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ievans

Modding the Peavey ValveKing Royal 8

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My main amp head (Ashdown Fallen Angel 60 DSP) stopped working a little while ago, so while I'm waiting for it to be fixed under warranty, I bought a Peavey ValveKing Royal 8. When I was looking at these small tube amps, the most important feature was a master volume. I mostly play with a good amount of gain, but don't want to piss off the neighbors, so getting good preamp distortion is a must. The Royal 8 has one, and the other 5 watt tube amps don't.

 

I had some plans for the Royal 8 when I ordered it. I already talked about replacing the stock speaker with a Weber Signature 8 AlNico here:

http://acapella.harmony-central.com/forums/showthread.php?t=1936132

 

In addition I wanted to add an output jack in case to connect it to an external cab (my Avatar 1x12 cab with a Hellatone 60). And while I was at it, I thought I'd add an L-pad to try to get some more gain by overdriving the power tube as well as the preamp. I'd never done one before, but was inspired by Verne Andru's mods to his Palmino.

 

I ordered some jacks, a jack plate, the l-pad, and some adhesive-backed tolex from PartsExpress (links to parts list down below, for anyone interested), and picked up some 1/4 inch plywood I had cut to size to replace the stock back baffle.

 

Preparing the back baffle

The first step was to sand down the rough spots on the plywood, and layout where I wanted the jack plate and l-pad to go.

IMG_2721.JPG.jpg

The part of the jack plate that goes in the back baffle has rounded corners, so the I measured and added lines for where the curve starts. I drilled some pilot holes for the jack plate hole corners and the l-pad hole. Then I used a 3/8 inch drill bit to drill the corner holes. The l-pad hole coincidentally also needed to be 3/8 inch.

IMG_2723.JPG.jpg

Then I used my new jigsaw to cut out the jack plate hole, from the outside edge of the holes to make a rounded-corner rectangle to fit pretty the jack plate more or less perfectly.

IMG_2724.JPG.jpg

 

At this point, my camera's batteries died, so I don't have pictures of me putting on the tolex and wiring up the components. More in a bit.

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Ok, continuing on.

 

Putting on the tolex

 

I used adhesive-backed Tolex to make it simple. It may not be the best or most durable stuff, but it was inexpensive, and the back baffle shouldn't get too much abuse.

 

I used the plywood back as a template and cut a big enough piece of tolex to give me an inch or so on the back of the plywood. The tolex was easy to cut with some sharp scissors, and the grid on the back made cutting a straight line pretty painless.

 

I cleaned the plywood to make sure the tolex would bond easily. I then peeled a bit of the backing off the tolex, and began applying it to the plywood. I worked from the short side down a couple inches at a time, using a plastic spatula to work out any air bubbles and smooth the tolex. After getting all of it on the face, I folded over the sides and trimmed the corners. On one corner I was a little too eager in cutting, but it doesn't show from the visible side of the back.

 

For the cutout and l-pad hole, I used an exacto knife to cut the tolex, and folded over and smoothed out the overlap. For the l-pad hole, I cut a cross pattern, and pressed the flaps as best as I could.

 

Finally, I used the plastic spatula to smooth out the sides of the backing.

 

Mounting the hardware

 

I screwed the mono NC Neutrik plugs into the jack plate, putting the solder flaps up to make it easy to wire up. I then screwed in the l-pad, putting the solder tabs to the side facing the plugs, again for easy wiring. I used two adjustable crescent wrenches, and adjusted it so the indicator plate on the back was straight.

 

Using an awl, I marked where I needed to drill pilot holes for the jack plate screws. I drilled the holes, and screwed in the jack plate.

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Wiring it up

 

The idea here was to have the l-pad work regardless of whether you were using the internal or external speaker. So it comes first, then the two output jacks (wired in series so it doesn't matter which one you plug into, and allows you to use 2 cabs in series if you want), then the speaker.

 

PeaveyModWiringDiagram.png

Pardon my amateurish wiring diagram.

 

I first just hooked the wires around the terminals and tried it out, just to make sure it would work. Then I soldered the l-pad and plug connections.

 

IMG_2729.JPG.jpg

 

For the amp->l-pad and plug 2->speaker connection, I used twist connectors, not solder, and allowed enough wire so I could take off the back baffle without pulling on the wires. That way I can easily take the back baffle off completely if I want, just by untwisting the wire connectors. After doing the final soldering of the wires to the speaker, I switched the amp on, and got sound.

 

The l-pad worked perfectly, as did the external jacks. The Weber Signature 8 AlNico sounds pretty good, but running the amp through my 12" Avatar cab with Hellatone 60s made it sound great.

 

IMG_2727.JPG.jpg

 

With both the preamp and power tubes fully saturated, this little Peavey growls, but the l-pad keeps the volume in check. I think it turned out nicely.

 

Parts list

 

Here are the parts I ordered for this mod:

     

    Total parts costs: $32

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subscribed

 

Well done.

 

I put in an internal speaker kill switch that I find quite useful. Unless those are switch jacks?

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Looks to me like you have the jacks and the speaker wired in parallel. You'll have to watch what you plug into the jacks - e.g. if your internal is 8 ohm and you put 2 more 8 ohm loads on, you start drawing down to 2 ohms which may cook your transformer.

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The jacks are normally closed NC switch jacks, so the internal speaker is turned off whenever one of the jacks is plugged in.

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I doubt I'm going to be doing this, but if I did want to plug in two external cabs, I'd want to make sure they each drew 4 ohms, so the total load is 8 ohms, yes?

 

Or am I misremembering how this works?

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Seems to me, if both are switch jacks, as soon as you plug something into the first, the second and the speaker are disabled - no? If this is the case then Plug 2 should be the switch and Plug 1 a normal jack so you can use both as it seems you want to.

