Magic Eye level indicator

TDS · 01-24-2009, 05:37 PM

The Trace Elliot V8 mk II bass amp has a magic eye indicator to show full power. I would like to include something like this in a 220 watt valve bass amp I am currently based on a Marshall VBA400 but using 4 KT88's.

I do not have a problem with the circuitry for the magic eye (EM84), but what I would like to know is where is the best take-off point: speaker out, PI out, PI in etc. I have schematic for the V8 but I assume there must be a sheet missing as it does not show the magic eye.

Any pointers or advice anyone?

Steve Conner · 01-27-2009, 01:14 PM

Speaker output worked fine for me in the past. I used a pot so I could adjust it to have the magic eye just closed at full unclipped output.

TDS · 01-27-2009, 09:20 PM

Thanks for the info Steve. An attenuated signal direct from the output makes sense, especialy on a high power amp where there is plenty of voltage to play with. Since posting, I have also found a low power p/p amp on Steve Bench's site using a magic eye peak indicator. He is only dealing with 2 watts, but that amp attenuates the signal from the anode one of the push-pull output valves.

01-24-2009, 05:37 PM	#1
TDS Member Join Date: Aug 2006 Location: East Grinstead, England Posts: 28	Magic Eye level indicator - where to connect it The Trace Elliot V8 mk II bass amp has a magic eye indicator to show full power. I would like to include something like this in a 220 watt valve bass amp I am currently based on a Marshall VBA400 but using 4 KT88's. I do not have a problem with the circuitry for the magic eye (EM84), but what I would like to know is where is the best take-off point: speaker out, PI out, PI in etc. I have schematic for the V8 but I assume there must be a sheet missing as it does not show the magic eye. Any pointers or advice anyone?

01-27-2009, 01:14 PM	#2
Steve Conner Supporting Member Join Date: May 2006 Location: Glasgow, Scotland Posts: 3,005	Speaker output worked fine for me in the past. I used a pot so I could adjust it to have the magic eye just closed at full unclipped output. __________________ "Ohhhh miracle bulb shines feebly"

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01-27-2009, 09:20 PM	#3
TDS Member Join Date: Aug 2006 Location: East Grinstead, England Posts: 28	Thanks for the info Steve. An attenuated signal direct from the output makes sense, especialy on a high power amp where there is plenty of voltage to play with. Since posting, I have also found a low power p/p amp on Steve Bench's site using a magic eye peak indicator. He is only dealing with 2 watts, but that amp attenuates the signal from the anode one of the push-pull output valves.

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