So, the "super-conductive plastic poti" from Germany mystery is solved.
PD: "It looks like TKD pot that someone was selling on a forum, and also available from percyaudio.com"
If not the same TKD as at Percy, then one very similar. Percy Model # CP2511. Thel Model # CP2500.
Carlos: "outrageously expensive"
Percy: Thel:
$62.50 stereo Eu85.00 (approx $102)
$42.50 Mono
$73.00 balance
The reasons Thel gives for superiority of TKD (fewer solder points, and fewer material transitions) are interesting, but also apply to PEC. To think that for years he has been bandying the superiority of ELNA selector switches outfitted with Welwyn resistors ... and selling both to a good profit!
Has anyone compared TKD and PEC? I always wanted to try that TKD from Percy...
Best regards,
James
PD: "It looks like TKD pot that someone was selling on a forum, and also available from percyaudio.com"
If not the same TKD as at Percy, then one very similar. Percy Model # CP2511. Thel Model # CP2500.
Carlos: "outrageously expensive"
Percy: Thel:
$62.50 stereo Eu85.00 (approx $102)
$42.50 Mono
$73.00 balance
The reasons Thel gives for superiority of TKD (fewer solder points, and fewer material transitions) are interesting, but also apply to PEC. To think that for years he has been bandying the superiority of ELNA selector switches outfitted with Welwyn resistors ... and selling both to a good profit!
Has anyone compared TKD and PEC? I always wanted to try that TKD from Percy...
Best regards,
James
Konnichiwa,
Well, this is a general thing I have observed on Pots, be they Carbon, Cermet or Plastic. I always find that the linear version sounds MUCH BETTER than the "audio taper" one. I have no explanation for this, except perhaps that the different track sections have different resistances per degree rotation which suggests different material combinations which are most likely applied in a manner that causes distinct "breaks" in the structure of the track. With some pot's it is very easy to see these sections.
My recommendation is that if a TVC is not affordable to use a lawfaked linear carbon and/or cermet pot or indeed the 10-Turn Wirewound pot's previously discussed. You can easily "gang" up the 10-Turn dual mono pot by using a string or rubber belt and pulley system with shaft extensions to the front.
For lawfaking linear Pots consider a 20:1 ratio between lawfaking resistor and Pot and consider the Lawfaking resistors value the nominal resistance (load on source) and output impedance. The lawfaking resistor will have a fairly large impact on the sound of the lawfaked pot, even cheap large diameter conventional carbon pots sound surprisingly good that way using the right lawfake resistor.
Sayonara
KT said:
Well, this is a general thing I have observed on Pots, be they Carbon, Cermet or Plastic. I always find that the linear version sounds MUCH BETTER than the "audio taper" one. I have no explanation for this, except perhaps that the different track sections have different resistances per degree rotation which suggests different material combinations which are most likely applied in a manner that causes distinct "breaks" in the structure of the track. With some pot's it is very easy to see these sections.
My recommendation is that if a TVC is not affordable to use a lawfaked linear carbon and/or cermet pot or indeed the 10-Turn Wirewound pot's previously discussed. You can easily "gang" up the 10-Turn dual mono pot by using a string or rubber belt and pulley system with shaft extensions to the front.
For lawfaking linear Pots consider a 20:1 ratio between lawfaking resistor and Pot and consider the Lawfaking resistors value the nominal resistance (load on source) and output impedance. The lawfaking resistor will have a fairly large impact on the sound of the lawfaked pot, even cheap large diameter conventional carbon pots sound surprisingly good that way using the right lawfake resistor.
Sayonara
That is what I heard from other sources as well! As such I have just included the advice to use a Law-faked pot on my pre amp page at Decibel Dungeon.
(Yes Jan D has pointed out the error with the pot picture and I am correcting it)
I have recommended a resistor about one/sixth the value of the pot, not 1/20th.
I hadn't realised that T. If that is the case, it doesn't make much sense to Law-fake a 10K pot with a 1K5 as that would be a ridiculously low impedance to work into! Is that correct as I would like to ammend the pre amp page as it is aimed at beginners?
Konnichiwa,
I find that 1/6th does not give not the required function. I know who insists that 1/6 is the right value for faking audio taper and as usually that person is dead wrong.
Common "Log Law" Pots have an attenuation of around 20db at "12 O'Clock". For that to be present in a lawfaked linear pot you need with the pot set at 1/2 rotation 20db or more attenuation. That suggests a value for the resistor of around 1/10th of Rp/2 or 1/20 of the resistance of the Pot. I recommend a 10K/250K combo as minimum for audio.
It is correct insofar that when you have the volume control fully up the input impedance of the Pot/Resistor combo is Rp//Rlf so it is 1K5//10k or around 1k3. Once you attenuate the input imedance goes up quickly. At 6db attenuation it is around 2K7 and at 20db attenuation around 9K....
Sayonara
Nuuk said:
I find that 1/6th does not give not the required function. I know who insists that 1/6 is the right value for faking audio taper and as usually that person is dead wrong.