 

Here's some links explaining the series/parallel thang

 

http://www.bcae1.com/spkrmlti.htm

http://www.usspeaker.com/speaker%20wiring-1.htm

http://www.termpro.com/articles/spkrz.html

 

Google if you need more, there are a number of pages on the topic.

 

In short, if you keep everything in parallel your impedance drops to 2.667 ohms with 3 x 8 ohm speakers.

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Is the l-pad just just variable resistor that does the job of an atenuator?

 

Yes. An L-pad has a sliding resistor in it so as you turn the volume of the speaker up, the dummy resistance drops and vice-versa so it maintains a constant load. This is basically what an attenuator does, but the fancy ones add band-pass filtering [similar to cabinet simulation] to adjust for the fact that the speaker won't reproduce some of the frequencies very well as the power drops.

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Seems to me, if both are switch jacks, as soon as you plug something into the first, the second and the speaker are disabled - no? If this is the case then Plug 2 should be the switch and Plug 1 a normal jack so you can use both as it seems you want to.


Here's some links explaining the series/parallel thang


http://www.bcae1.com/spkrmlti.htm
http://www.usspeaker.com/speaker%20wiring-1.htm

http://www.termpro.com/articles/spkrz.html


Google if you need more, there are a number of pages on the topic.


In short, if you keep everything in parallel your impedance drops to 2.667 ohms with 3 x 8 ohm speakers.

 

Yep, you're right. I didn't think that through very well. :)

 

The chance of me running multiple cabs from the Royal 8 is pretty much zero, so it's an academic argument at best.

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Zawam, that's exactly my intent. Probably not today, though. Stay tuned. I'm going to do some clips with the 8" Weber, my 1x12 Avatar cab w/ the 12" Hellatone 60, and comparing just the preamp distortion with the preamp and power tube distortion.

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Without an FX loop [FX return in particular] I doubt you'll get anywhere near enough gain to drive the EL84 into distortion. They design the power sections so it provides clean amplification and rely on preamp distortion for girth. FX loop is [and the 10" speaker] why I opted for the V8 over the Royal 8.

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Well, the distortion is noticeably more pronounced with the Gain and Master Volume dimed. I don't know where the extra overdrive would come from other than the power tube. But I'm not an expert at this.

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I built almost the exact same thing a few months ago for my blackheart combo.

 

One thing that really helped to counteract the l-pad's uneven attenuation of higher frequencies was to put a bypass cap which is basically a brightness control if you put a switch in there. I went way overboard with 5 different cap values, a rotary switch rated for a nuclear power plant and turns out that only one value works well. I also put a brightness gain control which turned out to be a waste of money and time as well, just a cap and a switch will work great.

 

Heres a picture of mine, I plan on rehousing it with some mesh grill to match the original crap and to make sure that it doesn't interfere with the cabinets original design. I'll have to get on it because you frickin blew my sheetmetal crap away!

 

02260004.jpg

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Well, the distortion is noticeably more pronounced with the Gain and Master Volume dimed. I don't know where the extra overdrive would come from other than the power tube. But I'm not an expert at this.

 

As you increase the gain, you add more voltage to the preamp tubes plate causing everything to run hotter. And the components will react differently depending on the current level running through them. It is "possible" you are driving the EL84 into overdrive, but I highly doubt it and it's impossible to verify one way or the other with that amp. But even the really big 100 watters are designed to get their distortion from the preamp section. That's one of the reasons FX loops are desirable to some players.

 

But, at the end of the day, if you're getting a sound you like, that's all that counts.

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I built almost the exact same thing a few months ago for my blackheart combo.


I went way overboard with 5 different cap values, a rotary switch rated for a nuclear power plant and turns out that only one value works well.

 

If you don't mind, what was the value of that cap?

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Seems to me, if both are switch jacks, as soon as you plug something into the first, the second and the speaker are disabled - no? If this is the case then Plug 2 should be the switch and Plug 1 a normal jack so you can use both as it seems you want to.


Here's some links explaining the series/parallel thang


http://www.bcae1.com/spkrmlti.htm
http://www.usspeaker.com/speaker%20wiring-1.htm

http://www.termpro.com/articles/spkrz.html


Google if you need more, there are a number of pages on the topic.


In short, if you keep everything in parallel your impedance drops to 2.667 ohms with 3 x 8 ohm speakers.

 

You're right.. he needs to jumper those jacks... Honestly though... there only needs to be one shorting jack in that setup so that if he plugs in a cab it cuts off the internal speaker.. and he needs to match the impedance of whatever the internal speaker is.

 

edit: duh, the jack on the right needs to be jumpered to itself.. then needs to connect left prongs on the second jack. Leave that jack un jumpered then hook the other prongs up to the internal speaker. Then always use the left jack when plugging in an external cab. I dont know why I couldnt put that in my head when I first thought about it.

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Are you going to do any more mods to it? You could fire in an hammond 125ESE OT for more beef and better clarity. Looking at the schematic, there are a number of other mods you cuold do that should improve the tone

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Yeah, I'm also curious about the cap that ashasha added. I don't currently have any other mods planned, as I've got a few other projects to work on: a beavis audio Tube Cricket that should be arriving any day now from OL Circuits, and a conversion project on an old PA amp from the '50s.

 

I've been doing some housekeeping to my setup so I can record. I got an old 14 channel Peavey mixer from the '90s I found at the Goodwill when I went looking for old records. $25, and it works--a nice score, I think, especially here in San Francisco where every piece is picked over before it gets to the floor.

 

I also bought a Yamaha GO46 firewire interface, and have the mixer plugged into that. Now all I need is my buddy, who works at Sennheiser, to bring over some mics, and I'll be set to record some sound samples.

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