How do resistors effect tone?

[keithpgdrb]

I installed the resistors before the RCA jacks to give me more turn on the volume control.  I feel like the tone of the amp is a little more dull, muffled maybe.  not a lot, just a little, but enough for me to question. 

I will admit that the resistors I used were Really old, but right in spec.  I don't know enough about parts to know how they change with time.  I didn't think resistors would change the tone if their values remain solid.

thoughts? comments please?

 

[Grainger49]

Really old means different things to different people.  A really old resistor to me would be from the 60s.  Probably would be carbon composition.

Do you know if your resistors were carbon composition, carbon film or metal film?  Those are the three most likely types.

 

[keithpgdrb]

Yes, they are likely from the 70's.  I used them because I had them, but maybe I should trade them out for new.  They were scavenged when I rebuilt my stax headphone amp.  I kept them because their values were still good. 

I believe they are film.  I think.

 

[Grainger49]

The 70s would mean generally Carbon Composition 10%, or if from a higher line product, carbon film 5%.

Yes, do change them out.  Check at a local Radio Shack for a resistor assortment.  They have a few Carbon Film that are brown on the outside, but most are metal film.  Don't worry, Radio Shack doesn't make resistors they just resell them.

 

[keithpgdrb]

I am having trouble getting pics up.  they may be too big.  they are iPhone pics.. what a pain.

 

[Grainger49]

Go to Grainger's Corner.  Check the FAQ Thread.  It gives two ways to post pictures.  I know from experience that if the picture is too big the site tells you so.

 

[keithpgdrb]

Here's a pic of the resistors that I installed.  and the ones I plan on installing.  good?

 

[Paul Birkeland]

Metal oxide resistors have a pretty mediocre sonic reputation, but they will work in your situation.  They tend to be a solid choice for higher power situations out of the signal path (it looks like those resistors you got are 1-3 Watt resistors, you don't need anything bigger than 1/100 of a Watt).

The resistors you have in currently look like good specimens, your observations are quite interesting. 

 

[keithpgdrb]

Metal oxide resistors have a pretty mediocre sonic reputation, but they will work in your situation.  They tend to be a solid choice for higher power situations out of the signal path (it looks like those resistors you got are 1-3 Watt resistors, you don't need anything bigger than 1/100 of a Watt).

The resistors you have in currently look like good specimens, your observations are quite interesting.

not sure how to take that.. lol.

 

[Paul Birkeland]

Oh, based on your description of what the resistors did to the sound, I formed a mental image of what they must look like in my head, which looks nothing like your photo.

I had imagined a compact wirewound inductive resistor, but I have absolutely no idea what the composition of those resistors is, lol.

 

[VoltSecond]

I haven't posted in too long and I'm feeling Nerdy today. .

So off the cuff, -> what in the resistor <- affects the tone of audio?  I think we should look for things than change the gain (resistor value), phase (reactive value change) or noise with changes in signal level.

1. Microphonics

I've had resistor values change with pressure on the end terminations. It was a physically large resistor, but I can see it happening with smaller ones.  This means a two leaded resistor can be sensitive to vibration.

2. Changes in Value with Temperature  ( TCR )

Resistors have temperature coefficients. But I

 

[Paul Birkeland]

Your posts on this forum are sorely missed!

 

[Doc B]

Thanks VS, nice to have you around!

 

[Grainger49]

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VS is indeed missed.  He, like me, is using "vintage" Bottlehead gear for the most part.  (I do have an Eros!)  But the reason for posting is that he is in an industry where he deals with high frequencies and deals with noise and component interactions on a daily basis.

Listen to him!

 

[VoltSecond]

Thanks for the kind words.

 

[VoltSecond]

Work has been keeping my busy. I just opened my December AudioXpress. It has a good article on resistors.

 

[VoltSecond]

Feed your inner nerd  :

http://edn.com/Pdf/ViewPdf?contentItemId=4427151

The link above is a decent article on resistor history with comments on why old resistors have "polarity."

 

[johnsonad]

Thanks VS, that was an interesting read.

 

[STURMJ]

I downloaded the above article and could not open it. But, after renaming it to whateverthenamewas to whateverthenamewas.pdf everything was fine. (for those who might have the same problem)