Tube boost + overdrive running off a 9 volt battery

[Jdansti]

Correction- it looks like a voltage drop of 6 volts across a 10 ohm resistor would be around 4W, meaning I should use a 5W resistor. Any thoughts on this?

[waltk]

If your PS is unregulated, it would hard guarantee that the heater would be getting a specific voltage.  You might do better with an LM317 - it only needs a few extra parts.

[Jdansti]

If your PS is unregulated, it would hard guarantee that the heater would be getting a specific voltage.  You might do better with an LM317 - it only needs a few extra parts.

Thanks Walt. The PS is an off brand that doesn't say whether it is regulated or not. It delivers 12vdc on my Valvecaster, but if I bump the load up to 750ma from 300ma, the voltage could dip if it is unregulated. The best thIng would be to use the LM317 as you suggest and not worry about wall wart being regulated. Come to think of it, if I use the LM317 for the heater, I could use an 18vdc PS I have and get more headroom on the plates. Thanks again.

[waltk]

Thanks Walt. The PS is an off brand that doesn't say whether it is regulated or not. It delivers 12vdc on my Valvecaster, but if I bump the load up to 750ma from 300ma, the voltage could dip if it is unregulated. The best thIng would be to use the LM317 as you suggest and not worry about wall wart being regulated. Come to think of it, if I use the LM317 for the heater, I could use an 18vdc PS I have and get more headroom on the plates. Thanks again.

Sounds like a good plan.  One thing to keep in mind; the LM317 will have to dissipate (the voltage differential X the current) as heat - (18 - 6.3) * 750ma = 8.78 watts.  You'll probably want a decent heat sink on it.

[Jdansti]

Thanks Walt. The PS is an off brand that doesn't say whether it is regulated or not. It delivers 12vdc on my Valvecaster, but if I bump the load up to 750ma from 300ma, the voltage could dip if it is unregulated. The best thIng would be to use the LM317 as you suggest and not worry about wall wart being regulated. Come to think of it, if I use the LM317 for the heater, I could use an 18vdc PS I have and get more headroom on the plates. Thanks again.

Sounds like a good plan.  One thing to keep in mind; the LM317 will have to dissipate (the voltage differential X the current) as heat - (18 - 6.3) * 750ma = 8.78 watts.  You'll probably want a decent heat sink on it.

Right.  I've used the LM317 with one of those fin type heat sinks before and it was hot enough to burn me. I might try a larger chunk of metal and possibly put it in it's own ventilated box external to the stomp box.  I guess there really is "no free lunch".  Thanks!

[waltk]

Right.  I've used the LM317 with one of those fin type heat sinks before and it was hot enough to burn me. I might try a larger chunk of metal and possibly put it in it's own ventilated box external to the stomp box.

You might be able to use the stompbox enclosure itself as a large heatsink.  The "Tiny Giant" amp does this for both the chipamp and the voltage regulator, and it works great.  The only thing to be careful about is that the TO220 tab on the LM317 is internally connected to its OUTPUT (not ground).  So you have to mount it such that the tab is electrically isolated from the enclosure - but thermally connected to it.  The Tiny Giant uses a thin insulator for this.

[rugeb]

PS multi voltage

[Jdansti]

Right.  I've used the LM317 with one of those fin type heat sinks before and it was hot enough to burn me. I might try a larger chunk of metal and possibly put it in it's own ventilated box external to the stomp box.

You might be able to use the stompbox enclosure itself as a large heatsink.  The "Tiny Giant" amp does this for both the chipamp and the voltage regulator, and it works great.  The only thing to be careful about is that the TO220 tab on the LM317 is internally connected to its OUTPUT (not ground).  So you have to mount it such that the tab is electrically isolated from the enclosure - but thermally connected to it.  The Tiny Giant uses a thin insulator for this.

Thanks - that's a good idea. I haven't been brave enough yet to try using the insulator that comes with the regulators. I usually modify my projects, if necessary, to have a negative ring on the DC jack and make the case the ground. It would be nice if they designed the regulators with the ground on the tab so that they could just be bolted directly to the case for the most efficient heat dissipation. It's probably time to give the insulator a try.

[Jdansti]

PS multi voltage

Thanks Rugeb. I've been thinking about doing something like this for a pedal board PS with multiple voltages. I'm curious to know if there is an advantage to connecting the regulators in series as shown in your schematic as opposed to parallel.

[waltk]

Thanks Rugeb. I've been thinking about doing something like this for a pedal board PS with multiple voltages. I'm curious to know if there is an advantage to connecting the regulators in series as shown in your schematic as opposed to parallel.

Excuse for for butting in, but I think I can answer that.  One advantage would be that the 7809 and 7805 have a smaller voltage drop, and therefor have to dissipate less power (as heat)  than they would from the original 18v.  Don't know for sure, but they might also be less likely to have any ripple on their output (because their input is already regulated).

[rugeb]

Thanks Rugeb. I've been thinking about doing something like this for a pedal board PS with multiple voltages. I'm curious to know if there is an advantage to connecting the regulators in series as shown in your schematic as opposed to parallel.

Excuse for for butting in, but I think I can answer that.  One advantage would be that the 7809 and 7805 have a smaller voltage drop, and therefor have to dissipate less power (as heat)  than they would from the original 18v.  Don't know for sure, but they might also be less likely to have any ripple on their output (because their input is already regulated).

