SVK-22, slightly modified Fender Vibro King

[sluckey]

I've added a schematic/layout for my slightly modified Vibro King to my website. This is basically a single channel AB763 with 6G15 reverb unit and Trem-O-Nator all rolled into one chassis.  I've never heard or seen a Vibro King and I have no intentions of building one. I just got bored this winter during the Big Chill and drew it up. I had fun with Visio. Thought I'd throw it out there in case some of you may be interested.

     http://sluckeyamps.com/misc/Sluckey_Vibro_King.pdf

[SILVERGUN]

Man, you read my mind. I think it's been about 2 years since I told Willabe this was gonna be my next build ( I lied )
But, THANK YOU for doing this!
I might actually get to this one.
Great work as always and definitely a cool idea!
Here's my little snip so you can see how similar the thought was...it's crazy


I was gonna use the name TREM-O-KING. I like that better. 

[sluckey]

That's spooky! People will never know who copied who!   

I've always thought it was a neat idea and probably would have built one if I did not already have a Revibe. Forum member "tubegeek" sent me some hi-rez pics of a real VK. He also said he was not really impressed with the sound.

I'd love to see you run with this.

[SILVERGUN]

He also said he was not really impressed with the sound.

Yeah, I changed the "dry" preamp to 5F6A territory (and NFB), but I never got any further than a sketch.
I wanted the all inclusive board type design for this because I'm dumb enough to think I'm gonna squeeze it into this chassis. I have a cab for it, all iron...
So, I'm glad I waited for you 


5A40 Chassis Only – Weber Speakers (tedweber.com)

[shooter]

 
you're both tela-pathetic.

[sluckey]

A tweed chassis! That's just sick!   

[SILVERGUN]

A tweed chassis! That's just sick!   

OR, just plain ol' fashioned DUMB 

[tubeswell]

Never had a Vibro King to play around with, but I bet the reverb is impressive.


Going slightly off-topic onto sound of Zinky amps, I did have a Zinky Tone Master in for a recap a couple of years back. That was an impressive sounding amp - all-round clean and dirty sounds. But the one I recapped had a whole pile of parallel 20uF filter caps in the doghouse. And the main board was a real a tangle to behold with all those separate ground return wires. Maybe that sort of stuff is why Zinky got fired?

[sluckey]

But the one I recapped had a whole pile of parallel 20uF filter caps in the doghouse. And the main board was a real a tangle to behold with all those separate ground return wires. Maybe that sort of stuff is why Zinky got fired?

The VK does not look like what I'd expect to come from the Custom Shop! Crazy dog house, wild CBS era wiring, and look at that nasty circuit board! Man, at least clean up all that rosin!

[tubeswell]

LoL - Looks like the Tone Master - getting at the bias supply cap was a mean feat - the bias pot was underneath the main board! (Had to unmount the pot to get at it!)

[Bieworm]

The VK is -apart from its rats nest construction - hands down the best Fender amp I ever had. Still have it!
This amp just needs the blue frame emi’s! It sounds amazing, but is way too loud and way too heavy to haul around. The only thing I had to change was the tremolo. With a little help from here I modded it to power tube bias vary. Works reeeeeaaally well. The reverb is heaven, but the circuit is pretty different from the 6G15 IIRC.
Mine’s serial #894, so an early one with the EL84 in the verb

[SILVERGUN]

I know how much you appreciate accuracy so I must point out that the cathode bypass cap for the reverb driver appears to be drawn backwards on the layout.
I started looking over this last night and setting out some parts and seeing what is what.
I needed a chip-away- type project and this is gonna work well.
Every time I start a build and think I'm just gonna chip away at it I wind up getting completely obsessed and lock myself in the basement. Not this time.

Making a parts list today. This'll be the 2023 project. I'm going with Trem-O-King

[sluckey]

the cathode bypass cap for the reverb driver appears to be drawn backwards on the layout.

Thanks. It's fixed now. LMK if you see other errors.

[shooter]

lock myself in the basement.

keep that option open, we're only a few weeks into the new year 

[SILVERGUN]

lock myself in the basement.

keep that option open, we're only a few weeks into the new year 

Even if I do get it done sooner I'm gonna hold off on posting until December so I won't get missed for "Build of the Year" voting.
I got railroaded by DL last year at the last minute.
And speaking of DL....how did he miss that backwards cap?
I don't know shooter. Thank goodness YOU are paying attention!

[sluckey]

Take your time. Compare the schematic and layout over and over until you are confident that they agree. There could be other "not so obvious" errors.   

[shooter]

 
I was too busy trying to see who stole from who to pay attention to details.

[SILVERGUN]

I was too busy trying to see who stole from who to pay attention to details.

If you ask sluckey, it's plausible deniability.
But, I've been stealing from him since 2012, so there goes my defense right out the window.
If you can see past the blur to my actual snip you'll see that 50% of "my idea" was 100% his Bandmaster schematic.

