Attenuators

[realysm42]

(I put this here as it might be a great tweek but I've not tried them yet, therefore they're not in my system).

Can anyone tell me the deal about these things please?

All of my audio is PC based and comes through my M-dac (Which is known for being loud). My volume never really goes past 11 on my system and that levels really belting it! According to some, that means I've got too much gain in my system. Do I need to use attenuators?

The reason I ask is, if all they do is make my volume less sensitive (or restore the full range as it were) then I'm not really that bothered. If however it's going to affect SQ, then I'd say it's worth investing.

Also, as they do they as they say on the tin, doesn't it mean that fitting them would mean my amp would have to work harder than ever to reach the same volume levels I'm used to without having them fitted?

[Audioman]

Martin.

They just change impedence to the amp. It depends as much on sensitivity of the amps input as dac/cd player output. Depending on values they reduce volume a bit. I have Kimber pbj with attenuators on my CD player as I could not get volume above 8 or 9 o clock without it being very loud. Able to reach 12 O clock originaly but with CDs now cut louder I am back down to 10 or 11. (bad CD's can be back down to 8) Frankly if you get to 11 O clock there realy isn't that much problem. They do have the effect of making the sound a little more relaxed without loss of detail and give more scope for fine volume adjustment.

Paul.

[realysm42]

Thanks Paul.

I'm not sure what impedance means, so am not sure I'm in the right place to understand how these things work. Do they make the amp work harder for less volume or am I missing something?

Cheers.

[Martinh]

The commercially available ones have a voltage divider circuit inside.

There are two resistors - one in series and another in parallel with the input.

http://www.sengpielaudio.com/VoltageDivider07A.gif

The attenuation is a simple calculation, as the input impedence of the amp is so high, you can effectively ignore it.

Edit: can you not change the output level directly on the m-dac?

Cheers,

[Audioman]

Thanks Paul.

I'm not sure what impedance means, so am not sure I'm in the right place to understand how these things work. Do they make the amp work harder for less volume or am I missing something?

Cheers.

I doubt the amp has to work harder. At moderate volumes it is using a fraction of available power. If your CD has above average output and the input sensitivity of your amp is high you will have a problem with inflexible volume control. Older amp inputs where generaly more sensitive to accomodate tuners etc with much lower output than CD. More recent amps often have far less sensitive inputs. Amps are often designed to reach high volumes early in the rotation of the control knob. It all depends on the combination of equipment as to how much attenuation is desirable.

http://www.russandrews.com/viewindex.asp?lookup=1&region=UK&currency=GBP&article_id=Attenuation&customer_id=PAA0211108612003IOIXVLIWYINFRLHS

The above explains attenuation clearly and gives table to determine correct amount. This was one of RA's better ideas before he started on the path of ludicrously expensive products and dubious technical claims.

[realysm42]

Hi Martin,

Yes you can change the volume on the M-dac; the reason I've not identified this as a solution is I'm pretty sure there are concerns of dropping bits, the lower the volume is set (I've left all digital volume on my system at 100%, so it's completely manipulated by the single volume control on the amp).

***EDIT*** Thanks Paul.

[Martinh]

The reason that i asked about he m-dac variable out was that many people use it as a preamp direct to power amps, so the volume control must be pretty decent.

Back to the attenuators...

If your interconnect plugs allow it, you can solder the resistors directly inside. This is a really low cost solution and doesn't add another 2 connections into the signal path.

I've done this with one of my interconnects and I bought some "hifi" resistors from HiFi Collective. Here http://www.hificollective.co.uk/components/allen_bradley_resistors.html

Cheers,

[realysm42]

I must admit I'm abit puzzled by this as well; I've heard it's got a very good quality volume control, but so many people speak of attenuation for it (in the pinkfish media thread dedicated to it) it's just got me wondering whih is th best solution...

[sq225917]

As long as you stay between 0-20db there's no risk of the volume attenuation trimming info.

[realysm42]

That about solves it then, cheers Simon :)

Saves me cost and adding things to the chain.

[Martinh]

A link to some reasonably priced units http://members.ebay.co.uk/ws/eBayISAPI.dll?ViewUserPage&userid=goldenjacks

[realysm42]

Just to clarify, if I drop the volume on the M-dac to say -15db I can just use this as attenuation? (I've tried this and it seems to do the trick, being able to turn my amp up louder seems to make the music better quality too).

If this is the case, why do so many speak about dedicated attenuators?

Apologies for being a bit thick...