Changing coupling cap values for 6v6 Lightning

[guntherbuffalo]

Hi,


I am sourcing parts for my 6v6 lightning style build. I thought it would be good if possible to give the tone a bit of a tweed deluxe character. Could changing some of the Lightning coupling cap values to that in a deluxe help the amp lean a little more towards a deluxe sound?


For example instead of using the 0.0015uF cap from the Lightning on the plate of the first 12ax7, I could use a 0.1uF cap, as in the tweed deluxe, and doing a similar thing for the other coupling caps?


I am guessing this would let a lot more bass through the circuit, and I have heard a lot of people say the Matchless amps are too trebly anyway. Would these changes work against how the tone stack currently works - would it mean I would have to change some of the tone stack resistors to work with the frequency changes ?


I guess not using the treble cap on the volume pot is an option too. A lot of people seem to do that I believe.


Thanks in advance.

[guntherbuffalo]

Awesome! Thanks!


I can see why you have made the changes around the power tubes - 470r resistors and 250/10w resistor (they match what I came up with which is encouraging!)


Would you mind explaining a bit of your reasoning for some of the other changes? Did you get the ideas from other amp schems you have looked at? For example - Any reason for 0.01uF on that 12ax7 plate cap instead of the deluxe's 0.1uF? I would guess because this is a higher gain amp than the 5e3, and that much bass could sound bad distorted?


I have been looking through lots of schems in my free time as you suggested to try and notice similarities/relationships between circuits and various tubes. It gets clearer the more I read!


Appreciate the help!

[tubenit]

Would you mind explaining a bit of your reasoning for some of the other changes? Did you get the ideas from other amp schems you have looked at? For example - Any reason for 0.01uF on that 12ax7 plate cap instead of the deluxe's 0.1uF? I would guess because this is a higher gain amp than the 5e3, and that much bass could sound bad distorted?

I selected values that allow good clear bass and a transparent mid and treble based on my experience. And based on what is often seen in 6V6 amps.

With respect, Tubenit

[guntherbuffalo]

Thanks,


My ideal outcome for this amp would be for it to sound like a tweed deluxe just with a master volume and treble/mid stack. So might use a 0.1uF cap for the first preamp tubes plate.


Would it be worth swapping the first 12ax7 for a 12AY7 to keep leaning towards the deluxe sound?

[sluckey]

Have you considered just building a 5E3?

[guntherbuffalo]

Yes I have, just really want an amp with a master volume  that has a bit more versatility in the tone department.

[sluckey]

I was just curious. I've built a 5E3 and a Lightning. They don't even have a similar sound. I can't imagine trying to make either one sound like the other without destroying the original sound. I still have my 5E3 and always will. Never bonded with the Lightning. It became a donor for a Vox AC-15.

[HotBluePlates]

And the Lightning's tone circuit (like similar Fender, Marshall, Vox and other tone controls) will always scoop the midrange... It's a desired feature of that system of tone control.

Conversely, the Deluxe's single-knob tone control does not scoop mids, it allows you to roll off treble or roll off bass. I think the strong low-mids is what you'll hear as missing when you try to turn your Lightning into a Deluxe.

Your shortest path there (assuming you don't have a fixed control layout due to a pre-drilled chassis and/or faceplate) is to change the fixed midrange setting of the Lightning. Look at the Bass control on the layout. See the 10kΩ resistor to ground? This resistor set your midrange response (and to some extent sets how effective the Bass and Treble controls seem). A blackface Fender uses a 10kΩ pot here when a Mid control is provided, or 6.8kΩ when there is no Mid control (so a fixed setting as though the Mid control was more than halfway up). If you replaced that resistor with a 250kΩ pot (with perhaps the existing 10kΩ between the new pot and ground), you could increase midrange to the point there is no scoop or turn all the way down for a stock sound.

Note that with 250kΩ to ground, at the maximum midrange setting your other tone controls will seem to have little-to-no effect.

