I'm new to the gainClone scene (meaning i'm trying to build my first one), and I was trying to figure out which potentiometer to get for my volume control. Unfortunately, I'm on a tight budget, or I'd buy everything and compare them myselves. What are the differences between stepped attenuators and POTs in sound?
And generally I find stepped-attenuators are not a particularly attractive option since they are so expensive, and I find the notches to be limiting. But if know of a cheap one w/ more than 12 steps, i'd me interested. (i know this has been asked before on the forums)
I've heard good things about the ALPS "blue" POTs, but these are using conductive plastics....I've heard that cermet type is the way to go?? but i really have no idea\experience. Any suggestions welcome.
I am also having trouble figuring out where to get these. I could only find the ALPS POTs at two places:
-Angela Intruments: www.angela.com
-World Audio Design
Notes:
I am making the non-inverted gainClone (positive feedback), so log tapered is preferred. I also want "dual-ganged" attenuation.
Thanks for any replies!
And generally I find stepped-attenuators are not a particularly attractive option since they are so expensive, and I find the notches to be limiting. But if know of a cheap one w/ more than 12 steps, i'd me interested. (i know this has been asked before on the forums)
I've heard good things about the ALPS "blue" POTs, but these are using conductive plastics....I've heard that cermet type is the way to go?? but i really have no idea\experience. Any suggestions welcome.
I am also having trouble figuring out where to get these. I could only find the ALPS POTs at two places:
-Angela Intruments: www.angela.com
-World Audio Design
Notes:
I am making the non-inverted gainClone (positive feedback), so log tapered is preferred. I also want "dual-ganged" attenuation.
Thanks for any replies!
those "blue" alps pots are $32 each!!!! how tight is your budget?
i used radioshack 100k stereo pots for about $3 each, and i am very happy with the sound. mine is linear tapered and if you use a linear taper instead of log taper you'll have a lot of volume change in the last 1/4 turn or so. some people hate that but i have no problems with it.
the angela.com site also sells riken resistors. if they don't have a min order charge it might be a good idea to order from them
i used radioshack 100k stereo pots for about $3 each, and i am very happy with the sound. mine is linear tapered and if you use a linear taper instead of log taper you'll have a lot of volume change in the last 1/4 turn or so. some people hate that but i have no problems with it.
the angela.com site also sells riken resistors. if they don't have a min order charge it might be a good idea to order from them
ALPS pots
www.goldmine-elec.com
P/N g6830
Alps pots 50K $1.00 ea.
I run them on my input with 22k resistor (input line) then the alps with the ctr tap going to ground.I found out that it will still make a loop but the pot is less in the input line.
ron
www.goldmine-elec.com
P/N g6830
Alps pots 50K $1.00 ea.
I run them on my input with 22k resistor (input line) then the alps with the ctr tap going to ground.I found out that it will still make a loop but the pot is less in the input line.
ron
The gain factor
The 220K feedback resistor on the inverted GC is absolutely correct for a power amp (feeded by an active pre).
If you are going to make an integrated GC amp, use 300k on the feedback.
The pot will be a log one.
It seams to me that some people are using linear pots because of the low gain with the 220k resistor.
julester said:
The 220K feedback resistor on the inverted GC is absolutely correct for a power amp (feeded by an active pre).
If you are going to make an integrated GC amp, use 300k on the feedback.
The pot will be a log one.
It seams to me that some people are using linear pots because of the low gain with the 220k resistor.
might be a really stupid question
Carlos,
I'm working on this project with julester and I was confused about your posting regarding the feedback resistor. Currently, we're using the schematic found at
http://www.euronet.nl/~mgw/diy/amps/uk_geenkloon_2.html
which calls for a 20k feedback resistor. The data sheet for the LM3875 also calls for a 20k resistor. Is there a reason you recommend 220k? Also, why do you recommend a 300k if it's an integrated amp? Thanks a lot for your time.
Doovieman
Carlos,
I'm working on this project with julester and I was confused about your posting regarding the feedback resistor. Currently, we're using the schematic found at
http://www.euronet.nl/~mgw/diy/amps/uk_geenkloon_2.html
which calls for a 20k feedback resistor. The data sheet for the LM3875 also calls for a 20k resistor. Is there a reason you recommend 220k? Also, why do you recommend a 300k if it's an integrated amp? Thanks a lot for your time.
Doovieman
Carlos & Doovieman:
The pot in the inverting GC should be linear because it is effectively in part in parallell with the 10 K resistor and thus will assume a near log scale anyway. The call for the 220 K is that high for the same reason and since the input resistor is in parallell with part of the pot and will, sometimes, be the input impedance as seen by the pre-amp. Using a 20 k feedback would have meant a 1 K input resistor giving less than 1 K input impedance in worst case. Could have worked with some pre-amps but not all.
The pot in the inverting GC should be linear because it is effectively in part in parallell with the 10 K resistor and thus will assume a near log scale anyway. The call for the 220 K is that high for the same reason and since the input resistor is in parallell with part of the pot and will, sometimes, be the input impedance as seen by the pre-amp. Using a 20 k feedback would have meant a 1 K input resistor giving less than 1 K input impedance in worst case. Could have worked with some pre-amps but not all.
so....
So in answer to our original question, what are the differences between a pot and an attenuator (in quality)? What makes the ALPS pot the pot of choice by so many GC designers? Is there actually an audible difference between the ALPS pot and cheapo from radioshack? What makes a good pot a good pot? If there is actually an audible difference between different pots, is there a consensus on pots that are "good"? If so, please elaborate as to costs and locations of purchase. Thanks for your time,
Doovieman
So in answer to our original question, what are the differences between a pot and an attenuator (in quality)? What makes the ALPS pot the pot of choice by so many GC designers? Is there actually an audible difference between the ALPS pot and cheapo from radioshack? What makes a good pot a good pot? If there is actually an audible difference between different pots, is there a consensus on pots that are "good"? If so, please elaborate as to costs and locations of purchase. Thanks for your time,
Doovieman
Hi!
