Krank sweep control

[Dmoney]

having only seen kranks live, and never having played or tweaked one myself, i have a question...

is the sweep control worth having?

as far as i can tell (having stumbled onto some schematics) its a very very very simple mod.
I have my JCM800 pretty much where i want it, but i have a few free pots on the front panel, so im looking for stuff to do with them....

right now i have

Gain, Volume, Bass, Middle, Treble, Depth, PPIMV, Presence.

I could have 3 more controls. or 2 plus a lo input that skips the first gain stage.


hence looking at schems for ideas!
im also debating a half power switch.

[LazyNinja]

Some more power stage controls like resonance or sag might be nice. Unoriginal but switchable boost is always useful.

edit:just saw the depth thing. Is it the same as a resonance control?

[Dmoney]

Some more power stage controls like resonance or sag might be nice. Unoriginal but switchable boost is always useful.

edit:just saw the depth thing. Is it the same as a resonance control?

yeah it is the same.
yeah i thought about using the empty holes in the chassis for switches too.

i'll have 1 hole at the rear (the others filled with jack socktes that are mostly unused)
and possibly 3 spare chassis holes at the front.

I also just stumbled onto some schematics of the Krank Rev1 and the Sovtek Mig100H. pretty similar!

[Copperhead]

The Sweep is a parametric EQ that effects the whole tone stack. It spotlights a narrow band at the frequency you're pointed at from low to high.
It is very different and takes a little while to get the hang of dialing in certain tones, but it makes the amp very versatile as far as what you want it to sound like.
I keep mine at 1.5, very low.
Really beefs up the bottom end and helps with harmonics and pick squeals.

[Copperhead]

I also just stumbled onto some schematics of the Krank Rev1 and the Sovtek Mig100H. pretty similar!

The first Revolutions were built on these chassis, completely gutted except for the transformers, which were awesome!

[Dmoney]

The Sweep is a parametric EQ that effects the whole tone stack. It spotlights a narrow band at the frequency you're pointed at from low to high.
It is very different and takes a little while to get the hang of dialing in certain tones, but it makes the amp very versatile as far as what you want it to sound like.
I keep mine at 1.5, very low.
Really beefs up the bottom end and helps with harmonics and pick squeals.

its a pot that replaces the slope resistor in a standard marshall tone stack. only its fed from the plate in the Krank so it has a couple of hundred volts going through it i think. which i must admit, having been shocked by plate voltage, kind of worries me.

I got out the tone stack calculator to figure out the effect. seems interesting. and it would be safer in my amp as the tone stack is fed from the cathode of the previous stage.

[Dmoney]

I also just stumbled onto some schematics of the Krank Rev1 and the Sovtek Mig100H. pretty similar!

The first Revolutions were built on these chassis, completely gutted except for the transformers, which were awesome!

gutted and the circuit rebuilt almost identically?

[Copperhead]

I would guess Tony used the same boards. He is a stickler for quality components though. He started out as a Marshall modder. He still does what he calls the "Plexi thing" for friends by request.

I asked him what that meant and he said "First, you get a propane torch and melt all that shiteeeee of the board.... then build it right..."

So I would imagine the first Revs were Tony doing exactly that, plus his own touches to the circuit; adding, subtracting or changing things he thought needed to be better.

[Dmoney]

I asked him what that meant and he said "First, you get a propane torch and melt all that shiteeeeee of the board.... then build it right..."

I can imagine someone taking an amp doing a few little tweaks and selling it on as a new amp. I heard that when Krank FIRST started they marketed modded sovtek's.

by shiteeeeeeeeee does he mean white gooey stuff like this...

[Copperhead]

Hahahaha....

No, I think he meant he strips off all the components and wiring and replaces them with what he likes. Some things are siliconed for vibration protection.
Here's my modded Rev:

[Copperhead]

Amazing, I'm having the exact same argument in reverse over on the gear page.  :lol:

It's a Dumble thread. I said "Why the heck can't someone just saw apart the transformers and clone the whole amp?"

Hahahaha.... OH THE BLASPHEMY!!!

I've learned today that there is a Dumble religion and I'm a SINNER!!!