Ok Waltk!
With a serial connection, the 7809 and 7805 have a smaller voltage drop. The paralell connection increases the voltage drop in the 7809 stage, and much more in the 7805 and has to dissipate more heat.

[Mustachio]

I ended up putting an 7815 in mine before it went to B+. to regulate my 18v coming into it. minimum of the 7815 is 17v so I wanted to play it safe. It took out the hum when using a 12au7. Popped in the 12bh7 last night with same set up and hum came back  Im only using a single 100uf at the first regulator a 7812.

So I have a lil more experimenting to do. What I've noticed with mine so far is it has lots of volume (unity around 10 O'clock) and the only gain settings I like are when its all the way maxed, and I'm not a high gain player. It sounds pretty nice tho going into a clean bassman amp for blues, but still need to tweak it a bit.

Gonna play with resistor values for more gain. Also I noticed when I back off the gain is when I get more hum. I might try putting more caps across the regulators.

I wanna say thanks to all nerds in this thread!  This is my favorite thread of all time! You guys are great for all the knowledge you pass along. Ive learned sooo much in a short time from you guys. This is what the internet is all about!  shucks guys ya done got me going

[rugeb]

PS multi-voltage mod:

A solution for heater: Add two 1N4007 standard diode it will give you 6,4V (1,4V extra).
They are increasing in steps of 0,7V.
Output voltage= 5 + 0,7 + 0,7 = 6,4
It's cool!
 

[runmikeyrun]

I am in the middle of a valvy and I just wanted to report some observations on tube brands and voltage readings, specifically on the plates (pins 1 and 6) at idle.  I am using stock 220k and 100k plate resistors, and 12VDC regulator.

-With a new production JJ 12au7 I am getting 10v on pin 1 and 9.6v on pin 6.  The sound is fizzy, dull, and thin, and output is near unity at max.

-I swap in either of two early 60's RCA black plate 12au7s and voltages drop to 3.6v on both pins 1 and 6.  Tone is full, rich, and fuzzy and output is much much higher.

No matter what I did to try to reduce the voltage to the plates with the JJ tube, the tone just got worse and worse.  Which is weird, because the JJ 12au7s i've used in the past in valvecasters sound really really good.

The reason I posted this is because there are quite a few people who have issues with their valvy and plate voltages usually seem way off compared to Rick's.  So when you're checking voltages and things look amiss, try a different brand of 12au7 after you've given your soldering job the once over.  It might be all you need to do.

[runmikeyrun]

Now for a question- I am getting a good amount of sag when I hit the strings even moderately hard.  I can't figure out why.  I am using the standard valvy schematic except for a 1M pot in between pins 1 and 7 (gain pot) and both cathodes are grounded, no resistors.  I'm using a 16v supply regulated to 12v via 7812.  Upon audioprobing, signal into pin 2 is just fine, but coming out of pin 1 I already have the sag.  I checked the current to pin 1 and it's 73ua at idle, and drops to ~35ua when hitting the strings.  That's MICRO amps, not milliamps.  This seems low, because I checked the RCA datasheet for my tube (an early 60s 12au7a) and it says I should have 2-3ma of plate current @ 12v.

I've got a 220uF cap to ground from each the input voltage and regulated voltage.  I'm using a 1A supply and my regulator is rated for 1A.  I've tried different tubes, a different power supply, different cables, going into the amp's effect return, still no change.  My guitar is passive.  I am getting no voltage sag on the supply or regulated voltages when I play.  Could it be the gain stages are misbiased?  I really can't figure this out.  Help!!  


EDIT:  Nevermind, I got it.  As soon as I put some sort of resistor on pin 3 the sag went away.  Guess it was misbiased!

BTW... there's guys selling NOS RCA 12au7a tubes out there on eBay for CHEAP... I got two that were labelled Conn (organs) for $8 plus $2.50 shipping.  They sound incredible!  You can tell NOS RCA because they had an octagon around the tube number etched in the tube.

[Jdansti]

Thanks Rugeb. I've been thinking about doing something like this for a pedal board PS with multiple voltages. I'm curious to know if there is an advantage to connecting the regulators in series as shown in your schematic as opposed to parallel.

Excuse for for butting in, but I think I can answer that.  One advantage would be that the 7809 and 7805 have a smaller voltage drop, and therefor have to dissipate less power (as heat)  than they would from the original 18v.  Don't know for sure, but they might also be less likely to have any ripple on their output (because their input is already regulated).

Ok Waltk!
With a serial connection, the 7809 and 7805 have a smaller voltage drop. The paralell connection increases the voltage drop in the 7809 stage, and much more in the 7805 and has to dissipate more heat.

Thanks Walt and Rugeb. It seems that the series arrangement would cause the individual regulators to be cooler, but the total heat dissipation would be the same-just guessing based on my limited understanding of the laws of thermodynamics.  On the other hand, there's a lot I don't know about regulators, so maybe everything would be happier in series.

In Rugeb's schematic each regulator could be connected to a load as well as the next regulator in series, so you would have to avoid exceeding the current limits of the upstream regulators.

[rugeb]

runmikeyrun: Do not change the 12AU7 yet. Try with another PS, may be a problem of PS.

Jdansti: Yes, you would have to avoid exceeding the current limits of the upstream regulators.

[rugeb]

For more current in first stage:
 

[runmikeyrun]

Rugeb,

see my edit to my post.  I got it, thanks!

[rugeb]

Rugeb,
see my edit to my post.  I got it, thanks!

Ok. Congratulations!
Post it with an image (for everybody with the same problem).