Tube boost + overdrive running off a 9 volt battery

[frequencycentral]

1: Heater voltage is 5.96v, datasheet says 6.0v to 6.6v. Am I close enough? All I had were 10.7 Ohm 7 watt resistors.

That's close enough I think! What's 0.04v between friends? The Subcaster was designed to run at 12 volts, so you're on new ground running it at 9 volts. I suspect you might have to experiment with the plate resistors, maybe sub them for pots and see if you can dial in the appropriate value? You should also be aware that 6111 will show very different voltages to 12AU7 using in the same circuit.

[svstee]

I was expecting I'd have to tweak a few things running it at 9v, (I had to for the pentaboost) but the fact that the gain pot has NO affect makes me think it might be more than that.

Oh well, I need more practice with a breadboard anyways.

[kurtlives]

Check your gain pot it might be faulty.

Clearly the pot has some resistance as if it didnt the tube would not work as it would not have a bias reference point. It could be shorted and going right to ground, this would provide a mu-follower and the circuit would work. Is there a lot of gain though, if so the cathode is going straight to ground.

It's hard to tell whats going on from your vero layout. The tubes are unclear.

[svstee]

Tube is the same way Rick does his, like this

I'm using a resistor instead of the LM317 setup, and the tube is oriented like this:

1         8
2         7
3         6
4         5

Thanks!

One other thing. Why not use a 6.2v Zener diode? You can buy ones rated at 500mA for peanuts. This curcuit only draws 300mA, right? wouldn't work for all the submini stuff, but a cheap, easy and safe alternative for others. No clue why I just now thought of it.
http://cgi.ebay.com/50-pcs-Zener-Diodes-500mW-6-2V-5-Axial-Motorola-HQ_W0QQitemZ300304216297QQcmdZViewItemQQptZLH_DefaultDomain_210?hash=item300304216297&_trksid=p3286.c0.m14&_trkparms=66%3A2|65%3A15|39%3A1|240%3A1318

[1878]

I haven't been able to get my Valvecaster build to work properly. It's got plenty of clean boost, but no overdrive. I'm putting an order in for parts tonight, so I'll get a couple of new pots etc and re-build the thing from scratch.

Also, I'm thinking of putting in a voltage doubler to boost it to 18v. Would there be any probs in this ??

[703224796]

Hey guys........I've been eyeing this project for months now, and just recently I got my hands on a 120v > 9v transformer.  if I flip it, I can crank out 120v from a 120v>9v wallwart. Now I know that the 12--7 tubes like these values a lot more, so I was wondering if any of you know where I can find a project like that, OR how can I Mod this guy to make it run off of 120v.  


ohh yeah, I would heat the heaters from the 9v coming from the wallwart.......smart or not?

[Renegadrian]

I know very little about trafos, anyway I read somewhere you should be able to turn the trafo the other way around and get a good voltage - I believe it should be something less of the specified value, but no less than 100V in your case.
I also feel that you should somehow turn that AC into DC (is it mandatory, is it a better or it just doesn't matter?)
Also, sure you have a 9V (AC?) for the heaters (while 12V would be surely best)

I don't think there are mods to be applied at the main schem - I run mine at 50V - just apply the V at the plates...(pins 1 and 6)

[Ripthorn]

The only problem I see is that you might not have enough juice in your wallwart (but then again you might).  Your heaters will need a few hundred ma and then you have to remember that if you need 10 ma for your plates (not likely) with a 10:1 winding ratio, you will need at least 100 ma from your wallwart.  I would recommend a fairly high powered zener for the regulation from 9V down to 6.3V.

[kurtlives]

Tubes must run on DC.

The 9V AC when rectified will be 12.7V so that is fine for series wiring of the heaters. Add some filtering and regulation and your set!

Your transformer setup will work fine as long as you put 9V AC onto the 9V side of the transformer.

The plate resistors and cathode resistors will need to be altered with the increased voltage. Cant say where to, I would experiment on the bread board first.

