100K Noble logarithmic pot

2Bak · 27th January 2004, 07:20 PM

I'm building another GC using the below schematic.
I have a Noble 100K logarithmic pot, type 204.
I've seen that people recommend linear pots for GC's.
Can I compensate in some way using this logarithmic Noble? If possible, what should I do...?
By the way, why are logarithmic pots not recommended?

(Haven't soldered it in yet, so I haven't heard the amp in action with this Noble).

Thanks.

/Jan

2Bak · 27th January 2004, 07:23 PM

this one

Peter Daniel · 27th January 2004, 07:38 PM

I'm very curious why they are not recommended? I used exactly the same pot in the same circuit and it works fine.

Wht is not recommended, is the 100k value. I'd rather go for 50K, but if not available 100k will work too. Actually, I tried linear pot in this location, and I prefer the action of the logarythmic one.

2Bak · 27th January 2004, 07:49 PM

Quote:

Originally posted by Peter Daniel
I'm very curious why they are not recommended? I used exactly the same pot in the same circuit and it works fine.

Wht is not recommended, is the 100k value. I'd rather go for 50K, but if not available 100k will work too. Actually, I tried linear pot in this location, and I prefer the action of the logarythmic one.

Thanks for your information, Peter. I didn't mean that Nobles were supposed to be not recommended.
However, in this schematic someone (?) recommends linear tapers: http://ampchipdiy.com/invertedLM3875_r2_1.gif

I will use this 100K Noble 'cause I have it already.

/Jan

Peter Daniel · 27th January 2004, 07:51 PM

Well, I tried both (linear and logarythmic) and logarythmic gives better control range. BTW, those Nobles are pretty good sounding pots.

Also, Noble 204 curve has pretty nice split and might work better than some other logarythmic pots (with 10/90 split)

2Bak · 27th January 2004, 07:56 PM

Quote:

Originally posted by Peter Daniel
BTW, those Nobles are pretty good sounding pots.

Yep, I've seen you mention this before...I tried an old Alps Black Beauty 100K first, but took it out 'cause channels were not in balance. Looking forward to trying this Noble.

GrahamnDodder · 27th January 2004, 10:26 PM

Peter-

I am building stepped attenuators for an LM3987 IGC feeding a pair of 90db speakers. But I only have 12 steps to my switches. Can you rec 12 resistor values for a most useful set of 12 steps?

Thanks,

GnD

Peter Daniel · 27th January 2004, 10:46 PM

There is a 12 step attenuator in this link http://www.geocities.com/rjm003.geo/...io/diy_gc.html

If I would be doing one for me, I would use 2db steps from full volume down (-22dB would be 11 pos and OFF would be the last one). I don't listen at rally low volumes so this would work well for me.

In here, there are some values listed as well: http://www.penguinlovers.net/audio/Attenuator.html

Another calculator here: http://homepages.tcp.co.uk/~nroberts/shunt.html

27th January 2004, 10:26 PM	#7
GrahamnDodder diyAudio Member Join Date: Jun 2003 Location: Near Baltimore, MD	Peter- I am building stepped attenuators for an LM3987 IGC feeding a pair of 90db speakers. But I only have 12 steps to my switches. Can you rec 12 resistor values for a most useful set of 12 steps? Thanks, GnD __________________ I had the right to remain silent. I just didn't have the ability. (Comedian Ron White)

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27th January 2004, 07:38 PM	#3
Peter Daniel diyAudio Member Join Date: Jul 2002 Location: Toronto, Canada	I'm very curious why they are not recommended? I used exactly the same pot in the same circuit and it works fine. Wht is not recommended, is the 100k value. I'd rather go for 50K, but if not available 100k will work too. Actually, I tried linear pot in this location, and I prefer the action of the logarythmic one.

27th January 2004, 07:51 PM	#5
Peter Daniel diyAudio Member Join Date: Jul 2002 Location: Toronto, Canada	Well, I tried both (linear and logarythmic) and logarythmic gives better control range. BTW, those Nobles are pretty good sounding pots. Also, Noble 204 curve has pretty nice split and might work better than some other logarythmic pots (with 10/90 split)

27th January 2004, 10:46 PM	#8
Peter Daniel diyAudio Member Join Date: Jul 2002 Location: Toronto, Canada	There is a 12 step attenuator in this link http://www.geocities.com/rjm003.geo/...io/diy_gc.html If I would be doing one for me, I would use 2db steps from full volume down (-22dB would be 11 pos and OFF would be the last one). I don't listen at rally low volumes so this would work well for me. In here, there are some values listed as well: http://www.penguinlovers.net/audio/Attenuator.html Another calculator here: http://homepages.tcp.co.uk/~nroberts/shunt.html

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