Tube boost + overdrive running off a 9 volt battery

[lazerphea]

Ok, I had some time to make some experimentations, and here's what I've found:
- Just out of the adapter I read a voltage of 17.19V
- the output of the 7812 reads 11.01V
- if I add the 100uf caps to its input and output the voltage raises to 11.60V
- the same voltage is present an the pin N. 5 of the 12au7, when I connect the power to the circuit.

I get a very sloppy and uncomfortable sound out of it and the situation gets worse and worse as I play through the circuit; here's a soundclip of what I get after about 15 minutes of playing:
http://www.paoloscala.net/diy/12v.mp3
The sound degradates a lot...

So I tried to feed the tube with the 17.19V original voltage, and here's what I get:
http://www.paoloscala.net/diy/17v.mp3
Ignoring the hum, which I understood is given by the unfiltered adapter, the sound is still crappy and with no sustain at all... additionally, the tube doesn't lit up that much: I can see two filaments getting incandescent but that's it.
Maybe I should get a better tube (it's an Electro Harmonix)?
Thanks all.

EDIT: I forgot the adapter specs:
- it's a variable voltage adapter that spans from 1.5V to 12V, and I read: 500mA6VA(max)

[Renegadrian]

Ciao Paolo...
* Pins 4 and 5 of the 12**7 family are the heaters, one gets V+ and the other is tied to ground. So it's normal to have the same voltage from the power jack up into the heater (pin 5), that's how it's meant to be! 
* Regarding the light emission, the tube is not a light bulb!!! However each tube is different...I have a EH in my Valvy #001, and you barely can see the 2 filaments working - other tube do light up more, but that doesn't necessarely mean they are better...
* Regarding the wall wart - as you can read on the net, the heater current needed is 300mA, and you should add some more for the rest of the circuit - I believe it shouldn't be more than 400mA total. I run mine with a 500mA or a 1A, but never heard big differences, so yeah 500mA is good enough.
* I believe the problem you got could be related on the components/wiring on the signal part, and not a problem on the power part of the assembly.
Maybe you should try another wall wart, so we can be sure if that's to blame, or just go mad and start it over.

[lazerphea]

Ciao Paolo...
* Pins 4 and 5 of the 12**7 family are the heaters, one gets V+ and the other is tied to ground. So it's normal to have the same voltage from the power jack up into the heater (pin 5), that's how it's meant to be! 

Ciao Adriano! Yeah, I know but I specified that to make sure everything's fine with the circuit's alimentation

* Regarding the light emission, the tube is not a light bulb!!! However each tube is different...I have a EH in my Valvy #001, and you barely can see the 2 filaments working - other tube do light up more, but that doesn't necessarely mean they are better...

Ok!

* Regarding the wall wart - as you can read on the net, the heater current needed is 300mA, and you should add some more for the rest of the circuit - I believe it shouldn't be more than 400mA total. I run mine with a 500mA or a 1A, but never heard big differences, so yeah 500mA is good enough.
* I believe the problem you got could be related on the components/wiring on the signal part, and not a problem on the power part of the assembly.
Maybe you should try another wall wart, so we can be sure if that's to blame, or just go mad and start it over.

Good, I'll try to rewire it and get another wall wart asap!
Thanks for the support, man!

[Ripthorn]

When working with tubes and the sound degrades over time, that still makes me think that it is a power issue, because that is almost identical to a problem I had when working with the submini amp I am building.  It played fine, but then started dying out.  That was because the regulator got so hot it could no longer dissipate the power needed to keep the voltage regulated. 

First, your adapter is designed to deliver about 12V when run at max load (all 500mA) and a 7812 needs at least 14V on it, so if you are drawing 400mA, chances are your 17V is going to drop to maybe 13 or so, which won't be enough for the 7812.  If it does still provide 14V, then the 7812 probably isn't able to handle the power dissipation for too long, so you would need a heatsink there.

Second, it is entirely possible that it is a combination of something with the signal path and power supply.  Perhaps you accidentally put in a wrong value (10k instead of 100k or something like that)?  Also, how are you getting the 6V for the heater (or is this the twin tube version?).  If you don't have quite enough voltage to run a 7812 or similar, you can always get a zener diode and wire the anode to ground and the cathode to both the +V part of your circuit and the voltage in.  This will shunt anything over 12V, even if it is 12.5V.  Good luck.

