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

[J0K3RX]

Gabriel,

Do you think it would be possible to build this preamp using a nixie psu? Forgive me if it is a stupid question but I am a noob with the tube stuff...
http://diy-fever.com/amps/mesa-mark-iic-preamp/

[Hilli]

Hi,
this is my build of the GTOF. He sounds fantastic, no hum or other problems. First I had a few problems. I couldn't find a UF4004 in default thereof I had used a 1N4007. But It didnt't work, the highest voltage I got was 280V. It MUST be a ultrafast diode. Today I "killed" a old switching power supply and inside I found a BYV26E ultrafast diode (1000v 1A). Now I have 260-490V with load! This is my PSU, the changes are marked in red.
I've ordered a Hammond enclosure, I hope it will delivered tomorrow. If I finished the GTFO I will send a few another pics.




Thanks for the nice work and regards
Bernd

[J0K3RX]

Hilli - Nice build man!!

[iccaros]

Gabriel,

Do you think it would be possible to build this preamp using a nixie psu? Forgive me if it is a stupid question but I am a noob with the tube stuff...
http://diy-fever.com/amps/mesa-mark-iic-preamp/

most Nixie PSU's are not designed to run quietly.
This would work, as this is already a big pedal
http://www.ebay.com/itm/115-230V-230V-6-3VAC-Out-20W-Transformer-fr-Preamp-/250810391301?pt=LH_DefaultDomain_0&hash=item3a6576db05#ht_1307wt_1110

[Hilli]

Hilli - Nice build man!!

Thx, it's just a test set-up.

[J0K3RX]

Gabriel,

Do you think it would be possible to build this preamp using a nixie psu? Forgive me if it is a stupid question but I am a noob with the tube stuff...
http://diy-fever.com/amps/mesa-mark-iic-preamp/

most Nixie PSU's are not designed to run quietly.
This would work, as this is already a big pedal
http://www.ebay.com/itm/115-230V-230V-6-3VAC-Out-20W-Transformer-fr-Preamp-/250810391301?pt=LH_DefaultDomain_0&hash=item3a6576db05#ht_1307wt_1110

Steve,

How would I get the 400v required for this preamp from only 230V + 6.3VAC Out?

[Hilli]

I think it is not possible. 

[J0K3RX]

I think it is not possible. 

I think you're right...

This nixie on the GTFO pedal is surprisingly silent and I believe it would power the other Mesa Mark IIC+ preamp as well..!?

[gtudoran]

Hey guys, glad to see that are ppl intrested in this project. Nice build Hilli.

@Jim, i'm sure that you could use a SMPS for this project, but i do think you should do some testing - in theory it's possibile.

Best regards,
Gabriel Tudoran
Analog Sound

I think it is not possible. 

I think you're right...

This nixie on the GTFO pedal is surprisingly silent and I believe it would power the other Mesa Mark IIC+ preamp as well..!?

[iccaros]

Hey guys, glad to see that are ppl intrested in this project. Nice build Hilli.

@Jim, i'm sure that you could use a SMPS for this project, but i do think you should do some testing - in theory it's possibile.

Best regards,
Gabriel Tudoran
Analog Sound

I think it is not possible. 

I think you're right...

This nixie on the GTFO pedal is surprisingly silent and I believe it would power the other Mesa Mark IIC+ preamp as well..!?

An SMPS would work, you are only drawing maybe 8 ma.. but.. but the question was can a Nixxie power supply work, and in my experience they are not laid out in a way to be quite, when made for Nixxie tubes..  a 230v  rectified is 324v, which in my option with those tubes is good enough..  I do not believe you would hear that much difference. and that supply has 6.3v heater taps,
A SMPS will be smaller, with the GTFO supply you also need to use the heater ckt, as I believe it uses a higher than 12v starting voltage, so you will have to drop voltage to use on the heaters.

