Houston Mini 2004 Pot question - diyAudio
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Old 9th August 2007, 07:10 PM   #1
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Join Date: May 2006
Default Houston Mini 2004 Pot question

Hello,

the Houston Mini 2004 has an ALPS 250KAX2 pot between the RCA input and the preamp.

There is a 62k resistor soldered between pin 3 and pin 2, or between input and output.

Can somebody enlighten me about the potential purpose of this resistor?

As I would like to change the pot to a different type, I would like to reduce the pot value to 100k (any opinion?) and eliminate that resistor.

Best regards


Patrick
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Old 9th August 2007, 07:45 PM   #2
m6tt is offline m6tt  United States
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it would seem like that resistor might keep the resistance value of the pot from going lower than that. Is anything connected to pin 3 other than the resistor? Is it a 3 pin pot? what is connected to the other pins? (I assume you mean the input is going into the middle pin)
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Old 9th August 2007, 08:22 PM   #3
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Yes, it is a three pin pot.

The phono sockets are connected to the IN pin.
The IN pin is connected to the OUT pin via that resistor.
OUT goes to the preamp tube, GND to ground.

But what would this configuration be useful for?


Regards


Patrick
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Old 9th August 2007, 09:08 PM   #4
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Location: ffx station, va
You've got 62K in parallel with your 250k pot so effectively roughly a 50k pot. It will reduce your maximum attenuation, and alter the apparent taper of the pot. At max volume, it does not do anything at all. Unsolder one end, and see the difference. No harm in that.
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Old 9th August 2007, 09:24 PM   #5
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So if I remember the math correctly my total pot should have been reduced to roundabout 1/(1/250 + 1/62) = 50kOhm.

If so, I do not understand why the manufacturer did not simply use a 50k pot.

The tube following the pot has a resistance of 62.5 k (ECC83), and as by chance the resistor's value matches that. I honestly am a little bit confused... further enlightment is greatly appreciated!


Thanks


Patrick
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Old 9th August 2007, 09:37 PM   #6
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My guess is that they could not find a 50k pot with a taper they liked. Or they had some 250k pots lying around, and wanted to use them up.
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