Does anybody know who manufactures this pot called CP-2500
http://www.thel-audioworld.de/bauteile/regler/Potis.htm
(the second one on the page)
Thel says that it's better than any stepped attenuator, and better than all the other pots he sells, with best tolerances.
Anybody heard of this so far?
Maybe would be a new addition of a "high end" part to Peters commercial GC...
Bye,
Arndt
Does anybody know who manufactures this pot called CP-2500
http://www.thel-audioworld.de/bauteile/regler/Potis.htm
(the second one on the page)
Thel says that it's better than any stepped attenuator, and better than all the other pots he sells, with best tolerances.
Anybody heard of this so far?
Maybe would be a new addition of a "high end" part to Peters commercial GC...
Bye,
Arndt
Still wondering...
So I'm still trying to figure out the differences between an attenuator and pot. Does anybody actually know or is it all speculation. Is there an audible difference? What makes a "good pot" a good pot? What are the factors that one should look for when purchasing a pot? Is there an audible difference between the pots they sell at radioshack (they cost about $1 a piece) and this famous Alps blue pot that everyone is using? On a separate note, where exactly in the circuit does the pot go? We are using the schematic found at:
http://www.euronet.nl/~mgw/diy/amps/uk_geenkloon_2.html
Does it simply act as a voltage divide on the input? Does it go in parallel to the 22k resistor (which I assume is to prevent oscillation)? Does it go in series to the input? Thanks in advance for your help.
Doovieman
So I'm still trying to figure out the differences between an attenuator and pot. Does anybody actually know or is it all speculation. Is there an audible difference? What makes a "good pot" a good pot? What are the factors that one should look for when purchasing a pot? Is there an audible difference between the pots they sell at radioshack (they cost about $1 a piece) and this famous Alps blue pot that everyone is using? On a separate note, where exactly in the circuit does the pot go? We are using the schematic found at:
http://www.euronet.nl/~mgw/diy/amps/uk_geenkloon_2.html
Does it simply act as a voltage divide on the input? Does it go in parallel to the 22k resistor (which I assume is to prevent oscillation)? Does it go in series to the input? Thanks in advance for your help.
Doovieman
Konnichiwa,
Well, a few things first. Conductive plastic pots have a distinctive sound. You may like what they do, I don't. Secondly, log pots are "dreck". Due to the production process they generally offer poor tracking making well tracking examples the result of a selection process and making them costly, also due to the varying composition of the track to vary the resistance/length the sound is messed up.
The solution would seem a good stepped attenuator, however the series resistor chain types I have encountered are not very good, this includes the DACT. Kondo san once commented on the typchical series resistor chain attenuator by saying it causes "hilarious dummy sound" and I think he is right. If you want a stepped attenuator you MUST use the single series single shunt resistor (S4R) or "true ladder" topology and use really high quality resistors.
There are no commercial optiosn I'd consider good and even doing it yourself with switch and resistors costs a lot of money and takes ages (I have hand build quite a few resistor switched atts before I finally got decent transformers to do the job of the resistors without sonic problems).
So, I'm with Hugh on this. Linear Track carbon Pot or linear track cermet Pot. For a non-inverting Gainclone with a 22k Input resistor I'd recommend a 220k to 470k Pot, for the inverting Gainclone 100k and (yes, I agree Carlos) a 330k Feedback resistor.
However, if you want good realistic sound, NEVER, UNDER ANY CIRCUMSTANCES use Log pots and stay away from plastic track stuff. If you want that classic "High End HiFi" mechanical, artificial sound go for Alps plastic log. If you want natural sound simply use a good transformer attenuator.
Sayonara
julester said:
Well, a few things first. Conductive plastic pots have a distinctive sound. You may like what they do, I don't. Secondly, log pots are "dreck". Due to the production process they generally offer poor tracking making well tracking examples the result of a selection process and making them costly, also due to the varying composition of the track to vary the resistance/length the sound is messed up.
The solution would seem a good stepped attenuator, however the series resistor chain types I have encountered are not very good, this includes the DACT. Kondo san once commented on the typchical series resistor chain attenuator by saying it causes "hilarious dummy sound" and I think he is right. If you want a stepped attenuator you MUST use the single series single shunt resistor (S4R) or "true ladder" topology and use really high quality resistors.
There are no commercial optiosn I'd consider good and even doing it yourself with switch and resistors costs a lot of money and takes ages (I have hand build quite a few resistor switched atts before I finally got decent transformers to do the job of the resistors without sonic problems).
So, I'm with Hugh on this. Linear Track carbon Pot or linear track cermet Pot. For a non-inverting Gainclone with a 22k Input resistor I'd recommend a 220k to 470k Pot, for the inverting Gainclone 100k and (yes, I agree Carlos) a 330k Feedback resistor.
However, if you want good realistic sound, NEVER, UNDER ANY CIRCUMSTANCES use Log pots and stay away from plastic track stuff. If you want that classic "High End HiFi" mechanical, artificial sound go for Alps plastic log. If you want natural sound simply use a good transformer attenuator.
Sayonara
You don't really need a "pot" with the GC -- since this part of the circuit is "set and forget" -- build the amplifier with a trimmer pot, measure the resistance level on the potentiometer arm to ground that result in the output you need given the source, then substitute a pair of resistors. You should do your volume controlling in the preamp stage.
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