Diezel VH4/VH4S
Owner’s ManualChapter One
Safety Warnings
1.1 Safety Warnings
We want you to be aware of certain safety aspects, for reasons of product safety and liability. With
all due respect, please read the following before operating your new Diezel Amplifier.
-Do not use or store this Amplifier in or near moist or wet areas. -Check voltage selector at rear ofunit before plugging unit in. Make sure that voltage shown is the correct voltage for the location you
are using the amplifier at. Under no circumstances can the amplifier be used at different than shown
voltages. -Opening of the amplifier housing must only be done by authorized personnel. No user
serviceable parts inside. -The VH4/VH4S was designed to amplify a guitar signal and can be used
only for this purpose. -When transporting the VH4(S) please observe the following:
The Diezel VH4
is a vacuum tube instrument amplifier. Vacuum tubes are shock sensitive, especially when hot. To
avoid damaging the unit, we recommend using care during setup and tear down of the unit.
Allow
the Amplifier to adjust to ambient temperature before operating, 60 minutes should be sufficient inall cases. The VH4 4 lives inside an extremely rugged chassis, but for continued road use, please
protect the amplifier by using a professional flight case. Transport only in operating position. Do nottransport upside down or on it’s side. -The Diezel VH4 power amp is configured to deliver highest
tone fidelity at “ normal “ volume levels. ( 76-80dB ) We caution you for your own good not to
expose yourself to very high volume levels for long periods of time. It can lead to hearing damage.
-Blown fuses can only be replaced with fuses of equal values. The use of incorrect fuses is prohibitedand can cause severe injury and damage of the amplifier. Use only a grounded power cable in good
operating condition.

Chapter 2 Setting up your VH4
2.1 Power connection/Mains
Before connecting to a grounded power outlet, make sure the power and standby switches are in theoff ( facing down) position. Never turn this amp on without speakers connected. The VH4S requires
a speaker to be connected to side A and B of the amplifier output jacks. Obey impedance
requirements! ( see 3.4) The VH4 S cannot be operated in “bridged mono” mode. Once your VH4 isconnected to power and the speakers are plugged in correctly, then we can get started!

2.1.2 Power/Warmup/Standby Off
First turn the Power switch to on ( facing up). The indicator will light up. This starts the tube
heating process. After about 40 seconds, the tubes have sufficiently heated for normal operation.
Your VH4 is now ready for operation and the standby switch can be turned to “run” (also facingup). Premature activation of the standby switch will lead to unnecessary tube stress andsubsequent reduction of the power tube’s life span.

2.1.3 To protect and serve
Tubes are electronic components that only function with vacuum intact and under very highoperating temperatures. Each tube has one or more heating filaments, much like a light bulb. Thesefilaments heat up the Anode of the tube. If you switch the standby switch before these Anodes havereached their operating temperature then the Anode surfaces are not heated evenly yet; the“operating temperature” of the tube is not reached yet. This causes undue stress on the tubes andtheir related components inside the amp. One should therefore always give the amp it’s muchneeded warmup time, even if musical inspiration hits with full force.

2.1.4 Optimum Operating temperature
It will take a little more time after warmup until everything inside the amp is working in sync and to it’s
fullest potential. A trained ear will notice a slightly warmer tone and better complexity in tone after
playing the amp for a short while. It’s like warming up before running a marathon. Get it?

2.2.1 Factory Setting
The Amplifier is set to 110V/60Hz for use in the United States. Keep the amplifier on this setting foruse in US, and check it after servicing the amp of after receiving the amplifier from third parties.
The operating voltage is indicated by white letters inside a little window above the power input jack.

2.2.2 Traveling Abroad
If traveling to countries outside the US, then always check their local voltage before operating theVH4. Mismatched voltages can and most likely will destroy your amplifier. Should you encounter
voltages and frequencies other than those indicated, then a transformer must be used between the
power socket and the VH4. This transformer must be able to transform the voltage and frequency
to one of the indicated settings. The transformer must also be able to handle the necessaryamperage for your VH4.

