How can I change the eq on my vox ac30hw?

[cap217]

Out of all the el84 ac30 based amps, I kept the ac30 hw. I had pisonic mod it w sozo caps and correct silver micas but I want the eq to act in a different way. I'm not sure if what I am asking is possible here. I had 2 z wrecks and liked them but I thought the ac30 could do that and give me some more options like more headroom on the cool/low input setting and give me a normal channel and by passable master. I did like how the z wreck cut, bass, and treble worked though. They didn't need much tweaking but when you did, you got what you wanted. With the vox, I have to mess with the interactive bass and treble. If I want to add bass, I have to turn bass up, turn cut down, then go back and turn treble up. But when you turn the treble up, the bass goes down.

I liked how the z worked and I liked the frequency ranges on it. So how do I get that in my ac30?

[randalp3000]

The tone stack in the Z wreck has the ground lifted on the bass pot. That should be the only difference but might effect the interaction. The Z also uses CTS 1M Audio taper pots which have a different taper than Alphas or others. So 5 bass and treble on the Z might equal 4-6 on the Vox if that makes sense. I think the Vox cc series has a switch to lift the ground on the bass pot.

The Z also uses a 220k voltage divider going into the PI but shouldn't have any effect on the tone stack.

[Masco]

Ralph's schematic above shows the standard AC-30 TB tone stack, which is probably used in the HW. You can try the EQ shift by lifting the grounded lug of the bass pot and connecting it to the wiper(middle lug), so that it's grounded through the 10k resistor.

[randalp3000]

this might be more helpfull

[cap217]

Very helpful. I can't believe they are so close.

[cap217]

Does the hot/cool switch do this already. I think in hot mode it lifts the tone stack from ground. Is that different from just having the ground lifted on the bass pot?


Edit

Just messed with the amp. When I flip to hot mode the bass pot doesn't do anything. The treble pot acts like a cut. Turned up, more bass, tuners down less bass. The cut knob still works as it should.

Is this right? Why would the treble knob work like that in hot mode?

Here is a pic of my tb channel pots

[randalp3000]

Take the red wires off the bass pot. Keep the two red wires connected together and tape or shrink wrap them.

[Masco]

Yup, that's the ticket. The wires look brown to me, but yeah, just remove from bass lug and tie them together. You'll still be able to lift the ground via hot switch(FWIW). My suggestion was just the way the EQ shift switch was done in the AC-30CC where the switch connects the bass pot as a rheostat.

[cap217]

Thanks guys. I dont know much about this stuff but I am trying to learn as I go and read schematics and layouts and trying to implement them in real life.

Let me ask a couple questions:

1-What does the cool/hot switch do? I know lifts the ground on the TS but why does only the treble knob work and why does it work like a cut? Is this normal (I assume so)?

2-And how does taking the 2 wires off the bass pot still enable the hot/cool switch to work?

3-Input resistors (not sure what they are called but right after the input jack) 68 vox and z is 22. Then 500 v 470pf. The 50pf v 47 mica... These values seem pretty close to me but would changing them make a difference?

4-in the layout pic on the normal channel volume there is a resistor r17 connecting from the right volume lug to middle lug on bright switch. I attached a pic of mine and there is no resistor. Also, mine is a push pull modded by Lyle Caldwell so it is obviously different. I assume he might have taken this out to bring it closer to 64 Jmi specs?



Sorry, dumb questions....

[randalp3000]

Yup, that's the ticket. The wires look brown to me, but yeah, just remove from bass lug and tie them together. You'll still be able to lift the ground via hot switch(FWIW). My suggestion was just the way the EQ shift switch was done in the AC-30CC where the switch connects the bass pot as a rheostat.

yes brown, thanks Matt. Looked red on my phone.

sorry


here's a schematic I found, maybe it will help

[cap217]

Helps a lot. Thanks again.

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[cap217]

Helps a lot. Thanks again.


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[cap217]

More questions. I am really trying to learn this stuff so thank you for helping me. I have a lot of pics and a drawing to try and explain what I am looking at but I found that the ac30hw and the Z Wreck is basically the exact amp with component differences. My ac30 was modded by lyle caldwell and has sozo caps and Nichilon caps (not sure if these are good or not, I dont see them used much). He changed a lot of the values so at this point I am not worried about filtering or values as much as the basic tone stack.


1-You guys mentioned to lift the ground on the bass pot of the ac30. Its simple to do but the Z Wreck bass pot right lug grounds to the pot with a 10k resistor. I think by following what my ac30 does, the bass pot right lug grounds on the turret board after it goes through a 10k resistor.

Is this correct from my drawing and pic? The vox turret board confuses me with the additional turret points in the middle.

2-On the z wreck. The treble and bass pots go to a 22uf cap and then both attach at the same point in on the turret board and jump to a 100k resistor. How does this not create a loop to where the 2 22uf caps interact with each other?

The vox bass lug should go to 22uf to 100k to ground? But the diagram shows it jumping. Does the signal travel up? I attached a pic 22-100k path to show what I am asking.




Attached is my ac30, and my drawings.

[M Fowler]

The 50pf is the treble cap going to entrance of treble pot.

The 100K resistor is the slope resistor

The two .022uf caps are the tone caps one going to entrance of bass pot
and the other going to 10k resistor which sets the mid frequencies then to ground.

Mark

[rooster]

Randalp3000 - That last schematic is not showing a true TB circuit? It's missing 1/2 a triode.