Tube boost + overdrive running off a 9 volt battery

[aka_basse]

gaah!

Took long enough for the banzai shipment, (with several items backordered - including the tube).  When I finally get it.... there's no box. They forgot the box. Getting pretty pissed...

For my last orders some items were back ordered too. It took a bit more than one week to be shipped ... and most of the time I usually get the back ordered parts in a separate shipment (at no extra shippment costs) Last time I thought they forgot one item (as they did not have noticed it on the order list as they usually do)  But I finally got it a couple of days later

personaly I think the service is good  but you need a bit of patience  Good luck !

Yeah, I've only shopped there once before, that time everything worked perfectly. I only wish they had some kind of stock info about the parts available.

[LMJS]

Don't feel so bad.
My last order from Small Bear was the opposite.
They sent the box and forgot the rest of the order.

[aka_basse]

Don't feel so bad.
My last order from Small Bear was the opposite.
They sent the box and forgot the rest of the order.

hahah ok, now thats definitely worse

[aka_basse]

Yeah, excellent service after all, shipped the box straight away   

[Renegadrian]

Valvecaster IV

I made this for Santa Pazienza bass player - It's a local band here in Rome - it means "Holy Patience"
Took their logo, swapped the candle for the tube...et voila'!!!

[Jimmy-H]

Really looks great Adriano!
Nice job!!

[Darkness, Darkness]

Yes great job ! Happy bass player ! 

[letsgocoyote]

So I just ordered me a tube and socket finally, after this thing goign 32 pages I will take on a valve caster.  i already have a pretty cool enclosure for it too!  should come out looking pretty neat.


anyone TRY it with batteries?
of course its going to chew through them, but i could see this going on a mini busking pedalboard, so long as it doesnt blast through batteries any faster than my rc-2 loop station.

[andrew_k]

anyone TRY it with batteries?

I got 6 minutes. Once the battery starts going, the voltage output drops and the sound becomes mush.

[letsgocoyote]

figures.  i wonder what difference perhaps 6AA batteries could make instead.  regardless im excited for the build

[andrew_k]

regardless im excited for the build

It's a great build. I gave my twin channel version to a friend for his birthday, so now I have an excuse to build another for myself 
I'm going with a no-tone pot tagboard version this time.

[Renegadrian]

I'm going with a no-tone pot tagboard version this time.

No tone Valvy?
Well...Follow my layout then!!! 
I am so happy I built mine without that 3rd pot...

[aka_basse]

oo mine is turning out nicely... if I had a good camera at hand I would give you a little look inside (its pure spaghetti mayhem)
Havent got a tube to test it with, so I have no idea if its working or not. But its pretty neat on the outside, always something ei?

Here is a picture of the layout, I took renegadrians layout and modded a bit, and put the parts on a board. Probably not the easiest way to build this thing but hey
3 switches for different mods, tone on/off, 2 different input caps and 2 different values on R1&R2

[Jimmy-H]

Hi aka bass,


Sure looks like a lot of fun!!
Bur where are the meatballs?? 
No spaghetti without the balls!!
No just kiddin'.

Just let us know how it all sounds like!
And I'm very curious how it gonna look altogether!

have fun building it!!

[tranceracer]

Here is a picture of the layout, I took renegadrians layout and modded a bit, and put the parts on a board. Probably not the easiest way to build this thing but hey
3 switches for different mods, tone on/off, 2 different input caps and 2 different values on R1&R2

Your point to point layout is very cool!  Thanks for sharing!

[comfortably_numb]

Okay, here's another little mod for the Valvecaster:

A usefull tonal variation can be achieved by implementing a switchable negative feedback.

Put a 22k resistor and a spdt switch between the output and the cathode of the second stage (lug 8 ).
You can also make a "bass boost" filter out of it by inserting a capacitor between there as well.
I currently have a 0.056uF cap in series with the resistor. This removes some of the mid range and helps keep things a little bit more together. It sounds nice and clean at low gain settings and it also sounds pretty good with everything maxed. More defined puch in the bottom and not so shrill. I've tried this with larger caps as well but it tends to get a bit too boomy.
All in all this is a nice little mod which will tame the gain a bit. Nothing dramatic, but it helps if you want to tune the thing for a more clean boost.

I'm interested in the use of this negative feedback idea.  Is this similar to the theory behind the inverting input on an opamp, where what you feed back suppresses what comes out again?  So by allowing high frequencies through with a capacitor you actually suppress them in the output? 

Would there be a way to insert a more intricate tone shaping network, possibly bleeding highs to ground to accentuate them at the output?  Is there a way to implement something like the feedback loop of the Rat distortion, where there are different gains for different parts of the frequency spectrum? 

I'm I completely off base here?

[comfortably_numb]

I've explored the negative feedback idea some on my own.  It could all be for naught, as I'm not sure that the theory is sound.  But based on my work with inverting opamp circuits, and the fact that someone suggested negative feedback in this one, I've come up with my own variation.

The schematic below is the Valvecaster with the following modifications:

Input cap reduced from 47nF to 10 nF to tame bass.
Coupling cap reduced from 47nF to 6.8nF to further tame bass fed to second gain stage.
Negative feedback network established between output of second gain stage and cathode (pin to reduce gain in this stage and to shape frequency response.

The idea behind this is to make up for loss of bass in the eariler stages.  It won't distort so much in the bass and get flabby, but I still want a full bottom end.  This will also add some top end sparkle (apparently) because of the dip in the mids.

The feedback is a bell curve bandpass, with the lows being slightly more attenuated than the highs.  This of course, should have the opposite effect on the output, giving a mid dip (hopefully not a scoop) with a good amount of bass and treble. 

I don't have the resources to build this at the moment, so if anyone gives it a shot, please post the results.  Also, if my theory is totally flawed, let me know.

Here's the schematic - I know it says +9V, but I intend to build it at 12V.  Also, for a slightly flatter response, change the 200k resistor in the feedback network to 500k.  This is probably where I'll start.

[andrew_k]

Interesting!
I'll have to get your mods on the breadboard next week... I like the idea a lot 

[aka_basse]

I wanted to trie it with a 12ax7/ecc83 tube since my 12au7 is on its way. During this test I made 2 mistakes:

I mounted the DCplug the wrong way on the adapter, and I had wired one of the + wires to the wrong pin on the dc jack (thought that both + pins had connection all the time). So when I fixed this it still doesnt work - did I blow the 7812? It got pretty warm! How do I test the regulator without taking it out? (its buried beneath the cable spaghetti)

The led never lit, and I tested and it was in the right "direction".

!!edit: Ok never mind, im too stupid for this kind of stuff. Wired the + wires from the wrong pin AGAIN, but now the LED lights and everything. But there is no sound whatsoever. Can this be because of the 12ax7? If the box worked it would still give me some sound with this tube, right?

[aka_basse]

YES!!! It works!!! Playing with 12ax7 now, cant wait to my hands on a 12au7!

Sitting and measuring values and thinking and going mad... and then - without doing a thing - I plugged it in... and it worked!