Tube boost + overdrive running off a 9 volt battery

[esdiezy28]

Hi

I have not not read all of the posts so far. I read about the first 16 and then decided to post my question.

I built the circuit on a bread board, as originally posted and all was fine. (As I play bass I played around with capacitor values and settled on doubling all the values).
The heater was connected positive to pin 5 and earth to pin 4, giving 9V over both heaters. The circuit works well and is quiet.

I read the discussions regarding heater voltages and decided that a tweak could be in order. I wired up a LM317 voltage regulator to give 6.3V on the output, connected the output to pin 9 and pins 4&5 to earth. from what I understand this should be correct. Now I have a hum

Any suggestions to trouble shoot.

Bryan

I'm not sure about actually using pin9 of the 12AU7. As I understand it... running voltages from pin5 to pin4 (the tube heaters) can take 6.3V at 300mA or 12.6V at 150ma. Although I totally understand your attempt apply a 6.3V PS Voltage at pin9, it seems leaving it as a "No Connection" seems the safest route to pursue. Furthermore I agree with Govmnt_Lacky's addage; don't change what you've got that works. It's a great quote for life in general, and especially moreso in electronics IMHO. Hum is almost always creeping in on your tube heaters in the Valvecaster (once again in my experience and opinion. I've built 3 of them myself.)
A quick fix suggestion.... Remove the V+ connection from pin-9, leaving pin-9 as a no connection. Remove the ground from pin 5 (its the pin I use in mine for V+), and place your 6.3V power connection coming from your LM317 there. That should fix it outright, I believe. Best of luck, ToNy

[Govmnt_Lacky]

^Tony...

You may want to reconsider that. The 12-series tubes are rated for ~12V at the heater to maximize the tube's life. The way that Bryan has the heater connected right now is in parallel. Technically that should be OK however, since he is getting the HUM now.... I would recommend that he goes back to what worked and apply the 9V in SERIES as he had it on the breadboard. Better yet, try to run closer to 12V as this is what the tube is spec'd for and will prolong the life of the tube.

[iccaros]

the 12A*7 serries tube is made for 12.6 and 6.3 volts. depending on how you wire it.. Which way you wire does not matter, in most amps they are wired in parallel using 6.3 volts. but never 9v in parallel, as that can burn out the heater windings

The 12A*7 series has two heaters in it, each heater wire is required to heat its triode's cathode to have electron flow (they are dual triode tubes)
pins 4, 5, and 9 are connected to the heaters like this

pin 4-----heater wire-----\
                                     |--------->  pin 9
pin 5----heater wire------/


pin 4 and 5 are connected through each lines heater where pin 9 is attched to both heaters ends, acting like a center tap between them

so If you connect pin 4 to say positive  voltage and pin 5 to negative you are running in serries, and will need to drop 6.3 volts on each heater. Which means you need 12.6 volts.. note 12 is close enought and you get 6 volts on each heater

if you were to connect pins 4 and 5 together and put at positive voltage and pin 9 to negatice, you are running parallel, and you need 6.3 volts..

note heaters are rated at +/- .3  but lower is ok as long as the tube works, higher voltages will burn out the heater..

so wrap up.. These tubes work at both 12 and 6 volts, all dependin on if you are serries or parallel, and neither wiring has anything to do with noise.

[runmikeyrun]

I thought (some) noise was dependent on AC vs DC on the heaters and how you route the wires inside the pedal. 

[iccaros]

how you route wires can always add noise,

AC makes more noise than DC on heaters as that AC frequency can bleed inside the tube. But for most amps, DC is a pain to do for heaters, plus if you need to elevate them, well more issue come up.

but wiring parallel or in series has little to do with it.

plus these are tubes, you will get some noise, they are microphonic, and can act like an antenna.

I have mine on a APC ups to keep my amps and stuff clean..

[BryanC]

if you were to connect pins 4 and 5 together and put at positive voltage and pin 9 to negative, you are running parallel, and you need 6.3 volts..

...

so wrap up.. These tubes work at both 12 and 6 volts, all dependin on if you are serries or parallel, and neither wiring has anything to do with noise.

Problem solved.

I had pins 4 & 5 to ground and pin 9 at 6.3V. I think this might have caused a ground loop? I took pin 9 to ground and pin 4&5 to 6.3V. 

