Tube boost + overdrive running off a 9 volt battery

[turkey101]

Hey guys, here's my effort.  First off, thanks to all those who have participated and provided great ideas on this thread!   I am indebted to Matsumin, Beavis and all those who have followed.

OK, so my "Valve'd" has a few mods as you will see by the schematic below:

* The "Clarity" switch. As suggested by Krinor - refer http://www.diystompboxes.com/smfforum/index.php?topic=63479.msg518458#msg518458
* I added a power on/off switch and run the heaters at 12.6VDC & the plates at 24VDC using a customised power supply on my pedal board that has all sorts of outputs.
* The Gain Pot bypass for clarity at lower gain suggested by Ripdivot - refer http://www.diystompboxes.com/smfforum/index.php?topic=63479.msg516969#msg516969
* Various filter cap and plate resistor mods to vary gain and frequency range

I hope this helps some other people.  I really enjoyed this project - especially the extra hardware for the enclosure.  I also think running the pedal at the higher voltages helps the structure of the sound, but this thing will still run nicely at 9VDC on both power inputs - versatility is what makes this circuit so special!  Extra thanks to Renegadrian, who seems to be keeping this whole thread together!   


Excuse my Beavis-style schematic . . . 



I went for the all polished chrome/stainless look and added a high intensity blue LED up the centre of the valve socket that lights up when the effect is on - mmmm, blue! 





An nice old Mullard 12AU7 for that extra creamy goodness!



Obligatory gut-shot



And finally, the vero I used:



Cheers,

turkey101

[kurtlives]

Wow that is a great looking build, very classy.

Like the PVC(?) wire and your routing.


I don't understand your clarity switch though. It looks like when the switch is open you won't get any output.

[kurtlives]

Ah totally missed the schem. Very cool control, I get it now.

[w437776]

can someone please check my layout...

[DUY1337GUITAR]

This is my first time posting on DIY stompboxes (I think).  Now I blame you guys for getting me overly obsessed on this.....

Nah just kidding, I love this site. 

I was planning on building the Real Mctube, but I totally changed my mind when I found out about the Valvecaster.  I don't have money yet to buy the parts, since I just used it to make a gain boost, but I'm just here to figure things out and make my plan.  So far I'm thinking of getting a 2-amp 25.2v transformer and regulate it to 12v.  Tell me if there's any problem with this.

As a some of you guys done, I'm gonna place a high brightness LED underneath the 12AU7 (Turkey101, yours looks gorgeous!), but I'll be using a bicolor LED, making RED indicating bypass and BLUE as active.  The blue LED will light up to the guitar signal, so it will react to the guitarist's picking.  You guys may know this as the LED Twinkler on YouTube by JeonJoe, I found out how to do this with only just a cheap opamp and capacitor which can be found at radioshack.  Having the tube light up to the sound of your guitar would look amusing :3

As you guys can tell, I'm probably one of the biggest DIY guitar guru at my age, see here for proof:
http://www.youtube.com/user/duy1337guitar

[Ripthorn]

There are actually a ton of members here about your age, but welcome all the same.  The issue I see with regulating a 25.2V wall wart is that the 150mA needed for the heaters (at 12.6V) will mean you have to dissipate about 2W from your regulator, which means a big heatsink to keep it from shutting down.  Other than that, I can't think of anything, though 25.2V implies that is going to be an AC wall wart, correct?  If that is the case, you are going to be dropping more like 3W to regulate, but gets great plate voltage.

[kurtlives]

Calling yourself a guru

The LED sounds cool

[DUY1337GUITAR]

There are actually a ton of members here about your age, but welcome all the same.  The issue I see with regulating a 25.2V wall wart is that the 150mA needed for the heaters (at 12.6V) will mean you have to dissipate about 2W from your regulator, which means a big heatsink to keep it from shutting down.  Other than that, I can't think of anything, though 25.2V implies that is going to be an AC wall wart, correct?  If that is the case, you are going to be dropping more like 3W to regulate, but gets great plate voltage.

