Rumble's 1/3rd watter

[rumble]

hello all here on this forum.
please excuse my poor english.
searching the web to find a simple DIY tube amp i found this forum with the third watt amp.
http://www.el34world.com/Forum/index.php?topic=5039.0
problem is that i can solder the layout that can be found , but i don't have the technical background to understand the diagrams.
to me i see difference in the layout and drawings.
blind lemon has made his version with a tonepot, but his layout seems to be different than the layout .pdf
http://www.el34world.com/Forum/index.php?topic=3202.0

so i am in doubt if the layout pdf is a good one and if i can use this tone stack
http://amps.zugster.net/articles/tone-stacks#Moonlight

at this spot (red cross)


further more i live in the netherlands (power supply is 240V ac)so the transformers mention t
120:120 Isolation transformer for the PT
Hammond  262E6
P-T442  (from Antique Electronics Supply)
Fender replace reverb trannie used for the OT

i think i can not use them ore am i wrong.

so a lot of question from a noob.
hopefully someone can shine some light in my darkness

[7string]

Hi Rumble. I drew that layout. There is a missing wire at the V1 plate resistor. That one goes from where the two resistors meet in a V to the positive of the nearest 10uf filter cap.

 To add the tonestack, you might be better off using a 12AX7 or 12AT7 for the 1st valve like you guys were talking about in the other thread, using the AA764 Champ preamp instead of the 6AU6. That will give you an extra gain stage to make up for what the tonestack lost. That changes the layout, but there is one on the second page of that AA764 schematic. There are many ways to lay out an amp circuit. Builder’s preference.

 Spend some time looking at all the 5f1 and 5F2 Fender schematics and figuring out where they are in the amp. This website's Library of Information section is outstanding.

[PRR]

The amplifier is approximately a Fender Champ 5C1, except with a smaller "power" tube (6AU6 instead of 6V6), a 160V DC supply to suit the smaller output, and solid-state rectifier to keep it small and simple.

1953 schematic and layout:
http://schematicheaven.com/fenderamps/champ_5c1_schem.pdf
Don't copy this too exactly. The wall-power wiring is now illegal even in the US. The unbalanced heater wiring hums like a cheap amplifier. I propose omiting the 5Y3 rectifier. And of course the tube pin-outs are wrong for 6AU6. But that's the inspiration. You don't "need" a fancy layout; Fender just jammed things in there.

Hammond does not make the 262E6 with 230V primary for your part of the world. Can you find a 230V:115V transformer? It only needs to be 5 or 10 Watts. Also find a 230V:6V 0.6A transformer for heaters. Don't fret about 220V or 240V, 115V or 120V: everything is +/-20% or more.

After you get your wall-power converted to roughly 160V DC, everything else is the same. Yes, the "Fender Reverb Transformer" will be the same, and I know I saw it on a German site so you won't have to import it across Euro borders.

[ampgeek]

Rumble,
Attached is the stepdown transformer that I suggested in the other thread.

It is Mouser P/N 533N1X.  Hopefully others will take a quick look and confirm that it is suitable.

Dave O.

[rumble]

Rumble,
Attached is the stepdown transformer that I suggested in the other thread.

It is Mouser P/N 533N1X.  Hopefully others will take a quick look and confirm that it is suitable.

Dave O.

i quote  PRR from the other topic

> a step down power transformer that will likely work for your application.

NO!
You can't get your DC directly from that part, because it is an auto-transformer. There is NO isolation between input and output.

You could use this to change 240V to 120V, then go into the Hammond 262E6 to give isolated 120VAC and 6VAC outputs.

But it should be even easier to find a true transformer (not auto-transformer) to give 120VAC, and another one to give 6VAC.

Another trick is a 240V:6V transformer to heat the heaters, and a "120V:6V" (or "240V:12V") transfromer wired backward to step-up the 6VAC to 120V AC.

[rumble]

Hi Rumble. I drew that layout. There is a missing wire at the V1 plate resistor. That one goes from where the two resistors meet in a V to the positive of the nearest 10uf filter cap.

@7string, is it possible for you to draw the missing wire on to the layout, that is standing here?
to avoid translation problems and missing technical background of myself.

also do i understand correctly that the two - - - - - -    lines drawn on the layout are wires on the back of the board

that missing technical background does not help me chose the right tube.
i can get a sovtek 6au6  ore a general electric 6au6 / 6au6w

i only know that tube's can sound  different even dough the have the same number but are made in an other factory

step by step i find the pieces to this 'puzzle'  maybe slow, thats no problem  only thing count is that i get it finished.

