PLC1 MKII Passive pre help.

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audiobliss

PLC1 MKII Passive pre help.
« on: 29 Nov 2014, 03:32 pm »
Hi guys, my first time posting here. I had a issue with one of my PLC1 a few days ago. I have one in the tube system, and one in the HT system. I have the one in the HT system configured for bypass on input four, and I am using the tape input as input five for my turntable.

Well a few days ago I decided to play a LP in the HT system. I got the TT and phono stage going, lowered the arm on the LP, went to switch inputs from my tuner on input two to the phono input, but mistakenly hit input four, which of course produced no sound because that's HT bypass, then realizing that, I went straight to the tape input. The system then came on FULL blast, like the PLC let through the full volume to the amp. :scratch: I dived for the volume control, but that had no effect, I had to hit the power switch on the amp to save the speakers.

After I settled down from trying to figure out why that happened, muted the PlC then went to tape input again and the TT played normally.
So what I would like to know for sure is, did that happen because I went from HT bypass to the tape input and the PLC was still in pass trough mode ?
Will that happen only with the tape input ?
Should I always  get out of the HT bypass before going to the tape input.This was the first time I went straight from HT bypass to tape input, I have gone from HT bypass to the other inputs without any problems.

I hope this can by explained, because I can't  figure a reason why that should have happened except for some glitch.  :duh:

AB.

CIAudio

Re: PLC1 MKII Passive pre help.
« Reply #1 on: 1 Dec 2014, 09:07 pm »
I can only guess that maybe you connected the phono output to the HT bypass by mistake.
The tape input is connected to the volume control (just like the 1st three inputs).

audiobliss

Re: PLC1 MKII Passive pre help.
« Reply #2 on: 1 Dec 2014, 09:35 pm »
No, the phono has always been going to the tape input. I am tempted to try the same procedure again, but I have to use some cheap disposable speakers :(
Thanks for your reply anyway, good to know that the tape input is independent like the first three.

Btw, its a great sounding unit, just whats needed in a pre and nothing more.  The LEDs could be a little softer, less bright, especially with three or four on at the same time.

Allan.

RDavidson

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  • Posts: 2003
Re: PLC1 MKII Passive pre help.
« Reply #3 on: 1 Dec 2014, 11:00 pm »
Well, since the inputs are (assumingly) controlled via a microcontroller, which sometimes hiccup, it is possible that it didn't switch inputs accordingly. Did you switch inputs via the remote or by hand? Sometimes small electrostatic shocks can make the microcontroller go wacky. Seen this happen on a couple of components. It doesn't seem to damage anything, but may cause the unit to lock up and it may need to be reset (turned off or given another command). In the winter months, with less moisture in the air, electrostatic shock becomes more common. I suggest always using the remote....plus you keep finger prints and grime, like Cheetos particulates, off your gear. :thumb:

audiobliss

Re: PLC1 MKII Passive pre help.
« Reply #4 on: 2 Dec 2014, 03:24 am »
I think you might be on to something, at least it fits my glitch theory. I did use the remote, but sometimes I notice there seems to be some confusion between the remote and the unit, I will hit the mute button and the unit will go to the tape input instead, then I have to hit the mute again. :scratch:

RDavidson

  • Full Member
  • Posts: 2003
Re: PLC1 MKII Passive pre help.
« Reply #5 on: 2 Dec 2014, 03:55 am »
Have you ever tried unplugging the unit and plugging it back in (to reset it)?
If it glitched in the past, but has never been reset or only occasionally reset, it might continue to glitch as the microcontroller still hasn't been cleared of the hiccups. That's my theory anyway. I'm no genius, but experience and things I have read seem to hold water.

audiobliss

Re: PLC1 MKII Passive pre help.
« Reply #6 on: 2 Dec 2014, 05:37 am »
I will do that, thanks.

Allan.

CIAudio

Re: PLC1 MKII Passive pre help.
« Reply #7 on: 2 Dec 2014, 05:44 pm »
It could have possibly been a microprocessor glitch, although I've never experienced this.
Each input has a relay to connect it to the volume control. When an input command is given, the current input is first disconnected, then the chosen input is connected to the control. There is no way for the micro to connect the signal to anything but the volume control.

If the micro had a glitch, it would have to be that the HT did not disconnect from the output, so when the tape input was selected it was in parallel with the HT input, causing the control to be by-passed.

If this happens again (or any other command issues), I would suggest sending it to us for re-programming.