Peavey Bravo modifications

[bravo_fan]

Hello. I understand if this topic has been done to death, as it seems everyone who owns a bravo seeks to change it somehow.

In my case, I wish to achieve the following:

1 - Eliminate the slight, yet noticeable pause that occurs when I click the footswitch to go from clean to overdrive and vice versa; and

2 - Make the "pull gain" function accessible via a footswitch.

The former takes priority over the latter. I do not seek to alter my amplifier's tone in any manner whatsoever.

[bravo_fan]

Also, I remain ignorant of active equalization, what it means, and how it works. I seek the knowledge of this feature on the ultra channel.

[Chuck H]

As it happens a schematic doesn't surface easily with a search. Providing a schematic with a post like this is the best way to encourage participation.

[bravo_fan]

I wish to apologize for the thoughtlessness of my omission; I can understand the frustration of being asked to help in a matter of which one knows nothing.

Here is all the schematic information I saved prior to making the purchase last year (though for my neophyte eyes, it might as well be written in Sanskrit):

peavey-bravo-112-amp-schematic-diagram.pdf

PV Bravo.pdf

peavey_bravo_112_sch.pdf

[Enzo]

In channel switching, there are a number of relay contacts which switch over various parts of the circuit. When this occurs, there is the POTENTIAL for the amp to make loud noises as it switches. Not desirable. SO in most of their amps Peavey includes a clamping circuit to momentarily mute the signal as channels switch. This is what you hear.

The clamp is Q2. triggered by CR200, a triac. When triggered by a channel change, the triac shorts C300, discharging it. Then R302 recharges the cap. The cap and resistor form a classic RC circuit, and the combination of values sets the time. To speed it up, you could reduce the value of the cap or of the resistor or even both. Or you could eliminate the clamp completely by removing Q2.

How much noise your amp might make without a clamp, I have no idea. Maybe none, maybe a lot, maybe just a pop, maybe a squeal. I suppose you could remove the transistor and find out. And by keeping the clamp and speeding it up, then the more potential the circuit has for whatever noise it generates unclamped.



Any function controlled by a panel switch can be remoted to a stomp switch. Your pull=gain is just a switch to ground that turns on a relay. You want a stomp switch for it? Then interrupt the path from that switch to ground, and insert a jack for a stomp switch. Conveniently enough there is a jumper wire on the board exactly where you'd need it. Right behind that pull switch is a relay. Between that relay and a large filter cap is a smaller cap, C250. Just behind C250 is the wire jumper. If you follow the copper traces on the board, you will see it is connected. I;d remove it and wire its two holes to a FS jack. Make the FS jack a cutout type so with no FS plugged in,m the circuit still works from the puller.

If you don;t want to make a new hole for a jack, the common thing to do is rewire the reverb for always on, then use the reverb side of the existing footswitch to now control the pull gain circuit.

[Enzo]

Active EQ.

First, just google the term.

Active implies some form of amplification. Most EQ is passive, like most all the Fender amps in the world.That means really all it can do is cut. Like the tone control in your guitar. it can roll highs away, but it cannot add them. Active EQ includes some circuit that amplfies - it can actually boost an audio band. In a classic Fender, if you turn up the middle, all you are doing is cutting it less, and the highs and lows are cut more than the middle is. SO it sounds more middle-y, but it is still all less than you started with. In active EQ, you can actually increase the amount of highs or lows or mids.

[bravo_fan]

I wish to thank you for your assistance, Enzo, as I will now do: thank you.

I will research active EQ further. The one part remaining unclear to me is the idea that one active eq control also influences other controls. Is this true, and if so, how do I use this to my advantage?

Finally, regarding the mechanism to prevent loud noises from the amp when switching channels, are there any strategies employed by other manufacturers to address the same issue without the obvious pause? Are there any that might be adaptable to the Bravo?

[Enzo]

Other companies use things like LDRs (photocells) and JFETs to switch channels. The problem is trying to engineer some other circuit into this one. I am sure it could be done, but would take some work. Better to make the most of what is there now.

Most tone controls are interactive. All it means is they overlap, so turning one control also has some effect on the tones of the controls to either side.

[bravo_fan]

Does the Classic 30 feature the same mechanism as the Bravo?

[Enzo]

No. the Classic 30 has no noise abatement circuit.

[tedmich]

The old Bravo manual does a pretty good job describing the odd way its EQ works
http://assets.peavey.com/literature/...s/80301262.pdf

On the Ultra channel the bass and treble (bottom and edge) are fully active with +/-15db of cut or boost, while the mids (body) is a passive -15db cut. The XXX and Ultra/Ultra+ have all three bands as +/-15db boost/cut active controls. A lot of the Bravo mods mess with the mids. Bag the reverb and try a good speaker and the little guy is amazing!