GTFO - Full tube high-gain pedal (2x 12AX7)

[gtudoran]

Jesusss... well done guys! I'm back in business after a not so happy year for me, so i guess we will see much often on the forum. Again is nice to see that the work was not in vain.

Best regards,
Still me, Gabriel Tudoran
Analog Sound

[Hilli]

Hi Gabriel

some time ago you wrote that you are looking for a better way to generate the high voltage. Have you already found the time for this?

Regards, Bernd

[gtudoran]

Not necessarily a better way ... but an optimized one, yes, i've made some tests and the answer is ATTINY 25/45/85 with PWM and ADC so you can adjust duty cycle as a safety feature (if the current demand is too high then you can cut the fill factor to 0 so, you can stop the conducting device, in our case the FET) - but i do believe that there are also specialized IC for this thing.
I will try to gather all my info and post it here.

Best regards,
Gabriel Tudoran
Analog Sound

PS: I'm still batting on a uC rather then a specialized IC  

[Hilli]

Can't wait to see it. Thanks so much.

[Hilli]

A new one.    Regards, Hilli

[J0K3RX]

Found this, kinda interesting... Russian but translates fairly well.
http://bsvi.ru/impulsnyj-preobrazovatel-dlya-lampovyx-predusilitelej/#more-397

Have said it before but I will say it again... Hilli, your boxes are SICK!!

[gtudoran]

Yes  J0K3RX, is a standard configuration of a Flyback topology .... is a little difficult because of the Xformer, and not only the xformer but also the size of it. If you have the space to build a SMPS of that size ... then i could use a transformer


Best regards,
Gabriel Tudoran

PS: I've managed to burn 2xATTINY 23 ... i almost forgot that is always the magic smoke that drives them.

@Hilli: what size is that box? And ..man you are "sick" they look beautiful. What kind of stainless steel are those?

[J0K3RX]

Good idea mounting the inductor coil off-board 

[J0K3RX]

Yes  J0K3RX, is a standard configuration of a Flyback topology .... is a little difficult because of the Xformer, and not only the xformer but also the size of it. If you have the space to build a SMPS of that size ... then i could use a transformer


Best regards,
Gabriel Tudoran

PS: I've managed to burn 2xATTINY 23 ... i almost forgot that is always the magic smoke that drives them.

@Hilli: what size is that box? And ..man you are "sick" they look beautiful. What kind of stainless steel are those?

yeah.. the xformer is pretty small or I wouldn't even have considered it. Probably stick with what you came up with, very simple

[gtudoran]

Hmmm i will try to build one... if i will find some cores to buy, i will keep you informed guys.

Best regards,
Gabriel Tudoran
Analog Sound

[Hilli]

Hey Guys,

Thanks!!!  The enclosure is from "Musikding"   http://www.musikding.de/Alu-Gehaeuse-Typ-JJ
It is a little bit BIGGER than a BB. I think it's better to have more space when you work with 350V. The material is Aluminium diecast.

@Jim: cool schematic. Hope it works.

Bye, Hilli.

[bianghouse]

A new one.    Regards, Hilli

Hi Hilli, could You please post your layout ready to print and the component list?, I would build a new one but there are so many files in this thread and I'm a bit confused..

Many thanks in advance!
M.

[bianghouse]

Ok .. I redesigned the layout and removed the orphan islands. This should resolve the potential problem, right? It was better this way, amptramp? The credits of the project is in accordance with the rules of the forum? Thanks.

Hi fagnermonteiro, did You carry on project realization?
I'm really interested in your mods, cause I would put it into a 1590BB case...did You finish it?
Could  You please give to me your eagle  sch and brd files of this project?
Thank You very much!!
Great job!

[Hilli]

Hi bianghouse

this should be the files I used. You can open the *.SVG file with programs like Inkscape.

Regards Hilli

http://dl.dropboxusercontent.com/u/44238774/Dokumente/GTFO.svg
http://dl.dropboxusercontent.com/u/44238774/Dokumente/bom.doc

[Hilli]

Hi fagnermonteiro,

would you send us your layout-files? That would be cool. 

Redards, Hilli

[bianghouse]

Hi bianghouse

this should be the files I used. You can open the *.SVG file with programs like Inkscape.

Regards Hilli

http://dl.dropboxusercontent.com/u/44238774/Dokumente/GTFO.svg
http://dl.dropboxusercontent.com/u/44238774/Dokumente/bom.doc

Thank you very much sir!!

[Hilli]

Here is the same file as ready-to-print pdf.

http://dl.dropboxusercontent.com/u/44238774/Dokumente/GTFO.pdf

Hilli

[Uriziel]

So I decided to build this beast and this is my result

The schematic is based on Hillis latest build with the bypass from first stage... The layout is all me... made a small mistake and mirrored the 12ax7 footprint so had to use wires to correct it (first build using tubes  )... also the size of the pcb is exactly for the enclosure i used... These I get from my workplace and are custom made for our use...

https://www.dropbox.com/s/gny7m16lin78p9h/IMG_0336.JPG
https://www.dropbox.com/s/rse96iep9htmeuo/IMG_0349.JPG

Still have some issues though... some ground noise is present, have to trace the issue... SMPS will go over 400V in my case (I have a 2k trimpot)... Strange or not so much?
Also i hoped for tighter sounding gain, more of a modern touch, are there any mods to implement that?

[Hilli]

Wow, that looks very nice man. Well done!

[Uriziel]

I noticed that when I dial the SMPS over 150V with gain maxed the amplifier becomes a generator and I still getting a strong hum... I took a oscilloscope and noticed that the output waveform has little hairs spaced 80kHz apart... I traced it to 555 and the trigering freq is the same, 80kHz... also there is some strange waveform on the collector of the transistor, mostly garbage, looks like a diminishing sine with dc offset to the positive side and some other kind of signal overlapping it... does it have to be like that or is the smps supposed to work like that...

also do any of you have a good way of tracing ground bleed at some point to minimize hum and or to find a fault... maybe i left some trace clearence too small and the high voltage wants to take the short way to ground and capacitively couples to ground...

trying to figure these things out and need to learn more

thanks for any pointers you can give me

I'm adding a pdf containing the schematic I redrew and the layout i made (not to scale!!!)... I used PADS 9.2 and it can generate a interactive pdf so you can trace the schematic or layout by nets or single components... maybe I made a mistake or my layout technique is lacking or could be better... on this layout i fixed the tube pinout error without moving any of the components around... maybe you can spot something that i can address for ver2.0 of this an possibly getting it noiseless and right

https://www.dropbox.com/s/9cvfaust5e4nwoh/GTFO_sch_layout.pdf

you possibly need to download the pdf... firefox pdf viewer crops the edges of the schematic... but opening the file on hdd yields the correct picture in my case...

Merry Christmas to everyone