[gtudoran]

@iccaros - as far as i'm intrested this SMPS it's very good (as you can see there is other layout of the parts). Regarding the heaters i didn't understand your sentence but, as you may know 12AX7 also accept 12.4 - 12.6v for heater supply (150mA typical) and the whole pedal use a single 12V power supply ... sincerly i don't see where is the problem.

Best regards,
Gabriel Tudoran
Analog Sound

Hey guys, glad to see that are ppl intrested in this project. Nice build Hilli.

@Jim, i'm sure that you could use a SMPS for this project, but i do think you should do some testing - in theory it's possibile.

Best regards,
Gabriel Tudoran
Analog Sound

I think it is not possible. 

I think you're right...

This nixie on the GTFO pedal is surprisingly silent and I believe it would power the other Mesa Mark IIC+ preamp as well..!?

An SMPS would work, you are only drawing maybe 8 ma.. but.. but the question was can a Nixxie power supply work, and in my experience they are not laid out in a way to be quite, when made for Nixxie tubes..  a 230v  rectified is 324v, which in my option with those tubes is good enough..  I do not believe you would hear that much difference. and that supply has 6.3v heater taps,
A SMPS will be smaller, with the GTFO supply you also need to use the heater ckt, as I believe it uses a higher than 12v starting voltage, so you will have to drop voltage to use on the heaters.

[iccaros]

@iccaros - as far as i'm intrested this SMPS it's very good (as you can see there is other layout of the parts). Regarding the heaters i didn't understand your sentence but, as you may know 12AX7 also accept 12.4 - 12.6v for heater supply (150mA typical) and the whole pedal use a single 12V power supply ... sincerly i don't see where is the problem.

Best regards,
Gabriel Tudoran
Analog Sound

Hey guys, glad to see that are ppl intrested in this project. Nice build Hilli.

@Jim, i'm sure that you could use a SMPS for this project, but i do think you should do some testing - in theory it's possibile.

Best regards,
Gabriel Tudoran
Analog Sound

That's my fault for not looking again at your supply, I thought it was using 15 - 18v on the input to get higher voltages at higher amperage.
I was trying, in my sleep deprived poor communication skilled way, to say that if they buy a "NIXXIE" power supply, like those on ebay, they may be noisy.

[J0K3RX]

Steve - No worries man... It would be nice if I could find a small transformer that would fit the bill... looked all over the place but nothing but big old heavy things that cost big old $$$...

[zambo]

I was looking at tubes and more and there are some little transformers on there that will do 100 to 300 volts pretty cheap and pretty small. Hammond under power. part number P-T442 , has 12.6 filament and 125 secondary for plates. could use a voltage doubler to get higher plate voltage. El34world has on too. http://www.hoffmanamps.com/MyStore/perlshop.cgi?action=template&thispage=Transformers&ORDER_ID=145758238 about halfway down the page is a little toroid that takes 12 ac input and puts out 240 after rectification. They have a two tube chassis to. Hope that helps.

[Ripthorn]

Steve - No worries man... It would be nice if I could find a small transformer that would fit the bill... looked all over the place but nothing but big old heavy things that cost big old $$$...

Mouser has pcb mount transformers that I have used with 12VAC in then you have the 115 or 230 V "secondaries" that can be used for tubes.  Use them for my breadboarding all the time.  Very small VA rating, but serviceable for 5 mA or so, small size, and about $3 each or so.

[J0K3RX]

I was looking at tubes and more and there are some little transformers on there that will do 100 to 300 volts pretty cheap and pretty small. Hammond under power. part number P-T442 , has 12.6 filament and 125 secondary for plates. could use a voltage doubler to get higher plate voltage. El34world has on too. http://www.hoffmanamps.com/MyStore/perlshop.cgi?action=template&thispage=Transformers&ORDER_ID=145758238 about halfway down the page is a little toroid that takes 12 ac input and puts out 240 after rectification. They have a two tube chassis to. Hope that helps.

Greg - Thanks for that link man!! Tons of good stuff there and located in the US too!

[fair.child]

Hey Jim, that is no problem. So we will take it from bottom.