If you are buying a kit which include a pre-drilled chassis and/or faceplate, you might consider a mini-toggle switch instead for 2 or 3 fixed midrange settings. Say, one with 10kΩ to ground (stock), one with 250kΩ to ground (full midrange boost, tone controls out of the circuit), and maybe an additional median setting (you could temporarily use a pot to pick a preferred medium setting, then measure the pot's resistance to determine the resistor value needed to emulate it).

[terminalgs]

 

omitting treble bleed pot on volume pot:  If you are building a master volume (MV) amp with the idea that you'll overdrive the preamp with the volume knob at 10, and lower the speaker dBs with the MV, then omitting the 100pf won't matter much, even if the volume is at 7 or 8.


Whether bass frequencies from your E-string turn into air moving from the speaker depend on many things, not just the first coupling cap.  After you look at that cap, look at all of them, and the resistances to ground that follow. For each, solve for low frequency roll-off for all  coupling caps (you can find online formulas and calculators).  Note that caps feeding LTPI's are figured differently.  But also know that bass-frequency response is not couple-cap based alone.


Who knows what you'll get if you swap EL84s for 6V6s (especially if you keep with the lower 290-0-290 PT),   maybe tweak some caps here and there.   It probably won't sound like a matchless, or a vox, or even have a hint of a 5E3.




How did you pick this amp as the basis? 


If you want a 5E3 with more tone-shaping options at a 4W speaker level, then I don't think this amp is the starting point.

[guntherbuffalo]

I chose it because I have seen that CraigB has made a 6v6 spitfire called the "Cragar Atlas Tweed". - The name suggests that the amp would have a "Tweed" sound. The lightning is known as a spitfire but with treble and bass pots so I figured you could do a similar thing with it. Oh well, I guess experimenting with different set ups is what helps us find new good sounds, or at leasts gets us making the mistakes that help us learn!!


In terms of the mids HotPlateBlues. Maybe I will experiment with using the matchless' 10k and the Blackface's 6.8k resistors on the Bass dial to see which I prefer.

[tubenit]

Guntherbuffalo,

I have NO agenda for you and hope you will build whatever you want to build that you will enjoy.  I thought I'd show you something.

The changes I indicated on the Lightning schematic to make it more 6V6 friendly ............... are not that far off from the design I built for my son called the Texas Raptor which he loved.  It was a really sweet sounding amp!  It's my way of saying that the 6V6 Lightning idea I showed you was loosely based on what I consider to be a proven design that sounded good.

With respect, Tubenit

[guntherbuffalo]

Awesome! Thanks! Will have a good look at those two. - Just noticed on both schems - the 2 caps on V3 are .02, but on the lightning you have changed it from .02 to .047.


Why did you make this change when both schems originally had the same cap value here?


Cheers!


Paul

[tubenit]

Regarding changing cap values ...............

Same answer as before, experience from experimenting to learn what I like.  Sometimes, I think the changes are "better" sometimes they are just different in a good way but not better.

Again, these ideas are strictly to consider & I am honestly not pushing any agenda.

With respect, Tubenit

[guntherbuffalo]

Awesome thanks,


I think what I will do is once i get the amp working, I will buy a bunch of caps with different values based on your suggestions/what I see in amps, and experiment to see what I like the sound of. What works and what doesn't.


:D

[HotBluePlates]

I chose it because I have seen that CraigB has made a 6v6 spitfire called the "Cragar Atlas Tweed". - The name suggests that the amp would have a "Tweed" sound. The lightning ... but with treble and bass pots ...

Notice that CraigB's amp has a single-pot tone control, not the Treble & Bass tone circuit the Lightning has. Like I was saying, you'll need to have the option of disabling that Treble/Bass circuit if you want the midrange-heavy sound of the tweed Deluxe.

... the amp would have a "Tweed" sound. ...

You should know there are several "tweed" sounds.

The Champ, Princeton and Deluxe have similar basic sounds, mostly distinguished by power output and whether there is a (single-knob) tone control. The Deluxe augments the tonal options because the unused channel's volume control affects the tone of the used channel.

The 5F6-A Bassman has scooped mids compared to the small amps, is very much louder and is much cleaner until you get it cookin' (which is almost too loud for a mid-small sized club, if you really want it distorting).

