Houston Mini 2004 Pot question

p.heimpold · 9th August 2007, 07:10 PM

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

m6tt · 9th August 2007, 07:45 PM

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)

p.heimpold · 9th August 2007, 08:22 PM

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

ethermion · 9th August 2007, 09:08 PM

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.

p.heimpold · 9th August 2007, 09:24 PM

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

ethermion · 9th August 2007, 09:37 PM

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.

9th August 2007, 07:10 PM	#1
p.heimpold diyAudio Member Join Date: May 2006	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

9th August 2007, 09:08 PM	#4
ethermion diyAudio Member Join Date: Apr 2005 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. __________________ -e

9th August 2007, 09:37 PM	#6
ethermion diyAudio Member Join Date: Apr 2005 Location: ffx station, va	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. __________________ -e

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9th August 2007, 07:45 PM	#2
m6tt diyAudio Member Join Date: Aug 2007	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)

9th August 2007, 08:22 PM	#3
p.heimpold diyAudio Member Join Date: May 2006	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

9th August 2007, 09:24 PM	#5
p.heimpold diyAudio Member Join Date: May 2006	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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