High Voltage Tube Driven Overdrive Pedal Builderino

[AlexfromGermany]

Hi,

I saw your YouTube Video and thought maybe I can chime in and see if I could help you with your project.
I didn’t read the all the posts etc. right now.

I built a couple of HV Tube Pedals/Preamps in Hammond 1590XX and 1590D enclosures

Kingsley Page
Kingsley Harlot
Mayer Pre
Dumble Pre
Marshall JTM & JCM 800
Fender Bassman

Let me know, if you have any questions.

When you really want to save space
Use a SMPS like the
Sushi Box FX HV Daughter
or Tube Town VPUMP

Kingsley / Peace Hill FX etc also use this design for the power supply.

You get 300vdc B+ from 9 or 12vdc in a small package and they are save to use, if you know what you are doing.

I can also send you pictures etc

Hope my English was correct and greetings from Germany,

Alex

 

[kleydejong]

Hi,

I saw your YouTube Video and thought maybe I can chime in and see if I could help you with your project.
I didn’t read the all the posts etc. right now.

I built a couple of HV Tube Pedals/Preamps in Hammond 1590XX and 1590D enclosures

Kingsley Page
Kingsley Harlot
Mayer Pre
Dumble Pre
Marshall JTM & JCM 800
Fender Bassman

Let me know, if you have any questions.

When you really want to save space
Use a SMPS like the
Sushi Box FX HV Daughter
or Tube Town VPUMP

Kingsley / Peace Hill FX etc also use this design for the power supply.

You get 300vdc B+ from 9 or 12vdc in a small package and they are save to use, if you know what you are doing.

I can also send you pictures etc

Hope my English was correct and greetings from Germany,

AlexView attachment 1317869

Awesome builds! They look fantastic.

I did some fishing and found several helpful links. I'll post them here for my own future reference:

TT VPump - Voltage Converter

The TT VPUMP kit is a very effective working voltage converter which generates an output voltage of 90 V DC to 220 V DC from a 12V DC input voltage. The circuit is in use for many years now and it is proven. In this kit the circuit has been ...

www.tubetown.net

High Voltage SMPS PCB

This is a PCB for building a high-voltage “nixie” style power supply for tube projects. It has a trimpot to adjust the high voltage from about 30V-450V, be sure to choose the right rating for your …

c2celectronics.com

HV Daughter build doc draft.docx

Sushi Box FX – High Voltage Daughter Board The High-Voltage Daughter Board is designed to deliver reliable high voltage to your tube projects. It takes a typical 9-12V DC input and steps it up to voltages tubes like to see, adjustable from about 30V to around 450V. There is also a 6V regulator to...

docs.google.com

For a pedal like the Page with one 12AX7 do you think a 12vdc 1 amp power supply would be sufficient? Any issues with ground loops, or does that get eliminated by using an isolated DC power supply?

Any issues working with a 1590XX and 1590D enclosure? Looks like there was ample space to fit the tubes in horizontally and yet have the component board sit underneath? If you need to change components I guess you'd need to unscrew the tube mounts. Did you mount the tagboards pretty tight to the chassis? In my build I used a spacer and an air gap. Could you lay some kind of non conductive barrier and then screw the tagboard down tight? Almost like how Fender did their eyelet boards?

 

[kleydejong]

I made some more progress tonight. I fixed the wiring on the IEC so the hot wire goes into the switch / fuse. I added an LED indicator for the effect on / off with a nice secure screw on mount. I also got my cliff jacks in the mail and wired those in. I'm happy to report with the cliff jacks and the hum blocking circuit, the pedal is VERY QUIET now! Thanks a lot for the help there.

I also had some more time to play with the pedal. I'm really enjoying it. I would like to make some more tweaks to the bass and treble controls.