2.3 Safety fuses
2.3.1 Main Fuse
The Main Fuse is situated inside a little drawer which is part of the power input jack. This sliding
fuse holder also hides a spare fuse. The fuse values depend on the operating voltage in yourcountry. For 110V, the fuse is to be a 4A slow blow, for 220V operation, the fuse must be 2 A
slow blow. It is crucially important to use the specified fuse values only.

2.3.2 Tube Fault
Each power amp tube utilizes it’s own tube fault system, consisting of a tube fault fuse (250mA slowblow) and a tube fault indicator ( small red warning light). Ideally, a defective tube will blow it’s fuse
and illuminate the tube fault indicator. This is very very cool for several reasons: The tube fault
system will not shut down the entire amp and leave you or us embarrassed in the midst of a heatedset. The remaining tubes will continue operation and allow you to finish your song, or the set, or theshow. Output power, volume and tone might change some, but you will remain being heard. The
indicator shows which tube and fuse just gave up, and with a little effort and a spare tube and fuse,
you are back on stage with great tone and a smirk on your face. We do recommend you take a lookat the other tubes and replace them as soon as possible with a matched set, followed by carefulbiasing.

2.3.3 Causes for Faulty Tubes
There are different reasons for failing tubes. Often tubes fail prematurely due to strong vibrations.
Tubes are very sensitive to mechanical impacts and vibrations, such as happen when transporting
an amplifier or unloading/loading etc. The inside filaments of a tube deform easily and will cause ashort inside the tube, resulting in it’s early demise. This is why we can not extend our warranty to
the tubes. A relatively new, but defective tube can be replaced by a matching unit, no need toreplace the entire set. (Unless you want to, which is always a good solution) This is not age or wear
related, but accidental damage. Tube Failure due to normal wear and old age is also a common
cause. If this is the case, then it makes more sense to replace the entire tube set with a matched
quartet. Testing has proven that matched sets last longer and are more reliable than mismatched
sets. Also, if one tube of a matched set fails after a few years, then the general status of theremaining tubes is no longer a secret, because the tubes in a matched set will wear evenly, and at
the same rate. Yes - this means that the remaining tubes are likely to fail very soon and it is time
for a new set of matched tubes. The aging process is a slow depletion of the anode’s coating (Wolfram). The more power the tube has to produce, the quicker this coating wears off.

Chapter 3 Peripheral Connections
3.1 Front Panel Hookups
3.1.1 Signal In Jack
The input jack (“IN”) receives your Electric Guitar signal by means of a shielded guitar cordwith 1/4” mono style plug.

3.1.2 The CordYour guitar cord is an important part of your signal chain and it’s quality and construction typeclearly affect the overall tone of your rig. Try and buy the best quality guitar cord that you can orwant to afford. Call us if you have doubts and need recommendations. This is where the smart “weaklink” comment comes in. Get it? Some cords and cables sound very neutral, others color the soundspectrum and/or attenuate high frequencies due to capacitance inside the wire and shield. What are
we talking about? OK. A capacitor is used in electronic crossovers, amongst other things, to divide
low and high frequencies. Capacitance in an cable therefore cuts your guitar’s high end to a certain
degree. Generally, the longer of a cord you use, the more of the cords inherent characteristics will be
audible.

3.1.3 The right cord for the specific instrument
In certain instances it is desirable to match a guitar cord to a specific instrument. One can use theotherwise undesirable qualities of a cord to one’s advantage, if one has the time and patience toexperiment with different cords and guitars. This should be done while playing with your band, orwhen recording. Sometimes it is difficult to tell a components true advantages until it is used in theright context. A guitar that has very piercing highs could theoretically be tamed down somewhat by
the use of a long guitar cord that offers some high end attenuation. The inserts and loops of yourDiezel VH4 or VH4S send signals at higher levels and impedances, which makes this section of
wiring less sensitive. You should still use reliable and good quality wiring for all loops and inserts.

