2. amps-preamps
  3. 1254923842

Endler stepped attenuator w/Cary active preamp

I have an idea for fixing a little problem, but don't know if it makes any sense (I have no background in electronics).

I had been running a Modwright Transporter directly w/balanced outputs to a big SS power amp w/no active pre. W/o attenuation, the volume was too loud at even the lowest levels and I could hear some hiss during quiet sections in music. I solved both problems w/Endler stepped attenuators. They almost completely eliminated the hiss and yet seemed to be transparent.

I just upgraded my system by adding a Cary SLP-05 active preamp. Huge improvment in dynamics, detail, soundstage, image weight, etc. Dramatic improvement, actually.

One downside, I can hear a hiss during quiet passages. Not super bad, but loud enough to notice. I tried using the built in attenuators (input control) on the CAry. It helped but did not completely fix the problem.

Anyway, because the Endlers fixed the hiss problem before, I thought I would try using them in conjunction w/the active pre. I will just give it a try, but wanted to know if that made sense? What problems should I look out for? Is this a common set-up? Etc. Any input will be much apprefciated. Thanks.
128x128shredder
shredder's avatar
shredder OP
93 posts
 
And, where do I put the attenuator? B/w TP and pre or b/w pre and power?
shredder's avatar
shredder OP
93 posts
 
Oh, and the Endlers do not require another set of ics. It plugs into the ic on one end and into an input on the other.
newbee
4,093 posts
 
You would put the Endlers between your pre-amp and your amps. I suspect you will discover that the noise still exists when you do.

If you are concerned that the Cary might be the source of the hiss, simply turn your source off leaving the volume control in the same position that revealed the hiss. Once again, if the hiss goes away then you know it is not being introduced by the Cary.

Topographically speaking, the pre-amp amplifying stage is always at full power. When you use the volume control all you are doing is attenuating the incoming signal from the source before it gets to the pre-amp amplifying stage.
shredder's avatar
shredder OP
93 posts
 
Thanks. If the Endlers fixed the problem before (albeit w/o the pre), why don't you think it will work now (w/ the pre)?

I actually suspect the TP is the problem as the problem was present when used w/o either attenuators or a pre. If so, wouldn't I want the attenuation before the pre?

I really do ne3ed help with this.Thanks much.
newbee
4,093 posts
 
It is possible that the level of hiss that you are hearing, or not hearing, in the various configurations, has something to do with impedence matching between the sources and the amps, as well as the IC's used to connect them, when using either the Cary or the Endlers. I don't know. Passive pre-amps are problematic and improperly used could easily result in a roll off of frequency extremes. which you have interperted as a reduction of hiss.

What I do feel confident about though is that the TP is the source of the hiss and reducing the hiss at the source, assuming it is not inherrent in the design, is the best, if not only, way to skin this kitty.

The Endlers placed between the TP and the Cary will only reduce the overall output of the TP - it will not just reduce the hiss level and leave the rest of the signal intact (other than perhaps introduce some impedence issues referred to above). When you crank up the volume to the same levels at which you heard the hiss before it should still be there.

But you can't hurt anything by trying both locations for the Endlers just to satisfy your curiousity if not solve your problem. And if it does 'solve your problem', used in either location, and doesn't introduce any degredation to your ears, then great.
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