Has anyone ever experienced a system malfunction like this?

Audio Components
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This was a first for me in my 50 years of being an audiophile. I was listening to my system when there were around 60 seconds of distortion like the signal was being run through a guitar fuzz box, then it was fine again. After another .5 hr, the distortion started again and the volume started decreasing over 3 secs. or so and then silence.

It was likely either the streamer or the preamp because both channels failed concurrently and I’m using mono block amps.

I immediately thought the Mullard gz34 rectifier in the preamp had failed as it sounded like a bad tube expiring. I replaced that with a brand new one, still no sound. I reinstalled the original rectifier tube. I tried the cd player into the same inputs as the streamer and it worked fine. I tried exchanging the streamer’s xlr output cables for rca cables. Still no sound. The analog rig also worked fine. The system has run without issue for the last eight days using cd and analog sources. I’ve been using the preamp’s xlr input that the streamer also used (which is transformer coupled.)

I did not change any of the two 6h30 tubes (one for each channel) in the pre because the problem happened simultaneously in both channels.

The streamer is now back at the manufacturer’s USA facility and they say has worked fine for the last two days.

I contacted the manufacturer of the preamp and asked if they’d ever had anything like this happen. They checked their service records for the ten years or so it was in production and said “no.”

So, has any one ever had rectifier or other tubes act up and quit only to come back to life sounding fine? Am I overlooking any other issue that could be at fault? The period of fuzzy sounding audible distortion prior to the output signal eventually ceasing makes me think it unlikely a loose power connection or faulty interconnect was at fault. I’ve had that happen before of course, but then it was either on or off in my experience.

The streamer is only six months old and under warranty, just trying to decide how to proceed if they can’t duplicate the problem.

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Can you list your components?

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The preamp and amp in use are a Modwright LS36.5 preamp and KW99 mono blocks. Modwright has been exemplary in offering suggestions and checking service history for any similar occurrence. Power supply is a Shunyata passive unit with numerous High Fidelity Cables magnetic power conditioners (2 MC .05s, a Helix +, and a MC-1 Pro.)

I don’t see any reason at this point to name the manufacturer of the streamer because they’re doing all they can to diagnose and haven’t given me any reason to doubt their findings to this point. It is a mid level unit at around $7k US. These sort of threads can derail a manufacturer’s reputation when people read too much into a thread like this.

I’m mainly interested at this point in whether anyone has had preamp rectifier or driver tubes quit functioning intermittently or whether I overlooked any other potential reason for the issue.

2 Likes
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The only time I ever had a similar tube happenstance was using a 1959 EICO integrated amplifier. It was all point to point wired and over the years a soldered connection to one of the rectifier wires had gone bad and was slightly detached from the chassis. Once or twice the connection failed. . . and then perhaps just jiggling the source switch as a test for what ailed it would restore the connection by a vibration on the chassis.

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I experienced something similar that was due to a bad contact.
Oxidation of one of the contacts (RCA or tube base)
Take tubes out and put back can solve this.

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It had occurred to me that the tube socket or wiring to the socket might be an issue that could cause similar sounding malfunction. The rectifier socket is firmly soldered in place on the circuit board though. Dang intermittent problems, the bane of the audiophile!