 100 unit quantities. Setting aside sound quality, it's not at all clear that you are getting any kind of material benefit at all by getting the expensive parts. Instead, it really just seems to be the whim of Mouser's inventory management. The standard line items are going to be relatively cheap. Non-standard values or low volume part numbers are going to cost you.
Here at RJM Audio I've always used Vishay CMF55, but lately the prices - and the inconsistency of the pricing - has been getting out of hand. If you want to use these throughout, you'll perhaps find 70% of the resistors you need at a reasonable price, and then find the remaining ones cost 10x as much. Also, there's about a half dozen obscure variations of each part, tolerance, tempco, and packaging ... sometimes 100 ppm/C bulk KHEK will be cheaper, sometimes 50 ppm/C tape FKEB will. I was having to re-optimize my BOM line by line each time I ordered, which is hugely time consuming.
Cut to the chase, I'm throwing CMF55 under the bus and moving to KOA Speer MF 1% 100 ppm/C metal film resistors. Updated BOMs for all projects will be propagated shortly. It's cheaper, but more importantly it's consistent - every value I need is available within the model range, and apart from tape vs. bulk packaging, there are no variations.
I briefly considered Vishay RN60, which Mouser also seems to keep a large stock of. Most of the values are available and the prices are reasonable. The problem is these resistors are actually CMF60 in military uniform, it's a larger 1/2W body de-rated for military use and won't fit comfortably in my boards, which are 0207 packages for the most part.
Finally if you just want to stick with standard values the CMF55 KHEK are still reasonably priced if you really want to go Vishay. Just be aware that the available values are somewhat limited and if you need anything off that range the price goes up exponentially.
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