Green pre resistor query

[Ptownkid]

The resistors that go on the lorlin switch, do they all have to be the same wattage and % (tolerance i believe)?

I've got some that are 1% and some that are 5%, does this matter?

Also, does 2k2 translate to 2.2kohms

 

[Svart]

that's a roger to all. :green:

 

[Ptownkid]

so even if they're all 1/4 watt, they all have to be 1%

 

[alk509]

Think about it for a second... All the circuit cares about is seeing the right resistance in the right place, not the size of the part providing that resistance. What difference does it make to the preamp how much heat the resistors can dissipate?

And by similar reasoning: the gain resistors in the green are spaced in 3dB steps. Now, we can't buy resistors in every possible value imaginable, so do you think the specified resistors in the green pre have the exact values that the math predicts will give spot-on 3dB steps? Of course not! So if the values of some of the resistors are off by 1%, and others by 5%, will this really be enough to overcome the fact that you're not using the "right" resistors in the first place?

Peace,
Al.

 

[Ptownkid]

ok, the wording in that last part is a little confusing, are you saying that the resistors that get soldered to the rotary gain switch can be a mixer pack of 1% and 5% 1/4 watt resistors without problems?

 

[peterc]

1% & 5% show the accuracy of the resistors. So if you use 5% the gain steps might not be exactly 6dB. With 1% the wont be exactly 6dB either. But I gaurantee you will not be able to tell the difference if you built one switch with 5% & one with 1% resistors.

Yes you can mix 1% & 5%.

The wattage determines the ability to carry current. In low level audio ccts like this one, we hardly ever push the power ratings. i.e. they are low current ccts. So 1/4w is fine.

What would happen if you used a 1/2w resistor? Practically, nothing. You could also use a 1W or a 5W part in an emergency.

Bottom line is not to exceed current carrying capacity of a resistor.

Peter

 

[alk509]

Eh, so much for the "teach a man to fish" approach! :green:

Peace,
Al.

 

[PRR]

> do they all have to be the same wattage and % (tolerance i believe)?

Some (the higher-ohms ones) have to be bigger than 0.01 Watts. You probably can't buy anything that small, so you use what you have. 0.25W works. 50 Watts works too, though the cost and size of 50W resistors is a waste for a 0.01 W application. (Actually 50W may be "too big": can't make a compact layout. But 0.125W, 0.25W, 0.5W, and even compact 1W are fine, even mixed.)

The tolerance should be much better than 10% for reasonable gain accuracy. Absolute accuracy may not be important, but it would be nice if multiple channels gave about the same gain at the same knob position. 5% all around is reasonable. If you have some 2% or 1%, use them. They do not "need" to be that precise in most DIY, and cost more, but DIY isn't about a few pennies. If you only have some values in 10%, use them. If you notice that the gain-steps are not all the same, or your precision dB meter disagrees with the knob-marks, replace the 10% with low-% or selected 10% resistors.

 

[peterc]

Eh, so much for the "teach a man to fish" approach!

I did consider that, but sometimes you have to tell the man how to tie a proper fisherman's knot & what kind of bait to use.

I once spent 4 months doing pottery classes with an instructor who used the "silent/learn-by-your-mistakes" method & it was a complete cock-up. I was taught a few basic techniques but needed more to progress. After 6 weeks of collapsing vases I left. Went to another teacher & within 2 lessons had been taught how to stop the collapses.

As far as I was concerned, I had 6 weeks & much money wasted by the first teacher.

Regards
Peter

 

[Ptownkid]

Peter and PRR. thank you, that makes things much clearer. it now makes sense. I assumed that it was fine, but when we're talking about 5-10 cent resistors, I didn't want to do something that would sacrifice the quality of my project.

Al, i appreciate your appoach and it usually works with me, but when it comes to a topic that is VERY new to me and is costing hard earned money, I don't want to do something unless I am absolutely sure. Therefore; ask those in the know.

Thanks everyone, it's sinking in.