5E3 with Presence control. How?

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tubeswell
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Re: 5E3 with Presence control. How?

Post by tubeswell »

Or you could do a variable treble boost at the cathode of the 5E3 driver stage

1k5||[5kA+1uF]

or a variable stepped treble boost

1k5||[5kA+1uF]||100nF
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MHProd
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Joined: Tue May 07, 2013 6:47 pm

Re: 5E3 with Presence control. How?

Post by MHProd »

Thanks Tubeswell.

Right now, I'm trying to understand why the 500pF cap I soldered on Vol.1 doesn't do much while the one on Vol.2 is great. If I can reproduce that effect on Vol.1, that's all I need...

Having said that, I'm intrigued by the variable treble boost suggestion. So a 5K pot between 1K5 and V2 pin 8 with .1uF on the pot to ground?
tubeswell
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Location: Wellington. NZ

Re: 5E3 with Presence control. How?

Post by tubeswell »

Here are some suggestions. You might want to experiment with various resistor, pot and/or cap values until you have something you like. YMMV
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MHProd
Posts: 167
Joined: Tue May 07, 2013 6:47 pm

Re: 5E3 with Presence control. How?

Post by MHProd »

Thanks!

Do you or anyone have any idea what could be going on with Vol.1 and the cap not having any effect? That's what i'd like to figure out first before I do anything else...
tubeswell
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Location: Wellington. NZ

Re: 5E3 with Presence control. How?

Post by tubeswell »

MHProd wrote: Sat Mar 18, 2017 3:48 am Thanks!

Do you or anyone have any idea what could be going on with Vol.1 and the cap not having any effect? That's what i'd like to figure out first before I do anything else...
What do you mean by 'Vol. 1"? the channel not directly connected to the tone control? Have you got the cap located between the vol pot input and the wiper (as a bright cap?) The 5E3 vol and tone controls are interactive and the position of each pot affects the a/c load seen by each side of the V1a stage and also the effectiveness of the other vol pot. You might have to have the other vol control up slightly for the effect to kick in. Try messing around with the controls a bit. Note the setting where it isn't doing what you expect? (Also note that it won't have any effect when the vol control is dimed, because the cap will be completely bypassed by the pot wiper being at the pot's input end.)
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MHProd
Posts: 167
Joined: Tue May 07, 2013 6:47 pm

Re: 5E3 with Presence control. How?

Post by MHProd »

No, sorry. I'm talking about the first pot right after the tone control with the cap between the two (Volume Bright Channel).

I soldered a 500pF between the wiper and input of Volume Normal channel and it worked perfectly. BUT when I tried the same thing with Volume B, I'm not getting much extra brightness at all and it still sounds dark, even with the Tone control maxed out.

I know how these amp sound and quite familiar with the pots interactivity. But this is something else...
tubeswell
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Location: Wellington. NZ

Re: 5E3 with Presence control. How?

Post by tubeswell »

MHProd wrote: Sat Mar 18, 2017 8:48 am I know how these amp sound and quite familiar with the pots interactivity. But this is something else...
Actually, its the same thing. And you need to take a look at the schematic to see why. Actually this is a good opportunity to draw a schematic and analyse what's going on. I can't right now ( have to go off to a gig in a couple of hours and I need to do some last minute practice). But feel free to mark up a 5E3 schematic and see. Note what happens to the AC load at different tone and pot settings with the stock 5E3, and then note how the HF bleed is changed with the extra 500pF bright cap. The 500pF cap isn't just bypassing the Vol B pot, its also connected directly to the wiper of the tone control, so the tone control setting will affect the HF bleed off, and so will the vol control setting on the other vol pot. As well as the AC load interactivity, the capacitance of the 500pF cap interacts with the AC resistance of the whole shebang to determine frequency roll-off points
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MHProd
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Joined: Tue May 07, 2013 6:47 pm

Re: 5E3 with Presence control. How?

Post by MHProd »

Nope, there must be something going on. I just played my original 5B3 and it's so much brighter... Granted, I didn't plug it in the 4x12 (I can't as the OT is soldered straight on the speaker) but still. I changed the 500pF bright cap (measured fine), soldered a 680pF instead, checked all the ground connections, the pots measure just under 1M... It's still sounding muffled, a bit like a guitars tone pot being turned down. I'm confused...
tubeswell
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Location: Wellington. NZ

Re: 5E3 with Presence control. How?

Post by tubeswell »

Have you got a wrong-value coupling cap? or a miswiring somewhere?

Or maybe the screen supply node filter cap or the pre-amp node filter cap is not decoupling properly? (Check for DC continuity between the ground lead at each filter cap and the amp's chassis)
He who dies with the most tubes... wins
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