So I've hooked up a Haller circuit to connect to my Magnavox 9304, but its acting weird. The volume pot only works through about 1/4 of the rotation and when it is at medium quality there is a huge quality loss. I'm using 100k alps blue velvet (from ebay, could be fake) and a 10k resistor. Should the values be adjusted or is the pot actually linear instead of logarithmic as was advertised
A quick bit of Googling tells me that the Harry Haller circuit is a peculiar volume control which uses the pot back to front as a shunt element, with a series resistor on the input. I hope I got that right! If so, there are several problems with this design:
1. lowish and variable input impedance (normal volume pot: high and fixed input impedance)
2. highish and variable output impedance (normal volume pot: lowish and variable output impedance)
3. high load on wiper-track interface (normal volume pot: low load on wiper-track interface)
I cannot imagine what sort of 'creative engineering' would come up with such a bad design, unless it was someone who believed (wrongly) that shunt elements are not in the signal path.
You can't debug a bad circuit. Just use the pot in the conventional way.
1. lowish and variable input impedance (normal volume pot: high and fixed input impedance)
2. highish and variable output impedance (normal volume pot: lowish and variable output impedance)
3. high load on wiper-track interface (normal volume pot: low load on wiper-track interface)
I cannot imagine what sort of 'creative engineering' would come up with such a bad design, unless it was someone who believed (wrongly) that shunt elements are not in the signal path.
You can't debug a bad circuit. Just use the pot in the conventional way.
HarryHaller was a former member here. I don't remember when or why he was banned. I guess he has achieved some following if it is actually is called a "Haller Circuit".
http://www.diyaudio.com/forums/everything-else/2608-passive-preamp.html
http://www.diyaudio.com/forums/everything-else/2608-passive-preamp.html
I wonder why there are tons of people over on Audiokarma talking about this circuitry and how good it sounds. Kind of a bummer that it doesn't seem to pan out for me.
I'll rewire the conventional way and see if that works out any better
I'll rewire the conventional way and see if that works out any better
"Harry Haller" was a spoof account created by a rather... unusual person to deliberately spread misinformation. He thought it was funny when people believed him.
He is the best audio related troll in history... People still talk about this circuitry all the time!
So was HH a competent engineer wanting to demonstrate how gullible are some audio people (i.e. doing a Sokal hoax) or was he merely confused?
OK I went back and wired it in the traditional way, but the pot still only wants to work through the first 1/4 turn or so...
I also changed from a 100k pot down to a 50k as it seems to sound better. Same issue on both, both labeled as log stereo pots
I also changed from a 100k pot down to a 50k as it seems to sound better. Same issue on both, both labeled as log stereo pots
Just a clarification about the so-called "Haller circuit": this configuration has been in use for a long time, probably decades before Haller republished it, in electric guitar controls: apparently, the shunting of the sensors rather than mere attenuation brings some benefits.
People better qualified than myself could probably talk about this in more details.
However, for a general purpose volume control, it is a complete nonsense....
People better qualified than myself could probably talk about this in more details.
However, for a general purpose volume control, it is a complete nonsense....
Nbriles, can you post a picture of how you've wired the pot, and maybe a wiring diagram as well. What is the input impedance of the amplifier circuit the pot is connected to?
It certainly is, but it was probably inspired by practices in the electric instruments field.
I do not know whether it has definite advantages for this particular type of application, but the end users (performers and musicians) clearly wanted it, and I never questioned their choice or tried to convert them to more orthodox control means (hopeless task anyway)
I have it wired like this..
controls_pot_tkd
Honestly I'm not sure what the input impedance is. I need an oscilloscope to check that, right?
Note what is shown is the bottom view, you haven't reversed the input and ground connections have you?
You don't need a scope to measure input impedance, to the closest approximation it will be the value of grid bias resistor to ground, ignoring the effects of miller capacitance.. (If present which it should be in the event of an open spot on the pot wiper)
You don't need a scope to measure input impedance, to the closest approximation it will be the value of grid bias resistor to ground, ignoring the effects of miller capacitance.. (If present which it should be in the event of an open spot on the pot wiper)
It in connected exactly as shown in the picture.
And I'll see if I can figure out which resistor you're talking about when I get home from work! 😕
And I'll see if I can figure out which resistor you're talking about when I get home from work! 😕
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