3.1.4 Signal Splitting via “Thru” jackThe “Thru” jack is wired in parallel to the input jack. You must be careful not to hook up low
impedance tuners or other devices to this jack, because if you do, the signal portion that is split into
the amplifier might be compromised. In other words, you want more signal to go into your amp theninto your tuner or other device. This jack was designed to be used for high impedance tuners or to
go into a second amplifier input stage. You can try this out by plugging a secondary device into thisjack while playing, and listening to your tone. If you notice a change in sound quality or volume,then you should not use the device in question at this jack. There is a better solution to connect atuner anyway. See section 3.3.2

3.2 Rear Panel Jacks
3.2.1 Loops, Sends, Returns
The Loop System consists of “Send1”, and the switchable/programmable “Send2”. “ReturnA” with parallel or serial option and “Return B” (VH4S only). Send 2 only works with theparallel return.
The individual channel volume controls determine the signal strength at the send jacks. The range is- ... to +10dB. The output impedance is 4.7 kΩ. If you want to use the loops, then connect the“Send” to the input of the Effects unit. Be sure and adjust the input level of the effects unit to theamplifiers level. Most effects units have a led bar or other level control devices. The Output of theeffects unit must be connected to one of the two return jacks, parallel or serial. If you use theparallel return, then the signal can be mixed to the original signal via the front panel mounted“Mix” control.

3.2.2 Send 2 Functions
Send 2 has an edge over send 1: it is switch able and midi programmable. This is especially handy
if you are using a multi effects unit in this loop, but don’t want it in the signal path all the time, but
only when you are using it’s effects. You can activate or deactivate this loop by pushing the red”Send2” button on the front of the amp, or by assigning it a midi command. Send 2 only works
with the parallel return.

3.2.3 The Returns: Parallel or Serial?
Which is better for you? Read on. There are 2 ways to handle effects signals. If you use the serial
return, then the signal path of your VH4 is interrupted, the signal is sent to the processor, gets moreor less processed, then sent back to the serial return into the power amp. Digital effects units often
digitize this signal, then process it, then convert it back to analog, then send it to the amp. This iscalled ADA conversion. It is necessary for digital effects units to do this to your guitar signal, so thatit becomes a digital code which the processor can read and understand. Your tubes, however, need aold fashioned analog signal, so the processor needs to convert the signal back to analog before itgoes back to the amp. Generally, even in highest quality effects processors, this causes a change inthe original signal, typically a loss of tonality and warmth, also noticeable as a “harder” sound. Whenyou use the serial loop for an effects unit like this, then your signal will have been ADA converted atleast once. Tone junkies and vintage freaks alike will more than likely have hives developing by now.
But - as always, there is a better way. Use the Parallel loop and the mix control in the front
determines how much effect signal is being added to the original signal, which now still flows
through the amplifier. There is always an analog connection between the send and return jacks; aparallel loop! Important: You must set the mix control on the effects unit to 100% wet when using
the parallel loop. Otherwise there will be nasty phasing problems resulting in unsatisfactory tone.
The signal portion that is unaffected by the mix control in the effects unit would reach the amplifier
at a different time due to the cabling, and cause phasing cancellations.

3.2.4 Loop as Second Master Volume
Those of you who can live without processors in the parallel loop can use this loop for a second
master volume for each channel. To do this, just loop a short 1/4” cable from send 2 to parallel loop
return. Now you can choose a second master volume by turning the mix control past 1:00 PM to fullopen, and push the send 2 button to activate your second master volume. To do this for the VH4S,
you must use a Y-cable and send the signal from send 2 to parallel return A and B.

3.2.5 Reasons for Loss of Dynamics
Many different factors can be responsible for loss of dynamics, aside from those mentioned in 3.2.3( ADA conversion). A vital point that often leads to frustration is a maladjusted output level of aneffects unit. If the output level is too high, then unwanted distortion is caused in the power amp. If
it is too low, then the rig will not sound punchy and might get lost easily in the band sound. Whenused in the serial loop, the output of the effects unit determines the ultimate drive signal strengthof the power amp. The output level should be matched to give the best possible sound with all 4
channels without over driving the power amp section. Headroom adjustments of 10% are usually
sufficient.

