2 x 12au7 amp running on 9 volt adaptor and smps

[iccaros]

so 1/(2*3.14*22*2.2) = 0.00328832709647294035632312417381

so what does that mean? is that 3288 hz? or do I need to put capacitance in a different form?

[DougH]

Sounds nice, Greg!

11k is fine. I liked 22k for my Firefly 2x12au7's, since you have two of those in parallel, 11k makes sense.

Are you planning on mounting all that high voltage stuff on a board? It's kind of dangerous the way it is spider-wired right now. I assume that's a prototype (?).

[zambo]

yeah i am going to put it on a board and mount it. Its totaly a prototype. Also an exercise in counting ground loops. Kind of a wheres waldo ( ground loop) thing. Thanks doug!

[Yazoo]

It sounds really good. I keep looking at tube amps and would love to build a low wattage amp for bedroom use. It looks like it wouldn't cost that much to build either. Keep up the good work and let us see your revised layouts please. 

[zambo]

Revised schematic! 


please double check if you would, and thanks for the corrections already!

[iccaros]

Revised schematic! 


please double check if you would, and thanks for the corrections already!

Have you thought about putting 10K or so grid stoppers on the output tubes. While you do not seam to be getting any oscillation right now, changing tubes may make that an issue, Grid stoppers would not really change the sound but may make it more stable with different tubes.

[zambo]

if it starts to oscilate I will, but its so quiet i dont think it will need them. I may change the .022 coupling cap to a .01 to tame the bass farts a little. Either that or the slope resistor..not sure yet.

[iccaros]

if it starts to oscilate I will, but its so quiet i dont think it will need them. I may change the .022 coupling cap to a .01 to tame the bass farts a little. Either that or the slope resistor..not sure yet.

The .01 could roll off some of the low end, but your eq values look weird, not that I can do the math well The bass fart does not come over camera well, so I am not sure, I like the tone, but these values from the Jalapeño tone stack according to the calculator puts everything in the center and keeps the signal boosted over all


I used this app
http://www.duncanamps.com/tsc/ to look at this stuff, I am too dumb to do real math.. I am trying, but well as good as it gets sometimes.


this is yours



*** I have a question on your power supply, It says 65 milliamp max, I am wondering if its putting out enough and could that lead to not being able to put out bass as clearly as the treble. ? I wonder if we put two, one for preamp and one for power section? A >1 amp power supply should not have many issues with that.  I have two on order to test..

[iccaros]

Zambo
This is a first attempt at redrawing your schematic, Make it a little easier to edit when you have changes its in Visio so I am including that file so people can edit. I have not added the power supply yet, need some sleep, I am on travel to the east cost so my schedule is way off..
PDF
http://dl.dropbox.com/u/14312589/Twin-12AU7-AMP.pdf
PNG

Visio
http://dl.dropbox.com/u/14312589/Twin-12AU7-AMP.vsd

This amp needs a cool name..

Will add power tomorrow, just ask people to review so I can update what I messed up or what is not clear..
Need to add Pot connection numbers and a Attribution box...

[DougH]

this is yours

Looking at that EQ curve, that could explain some of the bass fartiness he's experiencing.

[zambo]

@ iccaros - Thats super cool and appears to be correct to me! Thanks for drawing it up for real!! The bass response isnt as bad as I made it sound on the vid and its actualy nice for the clean settings. I put in an eq lift switch anyway so i can put a booster pedal in front with its own eq. I was debating the seperate 1363 for the preamp as well and have one to do it with. When I get some more time I will spider wire it for fun and see how it works. I like the reservoire caps and they seem to make this ps work quietly. I was getting whining before unless loaded just right. Thanks again for working on this. Its the most requested schematic of all the stuff Ive built so far and a bunch of people (including me) will appreciate your work on here.
I am going to post another vid with my trainwreck pedal in front of it soon here...Thanks again.
Cheers! Greg

[iccaros]

!!!!!!!!!!!!!!!!This design is not tested... Build at your own Risk 

Ok I updated the first drawing see above

For openion.. I can see where the tubes on this amp will draw too much current, leaving it current starved..

