Matsumin valve caster

[alexxxx]

Hi guys,
Lately I decided to make matsumin valve caster using vacuum tube from jj electronics- 12au7.
Everything works fine except the hum I am getting from pedal.
Anybody got advices hot to get rid off the hum or how to reduce it ?
Thank you vry much for help

[GibsonGM]

Hi Alexxx, welcome!

Couple of questions:

-  Is the pedal inside an enclosure yet?  Is it near any transformers, fluorescent lights or things like that?

- what are you using to power the circuit?  It is "clean" DC, or just a generic power supply?  Can you try running it off a battery to see if it still hums?     I ask because most unregulated power supplies will have ripple, and are noisy.  It may be that you need to regulate and filter your DC power.

[vigilante397]

The valvecaster was my first ever build, and I definitely remember it being noisy.

However, since it was my first build, I didn't know anything about power supplies so not only did I use a cheap unregulated supply, I also didn't have any sort of filtering in the pedal. So I would definitely recommend trying it with a battery and see if that helps, and maybe add a simple RC filter in the front of the pedal.

[stallik]

The Valvecaster was my first too! I've build several and they are all quiet. I'd suspect the power supply too but check the earth connections

[vigilante397]

I've built several and they are all quiet

The odd thing is I haven't really built any since I actually started figuring out what I'm doing, maybe I should get another one going But I do remember building a couple for friends and they never mentioned anything about noise, so my savvy friends that bought them from me must have already had quiet power supplies

[alexxxx]

The problem is that i am currently using 9v transformer 1000mA power supply. And yes the pedal is in the box and i have already put the 20pF capacitor for filtering on output but doesnt help. I will try rc filter tho

[GibsonGM]

The problem is that i am currently using 9v transformer 1000mA power supply. And yes the pedal is in the box and i have already put the 20pF capacitor for filtering on output but doesnt help. I will try rc filter tho

But is it a regulated transformer??  If not, it is probably noisy.   Test the output with a DMM...if it reads something like 15 volts, you know it's not regulated.  "1000mA @ 9v" suggests to me that it will supply 9V when you are drawing 1A, and higher voltages if you are drawing less.   It will likely have a lot of ripple that is making noise.  Try a new battery.

A 20pF cap would help with RF, depending on where it is located, but not low frequency hum. 

[stallik]

Also be aware that most feel the valvecaster works better at 12v

[alexxxx]

Oh ye guys ! Thank you for help I will put everyting on prper pcb also with grounding and should be fine.
Also one think. Is it possible to use in the same circuit tube 12ax7 or at7 ?

[stallik]

I think the normal answer to this is use the 12AU7. Many have reported less satisfactory results with the 12AX7 though I've had excellent results with old Mullard and Brimar ECC83 (12AX7). Perhaps down to the way they used to be built?

[PFX]

Try to put a 220ohm res plus a big ele cap(100-220u) and a small cap (1nf) going to ground on the supply line. Best position is closer as possible to pin 1 and 6.