Sluckey's SVK22

[Bieworm]

Hey guys

Since the previous topic on this amp has run dry I decided to build one myself. Currently I've built the chassis an populated it with tube sockets, pots, faceplate and knobs, transformers. I have wired the power supply and finished the heater wiring.
I did some changes to the schematic. It will most likely run on EL34 tubes (have a dozen of real good old ones) that are switchable between fixed and cathode bias. I also added an on/off NFB switch and omitted the FX loop so the reverb is always running straight into the preamp. Oh, and it will have a fixed mid instead of a pot.

[Bieworm]

and 2 more pics

[sluckey]

Yay!!!

[kagliostro]

COOL 😎

 

Franco

[uki]

Looks really good !! 

[kagliostro]

Since the previous topic on this amp has run dry I decided ......

Can you share a link to the previous topic ?

Thanks

Franco

[sluckey]

https://el34world.com/Forum/index.php?topic=29802.msg328171#msg328171

[kagliostro]

Thanks Steve

Franco

[J Rindt]

https://el34world.com/Forum/index.php?topic=29802.msg328171#msg328171
[/quote

There must be some things that are better using this type of Trem
It uses a phase  shift oscillator to run the Roach............ why not just use that for the Tremolo.....why add the LDR.?
Thanks

[sluckey]

There must be some things that are better using this type of Trem
It uses a phase  shift oscillator to run the Roach............ why not just use that for the Tremolo.....why add the LDR.?
Thanks

My circuit is simpler and sounds better than the Fender neon roach trem. And there is no ticking.

BTW, the roach also has an LDR inside it, two leads for the neon lamp and two leads for the LDR.

[Bieworm]

Hey Steve

I found a discrepancy between the drill guide and the layout. Shall I note these all (if any more) at once, or report them immediately?

[sluckey]

Report them immediately and I'll correct as we go.

[sluckey]

I found a discrepancy between the drill guide and the layout. Shall I note these all (if any more) at once, or report them immediately?

Should be fixed now.

[Bieworm]

I found a discrepancy between the drill guide and the layout. Shall I note these all (if any more) at once, or report them immediately?

Should be fixed now.

Indeed👍

[J3ona1]

following!!

[Bieworm]

Steve

I the Fender VK schematic the volume pot is a dual gang 500k pot. It simultaneously operates the volume of the amp and a level control mid reverb recovery circuit. I guess this is to lower the wet signal when you dial the amp in louder? You didn't copy that. What's the reason?

edit: never mind, was looking at the 1st issue schematic

thanks

Bjorn

[Bieworm]

current situation. I know those 350V caps in the bias circuit are obese, but I apparently ran out of good sized 10uf/100V caps (only have smaller radial caps of that value)

[sluckey]

Looks good! Remember, you're the first. Lead on.

TubeGeek had sent me some hi-rez pics when he worked on a real VK a few years ago. I'll make them available so you can see how much better your version looks...

     https://sluckeyamps.com/misc/VK_pics.zip

[Bieworm]

Looks good! Remember, you're the first. Lead on.

TubeGeek had sent me some hi-rez pics when he worked on a real VK a few years ago. I'll make them available so you can see how much better your version looks...

     https://sluckeyamps.com/misc/VK_pics.zip

I have a real one. Love the tone, but I’m too lazy to haul that overweight thing around. 😉
Also, it might be just me, but IME vertical mount amps in a combo ( tweed style) sound better than blackface type combos. I think it’s the extra space behind the chassis is accountable for that. I will be building a 2x10 Gretsch 6155 type combo for it.

[Bieworm]

Tube sockets and pots wired to the board. Now I can start populating it with components

[Bieworm]

Finished the build. After some minor troubleshooting the reverb circuit it appears to be working great!
The problem turned out to be a classic, but rarely seen on a new build. The reverb cable was bad!!!

@Steve: the level/mix pot is wired backwards on the layout.

[tdvt]

That is a lot of circuit in a small space. Looks great!

Look forward to seeing the cabinet. That Gretsch is a pretty cool design. Never built one of those, but might have to down the road.

[tdvt]

Engraved plexi faceplate?

