pointers for the noob

[fossilshark]

i recently just spent the $400 on parts to build my first tube amp. ive done alot of solid state amps and ive been designing and researching this build for almost 6 months now. My main concern is the point to point construction on terminal strips i plan to do. i cant find any videos or instructions on how to do this correctly. im not building a turret board, i would prefer to use terminal strips for this build. does anyone have a video or something on p2p wiring with terminal strips? any other advice would be great. i am aware of the dangers of high voltage, i know to use shielded cable for signal lines, to keep the power and output transformers away from eachother, and im using the best-money-can-buy tubes (all brand new sovtek and electro harmonix). any advice is appreciated. thanks!
p.s. when i paralell my 6v6gt's its just connecting the output lines of the tubes together? any info on parallel tubes is helpful.

[eleventeen]

some disconnected thoughts:


-In general, I would probably arrange the terminal strips in two parallel lines and suspend the parts in between them.


-Look and study very, very carefully at the "official" Fender layout of the parts board in the model amp you wish to build and try to duplicate the general layout and sequence. This IMO is your best (well...second best) chance for success, let there be no question.


-make your layout on paper and diddle with it as much as necessary to make you happy such that when it comes time to build the real thing, you are making no changes of any kind, you are just "painting by the numbers", not thinking, just following the sequence of parts.   

-you will probably note that parts occur sort of in "clusters" and it is a good idea to leave a blank space every now and then, because the big smelly deal with terminal strips is if you goof up and forget to allow for a lug you need, it shoves the whole rest of the circuit down one lug and many times this creates weird issues...and if this is your first....it's safe to say this will probably happen to you.

-Not every part will span the entire width of your two major term strips. There are circumstances where you will need to connect a part to outer terminal strip "A" and outer terminal strip "B" but will want to make a connection in the middle. This, in my experience is the hard part to arbitrate. IF you make the two outer strips far enough apart to accommodate two parts connected "in series" they will be sort of too far apart for just a single resistor. Work it out on paper and don't be surprised if it takes several attempts. You really have to study some Fender layouts to get the gist of this, and if you are building a simple amp like a 5E3 Deluxe, go look at an AB763 amp with reverb and tremolo and get a feel for how Leo did it. 
 
-Most terminal strips, you lose the end terminals OR they end up being ground lugs which means they can't (or ought not be) used as tie points....at the risk of creating ground loops, because for low noise and no-hum we like to control our ground connections and make them at specific points. There are known, proven ways to do this and not to do this and we can help you and it is silly to try to invent something "novel".

-On Google images, there are some internal pix of Sunn amplifiers which were P2P.....look for Sun Sorado or Sunn 200S


https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwj3td-mx7jOAhVE8GMKHYWbBcYQjRwIBw&url=http%3A%2F%2Fmessageboard.tapeop.com%2Fviewtopic.php%3Fprintertopic%3D1%26t%3D35816%26postdays%3D0%26postorder%3Dasc%26%26start%3D15%26sid%3Dc507b47709518a093b92514e8b806790&psig=AFQjCNFKbjmaJ6_z2Z80zWSKYmyW5d5tfw&ust=1470977195085266

I am not sure what you're asking with "parallel tube" question...is this going to be a push-pull output config? Or are you paralleling tubes for a powerful class "A" amp?


*****************

-At the end of the day....I will assure you with total certainty, as a total cheapskate and one who scrounges parts and who has home-built Fender amps for 40 years....you will make your life 50 times easier buying the damn parts board. You've already spent $400 on parts. For $25 or $30 more, you will end up with better looking innards that we can help you troubleshoot should it become necessary, you will save half a dozen hours working out the layout (yes, if it is your first, it will take that long) and if your time is worth $5 an hour...in my humble opinion it is false economy not to use a/the parts board.  Turret or eyelet, makes no difference, eyelet is a bit cheaper.


End of sermon.

[fossilshark]

i  using a powerful class A, not push pull. thank you for the input

[MakerDP]

I've done a couple smaller builds on terminal strips. If you use a "can capacitor" it really simplifies things.

One trick with terminal strips is to use the top loop for component leads and the lower hole for wires. Really cleans things up and makes soldering a little easier too.