Common "Log Law" Pots have an attenuation of around 20db at "12 O'Clock". For that to be present in a lawfaked linear pot you need with the pot set at 1/2 rotation 20db or more attenuation. That suggests a value for the resistor of around 1/10th of Rp/2 or 1/20 of the resistance of the Pot. I recommend a 10K/250K combo as minimum for audio.
Nuuk said:I hadn't realised that T. If that is the case, it doesn't make much sense to Law-fake a 10K pot with a 1K5 as that would be a ridiculously low impedance to work into! Is that correct as I would like to ammend the pre amp page as it is aimed at beginners?
It is correct insofar that when you have the volume control fully up the input impedance of the Pot/Resistor combo is Rp//Rlf so it is 1K5//10k or around 1k3. Once you attenuate the input imedance goes up quickly. At 6db attenuation it is around 2K7 and at 20db attenuation around 9K....
Sayonara
Peter,
I'm trying to decide,which pot to buy for my GC.
At the moment I have some plastic cheap Piher
pot at the input.
All I could find here where I live are Blue Alps
and Alpha pots.
Blue Alps are much more expensive.
Do you have any experiences with Blue Alps;
are they good for the price or should I go for Alpha?
Regards;
Matjaz
I'm trying to decide,which pot to buy for my GC.
At the moment I have some plastic cheap Piher
pot at the input.
All I could find here where I live are Blue Alps
and Alpha pots.
Blue Alps are much more expensive.
Do you have any experiences with Blue Alps;
are they good for the price or should I go for Alpha?
Regards;
Matjaz
Kuei:
"My recommendation is that if a TVC is not affordable to use a lawfaked linear carbon and/or cermet pot or indeed the 10-Turn Wirewound pot's previously discussed. You can easily "gang" up the 10-Turn dual mono pot by using a string or rubber belt and pulley system with shaft extensions to the front."
Would you recommend a PC-mount bulk metal foil trimming potentiomenter like the Vishay 1280G as well?
In terms of ganging it up, I would try to use gears entirely. Because the trimmer would be mounted close to the power op amp, a rubber belt would probably stretch and dry out due to the heat.
"My recommendation is that if a TVC is not affordable to use a lawfaked linear carbon and/or cermet pot or indeed the 10-Turn Wirewound pot's previously discussed. You can easily "gang" up the 10-Turn dual mono pot by using a string or rubber belt and pulley system with shaft extensions to the front."
Would you recommend a PC-mount bulk metal foil trimming potentiomenter like the Vishay 1280G as well?
In terms of ganging it up, I would try to use gears entirely. Because the trimmer would be mounted close to the power op amp, a rubber belt would probably stretch and dry out due to the heat.
To Konnichiva : 600 Ohm - ( measured by my friend ) at 100 kHz drop is 1 dB. 10kOhm at 100 kHz drop is more than 3 dB ( depend on type ). It is not much, but exist it and by higher values it will be great. By the way, how you can make with this pot log. curve ? With linear curve we are back in early biggining of electronic .
.
Upupa Epops said:To Konnichiva : 600 Ohm - ( measured by my friend ) at 100 kHz drop is 1 dB. 10kOhm at 100 kHz drop is more than 3 dB ( depend on type ). It is not much, but exist it and by higher values it will be great. By the way, how you can make with this pot log. curve ? With linear curve we are back in early biggining of electronic
I think it was quite explicitly explained that they should be law-faked by means of a law-faking resistor?
Konnichiwa,
The -3db seems a bit low on that, based on my experience.
There are any number of ways of doing this, however with a 10-turn Pot I did not find the linear law a problem when I used 10-turn pots for Volume control.
This is not to say that it is the ultimate solution though. I prefer BTW wirewound attenuators with a VERY HIGH inductance.... ;-)
Sayonara
Upupa Epops said:
The -3db seems a bit low on that, based on my experience.
Upupa Epops said:By the way, how you can make with this pot log. curve ? With linear curve we are back in early biggining of electronic
There are any number of ways of doing this, however with a 10-turn Pot I did not find the linear law a problem when I used 10-turn pots for Volume control.
This is not to say that it is the ultimate solution though. I prefer BTW wirewound attenuators with a VERY HIGH inductance.... ;-)
Sayonara
Peter Daniel;
the stepped attenuator in the shunt position, is it constructed by a long serie of resistors or do you use only one resistor at the time to GND?
Also it would be interesting if you could try a simple metalfilm (vishay) voltage divider, using low value like 1k for the series element, and run it against your TVC.
High values and series attenuator like DACT is a no no IMO. If a stepped attenuator is to be used, it should be a two element shunt solution with lowest possible value for the given circuit.
You mentioned something about one/some of your volume devices "almost as transparent as a piece of wire" how did you come to that conclusion?
/Peter
the stepped attenuator in the shunt position, is it constructed by a long serie of resistors or do you use only one resistor at the time to GND?
Also it would be interesting if you could try a simple metalfilm (vishay) voltage divider, using low value like 1k for the series element, and run it against your TVC.
High values and series attenuator like DACT is a no no IMO. If a stepped attenuator is to be used, it should be a two element shunt solution with lowest possible value for the given circuit.
You mentioned something about one/some of your volume devices "almost as transparent as a piece of wire" how did you come to that conclusion?
/Peter
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