3.2.6 Function of the Channel Inserts
Stomp Boxes beware! These little jewels often cause a medium to heavy wiring nightmare. If put inthe signal chain between the guitar and the amp, then one must accept massive losses of signal
purity due to the long wiring length and all the electrical connections that essentially destroy the
weak signal coming from your guitar. This holds especially true when the units are turned off. It also
adds points of potential trouble. A noticeable improvement can be realized here by using the channel
inserts. Using the Send/Return System would add even more cabling, even though it would alleviate
the signal loss problem. Channel Inserts are perfect for the use of stomp boxes. And - they areprogrammable. The channel insert button turns the insert of the selected channel on or off. Some
tips: Channel one responds well to compression. Connect the send of the channel insert to the inputof the effects unit, and the output of the effects unit to the return of the channel insert. Turn the unit
on and you are done. Now just push the insert button and the effects unit is in the signal path forchannel one. You want to program this to a midi patch? Sure - just pick an appropriate patch on yourmidi controller, then hit the store button. All selected functions will now blink. Hit the store button
again and that’s it. Your channel insert for channel one is now programmed. We can not think of areally useful effects unit for channel two, so here is a way to loop in your tuner. connect the tuner tothe send of channel 2 insert. Now take a 1/4”jack and connect the tip and sleeve internally. Plug it
into the return of channel 2 insert. Yes - this shorts the signal and will cause a forced muted
operation of channel 2 with the insert on. Your tuner works, but the amp is quiet while you tune.
Very suave!
Advantage: No losses of tone due to splitting the signal at the “thru” jackIt is a midi programmable tuning loop. To program: Select a midi patch at your foot controller.
channel 2 on - insert on - push “Store” twice - done. Channel insert 3 and 4 allow you to use otherdiverse tone shaping devices, like noise gates, eq, etc. Remember that the effects units that areassigned to the channel inserts will only work for the selected channels that they are connected to.
Also, the “feel” of the effects units will be different due to the higher signal voltage to the input of
the effects unit.

3.4 Speaker Connections
As a rule, the impedance of the loudspeaker to be connected should match the designation of theoutput jacks that it is connected to. We suggest using speakers that have an impedance range of 4Ω
to 16Ω, as singular speakers or in combinations. Do not ever run the VH4/VH4S without having
speakers connected to the output jack ( both sides of the VH4S). Danger of Amplifier damage.
ΩΩΩΩΩ’s If you are using 2 ea. 16Ω speakers, then the total impedance is 8Ω. Really -trust us onthat. 2ea. 8Ω speakers make 4Ω. This is because the speaker jacks on the amp are wired in parallelmode. Your local library has many books on Ohm’s law.........

3.4.1 Choosing Speaker Cabinets
Oh boy. This is one big subjectivetug-o-war. Every manufacturer has it’s own philosophy, eventhough most cabinets are constructed surprisingly similar. The influences of magnets, coils, box
volume, open or closed backs etc, all this has a certain influence on the ultimate way the cabinet will
respond to amplifier input at different levels.The rule is that if you like the way it sounds and if itmatches the amp, then its a good choice. Make sure the combined impedance is no less than theamplifiers minimal requirements. Test your speakers at realistic volumes, as if you would play them
most often. Many cabinets sound very different at higher volumes than at low volumes like in amusic store. Ultimately this speaker will have the last word in at what you are going to sound like.
Many cabinets swallow the all important midrange of your tone spectrum due to internal
cancellations, which is often caused by a vibrating rear speaker cabinet wall. We have designed aspeaker cabinet that matches the Diezel VH4 series amplifier quite well. It is the Diezel V212/V412
speaker. The cabinets are Mono/Stereo wired and utilize Celestion Vintage 30 Speakers, or yourchoice of speakers on a special order basis. These cabinets are constructed by hand, from choice
hardwoods and with very good tolerances and internal bracing. They make an excellent all roundspeaker and can cover a wide array of styles. Of course, the VH4 amplifier will also work with otherbrands of cabinets, including your own favorite.

