tube cricket amp with valve caster built in!

[IbanezRG95]

Hi,
I would like to know the best way to implement the valve caster into/before the tube cricket amp, as i intend on housing them in the same enclosure/head . I thought about trying this out to get a bit more gain/drive out of the tube cricket amp . I intend to run the setup with a 12v power supply. I am also open to any suggestions to increase the gain.

Tube Cricket
http://www.beavisaudio.com/projects/TubeCricket/

Valve Caster
http://www.beavisaudio.com/projects/ValveCaster/

Thanks in advance for your replies!

[srv]

I have built something similar to this already and tested it into a 4x10 quad cabinet. Feedback from others is that it sounds awesome.

Found a few differences between 12AU7's. Ended up using a US National tube which sounded the smoothest.

Taking the tube cricket circuit I changed the following:
1. Removed the gain circuit from the 386 chip and replaced the VR5 gain pot with a 10ohm resistor (in series with the 10uF cap)
(This is standard 386 datasheet stuff, and it fixes the gain of the chip) I used a LM386-N4 which is the 1Watt version.
I found it worked ok , even though the circuit said not use the LM chip, but use the JRC386 one.

2. R11 in the second tube stage, I put a toggle switch across it for a gain boost. It makes subtle boost changes and varies depending on
single coil or humbuckers and the overall volume in use at the time.

3. R7 in the first tube stage, I replaced this 4k7 resistor with a 50k pot (from the valvecaster circuit).
One problem here that I am yet to resolve is that a cap is needed somewhere to cure some DC voltage shift
which makes the pot sound scratchy, but it is not the pot. Google cathode bypass cap and scratchy pot and you will see what I mean.

4. The resistor for the LED is not right for a 12volt supply, I changed it to a 560 ohm. I wanted extra bright LED to light up the tube.
According to my Altronics catalogue this is right for using an LED with 12volts.

5. I added a 7812 (12 volt regulator) since I was getting a bit of hum in the circuit.
I found this didn't make any difference. The problem was my AC adapter/plugpack was only rated at 500mA.
I suspect a 1Amp plugpack would be better. I ended up using a 12V DC computer adapter and there is no hum now.

I found that we could get a nice warm sound up to a screaming overdrive with humbuckers.
You won't get modern scoop distortion though, probably need to put a Rat pedal in front of it.

Will post some pictures later.

Feel free to ask any questions, I like this concept it works well.
I'd like to resolve the gain pot problem and also add an effect loop to add in a reverb pedal.

[srv]

Here's some pics

[pazuzu]

i'm drunk in the morning over here, but i don't see any schematics. possibly due to my diminished perception?

[srv]

Schematics:

Valvecaster is here:
http://www.diystompboxes.com/smfforum/index.php?topic=63479.0

Tube Cricket is here:
http://www.diystompboxes.com/smfforum/index.php?topic=66623.0

[srv]

UPDATED -- some more info:

Found a few differences between 12AU7's. Ended up using a US National tube which sounded the smoothest. (UPDATE: Tube has 5963 U.S.A marked on it )

Taking the tube cricket circuit I changed the following:
1. Removed the VR5 gain pot and replaced it with a 10ohm resistor (I measured the pot value when it was at the best setting and then set it at a fixed resistor value)
(in series with the 10uF cap)
(This is standard 386 datasheet stuff, and it fixes the gain of the chip)
I used a LM386-N4 which is the 1Watt version.
Datasheet is here: http://www.national.com/ds/LM/LM386.pdf
I found it worked ok , even though the circuit said to not use the LM chip, but use the JRC386 one.

[IbanezRG95]

Thanks for the replies. Those JRC386 IC's are incredibly hard to find in Australia. I will almost definitely end up using a LM386-N4 like you. With the 12AU7's, the only ones I can find in Australia are these:

http://australia.rs-online.com/web/search/searchBrowseAction.html?method=searchProducts&searchTerm=12au7

http://www.soundlabsgroup.com.au/p/VA-12AU7EH/12AU7+EH+Electro+Harmonix+Valve

Which one would be the best to use for this project?

PS: thanks for posting all the changes that you made to the circuit, it will make it a lot easier.   

[srv]

I got my 12AU7's from ebay.
I was lucky, found a local Perth guy had them, so he dropped them off to me
and I saved on postage. He had a few more, so I bought them all.
One of them is an original Mullard from the UK factory.

[srv]

Another pic, finished painting the unit.
Will post some sound samples once recorded properly.

[IbanezRG95]

That's a really nice build  Cant wait to hear the sound samples!

Just out of curiosity where do you get your DC jacks from? I cant find any that suit boss adapters.

[srv]

I use parts from Altronics in Perth.
The DC sockets for chassis mounting are:

http://www.altronics.com.au/index.asp?area=item&id=P0628
2.1mm

http://www.altronics.com.au/index.asp?area=item&id=P0629
2.5mm

Not sure what the Boss standard is , though I'm not running this at 9volts.
I'm using a 12v DC power supply and found that a computer one works best for low hum.
The original plugpack I had was only 500mA and caused a bit of hum even when using a 7812 regulator and filtering caps.
With a 3Amp computer supply there is no hum.

[Govmnt_Lacky]

Here's some pics

Is that a headphone jack that I see next to the 1/4" jack?

[srv]

@Govmnt_Lacky
That is a 3.5mm headphone jack, although it's not there by design.

I drilled the hole for the speaker output,
but then changed my mind and wanted a 6.5mm to run a speaker cabinet.

I ended up putting both in there because the 6.5mm wouldn't fit
where the 3.5mm is because of the output capacitor being in the way.
(see photo)

-----------
Couldn't get an effects loop in here that was satisfactory although
I did get the gain pot to be less noisy by putting a 10uF cap across it.