[MakerDP]

Do you have a layout of the amp already made or do you have to make your own?

[fossilshark]

im working on drawing up the terminal strip layout tonight. ill have it done by tomorow

[labb]

If you are not trying to do true P to P, take a look at a Hoffman Turret board and sub the terminals for the turrets.

[fossilshark]

thats pretty much what im doing. im basically designing a turret board and replacing the turrets with terminal strips. im trying to make this look extra impressive because im building it to show to my electronics teachers (im going into 11th grade) and i want to show them that i can do more then the crappy lm386 amplifiers they have the class do. and i really want a tube amp.

[eleventeen]

There are kind of two (at least) ways to execute P2P in tube amps that take advantage of terminal strips as support elements. Way #1 is to line up the terminal strips as if they were the outer terminals on an invisible parts board, then make the connections to the tube sockets "somewhere else". This is like the Sunn amp pix I linked to, above. The other way is how many Tektronix scopes were wired, which is to place the tube sockets in a row in between the lines of terminal strips, in which case most of the components mount from a term strip lug to a tube socket pin. This in some cases solves the issue that I originally stated, which is that plenty of times you want to mount a string of parts from one strip to the other and make connections from the junctions formed; but there is no official support for the junctions. It also produces problems of its own in that the rotation of the tube socket becomes somewhat important; you don't want to run parts leads across the tube sockets more than a scant few times, if you can avoid it.


In your situation, you have not looked at tube circuitry for 20+ years and have not seen hundreds and hundreds of examples from audio, industrial control, test gear, aerospace-grade tube gear, old TV sets, and misc consumer gear. Because that is really what it takes. The thing about hand wiring with tubes is that decision #2 affects decision #4, decision #25 and on and on down the line. Things you do at the beginning affect things way way down the line and it is very easy to back yourself into a corner that you simply cannot see from step #1, #2, and #5. I've never found a solution for this other than to provide for some spare terminals.


I would strongly suggest at google images you search for "Tektronix scope wiring" or "tube amp wiring" for some ideas. I found some good pix

[VMS]

Forum member darryl makes nice terminal strip amps. Here is a good example:

http://el34world.com/Forum/index.php?topic=20374.0

[VMS]

Carr amps use terminal strips:

https://www.youtube.com/watch?v=3Ms9EnR2FBI

[fossilshark]

thank you for all the tips. ill be keeping this in mind as i build the layout. i do plan on putting 4 or 5 extra rows of terminals in case i do mess up.

[fossilshark]

this is my layout. most of the power supply wiring wont need terminal strips or ill just throw in a 3 lug strip were the power transformer wiring comes into the chassis.

[HotBluePlates]

When I built my 25L15, I used the "Tektronix style" approach Eleventeen mentioned in his post earlier.  Yes, they are turret lug strips instead of terminal strips, but the construction is functionally the same (Tek didn't use terminal strips either, but ceramic rectangles with metal-covered notches).

You could do the same, but widen the space between the tubes and the terminal strips, and have resistors/caps which run with one leg on the terminal strip and the other leg in the tube socket pin.

Any good layout using this approach of "socket between parallel strips" requires good planning with a basing diagram of the tube (seen from inside the chassis) so you can determine the logical placement of parts for short wire runs which don't cross needlessly.

[eleventeen]

We could do a better job of critiquing your layout if we had a schematic of what you were looking to build.


Most simple LM386 circuits built on a perf board or plug-in breadboarding deal have very short leads and use very well filtered power because it's so cheap to filter the supply. ANd they many have common-mode noise rejection anyway so they are inherently quiet.  There is no AC anywhere near the circuit. So, lead dress is very forgiving.


In a tube amp, we have 6 VAC heaters right near our signals and 20-50 times as large as our signals and we have big signals right next to small signals. We have multiple circuit segments and snippets and connectors that are returned to ground. Some of those grounds are power supply and some are signal and (for optimum results) they have to be treated a bit differently, with the main layout rules observed. We have 120 VAC and we have power supply ripple that could be 20 times the size of some of our signals. Some of these elements can be remarkably UNforgiving when it comes to running this wire over here and that one over there.


