Peavey Decade Stomp

[Securb]

How does it compare to the actual amp?

It's hard to say. I blew up my Decade around '85, but based on fuzzy memories, it is pretty much in the ballpark of my style at that time and the tone I would have used and liked back then. Keep in mind, back then, I went from the speaker out of the Peavey directly into the Fender Quad. With a cranked MXR D+ and Morley BOOST in front of the Decade. I will probably take it downstairs this weekend and plug it int the Quad Reverb for poops and giggles.

The saturation switch engages a 22uF bypass capacitor to ground which boosts the entire frequency range. Engaging a bypass cap makes it sound louder and higher gain.

That makes sense, I noticed with SATURATION engaged, there was no extreme change in the EQ. SATURATION seems to just give more of everything across the board.It is also more present and upfront. ​

 

[Securb]

Here’s the breakdown. I played with the cover band last night, and the Decade sounded incredible through the Carvin. The tone I was looking for with the original band is definitely there. In regular mode, it delivers a great overdrive, and with SATURATION, it absolutely screams. I used it on "Cheap Sunglasses" in SATURATION mode, and it sounded fantastic.

However, when I tried using it on "Running With The Devil," it sounded terrible. But for songs like "Be My Girl" and "Can't Get Enough of Your Love," the pedal was spot on. I did gain-stage it with a downstream boost, which fattened it up a bit and added some extra gain. I also kicked on the MXR D+, expecting a ton of noise, but it was dead silent—with a crushing metal tone. This is most likely the setting I was getting back in the '80s.

I noticed these pedals are sold out again on Sweetwater, with the Bandit pedal being the only one currently available. Based on my experience with the Decade, I would be interested in trying the Bandit. If anyone is looking for a new and unique retro flavor for gain, this pedal is a must.
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[idsnowdog]

With a triode based amplifier like a 12ax7 (dual triode) or a Bi Junction Transistor (single triode) you have three input/outputs. Positive voltage, negative voltage, and signal input. With a BJT the emitter goes to ground/negative and the collector goes to positive while the base is the signal input. Normally there's a resistor on the emitter which acts as a gain control. Less resistance equals more gain and more resistance equals less gain. A bypass capacitor creates a T before the resistor which creates and alternate path to ground. A large value capacitor emphasizes the entire audio frequency range which you perceive as a volume/gain boost centered on bass frequencies because those frequencies are no longer being bled to ground. With a smaller value capacitor bass frequencies are still being bled to ground emphasizing middle and treble frequencies. These treble frequencies give the sound an edge, sizzle, or presence.

 

[Chistopher]

The circuit is pretty conventional. This schematic is from a clone kit. It uses a JRC4558 dual op-amp. The first stage has a symmetrical soft clipping circuit using 1N4148 silicon diodes with 100pF smoothing capacitors like a tube screamer. The saturation switch engages a 22uF bypass capacitor to ground which boosts the entire frequency range. Engaging a bypass cap makes it sound louder and higher gain. A Fender Deluxe uses a 25uF bypass cap on the first triode of V2. I don't go above 10uF because the bass response gets mushy. When people mod Deluxe, Princeton, or Champs they reduce the bypass capacitor value to tighten it up and reduce blocking distortion.
After the first stage there's another symmetrical hard clipping stage using 1N4148 diodes. Then there's the tone stack and the second stage is basically a make up gain stage with some smoothing capacitors in a feedback loop but no soft clipping diodes. There's another 22uF non-switchable bypass cap on stage two. After stage two there's another symmetrical hard clipping stage. I wouldn't have expected that after a make up gain stage but its there.

Thats a great diagram. I would have to do some actual measurements to tell, but my guess is that the second hard clipping stage doesn't do too much clipping with the tone controls set flat.

My guess is that the EQ controls add a little too much volume as you turn them up, and the second clipping stage compresses the volume of the EQ controls and allows you to use them to control the texture of the sound.

Don't think of it as a distortion stage or make up gain stage, think of it as a way to make the EQ stage behave in a more refined manner.

 

[idsnowdog]

Thats a great diagram. I would have to do some actual measurements to tell, but my guess is that the second hard clipping stage doesn't do too much clipping with the tone controls set flat.

My guess is that the EQ controls add a little too much volume as you turn them up, and the second clipping stage compresses the volume of the EQ controls and allows you to use them to control the texture of the sound.

Don't think of it as a distortion stage or make up gain stage, think of it as a way to make the EQ stage behave in a more refined manner.

If I was to build one I would replace the on/off saturation switch with an on/off/on switch. That would allow me to choose between a 22uF capacitor for rhythm, no saturation, and a cascoded 2N7000 mosfet plus a 4.7uF capacitor for lead. The cascoded mosfet would give a slight gain boost because the triode would now be a pentode. I would also have both hard clippers ground legs going to a four pole on/off switch so they could be turned on/off. Which might make it less compressed and more touch sensitive with the saturation control off.

 

[Securb]

Another Peavey amp clone this time the Bandit, not a horrible price

https://ghostnoteaudio.uk/products/red-stripe

 

[ehdwuld]

Another Peavey amp clone this time the Bandit, not a horrible price

https://ghostnoteaudio.uk/products/red-stripe

Dang it remember not long ago you could get an actual bandit for less