Another Concept Amp.......

[Jack_Hester]

As I have an abundance of octal tubes.  And, though I made my last concept drawing to be modeled after Tubenit's Tweed BluezMeister 5879, I actually wanted to do so with all octals.  Following his design made it easier to work that drawing up.  This time, I decided to go back and do it with the octals.

The amp draws on one that I have already built, using 6SL7's, 6SN7's, a 6SJ7, 6L6's, and a 5T4 rectifier.  I chose the 5T4 rectifier, because I'll be quite a while using up what I have on hand.  Maybe overkill, by the specs.  But, I have 'em to use.

So, I used a 2-channel input (Normal and Bright), each feeding a triode in a 6SL7.  From there, I combine the signals to feed a triode in a 6SN7.  The signal leaves here and enters the second triode, which is serving as a Cathode Follower front end for the Tone Stack.  

Here is where I borrowed from Tubenit's amp, and used his Tone Stack.  Mainly because it was a copy and paste from my last drawing.  Plus, I had never used it before.  

I followed the same scenario with the OD switching and FX loop, but once again used an octal (6SN7) in the active loop.  

For the Overdrive, I departed a bit from the last by leaving out the Trim and instead using a Morphing Control on my pentode (6SJ7), to serve the purpose of taming the OD.  I used this with success, on a 6SJ7, in the same build that I stated above, though it was a 3rd channel input in the pre-amp of that build.  It transitions from a very mild, clean to a very high gain signal.  Maybe too distorted.  But, it works.  So, I decided to put that in the OD, which in turn feeds half of a 6SN7.  The other half serving as my Cathodyne Phase Inverter, taken from my build design, again stated above.  

Finally, I'm using my Fixed Bias Power section, with adjustable Bias, splitting out the two, for individual adjustments.  As I'm not trying for lots of power, and have many metal-canned 6L6's on hand, the design of the Bias is around them.  I went through a large number of them, trying to find some close enough to be considered matched, and it didn't happen.  The build that this power section comes from only has a single adjustment.  I used that amp to try and find a fairly close pair.  I finally settled on two, and biased it to split the difference.  With this, I hope to set the idle Bias and hope that they are close, when the amp is anything but at idle.  

Please take a look at this first draft, and comment.  Please note any discrepancies and suggest mods that may improve.  It is a concept, only.  I know the front end and the tail end work just fine.  The in-between is unknown.

Also, the name Sonitus Lepidus is from Latin, meaning Pleasant Sound or Good Sound.  You'll also note that this is version VIII.  Version I was built.  The 6 in between are on paper, only.

Jack

28Jan14 - Note: See below for rev-C. 

[sluckey]

I know that your schematics make sense to you but your colors make it very hard for me to follow.

Not being critical, just making a statement.

[Jack_Hester]

Thanks for the comment.  I can understand the confusion with some of the colors.  My drawings are on a black background, and my signal wires are white.  That's just one example.  When plotted to paper or PDF file, the white wire colors and white text are converted by ACAD to black, which in the amp world is a negative DC line. 

So, I let the black stay as my signal wires, and I use green for my negative DC line, though I would normally use it as Earth Ground.  Is there another color that is acceptable for signal wire color?  And, negative DC line color? 

The component colors are taken from those that have been used by our plant, for the past few decades. 

ExpressSch uses all black, and I'm fine with that.  But, I like color changes to better follow a line from point to point, though the color yellow is almost impossible to read on a white background. 

Is the schematic, itself, difficult to follow?

I'm open for suggestions, as I want them to be easy to read. 

Jack

[overtone]

Jack,

I don't get much time to contribute here, but I'm always interested in what you are up to. We are so used to those old Fender schematics that it can take a while to get used to a different schematic style. I really like the schematics that Tracy Norton drew up (member KT77). They break down each section of the amp into a single page and allow a lot of space to allow the eye to flow through the circuit.

I trained as a draughtsman in the days when we used to sharpen pencil on emery paper, then we had races with the new fangled computers and, for a while, we won. These days I use AutoCad but have noticed that a pencil drawing can communicate the intention much clearer than most CAD drawings. It is a huge skill to get a CAD drawing to convey the most important information because the environment tends to treat everything equally.

