Tube boost + overdrive running off a 9 volt battery

[stallik]

OOPS! Think I may have found the cause of my problem. I've been working to the wrong layout. On mine, R1b is missing. Will solder one in there this evening & keep my fingers crossed

[zambo]

lol yeah that would do it. glad you found the prob. 

[deblacksin]

wow this pedal rocks!!
I use 1A 12V power supply and a 12ax7 (I don't know what you guys are wining about, it boosts the amp beautifully )

I only have a tiny question.
this pedal runs on a very low voltage. how long the tube's life will probably be, without smashing the pedal with a sledgehammer?

[tasos]

Hmmm...i am not an expert on tubes however a cheap tube i believe would keep good for around 2-3years?(with daily use)
Most tube datasheets provide hours of life....You should ask there!

[iccaros]

wow this pedal rocks!!
I use 1A 12V power supply and a 12ax7 (I don't know what you guys are wining about, it boosts the amp beautifully )

I only have a tiny question.
this pedal runs on a very low voltage. how long the tube's life will probably be, without smashing the pedal with a sledgehammer?

Sadly different 12ax7', even from the same run,  can react differently at low voltage, and of the 12 I have tested in this design only one boosted, the rest did not boost at all, got distortion but no real signal boost.

Longevity, Tubes are rated @ hours of life based on expected use. So at a heater voltage with a given plate voltage the tube should get to a specific temperature. In this design with Plate voltage so low, I believe, but could be wrong, the heaters will die before the tube does. I have killed tubes with this design, mostly 12u7 and 12ae7 using 30 volts on the plates.. but that is another issue.  

[zambo]

I havent killed any tubes yet and its been a couple years now i believe. Some 12ax7 have more resistance than others and thats why some work better than others. 12au7 has much less resistance and thats why they work better in starved plate designs. above 24v I have had better and more consistent results with 12ax7  but I think they sound best at over 100v most of the time. 12au7 acyualy sounds great to me at 9 or 12 volts in this design. Just an opinion, and we know what they say about those 

[beaker]

Hi there, new guy coming very late to the party. I have a question for you guys that I can't seem to find an answer for anywhere else.
I have a load of 18650, 3.7 Volt  2400 mA/hr Lithium ion recheargeable batteries lying around, that I use for flashlights. Three in series would give 11.1 Volts. Is there any reason why using these to power my Valvecaster would be a BAD idea? I still like the original idea of the Valvecaster being wall wart free.

[iccaros]

I don't see a reason, the load should should be about 160ma +/- 10% with heaters. the 11.1 is a little low, but will work for the heaters. 

[zambo]

it will work fine. it will just drain them fast. at least i think it will.

[stallik]

I've found a solution to the compression/sagging problem I've been experiencing with the Twincaster & thought I'd share it in case it's of any help.
This is a standard build using NOS Phillips JAN 12au7's which both work very well in a single valvecaster. I've added a switch to change between 2 values of C1 as my amp is rather heavy on bass.
The solution was found by changing 2 things.
1. C2a & C2b were changed to 63v 47nf radial caps  - the original wimpy ceramics were the right value but resulted in a total cut out of the signal when I hit a chord. (the signal returned after a second or so)
The bigger caps nearly cured the problem - I was left with a drop in volume at the start of the power chord. so..
2. insert a 22k resistor between pin 3a and the center lug of Gain 1 - this completely cured the issue though I might have achieved the same result with a different value pot. This was just easier.

thanks to everyone who helped me on this

difficult to see the resistor on the gut shot but here goes. Caps C2a&b are mounted on the top of posts in the vero to simpify changing them.

[seedlings]

2. insert a 22k resistor between pin 3a and the center lug of Gain 1 - this completely cured the issue though I might have achieved the same result with a different value pot. This was just easier.

Is this the same as turning the gain down, right?  Gain at full grounds the pin, so you're adding 22k at full gain, so it should be similar to half-gain without the resistor.  (If I'm looking at this correctly... big "if")

CHAD

[stallik]

I really thought that it was the same. My logic was that putting a 22k resistor in series with a 47k pot would change the range from 0 - 47k to 22 - 69k. YET, the pot turned down (to about half) did not give the same result as full up with the extra resistor in, even though the values would be the same.

The more I think I know about this new fangled electrickery thing, the less I really do.....

[zambo]

that would make it adjust between 69k and 22k. it never really gets to zero resistance to ground.  not turning the gain all the way up cures the compression no matter how you look at it, If you use smaller caps on the input and between stages it help with the compression a bit as well.  .002uf works good all the way around if your making twins or triples. putting them on switches to choose between fat and skinny is nice but i usualy just find a good setting and leave it so the switch isnt really all that. my opinion anyway..

[stallik]

Took the pot out and measured the resistance. it went from 16k to 0k! it is marked as a 47k pot! that explains why I was getting the difference. Replaced the pot but decided to leave a resistor in anyway to prent me turning the gain full up as I realy don't like the compression. Understand your reasoning regarding the switching input cap but in my case I'm using a tele that's light on base and a strat with a humbucker that's rather heavier. This gives me the chance to tune it for both guitars

[Dongle]

Hi!
Did anyone put this thing already into Eagle for creating PCBs?
CU

[tuckster]

Does anyone know if a russian 6H16б (6N16b) sub mini tube would be usable for a valvecaster (with the 100V mentioned in the data sheet I think)?
There's a guy on ebay who sell these.
The sub mini 1SH17b & 1SH24 are power amp tubes, aren't they?

Edit: found a thread for this tube http://www.diystompboxes.com/smfforum/index.php?topic=83164.0

[iccaros]

Does anyone know if a russian 6H16б (6N16b) sub mini tube would be usable for a valvecaster (with the 100V mentioned in the data sheet I think)?
There's a guy on ebay who sell these.
The sub mini 1SH17b & 1SH24 are power amp tubes, aren't they?

Edit: found a thread for this tube http://www.diystompboxes.com/smfforum/index.php?topic=83164.0

search subcaster, http://www.diystompboxes.com/smfforum/index.php?topic=63479.80

as to if they work.. @ 1.50 on ebay with shipping.. Who know but they are cheap.. may make a good SuperFly

[ayayay!]

I built this last night.  Normal original schem provided by Dano:  12AU7, 9vdc supply.   Started tweaking a little.  I think my PS was only supplying 150mA, which is probably why it couldn't quite reach unity gain.  I'll be addressing that shortly.  

My question is:  Is anyone getting a bit of static sounding "wool" when turning the gain knob?  Yes, this is a very simple circuit, but I was hoping I could clear that up.  Of course, it was late and I didn't measure voltage from pin 3 to ground.  Still, this crackle is not okay...

I picked up a 9AU7 to try tonight.   

[Renegadrian]

Good for the 9AU7, altough it won't give you huge differences...I used one in the past just for fun.

yeah the scratchy pot is intended in this ckt, it comes from varyng the value of the resistance at the cathode...

[ayayay!]

Okay, thanks Adriano.  That answered my question.