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Old 26th November 2008, 10:25 AM   #1
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Default attenuating......

Hi chaps, something I've always wondered about but never tried is regarding the volume pots on our beloved amps...
OK there seems to be some that go for the conventional setup and some for shunt but what if there was only a shunt to ground?

Specifically, my 'T' amps have 20K at the input and no input caps (DC coupled, ground connected to the bias pin) so could I just put a variable resistor to ground just before it ?

I suppose I could "just do it" and see but I'm lazy and wondered if anyone may have already tried it
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Old 26th November 2008, 02:56 PM   #2
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Not quite sure what you mean, Lee.

Do you want to turn it around so that the input is connected to the wiper?
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Old 26th November 2008, 07:27 PM   #3
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Default Long time....

Hey there Michael, hows tricks?
I believe you are a few time zones closer to Blighty now, that's for sure

I suppose what I'm saying is that I'm only going to be shunting signal to ground and not having the series resistor element of the pot... I think... like this

I think that's how it would be wired... basically a variable resistor to ground....
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Old 27th November 2008, 07:34 AM   #4
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Hi Lee, I would imagine this is not good for the source.
Variable load and grounding of the output may not be good for a lot of sources. You will still need a series resistor I would have thought?
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Old 27th November 2008, 07:55 AM   #5
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Hi Barry... it's the old T-amp crew thread

Yeah.... I was expecting someone to show the impedance card ....but isn't it just a shunt mode pot configuration with the input resistor being effectively the carbon track?

Oh, what the heck, I'm fixing a TA10.1 @ the moment so I'll give it a go and see what happens
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Old 27th November 2008, 01:16 PM   #6
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Hey Lee - yeah - I'm a few 1000 miles closer, now. And nearer your climate, too.

What you are doing there is counting on the output impedance of the signal source as part of the voltage divider. I leave you to work out the maths....


As audio1st says, not going to be good for the source (tho some are protected against this sort of abuse)
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Old 27th November 2008, 02:16 PM   #7
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Hmmm, yeah I see what you mean guy's... I'll stick with convention!
On a side note, this is the 1st time I've had a play with a Trends (always too expensive for my tastes I've just replaced a blown IC on this one for a friend) and it's surprising how it shuns the old Tripath specs... no smd's and components quite spaced out etc..... awful layout for the input section... traces everywhere.
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