[shooter]

everything I've build, I stole from somewhere, a wise man once told me wheels don't need re-inventing, just new rubber. 


enjoy the slow road, I'm slo-rolling my '55 Plymouth, I stole the PI from my last build, which I stole from Platefire, who copied from Silvertone, who probably stole from Vaco or Gibson....
to paraphrase a Book I read on occasion "There's nothing new under the Sun"...Hmm, is that an AMP reference.

[sluckey]

I had considered using a standard AB763 power amp but kinda wanted to hear the subtle differences with the VK power amp. So, the board was laid out for the VK but provisions were made to easily and neatly add NFB. All you have to do is replace the 39K with a 22K. Then replace the jumper between turrets 1 and 2 with a 100Ω resistor. Then add an 820Ω resistor between turrets 2 and 3. Finally, connect a wire between turret 3 and the speaker jack tip. Man, how easy is that!   

[SILVERGUN]

I threw some scrap wood together for a custom cradle and am still sizing it all up.
My Hammond 290DX bolted right in and I had snagged an OEM Bassman OT from ClassicTone before they abandoned us.
Got a big choke and a Champ OT for the reverb driver. I also splurged and bought myself some flux for Christmas, so I got that going for me.
This is gonna be fun. I gotta punch one of those little holes out, cause I want to use a 6K6/6V6 driver.
I'll start my own thread once there's more to talk about.
Just wanted sluckey to see what the right nudge at the right time can manifest.
Thanks again!

[Lectroid]

@sluckey,

I'm curious. Why did you elect to use the 6G15 reverb?

[sluckey]

@sluckey,

I'm curious. Why did you elect to use the 6G15 reverb?

Because that's what Vibro King did.

[Lectroid]

  I've never heard or seen a Vibro King

 a Vibro-King demo on YT. 
 
https://www.youtube.com/watch?v=3qnW5TnCIZ4

[SILVERGUN]

The "FAT" cap on the schematic is 22uf but is shown as .22uf on the layout. I noticed because I would assume your 22uf would be drawn as an electrolytic. Still lookin....
 

[sluckey]

The "FAT" cap on the schematic is 22uf but is shown as .22uf on the layout.

Fixed. Keep lookin'.   THX...Steve

[SILVERGUN]

I got through the Sunday morning coffee and highlighter routine and all is well.
My printout had a couple ghost resistors that I see you have cleared up on your own (I printed this out the first day)
So, as far as I'm concerned, it's confirmed.
Nice work Steve!

[sluckey]

My printout had a couple ghost resistors that I see you have cleared up on your own (I printed this out the first day)

Haha! Those ghost resistors were part of the NFB changes. They were on a separate layer and I had set the layer properties to not be visible but forgot to also set the layer properties to not print. Thanks for proofing the layout.

[Platefire]

I worked on one of these amps when I was doing amp repairs a few years back. It was fine sounding amp and the reverb was outstanding. It was one of the earlier models with an El84 rev driver. I can't for the life of me rememberwhat the problem was?
Anyway sluckey you have done a beautiful job on the schematic and layout. With your Trem=o-nator it will bea Knock Out! So I'll be interested in SILVERGUN'S progress! no pressure:>)

[sluckey]

Platefire, are you still happy with the TON in your Pro?

[Platefire]

Well, first of all I've got no intentions going back in and working on it because it's so much better than what I had in there and what I love about it is it's quite with no side operational noises. If I was going to try to improve mine I would:

a-have stronger intensity. I can get the intensity I like by turning it all the way to 10. So I'm not complaining because I can get the intensity I want. It's just my way to have a little bit more control than you need, even though you don't use it:>)

b-It seems to cut volume a bit when engaged but my Mesa Boogie does the same thing. That can be fixed by turning up your guitar volume. Most of the songs I play with trem are usually mellow type things that don't require as much volume anyway

So I'm really happy with it as is. I'm just providing this bit of comments because I think you looking for a honest answer cause I know your wanting to make the Trem-o-nator work as well as possible

[SILVERGUN]

So I'll be interested in SILVERGUN'S progress! no pressure:>)

The good news is I haven't had to lock myself in the basement. The bad news is that (of course) I'm not following sluckey's layout to the letter, so I'll be stalled here waiting on getting the board squeezed down to fit. I got some figgerin' to do. Every build starts with a tight power supply and this chassis sure is tight!

Plate'ie, Ol boy, here's one just for you. Don't show nobody else, now. I don't want 'em seein' how messy it's gettin' over here.

[sluckey]

getting the board squeezed down to fit

Would it help if you had the Visio file?

I don't envy you. What size is your chassis? Do you even have room for a 3-1/8" x 15" board? Keep us posted. I'll be painfully following your progress.   

[SILVERGUN]

I don't have Visio to work on it. I usually just hand draw out rough sketches. Or I'll cut and paste your board pic (like a 5th grader)
I'm using a tube rectifier (5U4GB), so that buys me almost an inch and I'm trying to squeeze the bias supply into the top left corner, so there's another inch'ish off of your board.


