Sonzera 20 Noise-Hiss?

PRS said it was a MOSFET driven effects loop. It doesn’t go away if you plug a cable from send to return.

That’s my diyaudio post above.

But if I plug a guitar into the return input, and set the guitar’s volume to zero, it is dead silent.

I am drawing the schematic from the pcb, but it’s a slow process.

I fixed another issue where the amp’s volume was on zero, but the guitar could still be heard thru the amp. I found two traces next to each other. I replaced one with a shielded cable and fixed that issue.

I will get back into it, and hopefully solve it. It is a glorius sounding amp.
 
I got my Sonzera yesterday and had exactly the same problem. When I switched it on without any cable attached and volumes at zero the hiss on the clean channel was very prominent. First I thought that this noise is coming from the outside as it was so loud. It is very stable shhhhhhhhhhhh... it is much less on the drive channel. the sound of the amp is really nice and organic but the hiss is absolutely unacceptable. In the same room i have other tube amps being completely quiet ... i assume and hope it was bad luck and inadequate quality control. Returned the amp the same day. Very sad and disappointed as I liked it otherwise.

cheers Sacapuntas
Last online July 10, 2017 with no other posts.
 
Same here. Brand new 20 hiss was unacceptable. Clean channel, volume at zero, nothing plugged in. Dramatically worse with a pedal (BB Preamp). Very unfortunate. This amp I want. Sorta takes me back to my Blackface Bassman in high school.

Considering getting again but I'd hate to return another. Seller should not absorb that, PRS hopefully does. I've seen enough complaints to make it something to be addressed. By now I am expecting PRS is. Manufacturing issue? Shipping? Maybe the tubes loosen, etc.?
Joined, posted this and hasn't been online since.
 
I'm adding to this experience. I just inboxed a new Sonzera 20 and heard the loud hiss and pops on the clean channel mentioned by others. All knobs were set to zero, nothing was plugged into the amp. Since I purchased this amp through Amazon (from GeraTree), I'm sending it back with paying return shipping. Two new Power Tubes would cost about $65, so returning it's the best bet. I'm giving this another try, purchasing a Sonzera 20 (demo) from Sweetwater. At least I know this one has no hissing on the clean channel.
Joined to post this and hasn't been seen since several days later
 
The only reason I posted the info on the three posts above is that those of you who are looking for answers may decide to discount what these folks posted. I just happened to check their profile pages because it seemed odd that they recently joined, had one post about problems with the amp and haven't visited the site again.
 
PRS said it was a MOSFET driven effects loop. It doesn’t go away if you plug a cable from send to return.

That’s my diyaudio post above.

But if I plug a guitar into the return input, and set the guitar’s volume to zero, it is dead silent.

I am drawing the schematic from the pcb, but it’s a slow process.

I fixed another issue where the amp’s volume was on zero, but the guitar could still be heard thru the amp. I found two traces next to each other. I replaced one with a shielded cable and fixed that issue.

I will get back into it, and hopefully solve it. It is a glorius sounding amp.
Interested in any further progress you may have made. Thanks for the effort!
 
John Mann’s Guitar Vault has them as well. Fwiw. They were quiet.. I tried them

I have another brand of tube amp, begins with an F. It hisses as well. In fact, when I first got it, I could hear radio coming through the amp. I did some research. I had it plugged into an outlet on an outside wall that was also close to a cable TV outlet. I moved it to an inner wall and it was much better (at least I wasn't receiving radio shows through the amp). Check around on the internet, I remember seeing articles about this issue.
 
I've just purchased a Sonzera 20 and love the tones but the noise it makes when I'm not playing bothers me, especially with the clean channel. It's a pronounced hiss and has nothing to do with the volume.

Is this typical for the amp or is mine problematic?

Rob C
I have two Sonzera 20's that make noise, solved by inserting a gate pedal in the FX Loop..
 
I have two Sonzera 20's, I inserted a noise gate/ downward expander into the FX loop in the back, and noise problem solved.. Going to buy a simpler solution and try a Decimator II gate pedal.. great tone on these amps, and now, fully functional with zero noise
 
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