Baja B K Butler Tube Driver

DrNomis · Post by **DrNomis** » 16 Jul 2009, 08:10

Hiya Bajaman,

Just thought you might be interested in a possible modification to the Baja BK Butler Tube Driver,that I just thought about,
the output impedance of the BK Butler Tube Driver is pretty high,I'm guessing that it's about 100k,or it could be more than that,
a possible mod is to put a TLO71 op amp IC after the output level control,wired up as a non-inverting buffer.

Normally,the input pins on an op amp IC such as a TLO71,72,82,etc,are very high,about 1M ohm,the output impedance is something like 100 ohms,so the input pins would not load down the tone circuit,but you'd have a much significantly lower output impedance,which means that you would get a higher output signal level,as well as a brighter sound.

The TLO71 is equivalent to a single op amp IC like the well known LM741,the difference with the TLO series op amp ICs is that they have FETs as the input devices,this has at least a couple of benefits,the bias current for the inputs is very low,secondly,they are designed as low noise devices.

Connecting a TLO71 as a buffer produces an amplifier with a gain of 1,simply connect the output pin to the inverting input.

Let me know what you think about that idea.

regnad · Post by **regnad** » 28 Nov 2009, 19:26

hello all, o few questions:
1- how does this tube driver compare, tone wise, to the tubeworks 3 knob tube driver?
2- the power xformer, do i need a xformer with 12 vac on each leg or 6 vac on each leg?
3- what number is the resistor with a 10ohm value?
4- cant find r11 or r17 on device placment diagram. where are they?
5- cant find diode 3
6-is there clarification as to how the cap and resistor bundled with the high voltage is connected, and what there values are?
7-what is the physical size of that toroidal? or is there more to that part number?

posts edited to make a full list... There's a limited time for editing indeed.

regnad · Post by **regnad** » 28 Nov 2009, 21:14

wow! its magic! one post looks so much better!....

wheres a good source for double sided pcb boards?

regnad · Post by **regnad** » 30 Nov 2009, 03:52

hello??? did i make everyone mad with my questions? im ready to order my parts but need clarification...

Kazooman · Post by **Kazooman** » 02 Dec 2009, 20:35

I'll have a go at some of your questions, but please understand that I have not built this pedal (yet). The parts are literally in the mail.

I do not have any sound clips for the pedal.

Bajaman posted lots of pictures of the pedal. You can see how the 100 ohm resistor and 100 nf cap are hooked up in picture 21. They simply go from the ground wire of the AC to the ground/chassis lug of the jacks. You can also see the size of the components.

I think that the 10 ohm resistor is number 23, but it really doesn't matter.

I do not believe that R11/R17/and diode 3 exist. Just a skip in the numbering. Refer to the actual schematic. Actually, I would recommend sitting down with the schematic, the parts layout, and the top and bottom board traces and going through the entire circuit. You will have a much better understanding of how this all goes together that way.

The taps on the transformer just depend on how you hook them up. Many transformers will have leads that can be wired in series or parallel to give two voltages. Here is a listing of some Hammond transformers in the right size range. As you can see you can wire the primary in series or parallel for 115 or 230 volt input and you can wire the outputs for two voltages. These are not toroidal, but their design (called semi-toroidal) is seeking the same end, eliminating the need for shielding. I am going to try a 229A24. It is very compact, but it is a PC mount so you will need to deal with that. Alliedelec.com and others have them, for about $15.00.

electronicplus.com and elexp.com both sell double sided board. I am certain that you can find many others. I got mine from a local electronic parts place (kenselectronics.com). AVOID Radio Shack. I tried their stuff once and the layers of the board delaminated when I drilled it, ruining the traces on the backside.

Dick Thomas

regnad · Post by **regnad** » 03 Dec 2009, 04:47

thanks Kazooman!
let me read things back to you to make sure i understand.

so the 110 volt line connects to the primary leads of the xformer. and the cap and resistor connect to the neutral side of the 110 volt line and to chassis, right?

with your planned xformer, would you be wiring the 2 secondaries in series for a 12 volt output to the tube circuit?

thanks for the leads on the pcb, i REALLY didn't want to go to the crapshack!

heres both pcb layers together offset giving depth to tell the rear traces from the face traces. the purple info appears to be on the face side, but it is intended to be on the back side behind the grey traces. image is as if you are looking at the component side. also, i resized the component pic so it can be drug on top via MS paint to see all 3 layers on top of each other. question about the bias adjustment components. if this was built without the bias adjustment would you remove the the resistor, cap, diode soldered on the back side and keep the trace intact? or just the resistor and cap keeping the trace intact?

Kazooman · Post by **Kazooman** » 03 Dec 2009, 14:28

As I read it the 110 volt line connects to the primary of the transformer. The ground wire of the line input is attached to the metal chassis (look at the green wire running to a lug on the chassis in picture 5). Look at the schematic. The two line inputs connect to the transformer. Then you will see that one side of the 12 volt output connects to the ground trace on the PCB (labeled E for earth). All of the solid black bars are connected through the traces and wiring. This is the board ground. The input jacks are insulated from the chassis by plastic spacers. The board/jack ground is connected through the cap/resistor to the chassis (line) ground. The line input ground is shown by the solid bar with hash marks under it. I think that this connection is within the wire bundle and you can just see it in picture 21. Please be careful and get someone locally to help you out if you are unfamiliar with working with line voltages. You can get hurt!

