Passive Balanced Volume Control Questions

[SilverStrings]

HI,

I have a TC pilot passive control for my monitors which is pretty good but at the lower volumes I need its not as transparent as I would like it to be. I want a volume control that will give me better clarity and transparency of the sound at lower volumes.

Ive done some research and it seems a stepped attenuator may improve this. Will a stepped attenuator attenuator offer a significant improvement in sound at lower volumes than a regular pot like the TC pilot I have?

I found these on ebay

This one uses smd type resistors like the goldpoint attenuators do
Balance XLR 23 Stepped Attenuator Potentiometer 10K Log | eBay

10K 4 poles 24 Step Dale Res. Volume Control Balanced | eBay


I have 6 sets of monitors btw three are 10k but the others are 600ohm, 40k, and 50k.

Since my monitors have different input impedance's, is it possible to just get one 10k one for instance and be able to use it with all of them without any effect to the sound quality? on ebay they have 10k,50k and 100k balanced stepped attenuators.


They sell two versions logarithmic and linear, Ive done some research and looking at the graphs , it seems a logarithmic will give better tracking at lower volumes, is this correct?

[janneman]

I can't comment on the sound quality issue, but:

- You'd want to use the log taper models for audio level control. Since our hearing has an approximate log sensitivity curve, these have the most comforable rotation versus loudness correspondence. Practically all audio level controls are log taper.

- If your monitor has a 600 ohms input impedance, you can't use a 10k 'pot'. The low load will alter the curve of the pot and it will be pretty useless. You'd want to use a pot that's 5 times, better yet 10 x the impedance of the thing it drives. So for the 600 ohms monitor you'd probably not be able to find a suitable 'pot' but can use a 10k pot followed by a buffer stage.

Hope this is useful,

jan didden

[sreten]

Hi,

Balanced or not, 10K passive volume controls will severely limit the capabilities
of the the balanced XLR out to drive long cable capacitances, and it should
be placed at the end of the cables on the input of the driven device.

Cannot find specs on the TC pilot, but should be easy enough to measure
Rin and Rout. If they are too high that may be your problem, hard to say.

rgds, sreten.

[AndrewT]

I don't believe any, sliding contact across a continuous track type, pot can ever be manufactured accurately enough to maintain balanced impedance in a balanced connection system.
Even stepped is asking a lot in selection and assembly accuracy to maintain the necessary balance of impedances.

[DF96]

Maybe you need a loudness control? This fiddles with the frequency response of the sound at low levels to make it sound more like louder sound, but just quieter.

[SilverStrings]

Originally Posted by janneman

I can't comment on the sound quality issue, but:

- You'd want to use the log taper models for audio level control. Since our hearing has an approximate log sensitivity curve, these have the most comforable rotation versus loudness correspondence. Practically all audio level controls are log taper.

- If your monitor has a 600 ohms input impedance, you can't use a 10k 'pot'. The low load will alter the curve of the pot and it will be pretty useless. You'd want to use a pot that's 5 times, better yet 10 x the impedance of the thing it drives. So for the 600 ohms monitor you'd probably not be able to find a suitable 'pot' but can use a 10k pot followed by a buffer stage.

Hope this is useful,

jan didden

Hi, by "alter the curve"do you mean that it might go from low to high volume at a different curve than it would with 10k monitors lets say?


For the monitors with a 10k input lets say a 50k or 100k pot would be better ? Can you explain why that is?

Hi,

Balanced or not, 10K passive volume controls will severely limit the capabilities
of the the balanced XLR out to drive long cable capacitances, and it should
be placed at the end of the cables on the input of the driven device.

Cannot find specs on the TC pilot, but should be easy enough to measure
Rin and Rout. If they are too high that may be your problem, hard to say.

rgds, sreten.

Hi that was one thing I forgot to ask, I know that capacitance softens the higher frequncies and the transparency, how else will it affect the sound? I would like to have the convenience of changing the volume with just one control but if it would affect sound significantly then I would consider separate stepped attenuators for each monitor.

The cables from the attenuator to the monitor will be only 6ft long each at most.

The TC is a 10k pot, it works fine with all the monitors I cant really hear a difference except with the Tannoys which are 600ohm in which the tannoys are a bit louder at the same volume setting on the TC pilot compared to the other monitors.

[AndrewT]

Originally Posted by SilverStrings

...........I know that capacitance softens the higher frequncies and the transparency, how else will it affect the sound?

does this refer to the Low Pass (RF attenuation) filter extending down into the audio spectrum?

The cables from the attenuator to the monitor will be only 6ft long each at most.

why balanced connection for a 6' connection?

[SilverStrings]

Originally Posted by AndrewT

does this refer to the Low Pass (RF attenuation) filter extending down into the audio spectrum?
why balanced connection for a 6' connection?

From what Ive read cable capacitance can affect the higher frequencies of the sound, I dont know anything about RF attenutaion in that respect.

My soundcard and the monitors all have balanced connections

[SilverStrings]

Any more advice?

thanks

[Michael Bean]

Yeah, I think Jan mis-typed his response regarding the pot vs impedance issue. I think he meant to say that the input impedance of the device should be 5x to 10x the resistance of the pot, in other words, for a 600 ohm input impedance you should be using a 60 to 120 ohm pot, which would be impractical. That's why it would be better to use a 10k pot followed by a buffer stage as he stated.

Mike