So How about doing this.... See warning...


This works with a lM317... like that is the same thing..

[frequencycentral]

Two SMPS *might* be asking for heterodyning........

[iccaros]

Two SMPS *might* be asking for heterodyning........

I won't as for that then 

but seriously, could this be avoided by placing an bypass after the power supply, or is the nose on ground?  So say we put  a 200K in parallel with C8 and C11?
or what ever the frequency range is? This may be adding way too much work.

I ask because I have some tubes like the 6111, that have a 160 volt max plate.  which is too close to line power in for most transformers, as rectifying 120v (using a 12V transformer backwards for 12 in 10 out)  120*1.41 = 168 volts. maybe I am way over worried, and one is enough for this.

Math.... 

100K @ 200v is  (200/100000 = .002) 2ma per triode
but the power section
200/11K (?should this be half of either or both of these?)
is .0181
or 18ma per tube in the output section
18 * 4 = 72 MA for the power section

if impedance is halved (200/5.5k) = 36 ma per tube

Either way this more than this power supply can put out  65ma

I know the system can not draw more than it can give.. so we hit  a stage at which we are current limiting the output, or am I way off and have no clue what I am talking about?

[tasos]

what are smps?

[amptramp]

what are smps?

Switch Mode Power Supply

[frequencycentral]

One way I have considered (but not tried) for getting more ma from a SMPS is to use just one HF oscillator (NE555 or MAX1771 etc), but use it to feed 2x MOSFETs, inductors, UF diodes and reservoir caps. Theoretically you could double the ma but without the risk of heterodyning of using 2x HF oscillators. It would probably be really fiddly to implement this with 2x 1363 PCBs, but still possible I guess, if you were to disable the oscillator of one board and use it as a slave to the first.

[zambo]

Rick is it possible to design one of these from scratch? Might be easier than trying to rework an existing pair. Building it as one unit would be neat. If we could get 250v and 60 ma for a power section we would have tha basis of a sweet 4 to 5 watt amp in a very small and light package. I am thinking it would be a sweet guitar case amp.

[zambo]

Hey Rick i was wondering if you had ever bent your geniuse towards this thought..  http://www.diystompboxes.com/smfforum/index.php?topic=91565.msg781514#msg781514 . In series we could have like 400v at 50 ma if i understand it correctly  that would make a heck of a screamin amp! Any thoughts on it?

[frequencycentral]

Rick is it possible to design one of these from scratch? Might be easier than trying to rework an existing pair. Building it as one unit would be neat. If we could get 250v and 60 ma for a power section we would have tha basis of a sweet 4 to 5 watt amp in a very small and light package. I am thinking it would be a sweet guitar case amp.

Very possible, but I think you have to be a 'scientist' rather than whatever the hell I am.    I have a little knowledge of how they work, but I also know 'what I don't know'. I can build them, tweak them, but really I'm using them as pre-existing building blocks. When it comes to efficiency (which is where you'll get your high ma) various factor come into play such as layout, very specific parts, parasitic inductance and capacitance and proximity to other stuff. The MAX1771 based SMPS is certainly capable of 100ma plus with the right components. Have a read of the 'High Current Experiments' paragraphs of this page:

http://www.desmith.net/NMdS/Electronics/NixiePSU.html

Nick Smith also contributed to our own forums MAX1771 development thread:

http://www.diystompboxes.com/smfforum/index.php?topic=79736.0

...as does the 1363's Taylor himself:

http://www.diystompboxes.com/smfforum/index.php?topic=79736.msg761723#msg761723

Cliff Schecht was designing something along the lines of what you suggest, I don't think he finished the project though:

http://www.diystompboxes.com/smfforum/index.php?topic=80165.0

Most SMPS designs out there are developed for nixie tubes, where audio artefacts are not an issue, and generally the ma requirement is relatively small. I'm sure it's possible to design a nice high voltage high amperage SMPS for tube amp use. Sadly, I'm not the man to do it. But if someone else does, I'll be all over it.