I said I'm going to be using a 25.2v transformer from radioshack.  This one:
http://www.radioshack.com/product/index.jsp?productId=2102703
2 amps is more than enough to power everything I need for this project.

I'm gonna use a 12v voltage regulator so I don't get any noise or hiss. Just yanked off some heatsinks from scraps just a while ago.  I think it be cool to have 24v but a 24v voltage regulator requires at least 27v DC supplied.  I'll be using the 12v for the circuit itself and the heater.  If I'm informed correctly, it should be safe for the heater to have 12.6v plus/minus 10% (so ~11.3v to 13.9v).  Better than using 4.5v like from the original schem.

Maybe I could just make a switch for changing plate voltage.  Make it switch between the regulated 12v and the 25.2v directly from the transformer.  If there's no hiss or noise that i'd get annoyed of, I'll probably keep the switch.

If any of you guys are interested on how the LED Twinkler works I can post a drawing, super simple and would look great on projects.  Maybe looks even cooler with the light emitting border shown on this site 

[w437776]

...Make it switch between the regulated 12v and the 25.2v directly from the transformer. 

not a good idea...

[Ripthorn]

Here's the deal, you are going to totally fry something if you try to use that transformer with a voltage regulator.  You will need to go from that transformer, through a bridge rectifier, smoothing caps and chokes/resistors then into your regulator.  Rectified, that transformer will supply 35V.  So you are going to be dropping 23V ish over your regulater.  At 150mA, that comes to 3.5W, which is going require a really hefty heatsink with some good compound.  You really should study up on power supplies first.  Here are some faults with your current approach and their solution:

1) You HAVE to rectify your 25.2VAC to DC, you can't just run AC into a regulator, that thing will fry quick.

2) You NEED to filter after rectifying, otherwise you will get hum and noice up the wazoo.

3) If you use a 12V regulator on the rectified output, make sure the heatsink on it never gets much more than fairly hot to the touch.  Blazing hot means it is working too hard to dissipate the heat which can also introduce hum into your signal.

4) To use 12V on your tube heaters, you will have to use different pins on the tubes, the one for the heaters in series.

5) Number of amps from your transformer in this case is a non issue.

If you can't find a heatsink that is appropriate, you could probably rectify one of the 12.6V taps and regulate that, but the smoothing caps and resistors are still required.  Again, I should stress that if you want to do these things you propose, you have to read up on power supply design, or you will have youreself some nicely fried tubes/ICs/caps, etc.  not trying to be harsh, just trying to open your eyes a little before you go gung ho on something that will blow your project up.

[DUY1337GUITAR]

I guess I'll leave out the switch then

And when I said voltage regulator, I actually meant the whole system of components to achieve it.  I understand about the bridge rectifier and the caps to remove the ripples.  I know which pins to use for 12v, I did my research.

And just now I just learned that the bridge rectifier increases the DC voltage by ~1.41 times.  Is this true?  If so then I can just use a 12.6v transformer, use the bridge rectifier to make it ~17.8v, then use a 12v voltage regulator and have caps at the right places.

Here's my source:
http://diy-fever.com/index.php?project=power_box

I'm glad I'm asking you guys on this, thanks

[Ripthorn]

Yes, when you rectify, your AC voltage of 12.6V then becomes about 17.8V because that is the RMS and that is what diode bridge does.  If you go this route, then you don't need a super beefy heatsink, but it would still be wise to use one.  You can still put in a switch if you want, what you would do is tap off your power supply before it gets to your 7812 and filter some more (since there is only one filter capacitor up to that point).  That still gives you higher plate voltage, and your plate voltage doesn't have to be regulated, just rectified and filtered.  I would highly recommend reading "Power supply basics" at geofex.com.  Best resource on this stuff that I have found.