[sluckey]

Here's the missing wire...

[rumble]

Here's the missing wire...

thank you sluckey, this would have gone terrible wrong i understood it an other way  :-[

now i only have to know witch tube is better to use, the GE ore the sovtek, than i can start ordering

[Shrapnel]

usually tube choice will depend on your own ears, IF they're both cheap enough and your budget allows, grab the correct quantity of each brand and test for yourself. Who knows, you may even like a mix of the GE and Sovtek.

[rumble]

usually tube choice will depend on your own ears, IF they're both cheap enough and your budget allows, grab the correct quantity of each brand and test for yourself. Who knows, you may even like a mix of the GE and Sovtek.

good idea
prices are sovtek € 8,75 and the GE € 6,00, only not at one store so shipping kost rais the price with about € 5,- for each tube.
so i have to figure out what is best to do.

[danhei]

Soktek makes a 6AU6? In any case I'd go with the GE since it's cheaper.

[Shrapnel]

One detail I forgot... You may not notice any difference in the brands, and you may. But I think, personally, I'd side with danhei on the GE's since they are cheaper. (unless shipping charges change the balance the other way.)

That's the cool thing though: your build, your choice.

[PRR]

> witch tube is better to use

Which string is better? Which beer is better? Blondes or redheads? Coke or Pepsi or RC?

Yes, there are $90 strings and $1 beers. Some people don't care, and $1 beer is fine.

The Sovteks I have used were "fine". But I can't tell different beers apart too well.

Tubes made 1940s-1970s were good or bad; but we made so many in those days that even the low-price ones were mostly good. Tubes made 1990s-2000s are made in smaller quantities and mostly for very low-price buyers (tube-amp factories). There have been some bad tubes. Most affordable-price new tube amps come loaded with the cheapest bottles they could get, and some people hear a big difference after changing the tubes. Most shops which sell individual tubes have learned to avoid leftovers from low-bid tube-amp factories, and sell the best new tubes they can find.

Most of the popular "old production" tubes have become very valuable. Audiophiles and collectors buy them up.

The 6AU6 is different. We used a LOT of 6AU6 in the old days. Every FM radio had one, many military and commercial radios had several. There were vast supplies of spare 6AU6 tubes. And somehow it has never become "fashionable" among audio designers. While a few "extra quality" 6AU6 types demand $10, perfectly good "assorted brands 6AU6" sell for very little.

In this case, I'd get the old tube. It is probably good, and cheaper. I would not care too much if it was GE or Westinghouse or Fisher or Mullard or Toshiba.

[rumble]

thank you all for clearing this up for me.
now it will be shopping time to get all the parts i need.

and then, when building i will post it here to share my ups en downs (and thats the beauty of DIY)

[rumble]

parts are coming in to the house, ordert at tube town a, i hope nice 8 inch speaker
http://www.tube-town.net/ttstore/product_info.php/info/p3606_TT-Supra8-8----15-W---8-Ohms.html
for the little combo i want to build, with  , i think, a jack for the use of an external speaker.

looking at the diagrams i only wonder what this part in the nov '07 is for?
is it a tone controle, something about gain controle?
it isn't showin in the diagram of oct '07



another question that came up is about safety.
on a dutch forum someone said that after shutting down the amp there is a lot of power saved in the 'powercaps' we call elco's that can give you a blow long after the amp was shut down.
a solution was to ad a bleeder resistor like 270K/2W between the first high voltage elco + and ground that would unload all of the elco's after a few minutes

does this diagram have a safety resistor? and if not, would it be good to ad one .
if i look at the layout on this page, what is the first high voltage elco ?

[HotBluePlates]

looking at the diagrams i only wonder what this part in the nov '07 is for?
is it a tone controle, something about gain controle?
it isn't showin in the diagram of oct '07

I was not able to see the image that you attached, but I did look at the original schematic that you linked in your first post.

The added control in the Nov '07 schematic is for a simple volume control, which works by reducing the voltage on the screen grid of the output tube. Less voltage = less output.

does this diagram have a safety resistor? and if not, would it be good to ad one .

