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I have spent sleepless nights here, lurking and learning. I bought a used 834p unit last year, but I hadn't much time to listen critically. I am always moving stuff around and noticed a couple of things a couple of nights ago . big hum, mostly coming from right side and, well, a helicopter sound on the left. It happened as a result of me swapping a bunch of tubes back and forth, etc. Been trying differed 12ax7, one 12au7 and others. I eventually noticed that the ear was sitting near and above noise generating units, like Furman power conditioner and my streaming server, sonic transport, basically a small computer. Moving the 834p helped greatly and then I reinstalled the original tdp tubes. This morning the hum and helicopter sounds were gone and I listened for a while . yes there was a lot of gain hiss but not an abnormal amount of hum. Surely, since everything was working well, I was determined to tweak again. I read so much about putting a 12au7 in the v1 socket. I did that and tried different tele 12ax7 in the other sockets. Some of the teles are new, others are nos and used. Surely after, the hum (right side) and helicopter (mostly left) came out to visit. I'm taking a break.
Is this happening because of some capacitor overload and is that how it got better this morning, or do I just have a bunch of incompatible tubes? Also, touching the input cables at the rca base, changed the artifacts a little and can make the helicopter move to the right speaker. My system is marantz clearaudio tt15 with mm virtuoso wood, Octave audio v40 se amp, Quad 2805s.
Interesting that you mentioned gain hiss. I have a EAR 834P as well and thought that there was an issue with mine, but yours seem to have gain hiss at higher volume as well. However, when music plays I can't hear it.
I would be careful with swapping tubes in the EAR 834P. I find that the PCB bends a lot when you push the tubes into the socket. I would be afraid that one day all that pushing could create a hairline crack in the PCB, cutting one or some of the traces.
Just wondering if there is some dirt or oxidation on some of your tube pins or sockets that may cause some connection issues and therefore the sounds you are hearing.
I always stuck to 12AX7 or 5751 tubes in my EAR 834P
Ah you've been reading those guitar and musician sites haven't you?
Well Palustris is absolutely correct. Put those tubes back where they belong.
I believe that preamp uses three (high gain) 12AX7s. It's a wonder that it played anything at all with a (low gain) 12AU7 in there.
And while you are at it clean and retention those pins.
Also when it comes to electronics and tubes feel free to ask right here. I don't ask my doctor about car problems and I don't ask my mechanic does this lesion look funny.
"I read so much about putting a 12au7 in the v1 socket. I did that and tried different tele 12ax7 in the other sockets. "
Tubes are not like light bulbs regardless of what apocryphal nonsense you read on the internet. Vacuum tubes require very specific operating conditions to work properly. They need the correct load, plate voltages and bias. If you corrupt any of these conditions you corrupt the signal passing through the tube. The engineer who designed the circuit was not incompetent. He probably spent weeks, even months, tuning the circuit so that it performed precisely as he intended it to. If you replace a 12AX7 with a 12AU7 or a 12AU7 with a 12AX7, you are simply creating a noise generator or a filter of completely unknown results while destroying the carefully crafted work of the engineer.
It certainly not a good idea to have a source of RFI and/or EMI right next to an amp. It may be that one of the tubes was especially sensitive or microphonic and the proximity to the noise makers excited the tube. Try and turn off all the computer stuff including the furman and just plug the amp into the wall and see how much noise you get. If that makes a big difference i think you solved your biggest problem. You could also try some tested low noise tubes as a reference. cheers, Dak
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