Building a stepped attenuator. What resistor would you use?

[headphonejunkie]

I am building a broskie stepped attenuator and was wondering what would be the best type to use. I am new to this and instead of using the generic types broskie gives with his kit I wanted to use something upscale so I don't have to resolder everything later on. Any opinions will help be appreciated since I am a bit of a newbie when it comes to this stuff.

Thanks

 

[axiom]

Many say resistors sound very different from each other. I can say generic carbon do sound different from Dale Vishay metal film resistors, but asking something like this is like asking what headphone or opamp you prefer and not putting any other limiting factors on it.

You will probably get responses varying from generic carbon (for a total cost of probably a few cents each) to tantalum film resistors (costing $7 a pop!

).

So it really depends on how much you want to spend (and how many steps you need to buy for). That said, I can say Dale Vishay RN (~$.15 ea), Holco (~$1-2 ea.) and Caddock (non-TO220) would be my short list. Definitely diminishing returns.
If you find a setting on the stepper that you use a lot, you can make more of that same attenuation level with the different types of resistors to compare yourself

 

[vixr]

Quote:

Originally Posted by axiom /img/forum/go_quote.gif ...If you find a setting on the stepper that you use a lot, you can make more of that same attenuation level with the different types of resistors to compare yourself...

sounds like good advice...why spend a lot on areas of the stepper that wont get used much.

 

[headphonejunkie]

Thanks guys. Holco's sound like maybe something that won't break the bank. I am going to have to check those out.

 

[The Burn Pt.2]

You can do this- populate maybe 6 steps of most used values with vishay, 6 steps with holco, and the rest with a few tants instead of a full range with one type, this way you can compare resistors instantly without having to reconstruct!

 

[threEchelon]

The ideas you guys are suggesting only work on ladder attenuators. A basic attenuator will probably be a series one.

 

[headphonejunkie]

Broskies is a mixed step and ladder attenuator. maybe I should get a few of each type. Good idea.

 

[ericj]

mixed step and ladder? huh?

There are three kinds of stepped attenuators.

Series, shunt, and ladder. Series and ladder are the most common.

If you're worried about johnson noise, which would be the only reason i can think of to buy exotic resistors, a series or shunt attenuator will always have more of it than a ladder attenuator.

20 expensive resistors will make more noise than two cheap ones.

 

[headphonejunkie]

sorry. ladder and series.

 

[headphonejunkie]

I am going to pick up some holco/prp's they aren't expensive and look to be good quality. With this attenuator I only need 32 resistors altogether; I believe.Thats 12 bucks for 32 resistors(1/4 W) from partsconnexion.

 

[axiom]

Quote:

Originally Posted by ericj /img/forum/go_quote.gif 20 expensive resistors will make more noise than two cheap ones.

While this is true in general, resistors add more noise than just Johnson noise (except wirewounds). If you're really worried about Johnson noise use higher wattage resistors. The larger the resistor package, the lower the Johnson noise. If you're really concerned about noise, use wirewound resistors, since they only have thermal noise (although they may cause other issues). Check out this website for a little more (there are a bunch of others, this hits the highlights though): http://www.aikenamps.com/ResistorNoise.htm .

Nice choice headphonejunkie, sorry about the misquote on the price...

 

[headphonejunkie]

Thanks for the link that gives me some more info to think of. I think this attenuator should be a decent one and it won't cost 300 dollars like some of them. It should beat an alps blue velvet I hope.

 

[ericj]

Quote:

If no current (AC or DC) flows in the resistor, the noise is equal to the thermal noise.

That's the silliest thing I've read today.

 

[luvdunhill]

I'd use Roederstein Resista

 

[ericj]

All I'm saying is, if you're using a stepped attenuator to limit noise, ladder attenuators are the only logical answer.

A series attenuator will sound just fine, though, because at these power levels there is essentially zero resistor noise anyway.