Here comes the Valvecaster!!

ACS · May 10, 2008, 06:30:32 AM

Getting there! Decided on a point to point layout, cos I hadn't done one before and it sounded interesting! Minor issue with not having any pots at the moment, but should be able to rectify that tomorrow...

and the insides...

ACS · May 10, 2008, 06:34:48 AM

Ah, but one minor issue...

In Dano's original schematic, take note of C3, C4 and VR2

Now compare to the point to point version...

So, is the net effect the same, or is there an error in the PtP diagram?

Cheers
Aidan

frequencycentral · May 10, 2008, 06:45:57 AM

Yeah, I think the tone pot is wired in reverse too - if I remember my build rightly. I think the ptp error with C3, C4 and VR2 would make little differance.

Quote from: ACS on May 10, 2008, 06:30:32 AMMinor issue with not having any pots at the moment, but should be able to rectify that tomorrow...

If you hardwire pin 3 to ground you get maximum gain - so you can play while waiting for your pots!

slacker · May 10, 2008, 08:28:22 AM

Quote from: ACS on May 10, 2008, 06:34:48 AM
So, is the net effect the same, or is there an error in the PtP diagram?

They are functionally the same. The pot and C4 are in series with each other between the signal and ground, it doesn't matter which order they are in. I guess that way was easier to do PTP.

ACS · May 10, 2008, 08:34:00 AM

Awesome, thanks for confirming that guys...

ACS · May 11, 2008, 05:15:58 AM

AND IT'S FINISHED!!!

There were a few comments on the 'industrial' look earlier on, so I thought, why not? Let's make the most of it

Gut shot...

Anyone like spaghetti??!

Am stoked with the sound - lovely smooth overdrive from the 12AT7. Little bit of noise in there ('hum' I guess is the best way to describe it), but I suspect this is mainly from the cheapo 12V transformer. Is some basic filtering likely to improve this?

Cheers guys, what a great build!

frequencycentral · May 11, 2008, 06:44:18 AM

Haha! Mad Max does Valvecaster! Great look though.

If its low frequency hum and not hiss its definately from the power supply. Mine hums if I use a cheap unregulated 300ma wallwart - if you cut one of these open there's nothing inside but a transformer. I use a 500ma regulated wallwart for best results - which has diodes, a voltage regulator and capacitors inside. I guess you could regulate the supply yourself by using part of this: http://www.reconnsworld.com/power/12vpowersupply.gif Probably use everything from C1 onwards (?).

LMJS · May 11, 2008, 08:57:03 AM

And the award for best use of nylock nuts for knobs goes to.....

Take a bow! Very nice package you built there. Applause!

pravudh · May 11, 2008, 09:45:24 AM

awesome

Renegadrian · May 11, 2008, 06:37:36 PM

Aidan, schematic and noise/hiss issues have been largely discussed in the main original thread...I now it's 25 pages, but it's worth the reading...

ACS · May 11, 2008, 06:39:05 PM

Cheers guys! I love how the nut-knobs turned out

Glad I ended up with the 12AT7 as well, cos it sounds like it's got a lot more crunch than the AU7's... Me lika lotta...

I'll take some decent pix in some good light in a few days and post them up in the pictures thread.

Oh, did I mention that the tube GLOWS!?!?!?

Oh yeah

ACS · May 11, 2008, 06:40:32 PM

Quote from: Renegadrian on May 11, 2008, 06:37:36 PM
Aidan, schematic and noise/hiss issues have been largely discussed in the main original thread...I now it's 25 pages, but it's worth the reading...

