Studio Projects VTB1 on/off switch mod

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.

Tube swap

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.

IC swap

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.

Blue glow

VTB1 blue LEDs mod

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.

On/off switch

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.

VTB1 on/off switch mod end result


10 thoughts on “Studio Projects VTB1 on/off switch mod”

  1. After a while I look inside the VTB1 and found 2 infamous JRC4580 opamps. as well as a JRC2114 and JRC2082. Knowinghow Behringer stuff relies on these opamps I decided to replace them with something different. After some testing with some common opamps ihad around this is how IMO it sounded better:

    2 TI NE5532 for the JRC4580s
    1 LM833N for the JRC2114
    1 LM353N for the JRC2082
    I initially bought this unit after I compared it to much higher priced units in a Music store setting that I was working at.
    I replaced the “no name” tube for something better.

    I found that as a matter of fact the JRC4580s impart a very unpleasant characteristics: cold, brittle, hollow are just a few terms that maywell define their behaviour. Why do they use them? The ICs i have used as replacement cost the same yet they provide a more musical response
    (specially HF).

    Well worth the work to change them.



  2. I am purchasing a VTB 1 and have taken note of the JJ ECC308S. I wondering what you thought about the JJ ECC83 S. I understand it is 10% higher gain and I am wondering what this would sound like or if it is an issue.


    1. Hello Val.
      Good idea to replace the stock valve! I haven’t tried the JJ ECC83 S but I would guess it’s probably going to sound a bit ‘muddier’ to with 10% more gain… I’d get both if I were you, then you can compare ;).


    1. TI NE5532D or TI NE5532P

      According to the NE5532 datasheet, on page Addendum-Page 1, the differences between the NE5532D and NE5532P are:

      NE5532D: Green (RoHS & no Sb/Br)
      NE5532P: Pb-Free (RoHS)

      I would assume these differences do no affect the way it sounds.


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