Metal Film vs. Bulk Foil resistors - diyAudio
Go Back   Home > Forums > Design & Build > Parts
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Parts Where to get, and how to make the best bits. PCB's, caps, transformers, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Thread Tools Search this Thread
Old 3rd November 2011, 05:25 AM   #1
diyAudio Member
Join Date: Oct 2011
Default Metal Film vs. Bulk Foil resistors

Right now I have a voltage divider for each channel in my amp bypassing gain pots--fixed voltage divider of (0, 20k ohm). I am using a Metal Film 1% tolerance resistor right now for each channel--each measuring exactly 20.0k ohms on my multimeter.

Would I hear an audible improvement if I replaced those 25 cent metal film resistors with 20k ohm Vishay bulk foil resisters? They cost $20 for each resistor--so it would be a $40 "upgrade".
  Reply With Quote
Old 3rd November 2011, 01:48 PM   #2
diyAudio Member
Join Date: Mar 2001
Location: Brazil
Audible improvement will depend on how good your system (electronics & speakers) is in fine resolution.

There are also different types in Vishay BFs, and prices. Have a look at Percy's, that stocks them all and has good prices:

Michael Percy Audio Ordering Information
  Reply With Quote
Old 3rd November 2011, 04:12 PM   #3
diyAudio Member
Join Date: Nov 2004
Location: Germany
Originally Posted by audiogeekess View Post
Would I hear an audible improvement if I replaced those 25 cent metal film resistors with 20k ohm Vishay bulk foil resisters? They cost $20 for each resistor--so it would be a $40 "upgrade".
I very much doubt it. Metal films have good linearity and excess noise properties already. I think the only types of resistors with problematic linearity are carbon composition and thick film.
EDIT: Reading up, it seems carbon films aren't exactly the very definition of linearity either (though less bad than carbon comps), but I think they were used in lots of audio equipment in the past and few people ever complained. The voltage coefficient of metal films is only about 1% as high as with these.

Last edited by sgrossklass; 3rd November 2011 at 04:24 PM.
  Reply With Quote
Old 3rd November 2011, 05:42 PM   #4
diyAudio Member
Join Date: Nov 2008
Location: Oakmont PA
Spend your money on Linear Audio Vol. 1 where different resistors results are shown. With the change leftover you can buy some good resistors and a small bottle of wine.
  Reply With Quote
Old 3rd November 2011, 05:52 PM   #5
diyAudio Member
Join Date: Sep 2004
Location: Elk River MN
I've noticed more of an improvement by going to .1% from 1% then changing to bulk foil.

Susumu .1% 1206 SMT RG series from Digikey; 64 cents each.

Not a huge amount of money for a decent component.
  Reply With Quote
Old 15th November 2011, 08:37 PM   #6
diyAudio Member
Join Date: Oct 2011
Mike, can I use the surface mount resisters like I do the 1% metal film resisters, and not on a printed circuit board?
  Reply With Quote
Old 15th November 2011, 09:10 PM   #7
Bone is offline Bone  United Kingdom
diyAudio Member
Join Date: Jun 2004
Location: Dorset, UK
The audible improvement will be in direct proportion to how much you pay for them.
  Reply With Quote
Old 15th November 2011, 09:29 PM   #8
diyAudio Member
john curl's Avatar
Join Date: Jul 2003
Location: berkeley ca
NO, you are wrong, Bone. The best resistors will measure the 'best' as well for the most part. For example, $10 Vishay bulk metal does not sound better (to my ears and many others) as a Roderstein Resista ($0.10). The measurements show similar performance. So 100:1 difference in price is not that different. Trust me, I use both for serious designs.
"Condemnation without Examination is Prejudice"
  Reply With Quote
Old 25th August 2016, 01:30 PM   #9
diyAudio Member
Join Date: Aug 2016
Just came across this interesting post on Metal Film vs. Bulk Foil resistors from 2011 and thought I'd add my 2 cents:

Noise in electronic circuits is generally measured in nano-volts and is highly temperature and frequency dependent. For reference, one nano-volt is 0.000000001 volts, an extremely small value. In electronic circuits that use resistors and capacitors it is the resistors that contribute the substantial portion of noise and for the most part with audio circuits in the 20 - 20 khz, which is typically assigned to human hearing, you can completely ignore capacitors. In electronics the general formula for noise is E = 7.43 X SqrRoot(R X T X DeltaF) where E is in nano-volts, T is the temperature (in Kelvin), R is in K-Ohms, and DeltaF is in is the frequency bandwidth in K-htz.