[sluckey]

You did a fantastic job! Looks great. Glad it was a success. Did you find the schematic/layout easy to work with? I'd like to update my webpage to show the SVK-22 to be successfully built by you if you don't mind. Might encourage others to tackle this project. Maybe even inspire Silvergun to finish his project!

BTW, I've corrected the mix pot error and updated the pdf on my website.

[tdvt]

Might encourage others to tackle this project.

I see this as an intriguing project...look forward to hearing clips with the 10's. I know the surf guys like 15's, wonder how that would sound?

I have already built a 6G15 but these more unconventional mix of circuits is interesting.

Also interested to hear the trem, both for speed & depth.

[Bieworm]

You did a fantastic job! Looks great. Glad it was a success. Did you find the schematic/layout easy to work with? I'd like to update my webpage to show the SVK-22 to be successfully built by you if you don't mind. Might encourage others to tackle this project. Maybe even inspire Silvergun to finish his project!

BTW, I've corrected the mix pot error and updated the pdf on my website.

Sure, no problem! Layout was pretty easy and set up so the result after the build is stunningly tight looking.
I will draw the changes I made to it. For example, I wired a shielded wire from the input straight to a stand-off near V1B, and from there to the .047uf on the board. I felt more comfortable with that approach. It’s a very sensitive wire.
I also put the fat switch to the footswitch only and omitted the FX loop.

[Bieworm]

Might encourage others to tackle this project.

This reverb sounds exactly like the vibro king’s reverb. So it differs from the 6G15 somewhat. I ordered a 6K6 today. I think it’s sweeter than the 6V6 that’s in there now.

I see this as an intriguing project...look forward to hearing clips with the 10's. I know the surf guys like 15's, wonder how that would sound?

I have already built a 6G15 but these more unconventional mix of circuits is interesting.

Also interested to hear the trem, both for speed & depth.

[sluckey]

Did the tremolo work as expected? Did you have to experiment with the intensity pot connection?

[Bieworm]

Did the tremolo work as expected? Did you have to experiment with the intensity pot connection?

Not really. It works, but I did El Cheapo on the vactrol. I ordered the Xvive along with the 6K6. The one in there now delivers all the known problems such as volume drop and weird waveforms. It’s not as gradual as I want. I might end up changing the trem circuit to the IRF840 I usually use. But I’m not doing that until I find the Xvive not performing either.
What do you mean about the int pot connection?
Oh and something that may be important.. I used a 300-0-300V marshall 36 watt transformer. I needed to have a surface mounted type for the narrow chassis. The B+ on the 7581 plates is 360V. I will be poking around in the amp the next few days. When it’s set I will post voltages too.
Edit: I apparently forgot to connect the G2 on the 6V6 to the C node!!! Lol!! NOW we’re talking reverb😎

[sluckey]

What do you mean about the int pot connection?

Sometimes you need to experiment with the INT pot connection to the guitar signal path but your circuit should work just fine as drawn.

Edit: I apparently forgot to connect the G2 on the 6V6 to the C node!!! Lol!! NOW we’re talking reverb

I'm surprised the reverb worked at all without G2 connected.

[Bieworm]

Me too, but it was surprisingly present pretty much. But now it’s drippy surf territory 🏄‍♀️

[Bieworm]

Here's the layout with my changes:

- NFB with on/off switch
- Changed the input wiring
- Put the FAT switch on the footswitch
- Removed the FX loop
- Removed MID pot and put fixed 6k8 resistor

[clyde]

I had a VK back in the day, the EL84 one, hard on tubes it was, only certain EL84's survived.  I wasn't impressed with the tone either, it was always too dirty and I went back to my '64 Vibroverb for gigging.  I didn't realize 'till now that the dry input was off the cathode.  Fender used CF inputs in the early 6G- Bassman's but went away from that.  Although the topology was different, what are the pros and cons of using these two inputs?  Thank you.   

[Bieworm]

Here’s a sound clip:

[Bieworm]

I had a VK back in the day, the EL84 one, hard on tubes it was, only certain EL84's survived.  I wasn't impressed with the tone either, it was always too dirty and I went back to my '64 Vibroverb for gigging.  I didn't realize 'till now that the dry input was off the cathode.  Fender used CF inputs in the early 6G- Bassman's but went away from that.  Although the topology was different, what are the pros and cons of using these two inputs?  Thank you.