The bass switch is okay. I have it on the V1A cathode bypass cap to switch between either a 10uf cap (full bass) or a .1uf cap (tight bass). The difference is audible. Only issue is that I find that I really only ever use the .1uf mode. The 10uf is extremely fat. Maybe that's okay. I wonder about shifting the values to maybe 4.7uf and .047 uf for tighter bass in both modes. I also kinda wish it was a pot instead of a switch. I'm tempted to try a bass cut pot located near the gain control between V1A and V1B.

The treble control is also okay. It is very bright at full treble. At 50% on the pot it gets pretty dark. Anything below 50% on the pot makes it overly dark and not very usable. I'd like the treble control to be overall brighter. I took some measurements on the treble control and currently have a 100k audio taper pot and a 33nf cap.

To try and see what I'm currently doing and what a proposed change might make I found a tone stack calculator. I'll be messing with this for a bit.

https://www.amplifiedparts.com/tech-articles/filter-low-pass-high-pass?srsltid=afmbooqj1gh_vxrwm0ozrv6olz7-ig5qe6qwb2zxh8h8x09tyr0stf2k

 

[AlexfromGermany]

Awesome builds! They look fantastic.

I did some fishing and found several helpful links. I'll post them here for my own future reference:

TT VPump - Voltage Converter

The TT VPUMP kit is a very effective working voltage converter which generates an output voltage of 90 V DC to 220 V DC from a 12V DC input voltage. The circuit is in use for many years now and it is proven. In this kit the circuit has been ...

www.tubetown.net

High Voltage SMPS PCB

This is a PCB for building a high-voltage “nixie” style power supply for tube projects. It has a trimpot to adjust the high voltage from about 30V-450V, be sure to choose the right rating for your …

c2celectronics.com

HV Daughter build doc draft.docx

Sushi Box FX – High Voltage Daughter Board The High-Voltage Daughter Board is designed to deliver reliable high voltage to your tube projects. It takes a typical 9-12V DC input and steps it up to voltages tubes like to see, adjustable from about 30V to around 450V. There is also a 6V regulator to...

docs.google.com

For a pedal like the Page with one 12AX7 do you think a 12vdc 1 amp power supply would be sufficient? Any issues with ground loops, or does that get eliminated by using an isolated DC power supply?

Any issues working with a 1590XX and 1590D enclosure? Looks like there was ample space to fit the tubes in horizontally and yet have the component board sit underneath? If you need to change components I guess you'd need to unscrew the tube mounts. Did you mount the tagboards pretty tight to the chassis? In my build I used a spacer and an air gap. Could you lay some kind of non conductive barrier and then screw the tagboard down tight? Almost like how Fender did their eyelet boards?

For a 1 tube OD or Preamp Pedal a 1A Power Supply is enough if you are using 12v for the Heater Filaments. Personally I use a 12vdc 2A Power Supply, because it is also usable for a the other builds like 2 tube preamps or EF86 type builds, where you need 6v on the heaters and therefore the higher current draw.

Look for:

-Isolated
-Over Current Protection
-Short circuit Protection

to protect the power supply/the smps/the circuit and most importantly it could be a safety net for you, in case of failure.

Most of the Quality Power Supply’s should have that. They cost around 10-15 euros in Germany

The 220v that Tube Town is mentioning with there vpump is with 15mA
So for 1-2 tube 12ax7 designs you get around 270vdc B+

I never had issues with ground loops

The 1590xx enclosures are only for 1 tube pedals. And it’s a tight fit, because chances are low to get parts on the tagboard underneath the tube, because the enclosure has only approximately 30mm in height.
The 1590D is great for all the 2 tube builds. Enough space for complex designs.

Underneath the tagboard I have the typical Fender Isoboard material.
For the SMPS you should use 10mm spacing.

For the Layout you don’t have a lot of options with these enclosures, but of course it depends on the circuit.
I breadboard the circuits, so I don’t have to mess around with it anymore.
In case of changing parts, yes you have to loosen the tube sockets, but it’s not that big of a deal.