Kind of like I said earlier, with early decisions impacting later ones.....it is very very easy to 1: work hard on your layout. 2: Have the layout dictate the mechanical positioning of the tubes and trannies and jacks and controls (anything that requires a drill or cutout to mount 3: Mount the mechanicals where it seems like your layout would want them to go and 4: end up with a very grumpy hum monster that cannot be cured because it violates the mantras of lead dress and layout rules. Which are not complicated, really, but they will make you hate life if you violate them and then have to tear your project apart and have big open holes unless you plug them. And even then you have a kludgey thing with obvious drilling and cutout errors. 


Most noobs look at the guts of a Fender amp, for example, and think, "how primitive, just line this stuff in any kind of row and it will fit Leo's narrow chassis style and away we go. I could put anything anywhere and it would work, this is so simple".


What you see in the wiring of an old Fender amp (but only after you've seen dozens of them) was in many cases worked out over long periods of time or trial and error and dogged hum reduction work, and like many things, inexperienced folks don't have the innate appreciation for what went into these things.

[fossilshark]

i forgot to add the second 6V6 into my layout, man that could have been bad. good thing im still waiting for parts to come in. heres my schematic. can anyone tell me if my 6v6 in parallel is wired right? i was originally using the power amp from the basic fender champ amp but when i was buying the tubes i ended up getting a matched pair of 6v6s and someone suggested i put them in parallel for a little more sac on my amp. i know paralleling tubes isnt a very effecient method but i have all the parts and im already almost over budget so its my plan for right now. for a power supply im using a 5y3gt recifier. the 400v is actually going to be more like 350v after rectifier drop.

[eleventeen]

Do you know for sure if that schematic is of a proven functioning amp??


R24 10K seems like an impossibly high value for that position in the amp, it would badly choke off current to the paired 6V6. 35 mils (perfectly plausible amount of current for a pair of 6V6 in class A) through a 10K resistor would drop 350 volts and the resistor would dissipate 9 watts which means you'd want a 20 watter and it would still get fairly hot. You'd end up with maybe 25 volts on the plates of your 6V6 and they wouldn't produce spit in terms of voltage output. Usually the plates of the output tubes get the full on B+ with no intervening resistor. From that "highest of the high" B+ you string out resistors to provide lower voltage B+ levels to the PI and preamp stages. We usually call those power supply "nodes" which, again, referring to an AB763 Deluxe Reverb, are labeled "A", "B", and "C" and "D" high-to-low. The nodes are separated by 1K, 4700 ohm (aka 5K) and 10K resistors, usually 1 watt or better. Each node usually gets a filter e-cap of its own, for decoupling. Those other stages use massively lower current than the output tubes and it's not at all uncommon to see a 10K in the string. 


I'd also want a 470 ohm resistor from plate to screen on each tube, again, you can mount them on the tube socket from pin 4 (screen) to pin 6 (unused pin). This is exactly how Fender does it, consult any AB763 Fender schematic (even more, the layout dwg) for Deluxe Reverb.

I would use grid stoppers on the 6V6, usually 1500 ohm which you can wire from pin 1 (unused on 6V6) to pin 5 (G1, input grid) and feed the input signal to pin 1, the resistor carries the signal to pin 5.


I am not definitely mentioning ALL the things that strike me as unusual about that circuit. That's a pretty unusual beast, for about half a dozen other reasons.

[PRR]

My advice-- the questions you are asking, you should start with a simple known-working plan. I suggest any early Champ. Millions of them were built, so they work. One 6V6 is plenty of power, and a lot more than you will get with the circuit values you posted.

[fossilshark]

i designed that using the preamp from a marshall and the power amp from the champ. here are the schematics.

[Willabe]

im trying to make this look extra impressive because im building it to show to my electronics teachers (im going into 11th grade) and i want to show them that i can do more then the crappy lm386 amplifiers they have the class do. and i really want a tube amp.

Maybe try a Vibro Champ? It has bass/treble tone controls and vibrato.

http://el34world.com/charts/Schematics/files/fender/Fender_champ_vibro_aa764_schem.pdf

[sluckey]

and the power amp from the champ. here are the schematics.