[terminalgs]

pull the tube from the socket.  measure VDC across pins 4 and 5.   if you have 12V or more (and your power supply is at minimum 150ma + whatever the rest of your circuit will draw), you have enough filament voltage.

if it sounds bad try a different tube.  are you using the 12ax7 ? or 12AT7 or 12AU7 ??   in starved plate circuits,  12ax7s don't seem to sounds as good at the other tubes in that family with lower amplification factors.  Thats been my experience,  and it has been echoed in various forums for several starved plate circuits.    with my B.K.Butler TubeDriver, I  didn't get an overdrive sound that I liked until I dropped the 12AX7 to a 12AT7.     oddly enough, the 12AT7 is typically thought of as not a good tone-shaping tube for early gain stages  (compared to the 12AX7 and 12AY7), and it is often used a Phase inverter tubes. 

your sound clips sound similar to the sounds I was able to get out of some of the starved plate circuits I played with (one with 12VDC,  one with 40VDC,,,  and another with 28VDC ( http://www.guitarship.org/stp.html ).  it was disappointing to discover that I'd have to use SS op amps to get enough gain to feed the tubes (like a BK Butler, Guyatone, or Tonebone..), so I moved to High Voltage tube pedal circuits and its been a lot of fun.  -- not that there anything wrong with SS circuits, but if I'm going to build a SS pedal, there are other circuits I think I'd rather do...

[shimster]

Paolo,
  I just want to mention that the sounds you're getting don't sound anything like the bad power supply that I got from radioshack.  It does make me think you have a grid leak resistor that is too small or possibly a short somewhere in your circuit.  Sort of a wild guess, but if you're going to rewire it anyway, you might have already fixed it. Good luck!
-Dan

[lazerphea]

When working with tubes and the sound degrades over time, that still makes me think that it is a power issue, because that is almost identical to a problem I had when working with the submini amp I am building.  It played fine, but then started dying out.  That was because the regulator got so hot it could no longer dissipate the power needed to keep the voltage regulated. 

First, your adapter is designed to deliver about 12V when run at max load (all 500mA) and a 7812 needs at least 14V on it, so if you are drawing 400mA, chances are your 17V is going to drop to maybe 13 or so, which won't be enough for the 7812.  If it does still provide 14V, then the 7812 probably isn't able to handle the power dissipation for too long, so you would need a heatsink there.

I forgot to point out I have an heatsink mounted over the 7812.. 

Second, it is entirely possible that it is a combination of something with the signal path and power supply.  Perhaps you accidentally put in a wrong value (10k instead of 100k or something like that)?  Also, how are you getting the 6V for the heater (or is this the twin tube version?).  If you don't have quite enough voltage to run a 7812 or similar, you can always get a zener diode and wire the anode to ground and the cathode to both the +V part of your circuit and the voltage in.  This will shunt anything over 12V, even if it is 12.5V.  Good luck.

I checked everything again and I found some errors in the wiring... 
The sound seems to not degradate over time, but I couldn't play more than 10 minutes or so, and I didn't noticed any sound degradation... still the distortion is unpleasant, especially if I play low frequency notes (E and A strings).

[lazerphea]

pull the tube from the socket.  measure VDC across pins 4 and 5.   if you have 12V or more (and your power supply is at minimum 150ma + whatever the rest of your circuit will draw), you have enough filament voltage.

I measure 11.60V... is it bad, right??

if it sounds bad try a different tube.  are you using the 12ax7 ? or 12AT7 or 12AU7 ??   in starved plate circuits,  12ax7s don't seem to sounds as good at the other tubes in that family with lower amplification factors.  Thats been my experience,  and it has been echoed in various forums for several starved plate circuits.    with my B.K.Butler TubeDriver, I  didn't get an overdrive sound that I liked until I dropped the 12AX7 to a 12AT7.     oddly enough, the 12AT7 is typically thought of as not a good tone-shaping tube for early gain stages  (compared to the 12AX7 and 12AY7), and it is often used a Phase inverter tubes. 

I use a 12AU7.

[lazerphea]

Paolo,
  I just want to mention that the sounds you're getting don't sound anything like the bad power supply that I got from radioshack.  It does make me think you have a grid leak resistor that is too small or possibly a short somewhere in your circuit.  Sort of a wild guess, but if you're going to rewire it anyway, you might have already fixed it. Good luck!
-Dan

No way man! Maybe I'm doomed to not to get this beast working, maybe the karma is telling me to go solid state instead!

[shimster]

Paolo! Don't give up just yet! Can you post a sample of the current sounds? I found the distortion of the original valvecaster to be too dark and muddy so I tweaked the snot out of the circuit until it sounded good!  What kind of sound are you going for?

[Renegadrian]

quote author=terminalgs

pull the tube from the socket.  measure VDC across pins 4 and 5.   if you have 12V or more (and your power supply is at minimum 150ma + whatever the rest of your circuit will draw), you have enough filament voltage.
my bad, I wrote that the heaters wanted 300mA, while they want only 150mA when running at 12V - I believe the rest of the circuit needs no more than 50 mA?! but I may be wrong on that...Anyway you surely won't go over the 500 mA limit...