I was considering running the ground for the 6V6 driver back to my power supply ground and putting the cathode cap and resistor on that same buss instead of on the board. I would wire tie the ground wire to the B+ supply wire. Is that a bad idea?


I have about 13" of available board space. 3 1/8" would fit but I've been thinking about ripping it down. Haven't gotten there yet. Next time I have some available brain time I'm gonna break out the old paper and pencil.


EDIT: Oh yeah...and I already mounted the 1 ohm resistors from the sockets to a small terminal to my power supply ground.

[sluckey]

I would wire tie the ground wire to the B+ supply wire. Is that a bad idea?

That's fine. Both wires are AC ground.

[SILVERGUN]

Here's a quick cut and paste of the board I'm seeing (temp)

[sluckey]

My turret column spacing is 5/16". By squeezing the column spacing down to 9/32" and eliminating the columns you indicated, I decreased the board length from 15" down to 11-5/8".

[SILVERGUN]

I knew you were gonna do that. I should have stopped you. Wait for the final - final - final revision. 
I'm gonna eliminate the fat switch and just go 1/2 fat all the time. Like this.
I truly appreciate your Visio skills!


EDIT: My caps are gonna be bigger than what you have pictured so I'm gonna squeeze real estate down so I can then stretch it out to 13" (ish) and have room for Orange drops, (etc)
Double EDIT: I have never used one of your drilling templates. I use one of Doug's old template boards with all the holes in it. Not sure what that spacing is.

[sluckey]

EDIT: My caps are gonna be bigger than what you have pictured so I'm gonna squeeze real estate down so I can then stretch it out to 13" (ish) and have room for Orange drops, (etc)

Really! You will quickly find out how unfriendly my layouts are to ODs or other big caps.   

May I suggest Xicons? The caps on my drawings are scaled properly. Look at these two big ole ODs...

Doug's aluminum drilling blank has an oddball spacing, something like 29/64" IIRC. There's a story about the origins of that old relic somewhere on this website.

[SILVERGUN]

Really! You will quickly find out how unfriendly my layouts are to ODs or other big caps. 

Yeah, I still got some figgerin' to do. And cap ordering, so I'll see what's gonna be what. I knew I'd be using Xicons in the trem circuit.


What is up with the negative feedback loop around the input stage? (I see that's on the 6G15 also, and I assume Zinky copied).
I ask because if that goes away then so does the .047.
I'm only gonna have a single "HIGH" input.

[tdvt]

Next time I have some available brain time I'm gonna break out the old paper and pencil.

Maybe you are already doing something similar, but the from-scratch boards I have made are laid out 1:1 with the actual components in-hand, using good old graph paper, a ruler & a pencil.

I can adjust the grid size as needed by enlarging/reducing a blank sheet of graph paper on the home printer/copier. The example attached is 5/16" spacing.

When it's done I make another copy & use spray adhesive to stick it to the board as a drill pattern.

[SILVERGUN]

What is up with the negative feedback loop around the input stage? (I see that's on the 6G15 also, and I assume Zinky copied).

I went to RobRob's site and found the explanation of voltage divider. I realize now that that's how the cathode follower needs to operate.

[tubeswell]

What is up with the negative feedback loop around the input stage? (I see that's on the 6G15 also, and I assume Zinky copied).

I went to RobRob's site and found the explanation of voltage divider. I realize now that that's how the cathode follower needs to operate.

The voltage divider on the grid of the CF in the 6G15 is one method of applying fixed bias to a CF grid, and the resulting design in the 6G15 gets about 1M input impedance (2M2||2M2). There are other ways of applying fixed bias to that grid that yield higher input impedance (which could help a little with the dry signal in the 6G15).

[sluckey]

What is up with the negative feedback loop around the input stage? (I see that's on the 6G15 also, and I assume Zinky copied).
I ask because if that goes away then so does the .047.
I'm only gonna have a single "HIGH" input.

V1A is a cathode follower. That 10K dropper and .1µF filter cap on the plate is just an extension of the B+ rail. In reality, V1 pin 1 is tied to B+. The two 2.2M resistors are not a NFB loop. They are a voltage divider that provides fixed bias to the CF (just like the original 6G15). Since the grid sits at 1/2 B+, the .047 is needed to keep B+ off the input jack and also V1B grid.

[Platefire]

Just seems since the special reverb circuit is such a big part of this amp's sound, it should be included in the name along with the Trem or Vibro. I can't come up with a combination that really pops though? 

[bmccowan]

Delirium Trem King

[SILVERGUN]

Can I get away with this move?
It will really simplify my wiring. The original 6G15 schematic looks similar, but without the screen resistor.

[sluckey]

Looks OK to me.

[SILVERGUN]

Nice.
 I had already flew in the B+ on pin#6 and I was gonna connect the reverb xfmr there. Then I'll just shoot the screen R over to pin 4 from there.
 

[Platefire]

Tremonator-Verb King