But your schematic is wrong. The OT should connect to the right side of R24.

[fossilshark]

im eliminating R24 and one of the 4uf caps

[sluckey]

im eliminating R24 and one of the 4uf caps

You need R24 to drop voltage to the screens and you need both of those filter caps. In fact, you really need an additional filter cap on the left side of R9. IMO 4µF is too small for good filtering.

[VMS]

I think the cathode follower before tone stack is wrong. You don't need that R15 resistor.

[Willabe]

Do you play guitar? (Or any instrument?)

[fossilshark]

yes i play guitar lol im building this to replace my "frankenamp". its a crappy crate practice amp wired into the speaker cab of a different practice amp. would 16uf be too much to replace the 4uf filter caps with? i was told if they were too big they would draw too much current on startup and blow the rectifier. and wont r24 drop the voltage too much? what is a good value there. im thinking i should put one 16uf cap before r24 and another after r9, would that be ok? and i just want to say thanks again for all the help i really appreciate it

[sluckey]

5Y3 will be happy with 32µF. 10K is fine for R24. That's the value that Fender used on the champ. But you still must connect the OT primary to the right side of R24 (referring to your schematic).

There are still other issues such as eliminating the plate resistor on the cathode follower and adding a filter cap on the left side of R9.

[fossilshark]

heres the updated schematic. took out r15 and added the filter caps and fixed the OT primary.

[sluckey]

Getting closer. Now you need to put a cap on the LEFT side of R24. Don't know why you deleted that?

[fossilshark]

i meant to change it to 16u but forgot to replace it, problem solved. is there anything else?

[HotBluePlates]

C14 and C17 should be 22µF instead of 0.22µF.

A single-ended amp would likely benefit by having a filter cap to ground and a choke (or ~500Ω resistor) between the rectifier and C15 where the OT is attached. This will cut overall ripple some, which is not attenuated at the OT the way it is in a push-pull amp. If you use a choke, it will have to support the current of the entire amp, which would be easier (lighter, cheaper) if the output stage were a single 6V6 instead of dual-6V6.

[fossilshark]

22u on c16 and c14, are they in the right polarity? i feel like negative should go to ground but i seem to remember (maybe incorrectly) one of my teachers saying the signal should flow from negative to positive. and if theres too much hum (im expecting at least a little) ill add in a choke

[sluckey]

22u on c16 and c14, are they in the right polarity?

No. In this case, positive goes to tube. Negative goes to ground.

[fossilshark]

ok thanks. i need to redo the layout due to the changes in the schematic and the terminal strips i ordered are different than the ones i used to make the original layout. ill have that soon

[sluckey]

Why not slow down a bit and get the schematic just like you want it first. Layout will be easy once the schematic is solid. What you have now is workable but may need some tweaking.

[fossilshark]

where would i add a preamp gain pot?








/

[HotBluePlates]

where would i add a preamp gain pot?

You already have one: R3.

R10 & R11 form a fixed voltage divider, which can be naturally replaced with a pot. If you still want some signal-loss at that point, you could add a series resistor before the pot, as is the case with R4 going in series with R3.

[fossilshark]

i thought r3 was preamp volume? i need a pot to control how much the preamp overdrives, would r3 do that?

[eleventeen]

I hate to be the continuing voice of doom here, I just hope you realize there is no way at all to achieve a layout that you want to end up being neat (to impress your teacher) never mind possibly working as a functioning amp until your design is settled on and frozen.


Honestly I think you should go look at a Fender 5E3 Deluxe circuit (or, a AA764 Champ; or an earlier Champ) and just stare at it/them for a few minutes. First; the schematic. Second; the layout. Here is something so simple, so primordial, it's beautiful in its simplicity. Like a Telecaster. Classic. Minimalist. Still made today, 50+ years later. And it's not because it's a Fender, it's because it hit the right spot like very, very few things in the world as we know it today. It's like it rose up out of the swamp. I know a 5E3 would be problematical for you because you have a single ended output tranny. But that, other than some R/C value changes is the only rub.

Still. The exercise achieves little, in fact it achieves the opposite if you have a sloppily wired non-working amp, better if you have a nicely wired non-working amp, but best if you have a nicely wired working amp that you might actually use.