My next project is a Brownface Harmonic Tremolo in a 1590D enclosure

 

[2L man]

-Isolated
-Over Current Protection
-Short circuit Protection


I never had issues with ground loops

Most modern power supplys do not have Safety Earth and which have SE the output is isolated from SE and Ground Loop does not exists

 

[kleydejong]

Most modern power supplys do not have Safety Earth and which have SE the output is isolated from SE and Ground Loop does not exists

Can you clarify on this, does it create a safety issue if the chassis does not have a path to Safety Earth?

With a DC barrel jack the sleeve would be 'grounded' - but if that ground path to the power supply does not feed to Safety Earth that's a problem?

Or is that just an explanation as to why there would be no ground loop?

 

[Bergheim]

I suppose what he means is that those units are possibly double isolated: Firstly, everything on the DC side of the circuit is galvanically isolated from the mains, so it can't create a ground fault on the mains side. Secondly, it's not possible for any outside surface to become live, since it's all plastic. By having two barriers that isolate the insides from the outside world, it doesn't need a dedicated safety earth connection. The standard is called separated extra-low voltage (SELV).

 

[2L man]

Can you clarify on this, does it create a safety issue if the chassis does not have a path to Safety Earth?

With a DC barrel jack the sleeve would be 'grounded' - but if that ground path to the power supply does not feed to Safety Earth that's a problem?

Or is that just an explanation as to why there would be no ground loop?

No because "PWM switching power supply" has "double isolation". There is transformer and circuit is also construct so that mains does not leak to the secondary.

Most modern effect power supplys don't have Safety Earth. Usually multiple supply voltages all are isolated each other so there does not come ground loop between effects when patch cables are used.

In electronics there has not been "ground" almost 50 years! Only voltages and now it is 0V. When needed 0V defined as 0VDC or 0VAC.

Guitar strings get 0V / Safety Earth thru instrunent cables if the amplifier use SE.

I have collect many laptop power supplys which have different voltages 12VDC...28VDC and all have been free because often actual computer has broke replaced after few years of use.

 

[AlexfromGermany]

Can you clarify on this, does it create a safety issue if the chassis does not have a path to Safety Earth?

With a DC barrel jack the sleeve would be 'grounded' - but if that ground path to the power supply does not feed to Safety Earth that's a problem?

Or is that just an explanation as to why there would be no ground loop?

Use the Enclosure as a Ground, just like you do with your Amps.
Put the primary sides - of the smps…that comes from the DC Jack also to the enclosure. when, in case of failure the chassis is live, you have a dead short and the power supply protection kicks in.

also when the pedal is plugged into your Amp, you have a direct path to earth ground.

Hard for me to explain in English but I hope it helps

 

[kleydejong]

Very helpful, thanks everyone.

 

[kleydejong]

Question: How would you add an effect on / off indicator LED?

This is my attempt to answer my own question.

I have a 5mm blue LED. Datasheet says it could draw 20 ma of current with a forward voltage of 3.4 vdc.

I have a rectified B+ supply node at 189vdc. I also have two 3.3 vac heater supply nodes.

Input voltage - forward voltage of led = current x resistance

Let's say I use the 189vdc B+ node.

189-3.4 = 0.02 amps * x

X = 185.6/0.02 = 9280

So if I apply a 9.2k resistor to my 189vdc B+ node it should work?

Power = volts * current = 185.6×0.02 = 3.712

So a 9.2k at 3.7 watts dropping resistor?

Last night before I ran any math I just yolo'd a 470k 1/2 resistor and it seems to work fine. How can this be? Why didn't the resistor blow up?

 

[NTC]

Still has about 0.4mA flowing. Is it a bit dim? The resistor shouldn't burn out. It is dissipating about 0.07 Watts. Unless you did not mean 470k ohms.

If an LED is rated for 20mA, you really don't want that much flowing through it. 3 or 4mA may be enough to make it bright.

The resistor value sets the current. That LED will always have about 3.4V across it during normal operation.

