2. amps-preamps
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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.
shredder
shredder's avatar
shredder OP
113 posts
 
Hmmmmmmm, could it be just a bad tube in the TP?

Any downside to the attenuator even if just a band-aid?
newbee
4,817 posts
 
If the hiss is constant it is in your pre-amp. If it fluctuates when you use the volume control then it is in the TP. If it is in the pre-amp using an inline attenuator, either a constant fixed value or one which can be used as a stand alone VC will reduce the hiss below audibility, but depending on your expectations and listening skills you may note some minor degredation, especially if you have to use an addition set of IC's. I would prefer a fixed value resistor (like a Rothwell, but not necessarily one).

If the hiss changes with volume it is likely because of a noisy tube(s) in the TP or you may well have a noise floor issue. If the noise is the same in both channels it is likely a noise floor issue. You might have to plug in some new low noise tubes to ascertain this unless other owners confirm the noise floor issue.

FWIW.
shredder's avatar
shredder OP
113 posts
 
And, where do I put the attenuator? B/w TP and pre or b/w pre and power?
shredder's avatar
shredder OP
113 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
4,817 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.
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