So it's no secret that Krank started by buying wholesale lots of new Sovtek amps, gutting out the components and "building them right." So what. If you bought one of those vs. a virgin Sovtek, you got way improved reliability, better tone and a lifetime warranty.

So when the Sovteks were gone, they designed their own boards but basically cloned the circuit. Like that's never been done before... :roll:

Every production run in the Revolution Series One line has undergone redesigns and upgrades, it would be interesting to see the differences in the drawings between the first ones and the last run.

The Plus models are very changed, and the 1980 pre is based on the Chadwick but a whole new power amp section.

Tony has always got some experiment going on involving boards from other equipment cobbled together, but his stuff always sounds great.

[Dmoney]

I dont doubt he did more stuff since the first revision of the Rev1.
I didnt know they were based on migs before today, which surprised me for a couple of reasons.
the preamp is interesting because from what i've seen (based on mig schematics and schematics from a reverse engineered rev1) it has no cold biased triode clipping stage and no cathode follower. (Splawn and Bogner have a similar thing going on). There are differences in the circuit but nothing mindblowing.

I always thought it would be a take on the split channel marshall, since it has the clean channel. the mig was single channel.

a lot of amp companies dont need to use that horrid goo. i'd be bummed if i spent $1500 on an amp and it had goo all over it id be weirded out. i mean a lot of builders dont use it. it just looks messy and its probably annoying to work around if a part needs fixing.


here is a krank with no goo at all. so why do some have it and some dont?

are the caps really going to vibrate loose? i also like the squeezing fly leads between caps technique to secure wires.

im going to try the sweep idea in my amp i think. i feel safer doing it in mine as (apart from the fact its a really simple idea) there isn't going to be as much voltage attached to it i dont think. my tone stack being cathode fed.

I saw a schem for the chadwick too. the envelope control is a pot with a bypass cap before one of the gain stages. some buff might correct me but i guess that works as a frequency filter on the grid on a gain stage.

[Copperhead]

Mine got the goo after some upgrades. On warranty repairs, if they notice a trend, like cracking solder joints at the caps, then they start using that cr@p in the area.
They are all overkill there on being reliable and durable, hard use and transportation, etc. The traveling concert backline amp.
You can see on mine that the power tube board is different, this was a redesigned board after they had a trend in warranty repairs on the old board that had cracked solder joints and arcing causing power tubes to blow.
The Envelope control is after the last gain stage, it's how hard the pre is driving into the power amp. 5 or 12:00 is neutral, to CCW is less, etc. Dialing it back a little gives you really clean cleans.
What we can't figure out is what the Drive pot is doing on the single channel Chadwick. The Chadwick switcher has a Drive switch, but the single has a pot control. There are drawings for the Chadwick2 but not for the Chadwick single. Seriously, they have no pdf's or anything of that circuit at Krank. Which kinda annoys the tech guy.  :lol:

[Copperhead]

............Just got my Chadwick last week, I will take it out of the head shell and get some gut shots soon.

[Dmoney]

if the solder joints are cracking and they fix that with goo, that would worry me.  
I'd want all the solder joints heated again. They should last a lifetime.
at least they addressed the power board issue.

I thought the envelope was before the cathode follower feeding the tone stack.
the envelope i thought, was fed via 22n cap coming from the junction of the previous triode plate, and its plate resistor.
the envelope itself being a pot with a small value cap across the input and the wiper. the other leg to ground. the wiper feeding the grid of the cathode follower stage pre-tone stack.

i thought that was a kind of frequency filter???

the Drive i think... is fed from the cathode of the stage also feeding the envelope. it is a pot that is in series with a small cap before it, and both cap & pot are parallel to the cathode resistor of the stage feeding the drive control and ground.
I guess the cap in that situation the cap would usually be a standard bypass cap for the cathode resistor.
so my guess is, the pot & cap in parallel with the cathode resistor, works as a bypass cap, and also, the pot and cathode resistor in parallel effects the gain of the stage. as you turn the drive knob you increase of decrease the total resitance between the cathode of the stage, and ground, thus effecting the bias of the stage, and the gain of the stage.