Tube boost + overdrive running off a 9 volt battery

[DavenPaget]

Hi , can this be used as a preamp ?

[Edalicious]

I've just gotten my one breadboarded up! After some tweaking to suit my humbuckers it sounds incredible! My only problem is that I'm getting no boost. In fact, it is slightly quieter than clean guitar even when I have the volume pot cranked. It was even quieter before I started tweaking so I'm presuming that's not the problem. The volume drop is roughly equal to the amount of compression I'm getting so when I'm playing quietly, the volume is about the same with the valvey in and out but when I'm really digging in there is quite a big difference in level. Here are my voltages:

Pin 1: 6.2
Pin 2: -0.25
Pin 3: 0
Pin 4: 0
Pin 5: 9.3
Pin 6: 7.5
Pin 7: -0.2
Pin 8: 0
Pin 9: 4.67

My tweaks are:

R1: 1M and 220k in series
R2: 470k
R3: 220k
C1: 27nF
C4: Removed
VR2: Removed

The resistor changes are all to get a bit more drive and the C1 change is to tighten up the tone a bit. If needs be I can make it up with the stock resistors and caps and remeasure my voltages. Any help would be much appreciated 

[Dongle]

If you have anything on the brteadboard, you could also try a buffer!!
If your Amp does not fit the impeadance requirements of the valvecaster, that may be a good reason for your volume loss! You can stop it with the buffer.

Your mods give even more gain and should make the thing louder. So dont worry about that. The mods are good, I tried similar things. Thats for sure not the reason - but the impeadance might be...

EDIT: And you should also try 12 V - better 30 or 40! It makes a NICE difference - and gets louder
Do you have active or passive pickups?

[Edalicious]

A buffer? Would a Boss pedal before and after do the job? They're buffered, right?

[Dongle]

Yeah, that would do the job.
But in my first post I did not realize, that you are running with 9 V. My Vaövecsater had also low volumes with 9 V. If you can raise everything to 12, it will be much better!
If you can make it to raise the heating to 12 and the anodes to 30 or 40, it will be even better!!!

[Edalicious]

Passive p'ups and yeah I'm running it at 9v. I'll have a root around for a 12v wallwart. I was kinda hoping to get it going well with 9v because i'd rather not have to bring a second WW to gigs. Has anyone been able to get a volume boost or unity running at 9v?

Edit: I'll give the Boss before and after a go now too

[Dongle]

In principle, you did the right things:
- higher values for R2 and R4 increase gain


Its a simple and good standard circuit - but if the heating is not sufficient and the voltage in the tube is not big enough, there is nothing you can do...

[Govmnt_Lacky]

Has anyone been able to get a volume boost or unity running at 9v?

You could always try a charge pump (MAX1044) with a 12V regulator after it to get your 12VDC from a 9V supply.

[Dongle]

Did you try this? I am not sure, if a max 1044 gives enough current for the heating...

But it works for sure for the anodes! Best thing to do: 12 V wallwart directly to the heating. Try this first. After that, go and raise the anode V with a charge pump.
I am not using the 1044, but the 7660S. Its much cheaper and can also work with 12 V (up to 15). The 1044 only can handle 10.X V as input.

[Edalicious]

Ok, the buffered Boss pedals before and after made no difference to the level at all so I'm guessing making my own buffer probably isn't going to be much help. Would it be possible to use two 9v jacks to bring the voltage up to 18v and then reduce that voltage to 12 for the heaters?

[Dongle]

Sure, that works!
Good luck

For trying, you can reduce the voltage with a voltage divider (two resistors). In a first trial, I would not use a 7812 for that..

[Edalicious]

Yeah that's what I was planning . Would it be worth sending the full 18v to the anodes too? Would there be any problem having the two 9v dc jacks daisy chained from the same wallwart?

EDIT: Hmm, after some reading, it looks like I can't get 18v from one wallwart. It'll have to be the voltage pump so

[PaulBass]

Another way to brighten up the Valvecaster is to use a 500K or 1M for the tone pot. The tone pot is just a faucet to bleed out the highs to ground through the 10nF cap. A 500K or 1M pot gives you the option of darkening the sound or making it blinding bright, or somewhere in between. This can be an alternative to building a Valvecaster without a tone pot

[tjp78704]

This drawing of the Matsumin pedal is awesome, and very helpful! I finally got mine working today (using a cheap Sino 12AU7), but I noticed the tone pot is wired backward in the drawing, an easy fix though. I also tried it out with both 9v and 12v DC (using a Radio Shack adjustable wall wart), and both sound good, but I'll bet the 12v setting is probably better for the tube's health.

I hope to get a test video posted on YouTube soon. Thank you for making the nice drawings, they really help a bunch!  

Tim

Regarding the 386 amp, that's the route I'm taking with my wired tube socket thing. Trying to fit it in a small plastic case.

For the questions about using a tube other than the 12AU7, as said earlier, they are higher gain and won't work nicely unless you modify the circuit, I don't know how to do that part.

tubesandmore.com has the tube and sockets, it is the standard 9-pin tube socket you would use for guitar amp preamp sections.

Here is a rough *unverified* wiring diagram for anyone who wants to try it.

[tjp78704]

I built my Matsumin Valve Caster in a Hammond 1590BB style enclosure (PedalPartsPlus.com, #1126), with an inexpensive Sino 12AU7 tube, some cloth insulated wire and the terminal strip from TubeDepot.com, and most of the capacitors and resistors from Mouser.com. Pots and knobs came from PedalPartsPlus.com, and jacks and DC power jack came from Mouser.com. You can see the 12AU7 tube filaments glowing in the 2nd photo while powered by 12v DC (I also had good results with 9v DC too).


Valve Caster pedal guts by Tim Patterson, on Flickr


12AU7 Tube Powered Overdrive Pedal - with glowing filaments! by Tim Patterson, on Flickr


Tube Overdrive Stomp Box by Tim Patterson, on Flickr

You can see more photos of this build on my Flickr.com page.

[red_92]

i found the problem

here are the voltages at the pins

1- ~7v
2- (-0.5)
3- 0
4- 0
5- 10.7
6- 6.8
7-~(-0.3)
8- 0
9- 5.14

the voltage at pin 1 is way too big-how can i fix that?

[Steben]

why not with 12U7 tubes? they are designed for 12V car radio.
draw 150 mA though for the heaters.

[Renegadrian]

tjp78704, that is AWESOME!  F...ING AMAZING!!!  OMG!!! I love it!!!

[Perkla]

This seems to be something that i wanna build soon, can anyone that have one of these working upload a soundtest on youtube.... ? please...

I cant wait to hear what it sounds like...

[tjp78704]

I think your R2 mod might be the issue.. Have you tried the value called for in the schematic yet?

i found the problem

here are the voltages at the pins

1- ~7v
2- (-0.5)
3- 0
4- 0
5- 10.7
6- 6.8
7-~(-0.3)
8- 0
9- 5.14

the voltage at pin 1 is way too big-how can i fix that?