I understand your use of color, but it is risky because when printing in black + white you may loose some. I'm loosing the greens as shown on the b+w gif of part of the schematic that I made. (Cross fingers that it loads up)

But apart from that, I have some tips that may help the legibility:
- try not to rotate the tubes
- try to line the components up along imaginary lines: plate resistors all at the same height, cathode Rk and Ck all down below sitting at the same height
- give more line between the components to allow more space
- make a second page if it is getting cramped

All the best, tony

[Willabe]

Hi Jack,

Here's a couple more ways for a dual -bias, got them from KOC TUT books.

They will NOT work with an amp that has -bias tremolo on the output stage.

It should be a little cleaner raw -bias voltage with the 2x20uF caps and R (pi filter), probable not a big deal but your using 2 caps anyway. Also if the wiper on your -bias pot ever fails you'll lose the -bias voltage and that tube will fry, these are wired up that if they ever fail the tubes will get the full -bias voltage so you'll lose most/all the volume but the tubes won't fry.    


                Brad    

[Jack_Hester]

I understand your use of color, but it is risky because when printing in black + white you may loose some. I'm loosing the greens as shown on the b+w gif of part of the schematic that I made. (Cross fingers that it loads up)

But apart from that, I have some tips that may help the legibility:
- try not to rotate the tubes
- try to line the components up along imaginary lines: plate resistors all at the same height, cathode Rk and Ck all down below sitting at the same height
- give more line between the components to allow more space
- make a second page if it is getting cramped

Points taken.  I'll work on my symmetry a bit.  My problem is that I draw as if the components will go together as the actual build.  I suppose they don't need to be in the schematic.  I'll spread them out more.  Also, I have now darkened my green for signal grounds.  When plotted to a PDF, it is just light enough to see as green.  Should print in black and white better.  Also, I'll hang a ground symbol on the line, too.

Thanks for the tips.

Here's a couple more ways for a dual -bias, got them from KOC TUT books.

They will NOT work with an amp that has -bias tremolo on the output stage.

It should be a little cleaner raw -bias voltage with the 2x20uF caps and R (pi filter), probable not a big deal but your using 2 caps anyway. Also if the wiper on your -bias pot ever fails you'll lose the -bias voltage and that tube will fry, these are wired up that if they ever fail the tubes will get the full -bias voltage so you'll lose most/all the volume but the tubes won't fry.   

Thanks, Brad, for the diagrams.  I'm thinking that I like the Bias Balance better.  I'll work one of those up on my next revision. 

Keep the comments coming, please.  At some point, I'll make a layout to go with the design.  Have a good one. 

Jack

[Willabe]

I'm thinking that I like the Bias Balance better. 

In the end they both do the same thing even though they have a different name.

I think 1 has 1 less R so it's pretty much a wash either way.


             Brad     

[Ritchie200]

Hi Jack!

You mentioned you like to lay them out like it will go together.  Years ago Doug posted this layout and I have to tell you, numerous lights went on in my noggin about what does what and why the layout is the way it is.  I hand draw everything or take existing schematics and use colored highlighters to make it look similar to what Doug did.  It really helps me keep things in order and I find I am not missing that odd ground or signal path connection!  I'm now used to these colors, just like you are with yours.  I sure do like how Doug lays things out.  Makes a lot of sense to me.

http://www.el34world.com/charts/currentflow.htm

Jim

[PRR]

> your colors make it very hard for me to follow.

Also 1/8" lettering on 48-inch paper.

> better follow a line from point to point

I'm wondering why that green ground line jumps up and down. Worse than the ground on my property. _I_ tend to draw two strong horizontal lines (power and ground), and build in from there.

I'm also no fan of "socket pinout" drawing. A schematic, to me, is for circuit function thinking. Pinout doesn't come into the picture until Build. Yes, I see you wish to use the same drawing for Build. And your work with the twin-triode Octals is not so tangled as the old Rider radio schematics (aghk!).

> Years ago Doug posted this layout and I have to tell you, numerous lights went on in my noggin

Yes, that's an excellent drawing for someone who has not yet digested how amplifiers work. And if you work on same/similar layouts ALL day, you do start to think that way. But for basic discussion of a new amplifier plan, when you "know" (kinda) the general idea of amplifiers, a physical layout or even socket pinouts just IMHO gets in the way.

I did stare long enough to wonder why there are two bias rectifiers. They deliver the same thing. Total bias demand is far-far less than one rectifier can supply. Seems to me just more parts to fail.

Also wonder about 5T4 feeding two 6L6 at low impedance. It's more a 6V6 size of diode. Seems to me the full-power voltage will sag bad. And brush against 5T4's rated limits. If you have a bucketful, you could keep replacing them. Or if you have the 5V, you could run two (and get a "Twin Rectifier" badge from somewhere).

