I have seen a few people ask questions about electronics usually when they are looking to fix something or build a kit etc.. Thought it might be interesting to post the ongoings of my new pedal build?
I designed it and it may work great or could be a total Turdscreamer. We shall see.
First off the circuit. In a nut shell my idea is nothing groundbreaking just bags of gain and a passive tone control that can change the slope from bassy to trebly by just a few decibels. Dont see the point of complicated tone controls with huge adjustments as they tend to make bass flubby and can really suck the life out of the sound. This is probably the hifi person in me speaking here. The valves are 6/30L2; normally found in audio stages of old TVs. I've not designed the circuit to clip but the valves are not particularly linear. Hopefully a clean snappy sound with some nice euphoric sounding harmonics.
The rough circuit layouts:
I have used the chassis of the rather terrible Behringer VT999 Vintage Tube Monstrosity; a clone of an Ibanez Tube King. It was £30 and has no resale value.
Here is the powersupply. I bought some inverter circuits from Amazon that boost 12VDC to 220V square wave pulse. A quick hook up just to see if they work OK. I was hoping for around 175VDC and getting around 169VDC under a simulated load, which is close enough. It's all a bit of estimation when designing valve circuits anyway.
This may seem a bit anal but I kitted the parts that I need into a compartment box, but this is really helpful for keeping the work area tidy.
More to follow when I get round to doing some more.
Maintained it for 20 years. This old guitar's had 17 new necks and 14 new bodies in its time.
Comments
It was great, I wish I'd kept it now.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Just because I don't care, doesn't mean I don't understand." - Homer Simpson
Righto, I'm off to buy up all the cheapo Behringer VT999 Vintage Tube Monster pedals as I feel there's going to be an ebay run on them soon!
At least that's what normally happens on TFB when someone does a really interesting make and modify thread.
Pa MAX for each side is 2W BUT the total of both halves combined musn't exceed 2.5W, so aim for 1W each side to be safe. I tend to think of them as a fragile ECC82 without a CT heater - should work great in a pedal though.
Rift Amplification
Brackley, Northamptonshire
www.riftamps.co.uk
I understand the implications of mains powered products that are going to be commercially sold and the rules \ regs etc but as a one off for your own use that wouldn't apply
Anyway very interesting project
Some more wiring
I've actually finished all the wiring and fixed the errors - the biggest being that I numbered the valve pins in reverse, so 1 was 9 2 was 8 and so on - I felt a right turd when I realised what I had done there..
Anyway it lives!!
And how does it sound - terrible!!
I mean really bad....
The inverter was a bit of a unknown and I think I put it under too much of a dummy load when I tested it. I got 169VDC but now I am getting around 200 volts. However a quick check of the load line with these new voltages and the valves should still operate in a non-linear region. I think this is the reason for the terrible distortion sound, as opposed to a fantastic distortion sound. Plenty of gain though!
I think I will change the operating points of the valves to push them in a more linear region.
Did I mention how bad it sounds?
If your pedal has a proper earthed mains connection to the casing that can't happen. The only problem is that you may need to isolate the output to avoid a ground loop, but you can do that with a small transformer.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Just because I don't care, doesn't mean I don't understand." - Homer Simpson
The buffer stages are completely screwy. Did anyone spot the error on the circuit? The lower resistors are 680R & 17K, They should be lower.
I haven't designed a valve circuit for quite some time, so I know I would make a mistake, but I think I must have been drunk when I done this one!!
Turned out I had neglected to make the earth connection on the second valve. Changed some resistors and it works. Operating points are not particularly close to what my datasheet says, but I suspect the datasheet.
It's quiet - as low noise, bags of gain and very transparent. So much for euphoric sound. It's like not having there except for the gain and a nice punchiness when the gain is up full. very dynamic too and it does open up the volume and tone controls of the guitar.
The tone control circuit is a little too subtle though, so I will change it probably to something a little more simple that just rolls off the treble. maybe filter off the higher frequencies above 2 Khz.
Overall very nice and worth investing some time to make it look nice. Might spray paint it but I find that spray paint tends to be quite fragile these days. Might cover it in a vintage looking cloth and lacquer it.
We need a demo clip
After a bit more work it now looks like this:
Just a few finishing touches left like cutting the pot shafts down so the knobs sit lower and adding some guards for the valves.