[703224796]

you guys are great! thanks a ton for the prompt responses.......I'm guessing that SSrectifier would be used, so that the heater can be used in the 12v config.  also, I believe I would leave the tone and volume sections the same, while the plate resistors would need to be changed to something calculated from ohm's rule, right?  How about the Gain pot, does that stay?  I would also add something like an ssrectifier at the 120v section going to the plates and maybe a few large caps to filter............does it all sound correct?

[biggy boy]

Hey guys........I've been eyeing this project for months now, and just recently I got my hands on a 120v > 9v transformer.  if I flip it, I can crank out 120v from a 120v>9v wallwart. Now I know that the 12--7 tubes like these values a lot more, so I was wondering if any of you know where I can find a project like that, OR how can I Mod this guy to make it run off of 120v.  


ohh yeah, I would heat the heaters from the 9v coming from the wallwart.......smart or not?

I'm running mine well with 157 volts and just a couple of resistor size tweaks
Two transformers back to back   in 120 volt/ 12 volt---- 12volt/120volt out rectified it's boosted to 157 volts

Glen

[KorovaMilkBar]

hello! i just got a package from mouser and i messed up on the potentiometers. they are 1 b50k and 2 b100k (the plans call for a100k). they are also the receding (sp) thumbdial kind. so are these any good or should i head to radioshack? thanks!

mike.

p.s. i should be getting the tube anyday now, soon as i do i will be working away on this! im so excited!

[svstee]

Sorry to drag this up agian, but can I use a 6.2v Zener diode for the heater? Wouldn't work for all the submini stuff, but a cheap, easy and safe alternative for some.
http://cgi.ebay.com/50-pcs-Zener-Diodes-500mW-6-2V-5-Axial-Motorola-HQ_W0QQitemZ300304216297QQcmdZViewItemQQptZLH_DefaultDomain_210?hash=item300304216297&_trksid=p3286.c0.m14&_trkparms=66%3A2|65%3A15|39%3A1|240%3A1318

[frequencycentral]

Sorry to drag this up agian, but can I use a 6.2v Zener diode for the heater? Wouldn't work for all the submini stuff, but a cheap, easy and safe alternative for some.
http://cgi.ebay.com/50-pcs-Zener-Diodes-500mW-6-2V-5-Axial-Motorola-HQ_W0QQitemZ300304216297QQcmdZViewItemQQptZLH_DefaultDomain_210?hash=item300304216297&_trksid=p3286.c0.m14&_trkparms=66%3A2|65%3A15|39%3A1|240%3A1318

Are you still planning to un your Sub @ 9 volts? If so, you only need to drop 2.4 volts. That zener would drop 6.2 volts - ie. too much. Did you try 4x 1n4148 yet?

[svstee]

I did, they melted. I thought a zener ALLOWS 6.2v to pass? The Crowther Audio Hotcakes has an 8.7v zener right off the DC jack if I remember correctly.

[frequencycentral]

I did, they melted.

Heheehe - my favourite experiments are the ones involving melting/fuming components! At least now we know. 

I thought a zener ALLOWS 6.2v to pass? The Crowther Audio Hotcakes has an 8.7v zener right off the DC jack if I remember correctly.

Dunno, never used zeners.

[Ripthorn]

Zeners can be implemented to either drop their voltage or supply their rated voltage.  In series, a zener will drop its rated voltage.  If you stick it with the anode to ground, you will get their rated voltage at the cathode (this is how reference voltages are created, typically).  that is why I love zeners.  Also, you can get beefy 5W ones or bigger so that would handle subminis no problem, though you may have to glue them with thermal epoxy to the case or chassis for heatsinking.

[svstee]

Why would I need 5w? If I'm doing the math right, I only need  around .9 watts. 1 watt should be fine, right?

[Ripthorn]

1 watt will work, you might want a heatsink.  I only mentioned 5W because if you try to run multiple tubes, you need big ratings.  It was just a number.

[kurtlives]

Why would I need 5w? If I'm doing the math right, I only need  around .9 watts. 1 watt should be fine, right?

A good rule of thumb whenever designing tube electronics of anything with HV or heat...double you power ratings. If a plate resistor could be 1/4W double it up to 1/2W. 0.9W is too close to 1W for me...