The parts you have bought will not build themselves into a working amp just because you spent money on them.

With that in mind, it's my humble suggestion that you change to building a 5E3 Deluxe.

[fossilshark]

i appreciate the suggestion, and ill definitely take it into consideration. im going to try this as planned because so far it seems like it should work, and if it doesn't ill rip it down and make a fender champ. here's my layout, im going to put the tube sockets in between the parallel strips like a tektronix tube oscilloscope. the spaces between the strips are the spaces the mounting holes on the strips take up.

[sluckey]

I like that style of terminal strips.

[HotBluePlates]

i thought r3 was preamp volume? ...

What's the difference?

... i need a pot to control how much the preamp overdrives, would r3 do that?

Earliest Marshall was no different than the last tweed Fender Bassman. Two channels, each had a volume control in the preamp. No other volume control before the output tubes. When you turn up the preamp volume control, typically the output tubes distort first then the smaller tubes.

When Marshall added a master volume, they positioned it to control the signal level going into the output tubes. Now you could use the Master volume to control actual overall volume. You could keep that low while cranking up the preamp volume control, enough to make the preamp tubes distort.

If you had a pedal with some serious boost, you could keep the preamp volume low on your non-master volume amp and slam the input tube until it distorts. I've done it at whisper volumes with a 1/3w amp and a volume control positioned after the 1st gain stage and using an overdrive or boost set clean but with very high output level.

Since you already have a preamp volume and master volume, do you need an extra control to fiddle?

You may want to think about how big the chassis will have to be with all these controls, as that's likely to materially impact your layout. For typical knobs & pots, you'll need the controls spaced 1.5" center-to-center. You're already looking at 5 controls plus input jack(s), so that seems like a 12-13" wide chassis once you allow for a pilot light.

The very big challenge of a truly scratch-build not from a known-good plan is "everything affects everything else". Circuit affects number of controls and required transformers, and these dictate minimum chassis size, which then influences how much space is left for circuit arrangement, which then affects layout, which then might dictate how you go about the assembly stage...

[PRR]

> something so simple, so primordial, it's beautiful in its simplicity.

+1

[mresistor]

I like that style of terminal strips.

They look just like the ones in a Baldwin organ. I like this style because there isn't a terminal used to mount it which would be a grounded terminal.

[shooter]

Are your terminals *junk drawer* stuff, or did you get them on the web?
 I'm lurkin cuz I'm thinking of P2P for my next build.
anyway, thanks

[fossilshark]

ordered them off ebay, 10 pack

[sluckey]

I first saw those terminal strips in Sunn amps. There were two 12 lug strips around the PI tube.

     http://sluckeyamps.com/sunn/sceptre1.jpg

DummyLoad (Pete) has a bunch of them with a variety of number of lugs. He can probably point you to another source. I would think Mouser has them but I've never looked.

[danhei]

Your project looks quite similar to the AX84 Hi Octane: http://ax84.com/hioctane.html

Both have high gain preamps, 2x12AX7, with three gain stages and cathode follower into a TMB tone stack and master volume. The stock Hi Octane runs EL84, but if you search for "ax84 hi octane 6v6" you'll find info on projects using the 6V6 output tube. In any case a 6V6 won't require much change from the stock circuit, aside from a properly wired octal socket and a higher value cathode resistor. Some folks have even fitted their amps with noval and octal sockets in order to run EL84, 6V6, or both in parallel.

There are minor differences. Your project has a switch to bypass the first gain stage (easy to add to the HO). The Hi Octane has two preamp gain pots (I remember some people have felt the two gain pots were unnecessary and replaced the HO Gain 1 and Gain 2 pots with a single dual-ganged pot). You're running a tube rectifier, the HO is solid state.

Please do check out the Hi Octane. It's a mature, well-documented project including schematics and board and chassis layouts, and a wealth of info on the AX84 Forum. Even if you end up deviating from that project, given the similarities it's well worth your time to become familiar with it. Especially if you have never designed a tube amp nor done a successful layout for one.

[fossilshark]

thank you i will definetely look into it