Rivera K-tre too loud and hissing

[thomasdj]

Hi, I have a rivera k-tre humming and hissing at the crunch channel (ch1).

When master and gain is at 10 and the bas, mid and treb is at 0 the amp is quiet. But when I turn the EQ I can shape the noise. The noise gets louder when turning up the gain.

The amp has no headroom at all on both channels! Don't kow if this is normal for rivera amps?

Any ideas on what causing this??

Best regards

Thomas

[JoeM]

Rivera TV – Tube Trouble Shooting video and tube replacement for Rivera’s with 5 pre-amp tubes

Could be a tube. At least check the easy stuff first.

[thomasdj]

Rivera TV – Tube Trouble Shooting video and tube replacement for Rivera’s with 5 pre-amp tubes

Could be a tube. At least check the easy stuff first.

Hi JoeM, thanks for your reply. It is not the tubes, I've replaced all the tubes and tried swapping the tubes also.

It's seems like the amp has no headroom at all on both channels..It's either too loud or way too loud (when master is at 2 and gain is at 1). I've played "loud" amps like mesa dual/tripple rectifier..but the rivera master/gain pots is more like on/off knobs. However, there is know noise at all if I turn down the master so it has to be in the preamp section.

Best regards

Thomas

[JoeM]

Have you tried contacting Rivera?

[thomasdj]

Have you tried contacting Rivera?

Yes..they just told me to replace the tubes. what will normally cause this problem? a bad plate resister or leaking cathode cap at 1st gain stage or a leaking coupling cap between 1st and 2nd gain stage??

Can it be anything else?

[thomasdj]

If I turn down the gain pot the noise go away! This means that the noise occurs around V1. There is no noise at the clean channel..I think that Ch1/2 shares first gain stage...

Could this be the gain pot???

Best regards

Thomas

[Steve Conner]

Maybe it should be a log pot, and someone replaced it with a linear one?

[thomasdj]

Maybe it should be a log pot, and someone replaced it with a linear one?

Hi Steve, i've thought about that too..but I haven't checked. Thing is that it's my friends amp and he bought it used...so I don't know how the amp is supposed to be. However...the weird thing is that the 'way too loud' issue is on both channels??? ..and ch2(clean) only has a gain..

I don't believe that it's the lin/log mistake cause I don't think that the amp has been opened since it left rivera..the pain't on the pcb-screews are intact an so on...

I cannot check it right now..but I remember that the pots are standard 16mm alpha pots..I think I'll try to replace the gain pot..what do you think?

I've found this schematic at blueguitar:
http://www.blueguitar.org/new/schem/rivera/rivera.zip
but I don't think it's the same as the K-tre..however...I can see that the volume ch1/gain wiper goes to a vactrol that forms a voltage divider with another vactrol..what would happen if on of them fails?

Best regards

thomas