In general, the formula says that noise increases as the resistance value goes up, the temperature goes up, or the frequency (or bandwidth) goes up or any combinations goes up. In reality all electronic components contribute noise to the system in which they used. And to be more specific, the noise that is attributed to different compositions of resistors is actually referred to as Johnson Noise, which is the random noise created in the material due to atoms moving even in the absence of an electrical signal.

Without getting into some rather complicated theory and associated math, I'll conclude by saying that when comparing certain types of resistors such as metal film, metal foil, carbon film, carbon composite, and wire-wound, for audio metal foil has been found to produce the least measurable noise contribution. However, whether one can hear the contribution of a reduction in noise as a result of using metal foil resistors is highly dependent on the specifics of the audio equipment being used and what, or who, is listening or measuring the noise levels. Since noise levels are highly affected by the voltages used in a circuit, it's questionable whether a person with average hearing will be able to discern noise levels at the nano-volt, or even micro-volt (which is an order of magnitude higher than nano-volt) levels.

In the early 60's the well regarded and famous Harmon Hardon Citation I Stereo pre-amp used carbon composition resistors in its circuitry and you could clearly hear the increase in "noise", usually a "hiss", when you turned up the treble levels beyond their flat settings. The Citation I used lots of feedback and was also known as the Feedback Pre-amp in its day. So circuit topology can contribute to noisy design as well. The Citation I used tubes rather than transistors and some of the plate voltages used were in excess of 400 volts, a level you do not see in today's transistorized and even more modern tube designs.

So to close this comment, I'd say that unless the audio gear has carbon composition (as in the Harmon Kardon Citation I pre-amp) which are the noisiest and/or is a tube design, then replacing the current resistors with more expensive resistors is unlikely to result in an audible improvement IMO. Also, keep in mind that resistor value accuracy has nothing to do with their inherent thermal and noise characteristics. For example, a 1000 ohms resistor rated at 5%, regardless of its composition, simply means that its value - and not its noise - can vary between 950 ohms and 1050 ohms and still be considered a 1000 ohm resistor. Similarly a 1000 ohm resistor rated at 1% simply means its value can be between 990 ohms and 1010 ohms and still be considered a 1000 ohm resistor.

So replacing 5% resistors with 1% resistors is not always going to result in a lower overall noise level - unless you know the circuit design requires more precise resistance values to achieve a more precise results. But that generally has nothing to do with noise levels. Now it is also true that 1% resistors are generally not carbon film and so were of a less noisy composition type, but that's just a byproduct of the tighter tolerance and not directly associated with it. In any case, interesting discussion.

Last edited by Variac; 26th August 2016 at 01:24 AM.
  Reply With Quote
Old 25th August 2016, 01:41 PM   #10
diyAudio Member
Join Date: Nov 2004
Location: Germany
I've still got a spare bag of line breaks here, let me know where to post 'em...
  Reply With Quote


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Vishay bulk metal foil resistors 2kohms RNC90y elviukai Swap Meet 5 13th November 2013 07:12 AM
VISHAY VTA 55 Bulk Metal Foil Resistors? phrarod Parts 3 11th August 2011 07:42 PM
FS Vishay bulk metal foil S102K merlin el mago Swap Meet 12 3rd December 2010 10:42 AM
Vishay bulk foil resistors - where to buy? sublemon Parts 2 22nd October 2005 05:15 AM
Black gate caps and vishay bulk foil resistors biovizier Parts 1 21st June 2005 04:20 PM

New To Site? Need Help?

All times are GMT. The time now is 09:59 AM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2