No, the secondaries would be wired in parallel for 12 volts. Here is a wiring diagram from Hammond:

You might as well buy a good sized piece of PCB. It is much cheaper and you only pay shipping once. I bought a 2' X 3' piece of single sided board quite some time ago and I am still chipping away at it. The double sided board I bought was about 18" X 18" and cost me $20.00.

If you do not want to include the bias mod, eliminate the cap and resistor and leave the trace intact. The zener is not in the original schematic so I believe you can just delete that as well. I think that there is an error on the PCB diagram if you are going to use the bias mod. I believe that you also need to cut the trace running from the tube pin 8 straight down. If it is still there then that trace combined with the jumper simply reestablishes the connection you deleted by cutting the other trace. If you look at the right hand end of the jumper you can see that there is a trace connecting that pad to the pad four spots lower on the board. You can see that you could connect the latter pad to the pad at the other end of the jumper by drawing in a new trace on the component face of the board. That's what I am doing. You may need to move a few things around to get it to fit in. I plan to move the resistor and cap off the board and put them on the bias pot. This will make for a neater build. You just need to find two appropriate spots to connect the wires to the pots. I added two pads for this purpose.

regnad · Post by **regnad** » 26 Feb 2010, 02:00

question, what are the smaller physical sized resistors? is there a way to order the smaller footprint resistors, i dont want to cram a the "standard" size resistors where the smaller ones go....

Kazooman · Post by **Kazooman** » 26 Feb 2010, 13:46

It's the nature of the beast that some layouts get crowded. You will often have to bend the leads on a cap or resistor to fit into the available space. MANY layouts are designed to have resistors "standing on end" to save space. Just take one of the leads and bend it back around the length of the resistor. Makes it look kind of like a radial electrolytic cap. If you do this neatly they look just fine.

Here is a picture of the resistors you are referring to in my Tube Driver. NOT the prettiest job, but they work fine. The blue one is better than the other one.

I am having some probloem getting the image to show. Here is the URL

http://k41.pbase.com/o6/45/150145/1/122 ... istors.jpg

regnad · Post by **regnad** » 01 Mar 2010, 12:02

ok, i wanted to avoid that but it may be harder to track down the small resistors..... ok, i'm now over the small resisters, i will stand the larger resisters now!

how did that transformer work out? and have any of you guys found a single source for all the components for this build?

Kazooman · Post by **Kazooman** » 02 Mar 2010, 15:47

The transformer worked just fine and the pedal sounds great.

I don't know of any simgle source for the components.

regnad · Post by **regnad** » 06 Mar 2010, 03:59

great! im just about ready to order my parts. im going to build 4 of them! what brand of tube comes in the bk tube driver? also, can anyone confirm the exact measurements of the bottom of the pedal?

Kazooman · Post by **Kazooman** » 06 Mar 2010, 20:42

I don't know about the exact dimensions of the original pedal. You can get a very good idea from the pics Bajaman posted earlier (on the second page of this thread). His picture #5 shows the unit from below. You can get the dimension of the circuit board from the transfer pattern. Then you can use that as your "yardstick" for calculating the dimensions.

I would suggest getting your parts before you make any enclosures. If you transformer takes up more space, you will need to move the stompswitch up. Then you will think it is too close to the knobs on the pots. So you will want to move them up too, requiring a somewhat longer enclosure to allow room for the jacks. Then, if you decide as I did to put the LEDs in bezels you need to allow room for that. If you are doing the bias pot mod you need to allow for that also. My transformer was a PC mount style so I needed to allow room to the transformer and a small board.

So...... Gather your parts and then figure out the dimensions of YOUR Tube Driver.

The current crop of Butler Tube Drivers that have the bias mod use a 12AX7 (I believe) and the bias pot allows you to reduce the gain to be more like a 12AT7 or even a 12AU7. I built mine with the bias mod and then put a 12AU7 in it. I need to leave the bias cranked all they way up with that combination, but I like it. I haven't messed around with other tubes and tweaking the bias. I'll have to give that a try.

Kazooman · Post by **Kazooman** » 06 Mar 2010, 20:48

I'm trying a different site for hosting an image to show you the transformer in my pedal. Let's hope this works!

I could have made the board smaller, but it works for me.

Kazooman · Post by **Kazooman** » 06 Mar 2010, 20:51

OK, That seemed to work (for me at least) except the picture is huge.

Here's another try for the resistor standing on end pic I tried to share earlier.

regnad · Post by **regnad** » 07 Mar 2010, 03:11

are the measurements of the transfer in inches? i plan on building an "exact" replica....

Kazooman · Post by **Kazooman** » 07 Mar 2010, 13:46

Yes the dimensions are in inches.

lutor · Post by **lutor** » 05 Apr 2010, 17:58

I want to give my personal edition with mod. for constructions in single side of perfboard.It work very well, best of the original value and it is verified. Good work for all!
Thank to Bajaman!

Hides-His-Eyes · Post by **Hides-His-Eyes** » 05 Apr 2010, 18:20

I cannot believe that ANYBODY would try to perf this.

I applaud you!

lutor · Post by **lutor** » 05 Apr 2010, 18:38

some picture of my edition:

Baja B K Butler Tube Driver [documentation]