[DUY1337GUITAR]

I'll go with the 12.6v transformer then.  I got a heatsink that was originally bolted onto a voltage, and also got a 2x1 inch and 2.5x2 inch heatsinks.  I'll check out geofex soon, thanks!

Here's the diagram for the twinkler if anyone is interested, just quickly drew it on microsoft paint:


Many thanks to my friend who helped me with this circuit.  He just wired his the input and ground directly the audio jack, so the circuit is working in parallel to the guitar signal (if I worded that correctly).  Just wire the LEDs in series, parallel, or whatever and supply the correct voltage as usual.  But since the LM386 opamp has some resistance, I think it'd be best to supply a little more voltage to achieve full brightness.  So for a blue LED which has the typical voltage of 3.5v and 3.8v max, I would use 4v for each.

[shimster]

Hey folks,
  It's been a month or 2 since I've contributed to this thread.  I recently built a valvecaster for a friend of mine who loved my first invention (the tweaked valvecaster with an IC booster).  I suggested that I build him one without the boost circuit, so it's a nice clean single-valve circuit.  This time I put in a pot on both cathode resistors for gain just for fun to see what we can learn.  Didn't learn much but it does sound pretty good.  One thing I'm still dealing with is the change in tone between 2 identical tubes from different batches. I'm guessing I'll need to put in trim pots on the plates or grids for biasing but I have a lot of reading / comprehending to do before I mess around with that too much.
  Anyway, here are the photos of it.  It's basically a valvecaster running at 12 volts with 2 gain pots and a lower input cap.  Oh, and I'm using an EH 12AY7 tube.  This was a fun project.  Oh, I gave it a small power indicator light for safety. A small but nice touch if I may say so myself!  I'll build one for myself to use as a boost or to add some dirt to clean tones.  My wiring has gotten cleaner but it's nothing compared to the super anal designs I'm seeing on this thread. You guys are amazing!




Hope you enjoy the pics!
Cheers,
Dan

[Ripthorn]

That looks like a crazy bright LED.  Looks good otherwise.  Hope that tube doesn't get busted off up there...

[shimster]

That looks like a crazy bright LED.  Looks good otherwise.  Hope that tube doesn't get busted off up there...

Yeah, it is that bright too.  The guy I built it for likes them super bright. Seems like a lot of people like them that way, me not so much, it's blinding... The tube mounted on top is kind of silly looking and not so practical but I like it.  When I build something to take on the road I'm gonna have to design a bulletproof enclosure or buy an electro-harmonix chassis.

[guitarangry]

Been reading through this whole monster of a thread( taken 2 8hr shifts at work on and off to read) and would like to say i love all the versions of it. Im gonna have a go at building one of these myself just waiting on the tube and socket and my new soldering iron that ive been waiting for for a week. Have a nice wierd case hiding that i think will do the job nicely for what i have in mind.

[isildur100]

I don't know if this question has already been asked but this thread is getting rather large to read from the beginning , here goes:

I've been looking at the different brands of 12AU7 out there, especially on ebay. Some are rather expensive, other not. Is it really worth it to pay big money for such a tube? Is the difference in sound noticeable? Personally, I have tried Electro Harmonix and I'm satisfied but when I see those tube costing 80$ or more, I wonder what makes them so special.

I'd like to hear about your experience with trying different 12AU7 tube brands with this circuit.

cheers

[Ripthorn]

A lot of those really expensive tubes are rare NOS tubes that have taken on an almost mythological status.  Like old black plate RCA's or Telefunken's.  Do they sound better?  Depends on what you like to hear.  Are they worth the money?  How much do you have and how much does it matter to you?  Personally, I like my old no-name tubes that I picked up for a couple bucks a piece.

[kurtlives]

In a low voltage stompbox application use whatever working 12AU7 you can get a hold of.

I got a bunch of Conn NOS 12AU7s a while back for really cheap. Tbh though, in a lowish voltage setting they aren't that much different than the modern production tubes.