[Jack_Hester]

Also 1/8" lettering on 48-inch paper.

Will work on larger component labeling, as well as text.  I have found that if I plot to a large sheet, my numbers/text are high resolution when zooming in.  Not intended for printing to the same sized sheet.
 

I'm wondering why that green ground line jumps up and down. Worse than the ground on my property. _I_ tend to draw two strong horizontal lines (power and ground), and build in from there.

I'm also no fan of "socket pinout" drawing. A schematic, to me, is for circuit function thinking. Pinout doesn't come into the picture until Build. Yes, I see you wish to use the same drawing for Build. And your work with the twin-triode Octals is not so tangled as the old Rider radio schematics (aghk!).

Will try to improve to improve my grounding presentation.  And, I'll work on spreading out the components, dividing up the tube halves as needed.

I did stare long enough to wonder why there are two bias rectifiers. They deliver the same thing. Total bias demand is far-far less than one rectifier can supply. Seems to me just more parts to fail.

Also wonder about 5T4 feeding two 6L6 at low impedance. It's more a 6V6 size of diode. Seems to me the full-power voltage will sag bad. And brush against 5T4's rated limits. If you have a bucketful, you could keep replacing them. Or if you have the 5V, you could run two (and get a "Twin Rectifier" badge from somewhere).

As to the Bias rectifiers, just a first draft idea.  Brad posted a couple ideas from TUT.  I'll use one of those on the next draft.

I literally have a bucketful of the 5T4's.  As this is an experimental circuit (for now), the 5T4 will suffice.  Though, it may look cool to put two in tandem.  I won't rule that out, as sometimes novelty takes presidence over practicality.  For the moment, sag won't be an issue.  Will keep that in mind, if and when it does become a reality.  And, I will go ahead and draw two in tandem, just for the sake of novelty.  If the circuit inspires someone to try it, a single tube rectifier can be edited into the drawing easy enough. 

I really appreciate the comments and observations.  Continue to critique, as I want it to be a good build.  Have a good one.

Jack

[sluckey]

The green lines on a white background are really hard for me to see. By the time I zoom in close enough to see them clearly, I lost the big picture. Probably just these old eyes.

[Jack_Hester]

The green lines on a white background are really hard for me to see. By the time I zoom in close enough to see them clearly, I lost the big picture. Probably just these old eyes.

I've darkened the greens, but have not plotted a second time.  I've got the weekend off, so tomorrow will be a good day to revise, and try to implement some or all of the suggestions. 

Please look the circuit over and make note of any improvements in the design.  Thanks for your comments.

Jack

[PRR]

I confess that many tube-amp schematics annoy me.

Here's one I almost like:
http://www.el34world.com/charts/Schematics/files/selmer/selmer_zodiac_twin30_.pdf

The 4-page has good and bad. Certainly page-splits have to be on logical block-breaks, and this one is. (One preamp, another preamp, final, power.) Signal flows left to right, overall and in detail. Power flows top to bottom (I'll forgive the output stage ground return in the middle). Further it is BLACK and WHITE, no grey jaggies (like well inked velum, and quite unlike JPEG or some PDF conversions).

[Jack_Hester]

Ok.  Next draft of the pre-amp and Tone Stack.  I'll hold off on the rest, until I get this ironed out.  Hopefully, this is easier to follow.  I'll enlarge the component labels the next time around.  Comments, please.  If this is easier, I'll continue on with remainder of the amp.

The grounds are a darker green, than before.  But, if I make them any darker, they'll pass for black.

Jack

28Jan14 - Note: See below for rev-C. 

[overtone]

I confess that many tube-amp schematics annoy me.

Here's one I almost like:
http://www.el34world.com/charts/Schematics/files/selmer/selmer_zodiac_twin30_.pdf

The 4-page has good and bad. Certainly page-splits have to be on logical block-breaks, and this one is. (One preamp, another preamp, final, power.) Signal flows left to right, overall and in detail. Power flows top to bottom (I'll forgive the output stage ground return in the middle). Further it is BLACK and WHITE, no grey jaggies (like well inked velum, and quite unlike JPEG or some PDF conversions).

that one is drawn by member KT77 that I mentioned above. I learnt a lot from him.
I sketch myself a block diagram if the there are more than five pages or so, in case I loose the plot and fall off the edge. It is amazing how drawing helps one to see and to understand.

