Thermionic Deluxe: doubt about clipping diodes lighting up

M

micmac

Active member
Hi all!

I finished a Thermionic Deluxe a few days ago and I have one doubt.

Build Doc

When I'm in the "low gain" channel (channel LED off) and strum some chord, not only the LEDs L3B and L4B light up, but to a lesser extend also L3A and L4A. Is this normal?

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Hi Harry,

It does sound OK. I just found it a bit strange and thought lots of people already built it so maybe this doubt is easy to confirm or refute.

Kind regards,
Seb
 
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It's normal for one pair to light up brighter than the other.... one pair is soft clipping, the other is hard clipping. However it's a little peculiar that the LEDs are flickering in the inactive channel.

The channel switch doesn't ground the input of the inactive channel so it's possible that some noise is being picked up by that channel when you are playing.

Does the gain control for the inactive channel have any effect on how bright those LEDs are lighting up?

Is the opposite also true? Do both pairs light up when you're in the high gain mode?
 
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Hi there, yes indeed, when I turn down the gain of the high gain channel and strum while in low gain channel, then the high gain channel LEDs L3A and L4A stay off.
 
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Sorry, I don't think I answered your question correctly. Yes, the gain control of the inactive channel has an effect on those LEDs lighting up. When gain is increased they flicker brighter, when decreased they flicker less bright. And if decreased far enough they stop flickering altogether.
 
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Just saw your other question. Yes, when I switch to high gain channel and increase gain of low gain channel far enough, then also the low gain channel LEDs L3B and L4B start flickering a bit.
 
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Can anybody please check on their Thermionic Deluxe if this behavior is normal?

I saw some pictures where lug 6 (middle lug in bottom row) of the channel 3pdt is connected (contrary to PedalPCB build doc) and I'm wondering if this might be the solution. Although I can never see where lug 6 got connected to.

Example from @Hexjibber : Forum post
Example from @dmnCrawler : Forum post
 
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Does moving your long yellow wires affect this behavior at all? In some cases they can interfere with components and inject noise into the circuit if they are too close.
 
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Robert said:
The channel switch doesn't ground the input of the inactive channel so it's possible that some noise is being picked up by that channel when you are playing.
Click to expand...
I made a test and grounded the input of the inactive channel. That stopped the LEDs of the inactive channel from flickering immediately. It made no difference to the sound of the active channel.

I take that to mean there's nothing wrong with my pedal. Moving on :)
 
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