The mid-sized amps (Super, Pro, Bandmaster) are about as loud as the Bassman (though not completely, due to fewer speakers), and have a pretty solid sound with only a little sag. The Treble/Bass tone circuit takes some getting used to as you can get a mid-scooped, flat, and some oddly-shaped EQ curves. The controls can interact in ways you wouldn't expect when you're only used to the Treble/Mid/Bass circuit in the Bassman (and later Fenders).

Unfortunately, "tweed" is most used for marketing purposes since the prices of most of those models shot up in the late 80's to early 90's.

[tubenit]

As an FYI, there is a ExpressSCH layout where you can easily edit and modify the values of components to match the Lightning 6V6 values.

Look under Top Cat Reverb schematic and layout.

http://el34world.com/Forum/index.php?topic=2442.0

With respect, Tubenit

[guntherbuffalo]

Great thanks that is useful. I think I may give the 65 Fender Deluxe tone stack a try, to stick with the Fender deluxe theme (be it tweed or not) theme - 250k Pots for the treble and bass. 6.8k mid resistor, 250pF, .1uF, .047uf.

[guntherbuffalo]

Ooo Just found your thread on Tone Stacks Tubenit. You sell that Danelectro Centurion 2-knob stack very well! :D Can't find a schem for it as when I click on it it says access denied. It is treble and bass i presume?

[tubenit]

Did you look at the Dano Centurian schematic in Hoffman's Library of Schematics?

http://el34world.com/charts/Schematics/files/danelectro/danelectro_centurian_275.pdf

I think the attached schematic shows the values I ultimately settled on with the Carolina Blues Special which is still one of my favorite amps and sounded similar to HotBluePlates  5E3 Deluxe when we jammed together.  Except the CBS had a little more headroom and had reverb.

With respect, Tubenit

[guntherbuffalo]

Awesome thanks! Sounds appealing if you say it sounded similar to a 5e3! Would you reccommend that tone stack going before or after the volume pot? Or does it not make a great deal of difference?

[tubenit]

I am not saying the tone stack made the amp sound like a 5E3. 

The Carolina Blues Special has some similar topology to a 5E3 in places such as a similar phase invertor and two gain stages prior to that.  The entire amp (Carolina Blues Special) sounds somewhat similar to a cleaner version of the 5E3 but with reverb because of numerous similarities.

The Dano tone stack needs to be done exactly like in the schematic with tone stack feeding into the volume pot.  The Dano tone stack is somewhat more mid oriented and not as bright as a typical Fender tone stack, IMO.

With respect, Tubenit

[guntherbuffalo]

Ok cool. So if I use the Dano tonestack, and move the volume in the lightning so the tonestack feeds into it, could I still use the 150pF bright cap that is on the volume of the lightning? (I was thinking of maybe making the bright cap switchable as an added tone variable.)

[tubenit]

could I still use the 150pF bright cap that is on the volume of the lightning?

Sure.  But if you're meaning would it sound good,  I have no idea? 

Honestly,  when you do these kind of projects .......... you need to think of a template like this:  30 hrs to build it and the cabinet ..................... 40 hrs more to tweak it. 

When you're in "unknown" space and it's something that is sorta, kinda, quasi new, .................. then you have to accept the responsibility for yourself to make this work. It involves accepting reasonable risks meaning doing something that you can undo without "harm" if it doesn't work out. 

If you want something that you can count on and you know you will like and little to no tweaking is needed, then build a proven design that is very popular.  As soon as you move away from that,  you must have a mindset to build it and tweak it for hours on end to have it work well.

I love my two amps!  The Tweed BluezMeister and the D'Mars.  Having said that, I have tried maybe 30 different designs and while I really enjoyed most of them .......... a few of them were a bust and failure. 

Others have already mirrored some of this back to you before, but you have described something of a moving target that is somewhat undefined.  That's fine!  No problem with that at all, yet it create severe limits in knowing exactly how to offer you suggestions.  Ultimately, you have to decide what you are wanting and willing to do, accept the reasonable risk to give it a try and take responsibility to "own" the success and failure of the amp.

