Since Einstein (Herberts notes in brackets) has external bias points and its trimmer is accesable from the top, it is much easier and user-friendly . . . .


1) Remove the backpanel. You'll see three (four) jacks above the fuses.

2) Set your multimeter to mA and plug your black probe into the black jack and the red to one of the red jacks.

3) Remove the jack-corresponding fuse from the fuse holder which is located on the backplate, turn volume controls to 0 and make shure a load or speaker is connected to the amp.

4) Now switch it on and read the bias current from your multimeter. Adjust it to the proper value by turning the bias pot which is accessible with a little flathead screwdriver through the hole in front of the red jack.

5) When finished, turn off the amp, install the fuse and repeat the same
steps for the other pair(s) by using the other red jack(s) and removing the other fuse(s).

Here we go (keep in mind that there are 500 Volts on the OT, be careful, make sure the crocos are tight on the OT, use an insulated screwdriver for the trimmer . . . ):

1 ) take the chassis out of the headshell (and have a look if the bias selector-switch fits your tubes - it is labelled "EL34 and 6L6") and place the amp - pots facing you - onto two books, watch out for powertubes !

2 ) on the right you can see the output-transformer (OT). Its right side (red wires) is the secondary - you need to hook the crocos to the primary, so the left side

3 ) Set DMM to 200mA DC current (many DMMs need another slot for the red for current for voltage !)

4)Hook crocos to DMM leads and the black to the middle of the three primary OT wires, red to either left or right of it

Switch amp on, standby run-position, hooked to load - be careful !

5 ) read current and adjust desired value with the bias-trimmer on the left side of the mainboard, close to the midi board . . .

6 ) this way you are reading the current for one side of the quartet (so 2 tubes), which means that should read 60mA for EL34.

7 ) Switch amp off, you may want to repeat the whole procedure for the other side - in the case of this amp using the blue wire . . .

8 ) Put amp back into headshell after you've unhooked from mains

9 ) Enjoy your fresh biased VH4 !

Recommended current settings for pairs in a VH4:


EL34 BHT or =C= 60 mA

1. Take Herbie out of the headshell, place the transformers on two books (tubes !) with the pots facing you

2. upper right side: three fuses - from the left A, B, C

3. mid-left: three pots from the top: TrimA, TrimB, TrimC

corresponding pairs:

A = 3 + 4 (inner pair)
B = 2 + 5 (inbetweens)
C = 1 + 6 (outer pair)


4. gently push the first fuse out of its socket

5. install croco leads and hook them to your DMM, set to 200mA (!) DC (!)

6. now (not earlier!) hook to mains + cab, vol = 0 and switch on (both, power and standby)

7. read DMM until value doesn't change anymore (1 minute, new tubes may take longer)

8. adjust trimmer until you get the current given in the table bottom of post
clockwise: increasing current
counterclockwise: decreasing current

9. switch Herbert off and unhook from mains

10. reinstall fuse you took out

11. repeat for the three pairs/fuses/trimmers