Tube boost + overdrive running off a 9 volt battery

[zambo]

Checked. Both are indeed grounded. Dont have a housing yet though... Hopefully I'll have it by the end of next week.

Anytime you make a circuit like this and it starts to become Hi gain you you will get parasitic oscillations etc. Sheilded wire helps a ton.Good layout and a grounded enclosure also helps a ton. Also, tubes run at low voltage will start to get dc on the grids when pushed into clipping. put a capacitor on the input pins ( 2, 7 ) Thats what c1 does on the original schematic otherwise your guitar volume would be scratchy. make sure you put the grid leak resistor after the cap like the example of c1 on the original. Also putting small value caps from plate to ground to bleed of some of the extreme high end will help. I wouldnt do it on stage 1 but on stage two and three it helps a lot. Using small grid caps helps tame some of the farty sounds as well. When you run tubes in space charge they develop a lot of bass and a lot oh high end which is nice on a single tube. makes that warm tubey break up. cascade it through 6 stages and you get to many highs and to much bass amplified and reamplified. starts making weird feed back. that will cause signal to die out like that as well. by using smaller coupling caps ( .001 or .002 ) in the 3,4,5,6 stages you cut out some of the farty bass. bleeding off the extreme highs from the plates on the same stages leaves behind a signal thats been boosted in the mids a lot. I built one of the first ( maybe the first? ) triple valve caster and built several more versions of it experimenting as I went. This is what I learned along the way. Hope it helps and good luck!!

[toplak666]

Checked. Both are indeed grounded. Dont have a housing yet though... Hopefully I'll have it by the end of next week.

Anytime you make a circuit like this and it starts to become Hi gain you you will get parasitic oscillations etc. Sheilded wire helps a ton.Good layout and a grounded enclosure also helps a ton. Also, tubes run at low voltage will start to get dc on the grids when pushed into clipping. put a capacitor on the input pins ( 2, 7 ) Thats what c1 does on the original schematic otherwise your guitar volume would be scratchy. make sure you put the grid leak resistor after the cap like the example of c1 on the original. Also putting small value caps from plate to ground to bleed of some of the extreme high end will help. I wouldnt do it on stage 1 but on stage two and three it helps a lot. Using small grid caps helps tame some of the farty sounds as well. When you run tubes in space charge they develop a lot of bass and a lot oh high end which is nice on a single tube. makes that warm tubey break up. cascade it through 6 stages and you get to many highs and to much bass amplified and reamplified. starts making weird feed back. that will cause signal to die out like that as well. by using smaller coupling caps ( .001 or .002 ) in the 3,4,5,6 stages you cut out some of the farty bass. bleeding off the extreme highs from the plates on the same stages leaves behind a signal thats been boosted in the mids a lot. I built one of the first ( maybe the first? ) triple valve caster and built several more versions of it experimenting as I went. This is what I learned along the way. Hope it helps and good luck!!

Wow man, thanks! That sounds like a lot of good information that I would surely not have thought of by myself. I'll try each and every one of these as soon as possible and post the results

[zambo]

Glad to help  here is one thats been built like that and running at 30 or 40 volts on the plates. http://www.youtube.com/watch?v=YhyyYjY5CgA

[toplak666]

Glad to help  here is one thats been built like that and running at 30 or 40 volts on the plates. http://www.youtube.com/watch?v=YhyyYjY5CgA

Perfect. That's pretty much exactly the sound I'm going for. I'll get on it later today!

[capes83]

Hi all, first post! I've breadboarded one of these, totally new to diy though, so it works, but I don't know why yet. I've got an old mA meter, is it possible to wire it so it shows the effect on bias of turning the gain pot? As I say, new to all this so any help would be appreciated!

[zambo]

welcome! Not sure what you would measure other than current going through the tube. As you turn the gain put up or down more or less current should be flowing. try putting your meter in series from pin 3 to ground or use a 1 0hm 1 percent resistor in series ( before the gain pot ) and measure the millivolts across it. The closer the gain pot gets to 0 resistance the more current flows. I think i got that right anyway..  Current flows from anode to cathode and the grid in between acts like the valve gate restricting or accelerating that flow. the grid is your ac guitar signal. this causes the voltage of the plate to fluctuate in time with your guitar signal but at a much higher voltage. that is where you get signal amplification. the coupling cap to the next grid blocks the dc voltage and lets the larger ac signal through where it goes through the same process. Does that make sense? along the way the signal clips and developes harmonics etc. that also get amplified. thats where you get that tubey goodness. Kind of over simplified but thats my understanding of tubes in general terms.

[toplak666]

Glad to help  here is one thats been built like that and running at 30 or 40 volts on the plates. http://www.youtube.com/watch?v=YhyyYjY5CgA

Zambo dude if you were here right now I'd kiss you! Those tips you gave me not only removed all the farty and scratchy sounds but it really did boost the mids just like you said! The caps in the last stage still need some tweeking to get the perfect sound but that's a job for when I get the housing. Funny thing is that even though my circuit is built on a custom designed pcb I had no problems adding those caps and resistors. I'll post some pics soon. I think this build looks quite nice.
So thanks again! I owe you a beer!