First of all you have to be sure that the 3 jumpers are in place:

-the first one is under de 555IC
- the second one is from C1 to R25
- the third one is above the sockets and connects the V1 and V2 pin number 5 together (the heaters are there) - take care of the heaters pad you will also have to connect it to the 12V positive side.


After that:
- Input is from R2 and GND (any point from ground plane will do)
- Output is from R17 and R18 junction
- 12V input is on the positive side of the 470uF cap C9 on the layout

You will have to make the following checks before you put the tubes in the sockets:

- you have to have 12V @ pin 4 and 8 of the 555 timer
- you will have to have >90v at the positive side of C11 (4.7u) - is the HV out
- you will have to have almost the same voltage like above to the sockets V1 and V2 (pin 1 and pin 6 of the sockets) take your mesurment on the pin directly
- you will have to have 12V @ pin 5 of both sockets - there heaters voltage

After that, if everything is in place and good to go, disconect from the 12V supply, put the sockets in place, reconnect the 12V supply and you should see the heaters glowing. You should take the messurments again (the ones from above) - and @ point 3 from above you should have smaller voltage readings then the first ones. Only after that you should hear smth ... and btw keep the volume low and pay attention to your fingers - do not touch FET's metal tab.

Best regards,
Gabriel Tudoran
Analog Sound

Gabriel,

Ok, I have this thing all built using you latest instruction/pdf... I have a problem and this may sound stupid but can you help me with the off board wiring? I have all of the pots wired up and the IN and OUT and 12V but where do the negative/ground go? I tried attaching them to ground but it didn't work... I am not using a foot switch yet until I can actually get this to work then I will box it up and use a foot switch. Also is there supposed to be a jumper from pin 5 to pin 4 of the 555 chip?

Thanks,
Jim

Okay, the first one under the NE555 IC, Got it, the second one C1 to R25 ?, where it should be ? I can't find any jumper pad from C1 to R25. C1 is nearly input and R25 is close with C12, so where it should be ?

I've found the third one, a pad between both from fifth tubes pin.

So my question is, where is the Ground Pad of GTFO PCB ?

I'm using http://dl.dropbox.com/u/15275178/blast%20from%20the%20past/GTFO.pdf - The new version

I'm wondering the UF4004 diodes equivalency. Can I change it to UF4007 ? I heard there is a quite issue about this diode. So please tell me, what kind of diodes should I use, if I can't get UF4004 on my electronic store.

Thanks all
Cheers

[Hilli]

It is done! ;-) I have inserted a full tone stack. Here is Gabriels modified SCHEMATIC. He sounds great.



Greetings, Bernd

[fair.child]

Hey Hili, looks like awsome build,

I wanted to built this pedal too. Seems yours mod from the previous schematic is using Baxandall Theory. It is great idea to put into this pedal.
So, I want to asked about the R16 ,R17, and the rest (Pots,etc) question about your pedal. I still can't find where does it go. Could you please tell me ? I'm kind a confused here, and hope somebody will help me to built this pedal. I just need to know where is the ground pad of this Bad ass pedal.

If you don't mind, please share me about the grounding pad. I'm trying to understand the schematic and PCB, but I still can't found it.

And also, did you put a Silver Mica caps on C10 and C14 ?  

Thank you

[J0K3RX]

Hey Hili, looks like awsome build,

I wanted to built this pedal too. Seems yours mod from the previous schematic is using Baxandall Theory. It is great idea to put into this pedal.
So, I want to asked about the R16 ,R17, and the rest (Pots,etc) question about your pedal. I still can't find where does it go. Could you please tell me ? I'm kind a confused here, and hope somebody will help me to built this pedal. I just need to know where is the ground pad of this Bad ass pedal.

If you don't mind, please share me about the grounding pad. I'm trying to understand the schematic and PCB, but I still can't found it.

And also, did you put a Silver Mica caps on C10 and C14 ?  

Thank you

You can use anywhere on the circuit board ground plain for ground...  I would guess that silver mica caps would work fine for c10 and c14..