[overtone]

getting better
here is a quick b+w gif

[Jack_Hester]

Just about as quick as I posted it, I realized my copy/paste of V1b still had the same pin numbers as V1a.  The fixed pre-amp is now in place of the previous PDF.

Jack

[Jack_Hester]

You mentioned you like to lay them out like it will go together.  Years ago Doug posted this layout and I have to tell you, numerous lights went on in my noggin about what does what and why the layout is the way it is.  I hand draw everything or take existing schematics and use colored highlighters to make it look similar to what Doug did.  It really helps me keep things in order and I find I am not missing that odd ground or signal path connection!  I'm now used to these colors, just like you are with yours.  I sure do like how Doug lays things out.  Makes a lot of sense to me.

Jim -

Sorry, for being slow in responding.  I don't multi-task very well.  Got my mind on work and the freezing temps that we're having around the clock.  

Thanks for the link.  Colors help me to follow the flow of the schematic and layout.  I'm learning layout methods.  We had no such layouts when I first studied tube electronics.  At least, not that I remember.  The same, when I started work at the power plant.  I really enjoyed those days, as we did all component level repairs, and even some new, one-off builds on tagboards.  The company was too cheap to buy us replacement, populated boards.  So, we either repaired them, or built them from scratch.  They finally realized that it was cheaper to buy.  I'm sorry they did.  

Most were solid state, but our old trend recorders were Leeds and Northrup, and some had tubes.  I salvaged quite a few of those (tubes) back then, never thinking about how I'd use them.  Just a natural pack rat.  Sure glad that I did.  

Jack

[tubenit]

Man, I hope you (or someone) builds this.  Very intriguing amp design using octals.

THANKS for sharing the design.  I like what I am seeing of it. 

With respect, Tubenit

[Jack_Hester]

Man, I hope you (or someone) builds this.  Very intriguing amp design using octals.

THANKS for sharing the design.  I like what I am seeing of it. 

I must confess.  Going into our outage season at the plant means very little shop time, once the lawn starts growing.  And, cold (as in day and night freezing) at the plant, has not been the norm for the past several years.  The coverage is eating into my down time that I usually enjoy in January.  So, drawing is as close as I may get for awhile. 

However, Silvergun's threads on breadboarding has me intrigued.  Just like your amp designs, as well as those of others, I am inspired with a bunch of "what if's".  Yours already inspired two of them, recently.  Silvergun's pictures made me make a couple trips out to my shop, each day when I get home from work, to browse through what I may have to fabricate such as what he's built.  That means that I may be able to do more than drawings, in the short time spells for building. 

Anyway, today is 'inside' day.  With maybe another quick trip out to the shop to look closer at a panel that may serve as the base for a versatile breadboard.  Of course, that naturally goes into a drawing.  But, I'll hold off on posting any of that, until I know what I'm doing there. 

In the meantime, I'll finish out the existing schematic (the model for it will remain intact, for now), and submit it as the next revision for much needed scrutiny.  Then comes the layout.  My tendencies are still strong, to draw literally as one might build.  The Dark Side is still ever present.

More to come.  Have a good one.

Jack

[Jack_Hester]

Ok.  I'm going to take a 'brain' break from drawing, and post what I have completed, so far.  

This revision may have gone a bit overboard, but drawing's fun.  A bit tiring, but fun.  I spread it out, and blocked each section.  Maybe not necessary, but I'm thinking of those who may be looking at such for the first time.  

Larger component labels come on the next revision, along with one of Willabe's Bias schemes.  This time, I'm just getting it presentable.  If I haven't implemented all suggestions, they'll all (hopefully) come as time permits.  One thing.  The transformers are not necessarily the ones to use.  Again, a copy and paste from the original iteration of this amp.  The same iron that Tubenit used on his Tweed BluezMeister should suffice.  

Take a look and comment.  Thanks for the suggestions, so far.

Jack

28Jan14 - Note: See below for rev-C. 

[Jack_Hester]

Man, I hope you (or someone) builds this.  Very intriguing amp design using octals.

The breadboard guys could have built this, in almost the same time it's taken me to get this far.  Maybe they'll inspire us all.  They've inspired me.

Jack

[Jack_Hester]

I couldn't stop.  I added the Bias suggestion, from Willabe's drawing.  

Now, for a break.

Jack

28Jan14 - Note: See below for rev-C. 

