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Old 4th May 2007, 09:49 AM   #1
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Default Aleph P1.7 output potentiometer

Hi to everybody!

i'm doing researchs on the forum about the output potentiometer for the Aleph P1.7

I came across to this:

-Output pot suggested value is about 1-2Kohm

- Since i'm going to build a resistive with a rotary selector ,i found negative feedback about the Electroswitch 23position.

My 3 questions are:

1) can anybody give me an insight about the different configurations for latter potentiometer and which one is the best for this purpose or in general?

2) if i put the potentiometer on the output, is it not gonna be a problem for the output impedence that goes to drive a power amp, since it swings so much?

3) can i have some suggestions on a very good rotary switch to use for this project? i was thinking about Elma rotary switches (i think the same used on the renowed and very expencive DACT) ,but a couldn't find a good place where to buy a double 23 poistion or so.


Thanks in advance for al the kind advice.

Best Regards,
Stefano.
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Old 5th May 2007, 11:01 AM   #2
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i haven't seen any post at this 3d....

pleaseee Helppp

How can i make a 1.2K output 23 steps latter attenautor?
How can i evaluate the value of the components?

Please Help..
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Old 5th May 2007, 12:38 PM   #3
Yunick is offline Yunick  Sweden
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To calculate the resistor values, maybe this is helpful?

Look at the bottom of the page.

http://www.penguinlovers.net/audio/Attenuator.html
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Old 5th May 2007, 02:30 PM   #4
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I used the electroswitch brand and I had no problems with it. I never got a loose or bad connection.

I am not fond of switches that rely on bent metal to spring load the contacting force, but I suspect all commercially available rotary swithches are mechanically similar.

JJ
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Old 5th May 2007, 09:47 PM   #5
Fox is offline Fox  Netherlands
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Stefano,

Take a look here.


Hope this helps,

Fox
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Old 6th May 2007, 08:20 AM   #6
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Quote:
Originally posted by Yunick
To calculate the resistor values, maybe this is helpful?

Look at the bottom of the page.

http://www.penguinlovers.net/audio/Attenuator.html
it doesn't let me change any parameter; is it a problem of my computer?
The value are set fot 10K 23 steps...if i try to change any of this par nothing happens...
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Old 8th May 2007, 07:20 AM   #7
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i have one thing to ask, if possible, hope somebody will give me an answer:

since i decided to use the latter stepped attenuator as output volume control, i was thinking to take off the cicuit, referring to the Aleph 1.7 service manual,the resistors R72(100) and R64(4.75K).

I would like to know, what a good value would be for the potentiometer in this conditions.
Just making a simple analysis, if in the original circuit an optimum value would be around 2K....without this two resistors a good value would be 1.5K.
Is this calculation correct for you guys?

Do i have any drawback by taking this 2 resistors off from the cicuit and replacing with a corrisponding value with the Out attenuator?

Thanks in advance.


Best,
Stefano.
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Old 10th May 2007, 06:53 AM   #8
febytam is offline febytam  Hong Kong
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Good quality 10K volume attenautor seems hard to find in HK.
If use 100K, any affect of the output gain and impedence? ( I have much 100K ALPS attenautor remain by other project)
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Old 10th May 2007, 08:26 AM   #9
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Quote:
Originally posted by Stefanoo
Just making a simple analysis, if in the original circuit an optimum value would be around 2K....without this two resistors a good value would be 1.5K.
Is this calculation correct for you guys?

Do i have any drawback by taking this 2 resistors off from the cicuit and replacing with a corrisponding value with the Out attenuator?

If i may repeat myself: stop obsessing about the exact values. I don't know if the micro avoids some relay combinations but if it works as the P 1.0 the load may drop to a low of a hundred ohms for some positions. So much about "optimum value". R72 keeps the actual load from becoming too low and is also a part of the attenuator. No reason to keep it if using a 1-2k pot unless you use a high capacitance interconnect.


Quote:
Originally posted by febytam
Good quality 10K volume attenautor seems hard to find in HK.
If use 100K, any affect of the output gain and impedence? ( I have much 100K ALPS attenautor remain by other project)
A 100k pot at output is a complete disaster. In this particular case the value is too high to be ideal as an input attenuator either. Why don't you make your own using a switch and fixed resistors?
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Old 11th May 2007, 12:27 AM   #10
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If you are interested....

I have a mint condition 10K FULLY balanced stereo DACT attenuator. I'd be willing to sell it for $180usd plus shipping.

Here's a link to a picture of the DACT CT2 Balanced 4 deck attenuator.

http://www.dact.com/html/attenuators.html

-David
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