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 Post subject: 6V6 Lightning Variation
PostPosted: Sat Jan 14, 2006 9:14 pm 
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bitsandvolts wrote:
...I haven't even told you guys what I did to my lightning (I'll be posting pics soon, but I went to 6v6's, added a cut and mid control (stolen from the tophat club deluxe schematic) and changed the power section to be closer to the tophat club deluxe....-F


Frank, I think this would be an interesting project. Whenever you get a chance, we'd appreciate full disclosure.

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 Post subject:
PostPosted: Sun Jan 15, 2006 2:49 am 
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Yeah, been meaning to!!

I'll follow up with a post about this in the coming day or two!


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PostPosted: Wed Jan 18, 2006 9:03 pm 
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Hey folks...I've been meaning to post the final story behind my Lightning for quite some time...however, a new baby and a new sIII got in the way....the story still needs to be told:

Way back in the summer, I started a lightning build. I collected all the components, had the chassis and transformers delivered...and when the faceplates arrived...I went to town.

I completed the amp very quickly...but after firing it up, I found myself with what seemed like a very unstable amp. The input wires weren't happy with the 68k resistors at the jacks..I had grounding issues with the same jacks...and the amp as a whole, had a very annoying buzz that travelled with a distorted signal on the amp. The amp sounded great clean, but as soon as I notched the gain above 7 or 8, a fizy buzz would acompany the guitar signal.

I chased this buzz issue for roughly 5 months before determining that I either had to make a significant change to the amp or yank out the entire amp and start over. I decided to make some changes to see if I stumbled across the fix while making a change. Here are the changes:

1) First thing I did was pull the el84s, widened the sockets to octals and retrofitted cathode bias and grid resistors for 6v6s. I had been intrigued with the idea of converting a lightning to 6v6s for quite some time. Sure, I would be saying goodbye to the voxy sound of el84s....but I liked the idea of making the amp a little more 'fendery'...some added headroom and rounder bottom would be a welcome change.

2) Borrowed ideas from TopHat Club Deluxe to include a Mid control (lightning is fixed at 10k, the Club Deluxe utilizes a 25k pot) and a post PI cut control. These two mods seemed a no brainer, since I could easily set the mid contol so that the pot is delivering 10k of resistance and it would be like the mid pot wasn't even there. Same goes for the cut, when it was turned down all the way. In the end, I felt it could give me some added tonal control when using different guitars.

3) In order to make room on the chassis for the cut and mid controls, I got rid of the low input. I found the volume adjustment on the amp perfectly sufficient for achieving cleans, mid cleans and high gains with just one input.


After the above 3 changes, unfortunately, I still had the creepy buzz that had plagued this amp since birth. I decided to post the issue on a few boards I don't normally post on. I recieved a suggestion that the 22k resistor that follows the choke might be knocking down the screen voltage too much...and that it could be the reason for the buzz...and it would also be robbing the amp of some power. In this same thread, a highly respected amp builder with the initials RA came in and concurred but also added that the 22k resistor is there to protect the fragile el84s.

I didn't have el84s in this amp anymore! :?

As a result, I referenced the schematic of the tophat club deluxe (which for all intents and purposes, is a lightning front end on a 6v6 power section with a mid control and cut contol...hey, just like mine!)...and discovered that the power section of the club deluxe had 5 filter caps, not 6. Reviewing the schematic further, it showed that the 6v6 screens were fed immediately after the choke (which was really a resistor).....

So I decided that it couldn't hurt to try something similar...I could always revert. I removed the 3rd filter cap from my lightning and moved the screen connection from the 3rd cap (which was now pulled) to the 2nd filter cap.

I fired up the amp...and I was immediately blown away at the power that the amp had. It literally felt twice as loud....Then I cranked up the volume to see if the buzz/distortion was there. It wasn't!!! The distortion coming out of the amp was crystal clear, powerful, meaty....but not buzzy...at all!!

I had finally licked the problem...but I had an added bonus of a significant power boost.

The amp is quite a beast now...It's the loudest amp in my stable (although the sIII is a not-too-shabby second). I get slightly more headroom than the lightning, thanks to the 6v6s...but the added power makes the amp seem like it's got a huge headroom boost. The mid control is a nice addition, although due to the 1meg trebble pot, is very interactive with how the trebble is set. The cut control is a spectacular addition, since it immediately removes any extra brightness without killing the character of the amp.

Since the amp ended up being a sorta hybrid between a Lightning and Club Deluxe...I decided to call the amp the 'Lightning Deluxe'

Here's two frontal shots for you guys!

Image

Image

[/b]


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 Post subject:
PostPosted: Wed Jan 18, 2006 9:28 pm 
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Good job Frank, so as soon as you have drawn out the schematic/layout I might put one of these together ;-)

btw I think you should do a tweed bassman for your next amp.

Nigel


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 Post subject:
PostPosted: Wed Jan 18, 2006 9:43 pm 
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B&V, a great tale of two amps! Never had the buzz in one of mine but have wanted to do much the same thing as you did. Actually built a SpitV6 and it's not bad.
I'd love to see that schematic as well and would be more than happy to draw it up for all of us, plus a layout for those who might want to build one.

Did you find the cut control necessary with the 6V6??

Did you change anything else on the tone controls - is it still 'interactive' like the Lightning?

How would you characterize the sound now?

What B+ voltage are you running now?

Congrats on what must be a nince amp and well done on the cab & faceplate. Looks very Pro!

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Last edited by coco on Thu Jan 19, 2006 2:15 pm, edited 1 time in total.

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 Post subject:
PostPosted: Thu Jan 19, 2006 11:39 am 
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coco wrote:
Did you find the cut control necessary with the 6V6??