No. The schematic does not show a bleeder resistor or safety resistor. You could use a 270k or 330k resistor from the + terminal of the first electrolytic cap to ground (+ of the cap to - of the cap). We expect roughly 160vdc to be present across the resistor; 160v / 270k = 0.7mA and 0.7mA * 160v = ~0.11w. You could use a 1w resistor and have a large margin of safety. Using a 330k resistor, using a resistor rated at 2w, or both, will simply increase the life of the safety resistor.

[mackie2]

PRR--

I need a low watter, that comes with, a high octane redheaded woman--built like  a steel brick-- to  help with my TONE!!!

Mackie2

[PRR]

> a simple volume control

I would say "Power control".

Like you could get a Dodge Dart with the 95 Horsepower engine, or the 270 HP engine, or (with hop-up parts) a 500HP engine. Except instead of hoisting half-ton engines in and out to change power, this is just a knob.

The hop-up Hemi is fun on the big Daytona track. But total over-kill for parking-lot races. The little Six will run the cones on a small track, screaming its strong little song and moving the metal fine.

Full-up you get the full mighty 0.33 Watts.
Half-up it becomes about a tenth-Watt power amp.
It should be possible to choke it down to 1/100 of one Watt.

On a much bigger amp, I was thinking to mark it "Stage - Studio - Bedroom". You need full power on many stages. In a teaching studio, one Watt is plenty, and the teacher won't go so hoarse shouting over it. At home with the family reading or watching TV, a tenth-Watt may be all that your loved-ones will tolerate.

In this case, perhaps "Afternoon --- After Midnight". I suspect the lowest power levels will make less sound than even a solid-body guitar; the thing is that you can get the maxed-out flavor at loudness just a hair above an unamplified guitar.

[rumble]

thank you HBP and PRR for the explanation.
now i know i can forget that 'volume' part  in the diagram.

PRR, do you think it is useful to use a bleeder resistor, would you recommend it?

[PRR]

Part of me says... it is "only" 150 Volts.

But that can be dangerous.

100K to 270K at 1/2 Watt is a good value.

[rumble]

@PRR
thank you, than i will ad that to     

[rumble]

it is not a lot but some parts are in

chickenheads, tube's 1 transformer and a 8 inch Tube Town speaker



and i have added the missing wire and i hope i have got the right spot for the bleeder cap

[VMS]

Hi,

I'm borrowing this rumbles thread to ask few questions.

I just bought two 6AU6A tubes and I'm thinking of using one to make a small power amp.
My dilemma is that I only have 16ohm speaker cabinets so I can't use the reverb OT. If I use Hammond 125a (or 125c, same price) what would be the optimal primary impedance for 150VDC plate voltage?

What if I use higher plate voltage, for example 250VDC what would then be the proper impedance?

Thanks in advance,
Ville

[PRR]

> I only have 16ohm speaker cabinets so I can't use the reverb OT

Sure you can.

> what would be the optimal primary impedance

"Optimal" for what? Cost? Loud Power?

If a 6V6 or EL84 is "too much", then you do NOT want "optimal" power-matching.

Mis-match any convenient way, and try it.

So it may be quarter-watt or sixth-watt, so what? You are not looking for a specific watts-number, you are aiming for a loudness, and (if this plan is interesting) you can aim low.

[VMS]

"Optimal" for what? Cost? Loud Power?

For TONE   

So basically it doesn't matter what the impedance is as long as its >15k.

One thing that attracts me in 125a push-pull OT is that I could try to connect the tube as Ultra-Linear ala KOC.

-ville

[PRR]

> So basically it doesn't matter what the impedance is as long as its >15k.

Or less.

To "make the most" of the 6AU6, we want somewhere in the 12K to 50K range.

But it is VERY difficult (costly!) to wind an audio SE "power" OT above 10K. Our selection is limited. Yes, you "can" load a "7K:4" OT with 16 ohms, and pretend it is 28K... but it is still a low-Z winding and unless it is "large" this will be apparent in the bass response flatness and distortion, also you could have ringy treble. Sure, if you got it, try it. If you have to buy, the Reverb tranny is known to work acceptably with guitar sounds and relatively high impedance.

And in the end, if you "need the most", you do not have to work with the meek 6AU6, the world is flush with bigger bottles.

> One thing that attracts me in 125a push-pull OT is that I could try to connect the tube as Ultra-Linear

You are confusing Big-amp thinking with little amp scale.

The idea of ultra-linear is Pentode Power with Triode Sound. A couple big bottles can do 10W as triode, 50W as pentode. UL allows 35W real clean.