12ax7s don't seem to sounds as good at the other tubes in that family with lower amplification factors.  Thats been my experience,  and it has been echoed in various forums for several starved plate circuits.    with my B.K.Butler TubeDriver, I  didn't get an overdrive sound that I liked until I dropped the 12AX7 to a 12AT7.     oddly enough, the 12AT7 is typically thought of as not a good tone-shaping tube for early gain stages  (compared to the 12AX7 and 12AY7), and it is often used a Phase inverter tubes. 
Yeah, Me too, tried to experiment with the AX but no success...While I just LOVE the AT!!!I made my own layout for a heavy distortion!!!

it was disappointing to discover that I'd have to use SS op amps to get enough gain to feed the tubes (like a BK Butler, Guyatone, or Tonebone..), so I moved to High Voltage tube pedal circuits and its been a lot of fun.  -- not that there anything wrong with SS circuits, but if I'm going to build a SS pedal, there are other circuits I think I'd rather do...
Absolutely agree with you on that, I really don't like those "hybrid" circuits...I'd rather go all tube or no tube at all...

[silentmike]

Hey, I'm a complete noob at building pedals but would love to get into it. I was looking at building this pedal for a first project, but I was wondering if anyone would know how to make it with a boost "channel" on it? I love the sound of my mustang bass with a tiny bit of drive on it, so I was looking for one channel that just let it warm through the tube, and another for something a bit dirtier. Would it be simpler to just build two?

Cheers,
Mike

EDIT: I have just decided I am an idiot, the pedal (and whole thread) is already described as a boost. Perhaps my best option would be to build two into the same box, and have one running a bit harder than the other?

EDIT 2: My guitarist has just suggested putting in a switchable boost in front of the standard valvecaster circuit, with adjustable gain to drive it when needed. Would this be my best bet?

Sorry for asking such dumb questions!

[shimster]

EDIT 2: My guitarist has just suggested putting in a switchable boost in front of the standard valvecaster circuit, with adjustable gain to drive it when needed. Would this be my best bet?

Sorry for asking such dumb questions!

Mike,
  This is exactly what I did in my first attempt with the valvecaster. I just modified the input and output caps to reduce bass frequencies.  I've also built a dual valve circuit and I'm currently loving that, plus it's sweet having a pure tube circuit.  At any rate, all of your ideas sound great.
Cheers,
Dan

[lazerphea]

Little update: I'm @ work now, and I've found a 12V/1A wall wart... could this do the job?

[terminalgs]

Little update: I'm @ work now, and I've found a 12V/1A wall wart... could this do the job?

yes.  that would work fine.  the previous 11.6 you mentioned would probably work as well,  but the farther your voltage varies from 12.6v, the shorter the tube life will be.

[bassmannate]

Well, I got it all together. Aside from the horrendously loud hum from the unfiltered power supply, it sounds great on my bass! Just need to get that power supply now...

Edit: HOLY CRAP! Just tried it with a battery to eliminate the hum (DEFINITELY is the power adapter) and this thing just sounds so fat and warm with the gain turned down! I couldn't tell before because the hum was just SO loud. Really glad I built this instead of an orange squeezer!

[tranceracer]

Just tried it with a battery to eliminate the hum (DEFINITELY is the power adapter) and this thing just sounds so fat and warm with the gain turned down! I couldn't tell before because the hum was just SO loud. Really glad I built this instead of an orange squeezer!

[bassmannate]

Ok, I had some time to make some experimentations, and here's what I've found:
- Just out of the adapter I read a voltage of 17.19V
- the output of the 7812 reads 11.01V
- if I add the 100uf caps to its input and output the voltage raises to 11.60V
- the same voltage is present an the pin N. 5 of the 12au7, when I connect the power to the circuit.

I get a very sloppy and uncomfortable sound out of it and the situation gets worse and worse as I play through the circuit; here's a soundclip of what I get after about 15 minutes of playing:
http://www.paoloscala.net/diy/12v.mp3
The sound degradates a lot...

So I tried to feed the tube with the 17.19V original voltage, and here's what I get:
http://www.paoloscala.net/diy/17v.mp3
Ignoring the hum, which I understood is given by the unfiltered adapter, the sound is still crappy and with no sustain at all... additionally, the tube doesn't lit up that much: I can see two filaments getting incandescent but that's it.
Maybe I should get a better tube (it's an Electro Harmonix)?
Thanks all.

EDIT: I forgot the adapter specs:
- it's a variable voltage adapter that spans from 1.5V to 12V, and I read: 500mA6VA(max)

I just listened to your clips again and when I'm running from a plain unfiltered 12v power supply, I get EXACTLY the same hum as you do on you straight 17v clip. I hooked a 9v battery up to it and the thing was almost dead silent with the gain turned all the way up. It is most certainly your power supply. Don't give up! This really is a great overdrive! Just gotta get past that power supply issue.

[bassmannate]

While I'm looking, I guess I should ask what everyone here is using to supply their valvy with 9-12vdc. Obviously some are putting a 7812 or something in to regulate the power but are there any wall warts out there that will eliminate the hum without having to put more into the pedal itself?

[frequencycentral]

I use this power supply, available from Maplin in the UK: http://www.maplin.co.uk/Module.aspx?ModuleNo=32746

It's rated at 500ma, but I find I can run up to four tubes from it with a combined draw of 600ma with no hum whatsoever. I have a few, I cut off the multi option/polarity plug and hardwire a 2.1mm plug for centre negative - avoids nasty polarity switching accidents!