Now that you mention it, I do recall reading that when I went through the thread a while back... Will have to have a second look - when I have an hour or two spare!! It's a rather long thread isn't it?!

ambulancevoice · May 11, 2008, 06:48:59 PM

the hum might be because your using a non isolated dc jack, which you NEED to insulate from the enclosure
if you already knew this and have done it, and im just blind, then maybe a couple of filter caps or one big one like 1000uf (make it look like a tube amp, you know with the big caps) will help

(edit: ah i see you used the tip as positive, well, with the negative going straight to ground from via dc jack to the enclosure, and with the negative also grounded to the input jack, this might be creating a ground loop, plus hum, which means you need to isolate the dc jack)

btw man, those nut knobs (

) make the pedal look meaty as @#$%

ACS · May 11, 2008, 07:05:09 PM

Definitely see your point there - I hadn't considered that. See, THAT's why I love forums!!

+ve tip was just convenience as I had a 12V wall wart already, but it is wired that way...

What about just disconnecting the jack to jack grounf connection? That should break the loop...

ambulancevoice · May 12, 2008, 01:47:59 AM

Quote from: ACS on May 11, 2008, 07:05:09 PM
Definitely see your point there - I hadn't considered that. See, THAT's why I love forums!!

+ve tip was just convenience as I had a 12V wall wart already, but it is wired that way...

What about just disconnecting the jack to jack grounf connection? That should break the loop...

give it a shot

nico13 · May 17, 2008, 02:07:01 AM

Quote from: ACS on May 11, 2008, 06:39:05 PM
Cheers guys! I love how the nut-knobs turned out Glad I ended up with the 12AT7 as well, cos it sounds like it's got a lot more crunch than the AU7's... Me lika lotta...

I'll take some decent pix in some good light in a few days and post them up in the pictures thread.

Oh, did I mention that the tube GLOWS!?!?!?

Oh yeah

I've seen the pictures of your Valvecaster on the pictures thread.
Fantastic work and imagination!

The tube really glows (more than I thought). What brand is it?

ACS · May 17, 2008, 02:45:15 AM

I've got to admit the pic with the really obvious glow in the Pictures thread is a little deceiving - that was a 30 second exposure in relative darkness, so it has enhanced the glow quite dramatically. If you look at the other pictures, you'll notice that it's plugged in in most of them, and you can see a bit of glow there... For the record, it's a no-name second hand 12AT7 that I got off ebay with three others for very little

And it sounds like heaven...

earthtonesaudio · May 18, 2008, 01:34:23 AM

I would leave your DC jack as-is. The source of hum is most likely the adapter (unregulated, right?) or possibly due to the rat's nest wiring.

My opinion is that isolating the DC jack from chassis ground would create more of a ground loop problem, not less. But I'm interested to see the results if you decide to try it.

IIRC, ground loops are due to LARGE loops, big enough to pick up 50-60Hz waves. Just like you won't find a cell phone speaker with good bass response, you're not gonna get ground loop problems due to potential differences between grounds that are a few cm apart.

ACS · May 18, 2008, 07:01:12 AM

Had a play with this yesterday...

Dropped off the earth line of the twisted pair. No change.
Added a 100uF cap across the DC jack. No change.
Ran it off 9V battery. Clean as a whistle

So it's definitely the wall wart. I also thought I'd tried it with around 100ohms in series before the cap with no change, but on thinking about this at around 3:30 this morning when I couldn't sleep, I didn't have it wired right, so will try this again tonight. Might also see if I can get a small inductor to try as well...

Cheers
Aidan

ACS · May 18, 2008, 08:25:57 AM

Quote from: ACS on May 18, 2008, 07:01:12 AM
I also thought I'd tried it with around 100ohms in series before the cap with no change, but on thinking about this at around 3:30 this morning when I couldn't sleep, I didn't have it wired right, so will try this again tonight. Might also see if I can get a small inductor to try as well...

So I got this wired up correctly - 94ohms measured resistance, onto +ve leg of 100uF (63V) cap to ground. V+ from junction of cap and resistor to circuit. And here's what I don't understand: I get a measured 4.21V after the resistor. That just don't seem right to me! What am I missing here?

Cheers
Aidan

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Here comes the Valvecaster!!