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6E2 circuit

kodabmx

Member
Paid Member
2011-10-31 1:00 am
Toronto
I hate starting new threads for a single question [EDIT: after posting this, I laugh at my thought of it really only being one question], but I can't seem to find info upon searching...


I plan to use the attached circuit (or a variation of it) in my new build. I'm starting this thread because it might help someone else that isn't interested in the amplifier.

Ignore the power supply (I'm going to tap off of the existing B+).

I want this meter to be "peaky", I assume C2 makes the meter more normalized/smooth? If so, removing it should work?

Is D1 there to make the signal DC? W1 wiper connects to the top of R2. If I changed the 100k pot to 1M, would I have to adjust the capacitors to compensate?

Why can't I just drive it like a normal triode? I will have a 1:20 gain stage to boost the level from line already... Can't I just put a biasing resistor on the cathode and feed it AC signal?

W2 on the cheap 8$ VU meter boards almost always smokes after 5 minutes in my experience (literal smoke). Replacing it with a 2W 500k part just showed you only really need a ~100k part for adjustability.
 

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PRR

Member
Paid Member
2003-06-12 7:04 pm
Maine USA
www.diyaudio.com
Just build it. But make W1 and R2 variable, C1 removable.

You "can" feed it AC/Audio but only half the wave will show, and the peaks will be real faint and blurred. . You want to "catch" peaks so they linger long enough for the eye to see. This is a trade-off against "dance". W1 looks pointless to me but slows the attack. R2 bleeds the C2 cap for decay. This is a real crude audio peak catcher; it is still half-wave, but if you get fussy you go beyond what a eye-tube is really about (medium cheap).
 

PRR

Member
Paid Member
2003-06-12 7:04 pm
Maine USA
www.diyaudio.com
> The second anode is shorted via capacitor C3, to ground !

This is a Magic Eye tube. The "second anode" is the Glow Screen, not an electrical signal point. You make it +250V, electrons smash into phosphor, glow. Except the deflection rod, connected to first anode, bends the electrons to cover less or more of the glow anode.

You can find out more about Magic Eye tubes if you search.
 

kodabmx

Member
Paid Member
2011-10-31 1:00 am
Toronto
For those who followed this.

It is indeed working well.

D1 is SB1100, C2 is 0.033u.

100k pot is set for max volume and will be replaced by a resistor.

This is driven by a triode strapped 6J1. This makes the perfect gain for 1VU = 1.228Vrms = 80% scale on the tube.

If interested in the parts values, ask as I've forgotten. But the OP is like 280V, 8mA, plate resistor is 12k to 18k IIRC.

Koda