No idea. I have an original early 90’s VK and only play straight in with the reverb and all. The one I’ve built now has only one input and no dry input aka FX loop

[Bieworm]

Ok the parts arrived, so now there’s the 6K6GT in the reverb now. Sweeter as expected. A nice NOS RCA!
And boy!!! The Xvive is really a completely different animal than the cheap vactrol that was in there and giving ugly trem waves. The Xvive does make the difference. Trem is nice now! I think there’s some volume loss though, but nothing threatening. I can’t play on full blast because my son has exams in a few days, so I’m not bothering him with my noise while he’s studying.

[sluckey]

Trem is nice now! I think there’s some volume loss though, but nothing threatening.

That's just how this tremolo circuit works. It can't boost the guitar signal. It can only attenuate the guitar signal. So, with the trem turned off, you will have some max guitar signal. Turn the trem on and it will vary the guitar signal between that max level and some attenuated level, depending on the intensity pot. So, that's the volume loss.

[Bieworm]

Trem is nice now! I think there’s some volume loss though, but nothing threatening.

That's just how this tremolo circuit works. It can't boost the guitar signal. It can only attenuate the guitar signal. So, with the trem turned off, you will have some max guitar signal. Turn the trem on and it will vary the guitar signal between that max level and some attenuated level, depending on the intensity pot. So, that's the volume loss.

Might be it. But with all of my tremolos on the power tubes I don’t experience it. The tremolo wave form is nice though.

[sluckey]

Might be it. But with all of my tremolos on the power tubes I don’t experience it. The tremolo wave form is nice though.

Yes. That's because bias vary trem actually varies the conduction of the tube causing the signal to rise and fall, not just fall.

[sluckey]

How does this compare with your real VibroKing?

[Bieworm]

How does this compare with your real VibroKing?

I certainly recognise the tone in this build. It’s definitely a Vibro King. I am amazed how silent the reverb is concerning noise. It is really really quiet! But huge reverb! Amp cab is finished too. Waiting for the handle to arrive though

[Bieworm]

I’m building a 6V6 version right now. The cab is finished. I used the grill cloth from an old Gretsch amp. If you look close you see it’s upside down, with the discoulored marking of the slanted front panel. 😉

[Bieworm]

Hey Steve

It might be a good idea to add this remark on the layout?

[sluckey]

Hey Steve

It might be a good idea to add this remark on the layout?

I suppose so. But you would also have to mention to change the 470Ω resistor too.

[Bieworm]

Hey Steve

It might be a good idea to add this remark on the layout?

I suppose so. But you would also have to mention to change the 470Ω resistor too.

Yeah, but that info is already on the schematic. The shunt is more clear on the layout. Well, to me it is😎

[Bieworm]

Hey I finished the 20 watt version! Sounds tremendous. I used JJ 6V6 though to get more of that 6L6 vibe.
Also, I did the tremolo to bias vary on the 6V6 grid leak resistors. I’m more that guy.. the whooshy swampy loud trem!! Love it!
And I used a 6K6 on the reverb. I added another node on the B+ to get the 250V on the plate, biased the 6K6 at 45%

[pieterfx]

Incredible build!

Can you share the changes to the schematic and layout for this 6v6 one?
Also, can you share which transformers you used?

thanks!

[Bieworm]

Incredible build!

Can you share the changes to the schematic and layout for this 6v6 one?
Also, can you share which transformers you used?

thanks!

I used the transformers from Tube Town. They have a Marshall 36 watt PT and a 25 watt tweed deluxe OT. Both made in Europe. I have great experiences with both. The choke is a hammond 194A and the reverb transformer is the Vibro King replacement from Hammond (10watt)

I will post the schematic later when I get the chance. Will post the layout too, because I also changed the tremolo.

[sluckey]

Why did you change the tremolo?

[Bieworm]

Why did you change the tremolo?

Although the Trem O Nator is a nice tremolo, I like my tremolos louder. That’s what I’m used to. I’m a heavy trem user😎
Is the Trem O Nator applicable to implement at the power tube grid leaks? That would make it useful to me.