[zambo]

Awe shucks ... just glad I could help! I do like beer though so if you get to napa anytime, look me up  You should see all the weird tube stuff hanging around in my garage hahaha!

[capes83]

Thanks zambo, will try that!

[toplak666]

Finally got arround to uploading these images:

Power supply:

Yes, that 40mm fan is necessary. The 2 voltage regulators I'm using actually fry after a minute without the fan. They run pretty cool with the fan and it's actually quiet enough to the point where it probably wouldn't be picked up in a studio.

Switching circuit - top:

5V voltage regulator, 2 relays and 3 footswitches.

Switching circuit - bottom:

Looks complicated but it's mainly just bussing...

Main circuit - top:

Not much to say here...

Main circuit - bottom:

Basically the same layout copied 3 times. I think it looks pretty cool.

You have to excuse any bad or messy solder joints you spot. My cheapo soldering station broke and I was forced to use a huge old soldering iron. Got a brand new soldering and smd rework station now.
Enclosure should look pretty nice too. I'll post another update once I get it.

Higher resolution images:

http://i.imgur.com/t79KBfE.jpg
http://i.imgur.com/Crb6lEm.jpg
http://i.imgur.com/VPJcQxh.jpg
http://i.imgur.com/rKPtI6K.jpg
http://i.imgur.com/eyTzhLu.jpg

[Jdansti]

^Very nice!

Do you have any problems with the fan causing noise in the system?

[toplak666]

Do you have any problems with the fan causing noise in the system?

I had quite a bit of problems with that because at first I was using a lm78l08 Connected to the 12.6V rail to power the fan which was causing quite a bit of interference. I then started experimenting with 1 and 2 transistor constant current source circuits (still on the 12.6V rail) but if anything that somehow managed to make more noise... I then moved the ccs in front of the 2 regulators (so 25V, directly after the rectifier) and now it's not causing any noise whatsoever and it's keeping my regulators nice and cool!

[Jdansti]

I'll remember that if I ever have to use a fan. Thanks!

[EVAD]

Here's pics of my valve caster builds...





Hammond 1590B - 60's Canadian RCA 12AU7

No mods from the Beavis layout -  9V.
.......................................................................



Hammond 1590BB - New, Groove Tube 12AU7's -Nice/Good sounding tubes.

The circuit is on perf board. The perf board has two 7/8" holes drilled into it - to mount the tube sockets.

I used Renegadrian twin tube vero layout.

Smooth drive but gets noisy when you aren't playing.

9V. or 12V.
...



The top of the enclosure is made from a steel serving tray, bought from a thrift store - 2bucks.

The box is shielded inside and made of wood & covered in brown tolex.

The circuit is on perf board. The perf board has two 7/8" holes drilled into it - to mount the tube sockets.

I used Renegadrian twin tube vero layout.

Two new 12AU7 Chinese Tubes.

The new Chinese tubes when you look at them close
you can see the plate and cage aren't as robust as the old tubes.

The new tubes are harsher in sound.

Gets noisy when you aren't playing.

9V. or 12V.
...



60's  SYLVANIA 12AU7

The enclosure is some kind of electrical break out box made by Square D

It is solid steel and was very hard to drill.

But this valvecaster is VERY quiet.

No mods from the Beavis layout -  9V.
...



60's Canadian RCA 12AU7

The enclosure is some kind of electrical break out box made by Square D.

Thin steel , easy to drill.

Stands tall and stable on it's leg fins. Good creamy/cruncy sound.
...

This Valve Caster I sold - it has a ColorSound One Knob Fuzz housed with it.

[capes83]

Hi all, I asked a few posts ago if I could add an analogue mA meter into this. I've tried everything, in series like suggested, to every pin, and any other way I could think of. I can't get a reading at all. I want to be able to see on the mA meter the effect of turning the gain. Is the current too small to be read by a 1mA meter, or am I just missing something? Would really appreciate any help!!

[zambo]

did you try to put a 1ohm 1 percent resistor in series with the gain (bias) pot and measure across it in mv which will be the same as ma if i am not mistaken. thats how you measure the ma in a tube amp. kinda the same principal.

[capes83]

Hi Zambo, yeah I've tried that, tried it in series before and after the pot, still couldn't get any reading. Does the gain pot alter the amount of current going to pin 8 to being the other cathode? Really bugging me that I can't figure this out!!

[zambo]

yeah thats weird. you should be able to read something. current might be to small to read. both cathodes should be flowing  current. they are separate so they should give separate readings. I guess you could use ohms law to calculate how much current should be flowing so you have something to kinda aim for. I will see if I can do it tonight. I have one on my bench right now.

[capes83]

Cheers Zambo, let me know if you get it going!

[duck_arse]

capes - does your meter have "1mA dc fsd", or "mA _" and numbered "0" to "1" or something similar printed on the scale? and does it have some other current or voltage marking on the back of the meter case? very often, a meter with a full scale deflection of 1mA was fitted with a shunt resister to change the voltage or current read, without changing the meter dial.

you'll probably need to googoo "moving coil meter calibration" or similar, to see the method.