[AndrewFischer]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif There have been people who've built entire amps using Caddocks and claimed to notice a big difference (improvement) between that and using standard V-D's. The expense is enormous, though, and the effect probably varies with amp design.

And I was about to tell the OP that generic 100ppm metal film resistors from Mouser were good enough for nearly all applications

 

[qusp]

0.005 direct only costs like 14-15, but add relative matching and it goes up to 30-35, request that degree of matching at the very edge of the resistance range and your up to 40 and over.

I just bought some TX trimmer pots to put across my transformer coupled I/V to find just the right value since I dont know the exact output impedance of the dac (damn you ESS)

filling an entire amp with them would be derelict. but I have found good results from picking key positions like feedback, I/V etc.

but for sure there are other components that should be taken care pof first, while maintaining a certain level of quality resistor of course, then once youve left no other stone unturned, but well before you start tweaking fuses, go the resistors

 

[wink]

What happened to the old carbon pile variable resistors?

 

[rds]

Quote:

Originally Posted by nattonrice /img/forum/go_quote.gif For the tightest set-wise and then absolute-wise matching it is around that, yup. If you push the requested values towards the upper limit we discovered they get closer to 40 bucks a pop in small quantities... snap.

Wait... are you talking about .005% resistors for biasing transistors?

What is the point of that when the operating temperature and beta variation is going to be the limiting factor?
Also if you want .005% resistors why not just buy .01% from digikey or mouser and only use those within .005% tolerance. No doubt that is what those audiophile vendors are doing.
I can't think of an example where resistor matching would be so critical in audio. When you're talking about CMRR in an instrumentation amp then resistor matching is critical, but of course you don't actually match resistors by hand - you buy an instrumentation amp.

 

[nattonrice]

I didn't tell him to buy them.
I was agreeing with the price brackets he quoted.

 

[MikeW]

I just bought some TX2575, 1% matched, they where 9.40 each direct from Texas Components. I put them in the passive I/v stage of my dac, and they are pretty amazing. Very much worth the money here. Obviously it's very application specific and i'd only use them in the signal path or other critical area's.

 

[qusp]

Quote:

Originally Posted by rds /img/forum/go_quote.gif Wait... are you talking about .005% resistors for biasing transistors? What is the point of that when the operating temperature and beta variation is going to be the limiting factor? Also if you want .005% resistors why not just buy .01% from digikey or mouser and only use those within .005% tolerance. No doubt that is what those audiophile vendors are doing. I can't think of an example where resistor matching would be so critical in audio. When you're talking about CMRR in an instrumentation amp then resistor matching is critical, but of course you don't actually match resistors by hand - you buy an instrumentation amp.

yes, none of us recommended them for him, he just asked about whether there was such a thing as a good one, so I told him.

oh and BTW the rest of your post is off tilt if you actually know what/who we are talking about. i'm not sure I would call texas components an 'audiophile vendor' and no they arent matched like you say, they are laser trimmed; not really something the average DIYer can do at home

they are a military spec resistor (some say nasa), but somewhere along the line michael percy and some others started talking with them and convinced them to leave the epoxy coat off for the ones sold to our market. you can buy the regular version under the name Z201 which is the Z foil version of the famous S102. vishay sell the regular type and the highest spec are made by texas components under license. the matching is used for all manner of industry, not just ours. sure its not needed for all applications, but if you can, why not?? I only use such matching for some positions as I said and only if its for a high end build

 

[rds]

Quote:

Originally Posted by qusp /img/forum/go_quote.gif yes, none of us recommended them for him, he just asked about whether there was such a thing as a good one, so I told him. oh and BTW the rest of your post is off tilt if you actually know what/who we are talking about. i'm not sure I would call texas components an 'audiophile vendor' and no they arent matched like you say, they are laser trimmed; not really something the average DIYer can do at home they are a military spec resistor (some say nasa), but somewhere along the line michael percy and some others started talking with them and convinced them to leave the epoxy coat off for the ones sold to our market. you can buy the regular version under the name Z201 which is the Z foil version of the famous S102. vishay sell the regular type and the highest spec are made by texas components under license. the matching is used for all manner of industry, not just ours. sure its not needed for all applications, but if you can, why not?? I only use such matching for some positions as I said and only if its for a high end build

ah yeah, I didn't know what resistors you were talking about and just presumed they were some audiophile ones. Aerospace applications are a different ball game really. The tolerances and reliability required by aerospace equipment necessitates all sorts of extremely expensive custom parts. If you were to build a headphone amp with the same mindset as a mars rover I think you could expect to easily hit 5 figures... and that's not even taking into account the cost of hiring the most elite engineers in the world to design your amp