I assume you're talking to me, since I don't see a John in the thread! ;)

actually, I did not find the cut control necessary in the el84 lightning...I wanted to put the control on the amp to have some added tonal options. The cut as I have it (same as what's on the matchless clubman or cheiftan) adds a nice tonal difference...as I can get some darker moodier sounds out of the amp, that I wouldn't get with a regular tone control on a guitar.

coco wrote:
Did you change anything else on the tone controls - is it still 'interactive' like the Lightning?


It's still very interactive. I blame the 1mg trebble pot for that....if you download TSC, you'll see that the trebble pot tends to really govern the sound of the amp....if you changed the trebble pot to the traditional 250k, the amp would be a bit more traditional.

The added mid controls only really allows you to change the value of that 10k resistor in the lightning/vox tone stack. What seems to happen when I play with this new mid control, is that the mid control seems to more take over the role of the trebble pot and the trebble pot acts like a mid-sweep on a mixing board....it's very weird, but still very interactive.

I actually thought the original lightning stack was very interactive. I wasn't going to change it until I realized that I could very simply get the same results by turning the mid pot to a point where the pot is providing 10k of resistance...once that's set, the tone stack works like it always had...so it's a mod that isn't destructive.


One change I did make, which I didn't outline before (Because I don't feel it's relevant) is that I made some additional changes to the preamp to borrow more from the club deluxe. I was experimenting...and since these changes were easily reversible, I decided it was worth a try. The two major changes to the preamp were:

a) added a 1mg drop down resistor just after the volume pot. This probably dropped gain a hair...right?

b) changed the cathode resistor to 820 and bypassed it and the 22uf cap with a .1uf cap....probably increased gain a tad....

All in all, the above two changes did only very subtle things to the tone. Perhaps fattened it up a hair.....But not enough for me to go "Eureka" so I ended up just leaving them in...but if I pulled them and reverted back to the Lightning specs, I probably wouldn't notice too much of a difference! So thats why I felt it wasn't necessary to mention it....

coco wrote:
How would you characterize the sound now?


Well, first off, getting the doubled buzz out of the amp was what I really wanted...and it's gone now. Like I said, it's a WHOLE lot louder...and thats a plus too...

The amp definitely retains a rounder bottom end...and the top end is a little less sharp...but it's still definitely a 'lightning'...So the overall characteristics of the amp are still there in spades. I like the fact that the bottom end of the amp tends to be a tad fatter and rounder...since I can still dial that out with the tone controls.

The 6v6 is a superb tube...and whatever amp I build next, is going to employ them...I suspect I'm either going to be building mark huss's 6v6 plexi or s2's blackface...but whatever it is, Its going to use 6v6s.


coco wrote:
What B+ voltage are you running now?


I dropped the B+ earlier in the winter in an effort to kill the doubling buzz. It didn't work, but it *did* kill/reduce some other buzz which was probably some type of crossover distortion. Prior to the original transformation, the el84 lightning was running at 364v. In line with the 'change some things to Tophat', I've dropped the B+ down to about 344v with the use of Zeners. As I mentioned above, it definitely killed something undesirable....and an added bonus was that the amp sings a bit better...

With the added power boost I got from moving the screens line on the power tubes to the low side of the choke, I was less worried about losing a tad of power with dropping the B+....

coco wrote:
Congrats on what must be a nince amp and well done on the cab & faceplate. Looks very Pro!


Thanks!!!

Faceplates on the amp were done by Jeanne at BNP. She actually did the original lightning ones for me...The lightning one on the back is the same as the original...but the front, all I did was take the original corel file, more the knobs over one (so that the bass was sitting on the original hi input hole)....added the mid control and the cut control where necessary and sent the file to her for a reprint.

The cab was my 3rd cab done (I had previously done a head cab and 1X12). So I was started to get better at tolexing. It pales in comparison to the tolex job I just did on my sIII head (pictures to come soon). The tolex I had been using for most of my projects was really automotive vinyl with a very soft backing....it's very forgiving because of the softness and thickness...but also very difficult to line up or seam. So my cabs all have corner protectors to cover up the nasty corners...The sIII cabinet with the true tolex (supplied by trinity amps, thank you very much!) was alot easier to cover and a breaze to seam. My corners and bottom seam came out perfectly!


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 Post subject:
PostPosted: Thu Jan 19, 2006 2:20 pm 
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B&V,

Last queston: Output Transformer impedance - Original Lightning used 4K, 18W uses 8K, what did you use on this build?

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 Post subject:
PostPosted: Thu Jan 19, 2006 3:07 pm 
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s2 told me that 6v6s prefer 8k...I just ended up using the existing 4k...and it sounds fine...no problems.

I actually tried the 8k that eventually powered my sIII in there...and I didn't hear much of a difference....

-F


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 Post subject:
PostPosted: Thu Jan 19, 2006 9:07 pm 
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Probably could be louder/more efficient with the 8K because of the matching. Glad it worked tho.

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 Post subject:
PostPosted: Mon Jan 30, 2006 9:48 pm 
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I think I need one of these.


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 Post subject:
PostPosted: Mon Jan 30, 2006 11:27 pm 
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I have wanted a 6V6 ligntning for ever. lbet, you know it. We talked about it over a year ago. Only got as far as the 6V6 Spit, which, has it's own sound. Not a big deal to try it, just need to get an amp of my own to play with!

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PostPosted: Thu Aug 11, 2022 11:14 pm 
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These amplifiers' schematics are actually rather similar. The position of the phase inverter is the primary distinction. It has been moved in the sIII to a more sensible location
1v1 battle


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