Preamp Noise

[skeith]

I'm getting a sound like rushing wind out of one channel.... I switched tubes but the noise did not switch channels... so probably not a tube?

Any ideas?

[Larry Kart]

Some problem with that loudspeaker? If you have earphones, do you hear the same problem in that channel?

[jazzbo]

Did you switch ALL tubes left and right? That sound in my experience has always been tube related. Is there tube recification. . . one for both channels, or one for each channel?

[skeith]

thanks Larry and Lon

I don't have an earphone jack - so I can't do that test, but I don't think it is speaker related.

There are only 2 tubes in the whole preamp - I switched them and the sound continued in the same channel - makes me think it might not be a tube. Lon - what is tube rectification? Do you mean can I adjust the bias? The answer to that is no.

[jazzbo]

Well, if you only have two tubes then there's no tube rectification. Rectifier tubes are large and they are sort of "one way valves" that convert AC from the wall into DC for the electrical circuits to use.

I don't know what may be happening here, sorry. It might help someone to help if you tell us the make and model of the preamp.

[Kevin Bresnahan]

What kind of preamp is it? I agree with Lon that if there's only two tubes, you don't have a tube rectifier. However, a two tube preamp isn't really the kind of tube preamp I've ever worked with. With only two tubes, it's likely a "hybrid" tube/SS preamp. It's nearly impossible to get enough gain out of just two tubes.

Try swapping the speaker wires from one to the other and see if the sound tracks the speaker or if it stays in one channel. If it tracks, it's a speaker. If it stays in the same channel, it's the preamp.

Offhand, what are you using for an amp? In my experience, a lot of single channel audible problems are from the amp, not the pre.

Kevin

Edited April 2, 2013 by Kevin Bresnahan

[skeith]

The preamp is a Conrad Johnson PV14LS and is separate from the amp. THe amp is not the problem because when I switched the interconnects from the preamp to the amp - the noise switched channels. THat's how I determined it was the preamp.

Finally, I tried several sets of tubes last night and it did not affect the noise. I also noticed that the tubes placed into the noisy channel did not glow as brightly as the normal channel.

I may need to send this one back to the factory. Anyone have any experience with Conrad Johnson's service?