(Not that real-clean is necessarily good for e-guitar.)

When you get down to part Watt, you are NOT humping for a lot more Watts. At the part-Watt level, use a dang triode. Push-pull 12AU7 will do a big part of a Watt, I think FireFly is one such project. But any push-pull amp worth the work is significantly more parts than an SE amp.

My goal was K.I.S.S. Simplicity has its own charm. But what do I know?

Ken Fischer is quoted "The less components inside the amp that will do the job, the better the amp will sound." But what does he know?

Obviously there are other ways to design amps. Some are more complicated than the Space Shuttle. Sometimes you need a 47-blade tool.

And sometimes a sharp rock does everything which needs doing. Don't silk-purse the sow's ear TOO much.

[VMS]

Ok, reverb OT it is then.

K.I.S.S. is my motto too but I also want to add my own little twist in things.

For PT I'm thinking of using back-to-back transformers. (230VAC to 6VAC and 230VAC to 12VAC) By connecting the 12VAC to 6VAC I get 115VAC that I can rectify for the plates, right?

By doing this can I use those 100R resistor to make a elevated ct for the heaters?

-ville

[VMS]

Hi,

let me rephrase my question with help of an picture. Would this type of circuit work? Mostly I'm concerned about the center-tap in the heater wiring.

Also, I'm a bit unsure about the VA ratings for the transformers. Is 16VA enough for the 230VACto6VAC and 10VA for the 230VACto12VAC transformer? Assuming I need about 1A for the heaters and 50ma for the plates.


Any help will be much appreciated,
Ville

[PRR]

The B+ draw is under 3W.

Look-up the actual heater draw of 6AU6; IIRC you won't need a whole Amp for two.

[VMS]

Look-up the actual heater draw of 6AU6; IIRC you won't need a whole Amp for two.

It looks like the heater draw for 6au6a is 300mA, but I might try different tubes for the preamp, so the 1A gives me some leeway.

-ville

[rumble]

my life had a sudden stop moment and this project was one of the things i had to let go for a while.
but like the terminator said, ' i'll be back'  and here i am again and started the build.
will post some photo's soon.
 :happy9:

[bigdaddy]

Yes please let us know, I am very interested in this amp. I need a good sounding low output amp in the worst way.

[rumble]

stupid me, didn't read the answer from PRR good about the transformers and thought i could use 1 farnell fl14/6



so i ordered one new.

i am trying to build this amp in the casing of an computer power supply



the big strip you see will be the base of the two farnell devices.

this is how i made the layout.
note that not all the parts have the exact specs like it is drawn on the layout.



now i have some , sorry i am a dummy, questions.
the layout drawing of the tube sockets.
how do i have to read it, like A ore B



second question is what the best place is for the reverb transformer.
outside this power supply casing like the tubes?

[sluckey]

the layout drawing of the tube sockets.
how do i have to read it, like A ore B

B is correct. When viewing tube sockets from the bottom (the side you solder stuff) the pins count up in the clockwise direction. The first pin clockwise of the wide space is #1.

I'd probably put the reverb transformer on the outside.

[rumble]

i know i know, it took long again but the weather was that good that i had to work on my guitar-builds first because the woodwork had to be done outside.

but working this schematic out


and it looks like this now



because i did not wanted to get shorts i used a board to lay on the bottom of the metal case



the i mounted the complete board on top of it with in the middle a little bold that goos through both boards to fixate them.



so now i have to make the top of this metal case holding and keeping the rest of the parts like the tubes etc.

[eleventeen]

"B" is the correct tube pinout!!

Woe be upon he those who invert their nomenclatures!! 

[rumble]

"B" is the correct tube pinout!!

Woe be upon he those who invert their nomenclatures!! 

don't know what this means but my idea is that it warns four trouble connecting things wrong

did some work again  ant it looks like this

the parts that go in/on the other side of the pc power supply part





now i have to be carefull not to 'Woe be upon he those who invert their nomenclatures!!'

[jojokeo]

now i have to be carefull not to 'Woe be upon he those who invert their nomenclatures!!'

