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badger12345 5th March 2007 03:28 PM

CD player --> active speakers volume control
Hi there folks. Just came across this forum, and it looks like a great place to pick up some tips on home audio. I like to make my own music, so I've got a pair of Tannoy reveal active monitors for mixing. Last week someone gave me an old CD player (Technics 490) as I didn't have a decent one. Unfortunately, the phono output level is way too high for my active speakers, so I'm trying to build my own simple volume control. Could anyone suggest what kind of potentiometer I should look at for this task? Any help would be very gratefully received.


pinkmouse 5th March 2007 03:45 PM

Hi Mike and welcome to diyAudio.

There are several options, depending on how complex you want to get. Have a search on Passive Pre(amps) for some opinions. As for a pot, personally speaking, Alps Blue Velvet is a good start, or if you just have a problem with one channel, then you could sort your problem with a couple of resistors soldered inside your connectors. Search for attenuator pad.

richie00boy 5th March 2007 03:45 PM

Just try a 10k log pot and see how you get on.

badger12345 5th March 2007 06:05 PM

Terrific stuff chaps, thanks very much :)

I'd pretty much decided that something along the lines of a blue velvet dual channel pot would work nicely. Simple enough for me. Does the rating of the pot affect the maximum level of attenuation? I mean, is it critical that I choose, say, a 10k pot over a 50k?

It's great fun this DIY audio. Might just have to get into it..!

Thanks again.


richie00boy 5th March 2007 06:43 PM

Yes the pot value is quite critical. If it's too low it will load the CD player too much, if it's too high the speaker will load the pot too much and skew the response vs rotation curve.

TBH a passive volume like this is not ideal but it will work.

phase_accurate 6th March 2007 09:01 AM

IMO it doesn't matter that much when the response vs rotation curve is spoiled. I always set the loudness levels acoording to my ears and not to my eyes. I therefore even use a linear APLS in my "passive preamp".
Linear pots have the advantage that they have better channel similarity (don't know better words for that) than log types.

But the pot value definitely affects the upper cutoff-frequency by forming an RC lowpass together with the capacity of the cable connected to it.
My pot is a 10k type giving a worst-case cutoff-frequency of 200 kHz together with the low capacitance cable that I use.



badger12345 7th March 2007 10:14 AM

Thanks for that.

I checked the specs on my speakers and it turns out the inputs have a 37k input impedance. I 'think' therefore that a pot of either 10k or 50k would probably be ok. Does this sound about right?

Thanks again.

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