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Back from holiday - erratic volume performance

delta1

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Back from holiday - erratic volume performance

Postby Garrard301 » November 18th, 2017, 9:40 am

Hi all,

Just returned from a two-week break during which my recently-built preamp containing LCDuino was disconnected from the power for safety reasons.

I've just powered it back up and I now don't seem to be getting the correct half-decibel step attenuation - there is for example quite a significant jump in volume between -32dB and -31.5dB, (sounds like about 3dB) and then almost nothing on the subsequent upward steps. Sometimes I've noticed it get louder when turning down the volume!

Two things:

1) it was powered fully off for two weeks, could an error have developed in the software? Should I try resetting the EEPROM?
2) it also got pretty cold in the flat as we turned the heating right down - and it was probably still only 10 - 15 Celsius when I powered it back up - could that affect the relays? I thought being telecoms-grade they were supposed to be able to still work in cold temperatures.

I haven't opened it up and looked at the diagnosis LED's yet.
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Re: Back from holiday - erratic volume performance

Postby Garrard301 » November 18th, 2017, 10:30 am

Addendum - it seems to have settled down now, I don't seem to be getting the big jump from -31.5 to -32 any more.

I looked up the operating temperature range of the relays and apparently they should work down to -40C so the cold shouldn't be a problem!

So I just wondered if anyone else had experienced issues after having the "always on" power off for any period over a week or so? I should add that I don't have the real-time clock so there's no super-capacitor installed.
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Re: Back from holiday - erratic volume performance

Postby amb » November 18th, 2017, 11:29 am

Did the problem occur only with the remote control? Or was it only when using the pot? Or both? That might provide a clue... I don't think anything on the LCDuino-1 or the δ1 would be affected by 10-15°C temperatures. But I wonder about the remote control and its batteries.
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Re: Back from holiday - erratic volume performance

Postby Garrard301 » November 18th, 2017, 12:18 pm

It seemed to be with both - the dB display itself clicked up and down by 0.5dB at a time in line with the remote commands, so there didn't appear to be any problem with the remote control.

One thing I didn't mention, was that I also tested with the coarse (+6db) command, increasing from -32.0 to -26.0 in one click. Then I found I could step back down from -26 to -32 in 0.5 dB steps and not get the big change from -31.5 to -32. But then stepping back up in 0.5dB steps from -32, there seemed to be a >0.5dB change over -32 to -31.5.

Oh and I'm running the v1.01 Volumaster version as I bought the chip back in January.

That all said, the issue does seem to have fixed itself now, so I'm not going to worry too much for the moment - really I need to get it on a scope / sig gen and note what the LED's on the board are doing. I need to do that sometime in the near future anyway to test the hot/cold phases properly.
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