Much of amp building is knowledge and experience.  I have very little knowledge & some limited experience (compared to others here).   AND the other major part of amp building involved perseverance and patience.  I have not keep exact track of this, but I am willing to guess that once I build an amp that I keep one out of five tweaks/mods that I try.

Hope that makes sense and is useful to you as you approach this project.

With respect, Tubenit

[guntherbuffalo]

Thanks, that is very helpful and does make sense. I do understand I am going off on a lot of different tangents, and as I probably seem like I don't know exactly what I want yet, (which is probably true!) - I am still learning how this all works and find all the options in tone etc that you can customise yourself really interesting, and every suggestion I get seems to open up a new can of worms - which I really like, as I really enjoy reading about/researching this, it's a bit addictive!!!


I think I will go for it and just do a lot of experimenting as I build it - I reckon this way I will learn more about the process and how to creatively build an amp. It may not be a surefire way to an excellent sounding amplifier where you know exactly what you're going to get, but I reckon I will learn a lot more this way! Cheers for all the help!!

[shooter]

Tubenit has nailed it for you, I am quite new at this and the more you do, the more you do, or you give up and take up knitting!   document everything as you go so it makes sense next year not just tomorrow otherwise you will do what I have, ask the same, already answered questions.  BTW some addictions are legal!

[guntherbuffalo]

Just thought I would quickly post an edited version of that schem I have just made in case anyone sees any errors I have missed, then I will leave you all alone for a bit!!!. - This is what I will use for my first bash at this amp.


It is the same as the 6v6 edited lightning tubenit posted, only I have removed the old tonestack, and replaced it with the Dano one, feeding into the volume pot - I have also got rid of the trim between V2 and V3, and replaced it with the original 220k resistor as is in the original Lightning.


Cheers!

[tubenit]

I think that has the potential of being a very nice sounding amp.   

And it would be a unique design.  I will look forward to seeing how this unfolds. 

Only significant thing I am wondering is the 100k to ground after the cathode follower prior to the entrance of the LTPI?

I would be inclined to perhaps use insulated alligator clipped wires to experiment with 100k, 220k, 330k, 470k & 1M before selecting something?  OR .......... You could also use a small trim pot inside the chassis on the layout board to "adjust" the signal loss to ground.  You could even do something like a 100k trim pot with 220k resistor to ground.

With respect, Tubenit

[Willabe]

On the CF, why up the 56K to 82K then inset a voltage divider 220K/110K to knock the signal back down again?

Why not just leave the 56K and not add the voltage divider, 2 less parts on the eyelet/turret board.

And why do you want a CF to drive the PI instead of driving the tone stack?


                    Brad   

 

[sluckey]

Changing the value of the cathode resistor in the CF will not change the signal level. Signal level will still be about 90% of the grid signal. And the voltage divider is not strictly needed. In fact, the CF is not needed at all, but it may introduce some tonal quality that would be missing otherwise.

[guntherbuffalo]

Tubenit - Honestly, I was not entirely sure of the function of the "trim" pot that was on the original schem you posted, as I have only seen a 220k resistor and then a 100k on other lightning schems in that position e.g. the Trinity 15 schem, so I switched it to the stock values I found on the other schems.


Willabe - the changes in red were originally made by Tubenit, so I am sure he will be able to explain those changes better than I. Saying that - those changes were made before I moved and changed the tone stack. There doesn't appear to be a CF before the tone stack in the CBS where the Dano stack was taken from so I guess it could jut be removed with the voltage divider, to go straight from pin 8 to the .01cap


Paul

[sluckey]

The trim pot acts as a pre PI master volume. It could be beneficial since you have changed to a different tone stack with different losses.

[guntherbuffalo]

I will do some experimenting and try the amp with and without the 220k/100k voltage divider, or with some of the other options like the 220k/1M, or a trim pot/variable voltage divider as in the Muchle$$ Lightning reverb posted earlier, instead of the 100k to see what sounds good. Also think I will use the crossline MV as in the Ceriatone Lightning, but stick with 2.2M

[sluckey]

The cross line MV is the part I hated most about my Lightning. It never did what I was hoping for. Maybe if the amp had been dimed it would have acted differently.

