Tube boost + overdrive running off a 9 volt battery

[reddog22]

how have you wired the heaters? there is a number of ways I can think of because of the centre-split.

are you working from a circuit in this thread, or did you draw-up your own?

Cheers,in my original post i had i have built this to the schematic and layout by Renegadrian and have followed it to the tee(as far as i can tell anyway) Pin 4 grounded and 5 to 12v.

[duck_arse]

alrighty, what are your pin 9 connections, they should be empty. you need to disconnect power and probe for resistances. first measure across the valve itself, see what the heater resistance is/are.

from the 12V line to ground w/ no valves, you should have, well, I dunno, a high reading (relatively, it will get lower). measure from pin 5 of socket 1 to pin 5 of socket 2 should show 0R, or your meter's idea of. do that same measure for pin 4/1 and pin 4/2, and the answer should be the same.

now stick in a valve, and measure resistance across the other pin 4 and 5. what value? pull the valve, swap into the other socket, you can see where I'm going with this ..... what value? now stick in both valves and measure across either/both 4's - 5's. should now be around 1/2 the single valve reading.

if not, why not?

[reddog22]

Cheers duck,i appreciate yr help. I'll go through all of that later today and get back to you. Thanks

[reddog22]

alrighty, what are your pin 9 connections, they should be empty. you need to disconnect power and probe for resistances. first measure across the valve itself, see what the heater resistance is/are.

from the 12V line to ground w/ no valves, you should have, well, I dunno, a high reading (relatively, it will get lower). measure from pin 5 of socket 1 to pin 5 of socket 2 should show 0R, or your meter's idea of. do that same measure for pin 4/1 and pin 4/2, and the answer should be the same.

now stick in a valve, and measure resistance across the other pin 4 and 5. what value? pull the valve, swap into the other socket, you can see where I'm going with this ..... what value? now stick in both valves and measure across either/both 4's - 5's. should now be around 1/2 the single valve reading.

if not, why not?

I've just gone and done all the measurements.
Tube 1 in         Tube 2 out
4. 0.1               4. 0.1
5. 0.1               5. 0.1
T1 out             T2 in
4. 0.1                4. 0.1
5. 0.1               5. 0.1

T1 in              T2 in
4. 0.1 ohm       4.  0.1 ohm
5. 0.1 ohm       5.  0.1 ohm

12v+ to - 20M ohm
So 0.1 for all of the heater resisitances.

[duck_arse]

mmm. well. to me, 0.1 looks like a short somewhere across the heater lines. when I measured the 3x 12a*7's I have here, they showed 14R pin4 - 5.

it seems you may need to unwire your heaters, and do them again.

how are you on posting photos?

[stallik]

Sorry to stick my oar in but at there's a little voice in my ear asking if the valve base is wired from the top or bottom as it were. I appreciate that this was bread boarded first but still....

[reddog22]

mmm. well. to me, 0.1 looks like a short somewhere across the heater lines. when I measured the 3x 12a*7's I have here, they showed 14R pin4 - 5.

it seems you may need to unwire your heaters, and do them again.

how are you on posting photos?

Ah,i get you now Duck. Measuring the resistence across pins 4 & 5 on the same tube is 17.8 ohm's for both tubes.

[duck_arse]

ahh, no, maybe you're still missing my gist (ohh-er!)

we really, really need a circuit diagram for what you have built to show about now, so we can see what to expect across the heater connections on the empty sockets. I'm thinking you'll have a rectifier/cap looking into the heater, so it will read *some number* of ohms. your sockets show 0.1R across the mt heaters, so that looks to me like a short.

with both valves fitted, the 2 heaters should (*) be in parallel, and we would ekspekt about 8 or so ohms. at least we know your heaters are not open/short.

and anyone else carrying an oar, please! dip it in! bring life jackets and circuit dias, too.

[stallik]

Duck is right. Without a circuit diagram, we're all running blind. There is a circuit for a twincaster on these pages but it would be wrong to presume that you've used it. Please let us know which one you are using. Also, can you take pictures, upload them and send us a link? If you can't, PM me and I'll try to do it for you.
Now, one final thing. You state that all appears to work until you insert the second tube. How do you know that the second tube itself is not faulty? Have you tried both tubes in position one with nothing in position 2?

[wizdum]

Here is my 1u monstrosity:

.



