The VTB1 preamp from Studio Projects is a great piece of kit. I use it to record guitar and vocal tracks. It has a handy tube blend control that lets you how much of your sound you want to be going through the transistor section and how much you want to go through the valve.
As you can see form the pictures of its electronic board, the VTB1 is built to last. And very well designed.
Out of the box the VTB1 comes with a Chinese 12AX7 tube that tends to saturate a bit too rapidly for my liking. It wasn’t long before I replaced it with a ECC803 S from JJ Electronics. The 803 S valve has a much smoother transition into clipping and slightly compresses your sound before distorting.
I am happy with the way the stock transistor section of the VTB1 sound but there are a few discussions on the web about swapping some the ICs on the VTB1 for better components. I haven’t tried any of these yet and I’d love to hear from you if have tried this.
The second modification I made was unsoldering one of the ends of resistor R30 to permanently turn off the two blue LEDs glowing behind the tube.
I didn’t want LEDs powered with AC current this close to the tube. The main reason was is I didn’t like the blue light was flickering at 50/60 Hz (being AC powered).
Turning the LEDs off also reduces load (all be it by a minuscule amount) on the power supply.
There is in my opinion one design flaw with the VTB1: it doesn’t have an on/off switch! Well, not anymore. There is just enough room in between the 12VAC and the line out XLR sockets at the back of the preamp to add a toggle switch!
As you can see on the picture bellow, adding an on/off switch is a bit of a dirty job since you’ll have to cut two tracks coming from power socket, then solder two pieces of wire form these tracks to the on/off switch.
Below is a picture of the end result.