[Jack_Hester]

Even though this says rev-C, I'm not posting the major changes, just yet.  I've begun the layout in this one, but it's not ready for posting.

The reason for this is that I really didn't like the boxes around the different stages, so I eliminated most, and left dividers between each.  Makes the schematic more open.

On this drawing, I presented those individual stages as separate pages, to save zooming in on the whole.  Plus at the end, I added the whole just for reference, just in case one loses sight of the connections between.  This circuit is somewhat basic, but spread out.  Reminds me of most 60's vintage Ampeg schematics.  You do a lot of zooming in and out, as those are very busy schematics, and cover a lot of real estate.

So, I'm leaving rev-B, until I finish the first draft of the layout.  Then, rev-C will be it.  More revisions will come, if mods or suggestions dictate.

Jack

28Jan14 - Note: See below for the completed rev-C. 

[Jack_Hester]

I was fortunate to get a copy through the company, at a killer discount.  It's not been offered since.  Mine is an '05 version, which is still very up-to-date, as far as CAD work goes.  I haven't been required to do CAD drawings (electrical, only) since before then, but I took advantage of the cheap buy. 

I've used DraftSight before, and it would be my choice, being familiar with ACAD. 

I create layers for everything.  Not colors, but components/wiring.  Resistors, capacitors, transformers, signal wires, signal grounds, B+, tubes, all the labels, etc..  From time to time, I need to turn off certain layers, just so that I can see one tree in the forest.  By doing so, I can see what needs to be changed, to make the drawing less busy.  For instance, the layout that I'm working on had all the connections drawn.  What a mess.  So one by one, I followed Tubenit's lead and started putting bubbles on either end of a termination.  Bottom connections on my turret board have letters.  Top connections on the board have numbers.  Cleaned it right up.  I'm still not finished, but almost there (with the first draft, that is). 

I'm not a CAD expert.  Training was out of necessity (at the plant), in order that we could keep a grip on our drawing revisions.  But, that all went away, so I do it for my own enjoyment and needs.  Same for the hobbyist programming.  I was working from DOS machines, and some VAX, when I had to do that (boiler controls).  Now, for the same reasons.  My enjoyment. 

Anyway, I can learn a lot from 'real' CAD users, so drop the hints from time to time.  I'll truncate something going on in my head, to make room. 

Jack

[Jack_Hester]

Ok.  First draft of layout is finished.  Now I'll begin the tedious process of picking it apart, to better group sections.  The Bias is one that I'm not entirely satisfied with.  But, I got it all on the drawing.  I put the board dimensions in, so that you can see just how spread out it is.  Anyway, when I get the chance, I'm going to print it out on an 11"x17" sheet, schematic and layout, separate.  And, check for accuracy of transfer from schematic to layout.  

It was very enjoyable, but very tiring.  The hard part is done.  Please make suggestions, if you see some obvious improvements in the layout.  Sketches, please, if you do.  

I'll remove the other drawings, and post this as the first complete one.  More to come.  Have a good one.

Jack

29Jan14 - Note: See below for the corrected rev-C. 

[Jack_Hester]

Compacted the Bias layout a bit, allowing me to shorten the mainboard some.  

Corrected a component label.  I had one too many R15's (the hazard of copy and paste) in the schematic, and carried it over to the layout.

Corrected a plate resistor value in V1.  

Created a BOM, which shows just how busy this build is.  I didn't put the transformers on the BOM, as that can be a builder's choice.  The schematic still shows the transformer info, but for reference only.  Also, the rectifier tube is at the discretion of the builder.  It can be something other than the 5T4 that I chose, as I have many of those.  A 5AR4/GZ34 will be a more common tube.  

This is still rev-C, as there are no real changes.  Just cleanup.  

Jack

[Jack_Hester]

And, here's rev-D.  The only change is to the FX Loop.  

I implemented Tubenit's/Silvergun's Parallel FX mod.  I followed Silvergun's lead on eliminating the Send Level pot, and using it for a Mixing pot.  Please check my work, and confirm that both the schematic and layout are as they should be.  

I'm leaving rev-C, so that the original FX Loop remains intact.  

Jack

02Feb14 - Note: See below for the corrected rev-D.  This one includes a BOM. 

[Jack_Hester]

Just minor corrections, this time.  I left out a ground on the FX loop, when I made the mod.  That's back in.  

Included a BOM.  No change from rev-C.  But, I didn't include one with rev-D, so here it is.  

Jack