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8. Speaker Impedance and Cabinets
On the rear of the DH40H you’ll find a pair of output jacks along with an impedance select
switch. This allows for a variety of cabinets to be connected to your amp.
Take note that these jacks are connected internally in parallel. Here are some examples of
how to connect cabinets to your IronHorse:
• Connect a single Traynor DHX212 (8-ohms) to either output jack and set the impedance
switch to 8-ohms.
• Connect a pair of Traynor DHX12 (16-ohms each, 8-ohms total when connected in parallel)
to the output jacks – one cabinet per jack and set the impedance switch to 8-ohms.
• Connect a pair of Traynor DHX212 (8-ohms each, 4-ohms total when connected in parallel)
to the output jacks – one cabinet per jack and set the impedance switch to 4-ohms.
9. Power Amp IN / Preamp OUT (Effects Loop)
The IronHorse is equipped with a instrument level effects loop. The effects loops allows you
to place your effects pedals in the amps signal chain, post GAIN and tonstack circuitry, pre
MASTER. This is useful for delay and modulation type effects such as reverb and tremolo.
Using the effects loop is quite easy. Take a normal ¼-inch guitar cable, connect it to the
PREAMP OUT and run it to the input of your pedal chain. Then take another ¼-inch cable and
run it from the output of your last pedal to the POWER AMP IN jack.
The effects loop can also be used to slave a second amp if you need more power. Connect
a ¼-inch cable from the first amp’s PREAMP OUT to the second amp’s POWER AMP IN jack.
This disables the preamp of the second amplifier. Now the signal generated in the first amp
will feed the power sections of both amplifiers.
10. Footswitch
Any standard two button, latching footswitch can be connected to the IronHorse via the rear
Footswitch jack using a 1/4-inch TRS cable. We recommend the Traynor TFS-2B footswitch.
The two buttons are used to activate the PURE and SOLO modes respectively. The
SOLO mode will always dominate over the PURE mode. If you have the PURE mode active
and then activate the SOLO mode, you will be in SOLO. Deactivate the SOLO mode and
you'll go back to PURE. If the PURE mode is off and you hit the SOLO footswitch, you will
instantly jump to SOLO mode.
11. Tube Replacement and Biasing
When replacing the output tubes, it is recommended to use a matched pair and test the bias
voltage with a digital multi-meter. To adjust the bias, remove the amplifier's cage; there are
test points for measuring the bias voltage along with a note (printed directly on the chassis)
indicating the correct voltage for biasing a pair of EL34s. The trim pot is near the test points
and can be adjusted with a small screwdriver. If you do not feel comfortable performing this
operation, please seek the assistance of a qualified technician.
NOTE: In addition to matched EL34s, other tube types such as matched 6CA7s and matched
KT77s can be used.
