[Syzygies]

As far as I can tell, Vishay Dale Military, MIL-R-10509 Qualified, Type RN55E_BB14 are the best available resistors that fit 0.3" spaced boards such as the MINT, PIMETA, PPA. They have 25ppm, 0.1% tolerances, and are sold through Mouser.

However, Mouser doesn't list available values for this line in their PDF catalog, and their parts searching leaves something to be desired. I'd love it if there was an unambiguous master part number, and a property list { "ohms", 499 } (anyone here old enough to remember LISP) so I could search for nearest values available now in small quantities. Alas, the best they have is textual searching, and sort-by-availability.

I set up a fake order of one of every value available singly, and munged the results in a programmer's text editor, then set up an Excel spreadsheet with the results. I'm posting it here as tabbed text (import back into your favorite spreadsheet), to save others the trouble. Not everyone is even aware that resistors of this quality/size are available.

Edit: I added the RN55C_BB14, RN55E_BR36, and RN55C_BR36 resistors stocked in single quantities at Mouser, and combined these with the RN55E_BB14. This new list contains every 0.1% RN55 resistor sold singly by Mouser, to my knowledge at this time.

Download a datasheet from Mouser, using any of these part numbers, to decipher the part numbers:

RN55 = 1/8 watt
E or C = 25ppm or 50ppm
xxxx = 3 digit resistance w/ multiplier
B = 0.1% tolerance
B14 or R36 = "Tin/Lead, Bulk" or "Tin/Lead, Tape & Reel"

 

[ble0t]

Thanks

 

[doobooloo]

Very interesting! The prices seem to be a good bit higher but if the quality is that much better...

So who's the first one to try?

 

[Syzygies]

Quote:

Originally Posted by doobooloo So who's the first one to try?

I'm sure I'm not the first (though perhaps the first using the "E" 25ppm line?), but my PIMETA parts are finally on my way. My sound will be pot-limited until I can build one of my stepped attenuator designs.

In general, there seems to be a lag in part recs, i.e. our tribal elders keep mentioning the Panasonic FC line even though I've been told that the FM line is newer and better.

 

[twodeko]

im interested and will pick some up for my PIMETA project but was wondering what makes these resistors better.

of course the military won't cheapen parts but what PPM's will i be looking for and that, so far all ive dealt with is standard dale/vishays

p.s. anyone know the difference between the K and the K/R versions?

 

[tangent]

Quote:

the FM line is newer and better.

...and more limited in available values and case sizes. The FCs are still a better first choice. FMs are for those going super-tweaky, and who are therefore willing to sacrifice choice.

 

[Syzygies]

Quote:

Originally Posted by twodeko im interested and will pick some up for my PIMETA project but was wondering what makes these resistors better. of course the military won't cheapen parts

The military provides a market for these parts, for whatever reason. We're too small to matter, we have to be fleas on the elephant to get what we want.

There's good empirical evidence, surfing the web, that many audiophiles believe there are differences in resistors. I've tried making Etymotic 4p to 4s conversion cables using RadioShack's finest 75 ohm resistors, and I thought that the results sounded dreadful compared to Etymotic's $65 cable. It would be fun to make two identical CMoys, one with RadioShack metal film and one with Vishay Dale RN55E_BB14, to see how audible the difference is. I haven't, and I'm not about to make an intentionally inferior PIMETA to find out; PIMETAs cost too much.

My understanding of the mechanism is this: Manufacturing resistors that are this precise requires methods that incidentally remove some sources of resistor noise and distortion. (Some sources are intrinsic to the physics, read "Art of Electronics" on this, but some aren't.) For example, exactly trimming metal foil by laser leaves cleaner edges, and rough edges introduce noise.

 

[Syzygies]

Quote:

Originally Posted by tangent and who are therefore willing to sacrifice choice.

Ditto for these resistors. One has to have a reasonable grip on the schematic to figure out how sensitive each resistor value is to change. I have a ways to go, but I felt confident enough to spec a PIMETA just using these values. There are also various RN55C series resistors at Mouser, but their sporadic availability suggests that they're being phased out in favor of the slightly better RN55E series.

For example, no one really cares about the difference between a gain of 4.0 and 4.2, but the Jung topology has a definite sweet spot for how all the resistor act together. I was unable to figure out to my satisfaction whether I should really be changing all the values at once. I wondered, is just changing R4 on a PIMETA an expediency? Should I at a minimum optimize for my target gain (low, so I can use a 36 step attenuator) rather than the default gain of 11? I threw in the towel and ordered IC sockets and various choices for R4, I'll figure this out later.

 

[Syzygies]

I added the RN55C_BB14 resistors stocked in single quantities at Mouser, and combined these in a second spreadsheet. See my post at the top of this thread.

 

[twodeko]

does anyone know the difference between the K and K/R identification flags?

 

[Syzygies]

Quote:

Originally Posted by twodeko does anyone know the difference between the K and K/R identification flags?

K/R goes with the Vishay part number ending "R36" for "Tin/Lead, Tape & Reel".

There are only 23 0.1% values offered singly this way, but they're generally cheaper, and a few values are new. I added these to my second list at the top of this thread, which I now believe contains every RN55 0.1% resistor sold singly by Mouser. This kind of list goes out of date quickly, but if anyone can point out when it does, it only takes me a few minutes to munge the whole thing over again.

 

[Pars]

Quote:

Originally Posted by Syzygies <snipped>There's good empirical evidence, surfing the web, that many audiophiles believe there are differences in resistors. I've tried making Etymotic 4p to 4s conversion cables using RadioShack's finest 75 ohm resistors, and I thought that the results sounded dreadful compared to Etymotic's $65 cable.

I've read some evidence (from people who do express a preference for resistors and resistor "sound") that in general, the best sounding resistors have the lowest temp coefficient. These are 25ppm, which is pretty low (I think the normal Vishay Dale RN60s are 100ppm (maybe 50, would have to look).