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In the Forum: Audio Discussions
In the Thread: Initial thoughts about new/old Lamm ML2s
Post Subject: Meow ! No more hiss !!!Posted by jessie.dazzle on: 3/23/2007
Romy wrote :
"...You have too much gain in your playback for 109dB sensitivity... I used ML2 with 109dB sensitively and L2 with 12.5dB voltage divider at ML2 and I had no annoying noise at nearfiled..."
Ok so I made a couple voltage dividers for the balanced inputs on the ML2s.
And, ahhhh, nice.... Thank you Romy!
For the moment I'm using normal metal resistors, nothing exotic, no bulk metal foil etc. (and yes the elements are magnetic, but not the leads). Before spending lots for really good resistors (balanced requires 4/input), I wanted first to establish :
1) that this would cure the hissing issue, and
2) the correct values and level of attenuation.
I decided to start off with a strong reduction :
(R1=4K99Ω, R2=1K06Ω, into 41KΩ load)
If I've done my math correctly, that works out to -15.3 dB.
I seem to have got it right straight out of the box. Setting the volume pots at the 1:00 position (as Romy mentioned this is where the L2 is at unity gain) puts the level right where I would want it when seriously listening.
This very much took care of the hiss, so yes, problem solved. However, if I am really really picky, there is now a very faint buzzing... not something I can hear unless I put an ear right up into the horn.
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Can anyone comment on the likelihood that the buzz might be a product of the type of resistor I am currently using (which seem to be normal metal-coated ceramic-core type resistors)
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I did try substituting other resistors, but still of the same type; this yielded identical results. It should also be said that for the moment, the resistors are not soldered into place (they are held by very small clips).
The voltage divider assemblies are super well shielded, as they are housed in thick metal cases which are tied to system ground.
I did some research on low noise resistors, and of course Vishay has the answer... more than one actually. It seems from going over their data sheets that the VSRJ is probably the latest and lowest-noise offering ; quieter than the famous S102 or Z102 (correct me if I'm wrong here).
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Does anyone have any experience using any of these in a fixed potential attenuator circuit
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Thanks in advance for any comments,
jd*
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