It has had many versions, changes, mods, tests and failures.
The 12AU7 tube in the window is a later version of the Valvecaster.
which feeds into the 12AT7 tube, a banana boost.
(I removed a tube stage)

The control layout is:
6 Input cap selector for the Valvecaster
Gain for the Valvecaster
banana boost volume (main output volume)
Diode Distortion level pot.
6 Diode selector.
Valvecaster volume.
0-32 voltage adjuster (10 turn pot)

It is switched in/out with a relay controlled by a Rockman MIDI Octopus.
There is bright white 3 LED strip (on the bank of caps) to light up the tube.

I dig the overall character.
I use it to put a small amount of spice on the Carvin V3M's clean channel.
It was fun tinkering with it....but, wow...I would hate to count the hours.

Thanks to all who contributed...I learned a LOT!
~D

[reddog22]

Thanks duck_arse and stallik for helping me out here. I have no idea on uploading photos and links and am over this pedal atm... I'm gunna have a break from it for a while. I'll put up a new post and let ya's know how it goes. Thanks again.

[ghostsauce]

So, I came across this: http://stompage.juansolo.co.uk/btbuild.html

It's essentially a valvecaster with a proper gain control instead of the bias control we use for gain in the original. I already built one and would like to implement this gain control, but I'm struggling to figure it out if you guys don't mind proof reading for me here.. I *think* I just need to add a 47n + gain pot combo between pins 1 and 7, in addition to the 47n that's already there. Am I missing anything? Just wondering if I need to change anything else to make this work right. Toying with the idea of just building the boobtube instead and continue running it at 12v.

Here's the one I built:

[ghostsauce]

Mandatory tone sample:

Sounds good right?! He's probably running it at 40v though like the link suggests, where I am running 12v. But hey, gotta experiment.

[ghostsauce]

Well, I got around to trying it out and sure enough it does sound better than the previous bias adjustment knob. I removed the bias pot all together and pin3 now connects straight to ground. It's still not perfect, though.

In the vid he's got the level and gain on the pedal cranked, and it seems to be goosing his amp a little where before I thought all this glorious gain was coming from the pedal. When I do that I get pretty close to the sound he's got, but I think it needs more tone shaping. He's got a 470k and 100pF paralleled between C1 and pin 2, and I am guessing that this is shaping the EQ a little. EDIT: after some research.. seems like this is a high pass filter.. EDIT2: Actually no, neither part is in series with the signal. What do these do?

I also noticed he's got a 150n and 1.5k in parallel off pins 3 and also 8, so I'm going to attempt that and see what it's about. I'm thinking it biases the stages better? 

[JRM]

 !  I'm getting an annoying hum in my Valvemaster! The signal is ok until the valve's first stage but it gets noisy afterwards.
Voltages look OK:

Cathode 1 (pin = 0.018V
Grid 1 (pin 7) = -0.73V
Anode 1 (pin 6) = 7.35V
Heater 1 (pin 5) = 12V
Heater 2 (pin 4) = 0V (GND)
Cathode 2 (pin 3) = 0.017V
Grid 2 (pin 2) = -0.72V
Anode 2 (pin 1) = 7.35V

Checked for solder bridges, all wiring double checked... 

[Jdansti]

!  I'm getting an annoying hum in my Valvemaster! The signal is ok until the valve's first stage but it gets noisy afterwards.
Voltages look OK:

Cathode 1 (pin = 0.018V
Grid 1 (pin 7) = -0.73V
Anode 1 (pin 6) = 7.35V
Heater 1 (pin 5) = 12V
Heater 2 (pin 4) = 0V (GND)
Cathode 2 (pin 3) = 0.017V
Grid 2 (pin 2) = -0.72V
Anode 2 (pin 1) = 7.35V

Checked for solder bridges, all wiring double checked... 

Do you have it in a metal grounded enclosure?  Mine had a hum too until I boxed it.

[JRM]

Yes, it has a metal enclosure. After several hours of troubleshooting and checking I've come to the conclusion that the hum is induced by the psu. I've swapped it with a 9V/375mA one and the hum has gone. That's very weird as the psu was custom designed with a 15V/3VA transformer, rectifier, large filtering caps and 7812 regulator. It should be ok. And the current should be enough also☹

I've used a probe and the hum starts at the exit of the first amp stage. Before that it's quiet.

[Jdansti]

Glad you got it worked out.

[JRM]

No I haven't. It is supposed to run on 12V and with that still hums

[Jdansti]

Ah. Yes, it does appear to be your 12V PS. Can you post a diagram of the PS with cap values?