That just happened recently in a Firefly amp build thread a couple weeks ago. He only lost a power tranny and a tube or two? This is unrelated but is one of my favorites 

[simonallaway]

I am somewhat disappointed that tubes don't look like this during normal operation 

[rumble]

well like i see it now i have a big, that is going to happen to me factor.
i am a bit lost now about this layout



here there are two  voltage outputs
in the middle 6v to heaters and on the right 120V to rectifier.

so where do i have to place them on the layout?

yes i know i am a dummy in this

[rumble]

I am somewhat disappointed that tubes don't look like this during normal operation  

i know of a guy that made a stompbox that contained a working tube but didn't light up the way he hoped.

so he drill't  a hole int the tube socket and put a led in it to make the tube glow

[jojokeo]

  The stomp box couldn't have worked.

BTW, you don't have to keep your B+ that low (~160vdc) and anything will work as long as it's under 300v max after rectification that the tubes can take. Just a suggestion. For your first amp you want to make things a simple as possible and you're already into atypical territory using two power x-frmrs like that. Heck, there's even an error in the layout design you already had to navigate and be made aware of and wouldn't have seen. Avoid confusion at all costs w/ your first amp. That said, this is about as basic of an amp that there is. From scanning the thread for the first time, there's sure a lot of questions regarding tube types that go far beyond what you should be concerned with. That's like worrying about what brand of light bulbs you should buy (ie Sylvania, GE, Phillips, etc.) at the store when you haven't even built a house yet. You're off to a good start by being at this forum but it appears that you could benefit also from reading a good book or two to get some of the basics down - not mandatory but a good guide to follow keeps confusion & safety hazards down to a minimum. Good luck, try to have fun, and always double check your work. 

[PRR]

> you don't have to keep your B+ that low

The problem is the low load impedance and the low plate dissipation rating. The 6AU6 will take 300V but at such low current that it can't pull an audio transformer. 150V (or so) is a much better fit.

[sluckey]

I'd connect the 6vac leads directly to the tube sockets (You may want to build an artificial center tap). I'd connect the 120vac leads to the diodes on the board.

Have you verified that your transformer circuit actually works? I.E., plugging it into a 240vac wall source gives 6vac and 120vac where you expect. If not, I highly recommend you do this now. There are 8 windings involved and just getting the phase of one winding reversed will be a show stopper.

[rumble]

@jojokeo
the stompbox worked, the design was a 'real tubescreamer'  so something like a tubescreamer but with an ax12 in it.
the designer did't plan the led but one of the guys who build it did this mod.

about this little amp, i see it like lego, put pieces together using a good plan like the layout but it isn't that simple for a novice (but it could be)

@sluckey and PRR

the 'powerpack'is working althoug  the reading for the 120 V is about 100V

I'd connect the 6vac leads directly to the tube sockets (You may want to build an artificial center tap).

the sockets have a centertap but where is it for?


on the layout a line comes from nothing  on the left and starts with a 68K that is connected to pin1 of the first tube.
is this from the guitar input?

on the diagram there is the block 120V: 6VAC.
so these are the  6V lead of my powerpack.
on the diagram it says 'heater pins 3 and 4.

do i understand it correctly that these have to go on pin 3 and 4 of each tube?

one is never to dumb to ask questions, if one doesn't asks he stays it!

[rumble]

better be save than sorry i have taken the layouts en mar kt my point of doubts.



left at the top how i think the guitar input has to be connected.

the red A blocks are where i think the 120V has to be connected
the same for the 6V in the green blocks.

maybe stupid, but making it visible helps me with the lack of my not so good english technical understanding

[jojokeo]

> you don't have to keep your B+ that low

The problem is the low load impedance and the low plate dissipation rating. The 6AU6 will take 300V but at such low current that it can't pull an audio transformer. 150V (or so) is a much better fit.

Thank you for pointing that out. It's that kind of info I need a better understanding of. I have designed & made a SE low powered amp to use either 6aq5, 6ar5, or 6dl5 power tubes. It has a about a 265v B+ w/ a 5k OT w/ 4 & 8 ohm taps and is using an 8 ohm speaker.

I figured I'd need the 4ohm tap for using the 6dl5 & 6ar5 tubes for effective 10k primary load stated from data sheets and then use the 8ohm tap for the 6aq5 tube. But, the end result is that for ALL of the tubes the 5k:8ohm tap sounds best! The 6dl5 tube actually sounds best w/ the clearest high end and overall response and tone, even though the tube "should" sound best w/ a 10k primary impedance?! I realize that the factors you've stated play their part but I don't know all of the hows and whys excatly?

Can you explain the transformer loading concept and characteristics for me and how impedance and current factor in for their parts? Anything else I'm missing? Thanks-