[guntherbuffalo]

cool. Well will see how it sounds, it will react differently to all the changes I have made anyway. If I don't like it I will try the slightly more complicated dual gang method.

[darkbluemurder]

The cross line MV is the part I hated most about my Lightning. It never did what I was hoping for. Maybe if the amp had been dimed it would have acted differently.

Same experience here. I much prefer the LarMar PPIMV - more transparent to the tone at low volume levels, better tone at all levels below full up and if you have a cut control it will also work better at all levels except full up. When I wrote "except full up" or "below full up" I meant to say it works just as good as the cross line master volume.


BTW my first complete amp build was an amp based on the Top Hat Club Deluxe - basically a top boost preamp with a 6V6 cathode biased power amp. That was in 2008 and that amp has undergone several modifications until today - I stopped counting :)


Cheers Stephan

[tubenit]

The crossline master volume is my least favorite and sounds somewhere between too buzzy to just awful.

I like the LarMar best also.

With respect, Tubenit

[guntherbuffalo]

Fair enough! Dual gang it is then!


Have edited my draft schem again putting the CF resistor back to 56k and removing the voltage divider as suggested by Willabe. Less components = Less potential mistakes. Have started making a layout for this. I noticed the voltage divider is not present in the Spitfire between the volume and the PI.  which is very similar to the Lightning.  If that sounds bad will try the trim idea.

[guntherbuffalo]

Looking at the Hammond 1750 Output transformer. Rated at 20 watts. I am guessing this should be fine. Not sure how many watts this will put out with all the changes.

[sluckey]

Looking at the Hammond 1750 Output transformer.

Which one? 1750 is a whole family of transformers that includes single-ended and push-pull types.

[guntherbuffalo]

Sorry - 1750H.


Also will be using a solid state rectifier and a PT with a 275 or 300v secondary, to raise the plate voltage to around 370 or 420v on the 6v6's, as according to the cheat sheet they can deal with a higher B+ compared to el84s which were originally used in the lightning (I am using JJ 6v6s tubes, which i believe can take 420v on the plates and higher!) I have also found a transformer that has a 250v - 300v - CT secondary, so could even have an amp with switchable B+ for different tones/scenarios .


 I am guessing the higher b+ won't affect the pre-amp tubes too much, as a similar thing was done for the Cragar Atlas tweed? Or will some of the B+ dropping resistors need their value increasing?

[darkbluemurder]

I am guessing the higher b+ won't affect the pre-amp tubes too much, as a similar thing was done for the Cragar Atlas tweed? Or will some of the B+ dropping resistors need their value increasing?

If you want a certain voltage on the preamp tube plates then the B+ dropping resistors may need adjustment.


Cheers Stephan

[guntherbuffalo]

So to add the LarMar master volume, is it just a case of replacing my 2M2 dual gang pot with a dual 250k pot with two 2m2 resistors across 1-2 of the dual gang lugs. Nothing needs to change on the board?


I have seen some examples that remove the 220k resistors from the board, that use a 47pf cap between the 100K resistors.

[sluckey]

So to add the LarMar master volume, is it just a case of replacing my 2M2 dual gang pot with a dual 250k pot with two 2m2 resistors across 1-2 of the dual gang lugs.

yes. Also remove the 220k resistors.

[tubenit]

47pf cap between the 100K (plate) resistors

I would not do that. I've tried it a few times and every time I did,  I felt like it smothered the tone and made it dull.

What has worked for me is the "enhance" cap which you can do a search on.  Essentially, it is a smoothing cap across the plate resistor of the LTPI on the triode receiving the signal from the preamp.  Try a 120p-250p range.  I don't hear it killing any top end but simply smoothing the high end "hash" out and making it smoother. 

It has improved the tone on every amp with an LTPI that I've tried it on.

Just an FYI.   With respect, Tubenit

[guntherbuffalo]

Sounds interesting! For the price of a small Mica cap certainly worth experimenting with! :D Thanks