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Will An Attenuator Help Reduce This Hiss?

i've got a little bit of tweeter 'HASSSHHHH' that i'm looking to reduce. as soon as i turn on the amp and preamp it becomes audible. placing the preamp into standby, mute, or on an unused input does nothing to change the level. changing the volume of the preamp does nothing to change the level. the only thing i've found that changes it is fully powering down the preamp - this eliminates it entirely.

i've been advised to insert a line level attenuator (endler, goldenjack, etc) between the amp and preamp at the amp inputs to bleed off some gain and reduce this noise.

will an attenuator reduce the 'HASSSHHHH' sound when reducing the level, or even muting the preamp, does not change things at all?

thanks for any inputs,
Scott
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almarg
9,670 posts
 
Thanks for the response, Kirk. I see what you are saying. It is not so much the Johnson noise produced by the resistors themselves that is particularly significant (about 1.8 microvolts for your 9700 ohm example, or 1.5 microvolts for the Rothwells I referred to), but the fact that the amplifier's own input noise currents will be increased in significance by the increased source impedance.
I think in the majority of cases this will be instantly noticeable in a quiet room with no source playing and one's ear near the speaker. But at the very least it seems awfully ham-handed to instantly nullify all the hard engineering work it takes to build a low-noise power amplifier.
That provides a good perspective on the magnitude of what we are discussing. Which, as I see it, does not necessarily exclude the possibility that resistive attenuators could still be a reasonable low cost solution in some and perhaps many cases. Especially given that those kinds of noise levels will often be present anyway, as a result of the noise produced by the upstream components, ground loop effects, RFI/EMI pickup, the source material, etc.

Best,
-- Al
rgs92
974 posts
 
Those attenuators you mention ruin the sound (at least they did for me when I tried to reduce the gain between either my source and preamp or between the preamp and amp). They sound like an extra preamp in the chain, taking the life out of things and making the bass muddy.
rgs92
974 posts
 
If you want to buy my Rothwells or Godenjacks, SE or XLRs,
I can post them for sale on Audiogon. They're sitting in a drawer. They do reduce the gain, though.
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srosenberg OP
209 posts
 
thanks, all, for the EXTREMELY detailed and technical feedback - this is a fantastic community.

Ralph, the performance of your gear is exceeded only by your commitment to this community and your customers.

Al and Kirkus, while much of your exchange was well beyond my comprehension, i do appreciate the education. thanks for taking the time to comment here - i found this to be a very enlightening read.

Rgs92, i'm not sure how to contact you. seems like the 'contact member' feature was not carried over to the new audiogon system.

Thanks again, all, i've now got a few new avenues to pursue.
Scott
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