[smitty]

Hello,

Im getting ready to build my first valvecaster and had a quick question....   I am going to use an 18.5 volt wallwart power supply feeding a voltage regulator for
12 volts to the Heater using a 7812 voltage regulator.    Is it possible to run another wire off the Vin at the full 18.5 volts to feed the plates? or does
the voltage to the plates need to go through the 12 volt regulator as well......   I was thinking a few more volts on the plates would help.... sort of like this:

18.5v-------Vin-------------------18.5v---> (Tube Plate)
                  -
                  -
                  -
                  -
                  -
                  v
               7812 regulator   12v ---------->(tube heater)

Vin would be one of those input jacks where the wallwart connects to the pedal

[maxariez]

Hello to all tubeheads,
My first tube project - please help! 
I wonder if a change of R4 to 560Kohm can make the circuit make high-pitched noise and no other sound at all. I can post pics of my creation - my circut is just really messy because I scavanged parts from an old 70-ies stereo.

[merlinb]

Im getting ready to build my first valvecaster and had a quick question....   I am going to use an 18.5 volt wallwart power supply feeding a voltage regulator for
12 volts to the Heater using a 7812 voltage regulator.    Is it possible to run another wire off the Vin at the full 18.5 volts to feed the plates?

Yes you can do exactly that, although it must be a regulated wall wart or the thing will hum like crazy. If its unregulated then you'd better run the plates from the 12V reg.

[thereminator]

ECC81 = 12AT7
ECC82 = 12AU7
ECC83 = 12AX7

[esdiezy28]

Hello,

Im getting ready to build my first valvecaster and had a quick question....   I am going to use an 18.5 volt wallwart power supply feeding a voltage regulator for
12 volts to the Heater using a 7812 voltage regulator.    Is it possible to run another wire off the Vin at the full 18.5 volts to feed the plates? or does
the voltage to the plates need to go through the 12 volt regulator as well......   I was thinking a few more volts on the plates would help.... sort of like this:

18.5v-------Vin-------------------18.5v---> (Tube Plate)
                  -
                  -
                  -
                  -
                  -
                  v
               7812 regulator   12v ---------->(tube heater)

Vin would be one of those input jacks where the wallwart connects to the pedal

Adding more voltage to the plates will certainly help the 12AU7 which is designed to run at higher voltages of course. I run my main valvecaster with a TC1044 as a voltage multiplier giving me 42.4V at the plates. I LOVE the added headroom, it really opens the pedal up! The TC1044 idea came from Rick Holt's "Murder One Amp" http://www.diystompboxes.com/smfforum/index.php?topic=71381.0

ToNy

[iccaros]

thanks thereminator

I bought 15 6n2p tubes off ebay for $12.. so I was going to see how that worked in my pedal, your post is a good reminder for people to check the datasheet when doing things outside the original design, like using diffrent tubes, or changing how you wire heaters.

[thereminator]

6N2P are similiar to 12AX7 except heater. Pin 9 is a shield between triode systems and must be grounded.

[brett25]

I have finished the build. I left the wiring on the volume and tone lugs so i can switch them atound for testing purposes . Everything else is soldered in. Could anyone tell me which power adapter I need to get to make this run. I have a 12V AC adapter but that doesnt work. Can anything have been damaged from AC power?:

[iccaros]

The Electrolytic if you exceeded their voltage.. but probably not

you need DC.. Go ol DC 12v make sure you which is pos and Neg..

[brett25]

hi icarros, do you know the polarity based on my wiring. it looks like center positive?

[iccaros]

looks negative tip,but I do not use those DC plugs so I could be wrong.  but I would use a DMM or Volt Meter or a Batt to test first,

[brett25]

by the way i left the lug 3 volme/tone  unsoldered just for fun and i will try the wiring both ways and let you know how it goes. i think this will be good info for others on this forum

[brett25]

hi another quick question and possibly my last as the pedal is working , but with loud hum.

Does anything need to be rewired to operate at 12VDC? If im using the stock layout, should I run it only at 9VDC or will 12 v work with no mods? I tested it with an unregulated 12VDC adaptor (getting humming), and plan on getting a regulated one tomorrow, but dont know if I should go 12 or 9V.

Im sure this has been asked but its extreemly hard to search this enormous thread for specific answers (although I have beeen through it entirely once). Thanks again peeplz for the assistance and I will post pics of the completed build!
brett

[esdiezy28]

Brett25
Nothing needs to be re-wired to run the Valvecaster at DC 12V. All my power supplies are unregulated, and my first build hummed profusely. Stuck a 7812 (positive 12V voltage regulator) in the power section and removed all that atrocious humming.
If you have the option, IMHO, I would go with a 12V supply. If you can't find a regulated PS anywhere invest in some voltage regulators (like 7812, or LM317). I have used both sucessfully in my Valvecaster builds for power supply filtering, and am quite pleased with the results they have provided. Best of luck always, ToNy