 

[2L man]

Question: How would you add an effect on / off indicator LED?

This is my attempt to answer my own question.

I have a 5mm blue LED. Datasheet says it could draw 20 ma of current with a forward voltage of 3.4 vdc.

I have a rectified B+ supply node at 189vdc. I also have two 3.3 vac heater supply nodes.

Input voltage - forward voltage of led = current x resistance

Let's say I use the 189vdc B+ node.

189-3.4 = 0.02 amps * x

X = 185.6/0.02 = 9280

So if I apply a 9.2k resistor to my 189vdc B+ node it should work?

Power = volts * current = 185.6×0.02 = 3.712

So a 9.2k at 3.7 watts dropping resistor?

Last night before I ran any math I just yolo'd a 470k 1/2 resistor and it seems to work fine. How can this be? Why didn't the resistor blow up?

I think 20mA to 3,4V LED is much too bright for pedal!

 

[sds1]

2mA is usually plenty

 

[kleydejong]

Very helpful guys, thanks. I may shoot for 100k. Should drop from the 189v dc on the supply to the forward voltage of 3.4vdc while flowing 1.85 ma at .34 watts.

 

[kleydejong]

I've had some time to make videos on the build process. Here is part 1:



And part 2 (which has some tone clips):

 

[kleydejong]

I've spent several hours playing the pedal now. It is really a joy to play with! It has a very warm and creamy character. The EQ is on the darker side overall. Feels like an extension of the tube amp. It responds EXTREMELY well to a boost in front of it. It can get pretty heavy, well into JCM800 or even Mesa territory with enough boost.

I made some changes to the circuit and am ready to document the schematic at this point. I think I could reasonably call it 'done' at this stage. It isn't perfect. The gain control really only has usable sweep from 50% and up. It is pretty clean even at half way. The bass switch goes from extremely bassy to medium bassy. More on that later. The treble control is in a better spot now, but I also tend to go from about 70% to 100%. Below 50% its extremely dull. Probably a combination of finding some better component values in certain spots or maybe trying different taper pots.

 

[AlexfromGermany]

I've spent several hours playing the pedal now. It is really a joy to play with! It has a very warm and creamy character. The EQ is on the darker side overall. Feels like an extension of the tube amp. It responds EXTREMELY well to a boost in front of it. It can get pretty heavy, well into JCM800 or even Mesa territory with enough boost.

I made some changes to the circuit and am ready to document the schematic at this point. I think I could reasonably call it 'done' at this stage. It isn't perfect. The gain control really only has usable sweep from 50% and up. It is pretty clean even at half way. The bass switch goes from extremely bassy to medium bassy. More on that later. The treble control is in a better spot now, but I also tend to go from about 70% to 100%. Below 50% its extremely dull. Probably a combination of finding some better component values in certain spots or maybe trying different taper pots.

When building Tube Boost or Overdrives it’s often better to use Coupling Caps that are smaller in value. 22nF is often too much in the lower registers and the lowend pushes the Amps Preamp Section into muddy territory.
Try 1-4.7nF and it will clean up the lowend response. (At least after the first Triode)

Cathode Bypass Caps on both triodes is also little bit to much, when using such high values. Try 100nF-220nF in both stages.

when you have the overall voicing how you like it, you can then fine tune with the implementation of a Bass and Treble Pot or Switches.

 

[NickK_chugchug]

How did you find the input and output impedance matching?

The earliest tube opamp used three triodes (the tubes being differential amps):
* input
* amplification
* driver

That same setup can be made into a Schmitt trigger (when it started being used in a 'digital' context). Only issue is they had to use -300V and +300V B+ rails!


The tube input should be fine but the output may change tone depending on what's down stream. You could use a triode to simply provide a driver stage - so the 12ax7 or gain stages in one tube then a cathode follower in a second tube which is probably what the muff'n circuit does with the two tubes.
This will also help protect the tone circuit from variations too.