[Julien43]

I built another Bugle to use with low output MCs. I am new to analog, so please excuse my ignorance. The Bugle I built with 40db gain didn't seem very noisy. I do hear considerable hiss with my 60 db build. I am using a Rega P3 with the original, integrated, el cheapo patch cord. I did have to use polyester caps for the .22uf polys. I had planed on using some Jensen Copper PIOs, but the leads were too big to fit through the mounting holes. So, I was forced to use the best Rat Shack had. Could they be my problem. One more divergance from the original parts list was the use of Sonicaps for the .01uf Polys. When the music is palying it is glorious. Maybe I'm just being too sensative. With the volume set at normal listening levels I can hear hiss at my listening chair 8ft away. Any advice you could share will be greatlly appreciated!!

[Doc Jr 8156]

Julien,
Consider using a step-up tranny.  This will eliminate to much gain from the preamp and hence lessen noise.  What cartridge are you using and what is its output?  My Cornet with its 44db gain can handle my AT OC9 (.4 mv) using a Lundahl step-up at 1:10 ratio.  The Lundahl is great, flexible and quiet.  Godspeed.

[hagtech]

Not much you can do about hiss in the Bugle design (except for adding expensive trannies).  The noise floor is pretty much set by the resistance of the cartridge and the gain resistor and opamp of first stage.  Usually hum is the problem.

You could try adding more loading resistance.  Also, lower the 13k and 390 gain setting resistors in the first stage.  Try 3.3k and 100 ohms.  You could even do this for the second stage.  Also, lower the series 1k resistors to 100 ohms.  This will get you a few dB less hiss.

jh

[vfrpilot]

What do the series resistors do?

I am trying to reduce hiss (not hum) in my unit witch is setup for 63.5db gain.

What effect does changing them to 100ohms do this have on the circuit? Could the fact that I used 5% carbon films instead of metal oxide have an effect on overall noise levels?

Does lowering the first gain setting resistors reduce overall gain and by how much?

I am currently setup with 316ohm gain resistors in all locations.

[hagtech]

Series resistors do a couple of things, mostly stability, also low pass filtering.  You could try changing the opamp feedback resistors in the first stage by 1/10th.  That is, 39 ohms and 1.3k.  That would force you to lower the series 1k to 39 or so.  Should lower hiss a little, might add some susceptability to RF.  Carbon films ok.  They have a different type of added noise, more noticable as a distortion.  If you want to hear this type of graininess and smear, use carbon composition.  They take a little edge off if you don't like the detail.

jh