3.5 Midi Connections
3.5.1 MidiIn Midi in receives “program change” orders from commonly available midi pedals and control
systems. The VH4 is able to supply phantom power to your midi pedal via a 5-prong DIN midicable. Pin 1 and 6 = minus Pin 3 and 7 = plus Pin 4 and 5 = midi data
The voltage is 12VDC which is acceptable for 90% of all midi pedals. Maximum power usage ofthe pedal can not exceed 800mA

3.5.2 Midi ThroughThis jack routes the midi signal to other midi partners. Midi data not addressed to the VH4 getlooped through this jack.
See chapter 6 for midi programming instructions

Chapter 4 Pre-Amp Section of the
VH4/VH4S 4.1 Layout
The Diezel VH4/VH4S comes equipped with 4 different and totally independent preamps. This allows
the artist to play through nearly all musical styles without having to make major changes to his
amplifier. The preamps are voiced to deliver the 4 most wanted guitar tone flavors: 1-Clean, 2Crunch, 3-Heavy and 4-Lead. The Concept delivers 4 stellar guitar sounds with excellent playability,
warm dynamics and razor sharp equalization possibilities. The tone controls work in an unusuallywide range, so a little adjustment goes a long way. As with so many other things - less is often
more. We suggest you start exploring the channels with all controls set to 12:00 o’clock, and themaster volume just slightly cracked open. ( to avoid hearing damage)

4.1.1 Channel One ( Clean )This channel was designed for clean, undistorted sound with high power and good harmonics. With it’s
gain control to the upper third, it sounds soft and warm, gain at lower settings produce morepercussive and penetrating clean sounds. Full gain setting makes crunch sounds possible. The tone
reminds of a cross between a twin and a Hiwatt® 100, but with better overall dynamic response.

4.1.2 Channel Two ( Crunch)
Channel 2 is a blues guitarists closest friend. It’s dynamic spectrum is especially beautiful in thelower frequency range. It’s gain range goes from clean to distorted. Due to it’s different voicing the
2nd channel will sound a little softer than channel one in clean mode ( gain 2:00 -3:00, andapproaches channel 3’s tone in high gain mode ( gain 3:00-4:00, but with softer midrange and lesscompression. “Raw” probably best describes this channel.

4.1.3 Channel Three ( Distortion)It’s concept is heavy rhythm guitar. The distortion is noticeably tighter than in channel 2. The side
effect of this added compression is that he signal gets somewhat limited in it’s dynamic range. This
limitation hits mostly the lower frequencies. This loss is corrected by a negative feedback loop to thepower amps, which adds fat low end to this tone without muddling up the tone. The control for thislow end is in the master section and bears the “Deep” designation. The gain structure of channel 3 isdesigned to deliver great distorted sound even with guitars that have relatively low output, likemany vintage guitars. The side effect here is that guitars with very high output (active EMG® etc.)
might overdrive this channel too much and become too compressed. The guitar loses it’s punch inthe band sound and becomes very undefined. In this case, a radical gain reduction is the cure. The
guitar sound will clean up a little bit, and the overtones and harmonics will once again sparkle. It isbest to start with a 12:00 o-clock gain setting and start to feel your way to the point of perfection
and very little compression. This works best while the band is playing with you. Remember - less isoften more.

4.1.4 Channel Four ( Ultra High Gain)
The Solo channel. A little more mid heavy then channel 3, therefore punches through the bandsound quite well. See channel 3 description for gain control setting. Often a gain setting near
1:00 o’clock is sufficient for absolute high gain distortion. Use the volume control here and for allother channels to match the individual channel volumes

4.2 Preamp tubes
The preamps are stocked with 12AX7 tubes. These tubes are not used as power tubes and therefore
last much longer than the much larger power amp tubes. However, preamp tubes of different
brands and styles produce differences in gain and tone behavior.

4.3 Noises and Microphonic Preamp Tubes
the first preamp tube ( input stage is especially prone to becoming microphonic. This is noticeable bya feedback like tone at higher volumes. Replace the first tube with a 12AX7 High Grade tube if thishappens. Even though tube amplifiers are not typically very quiet amps, you should expect unusuallysmall noise levels from your Diezel amplifier. Some idle noise in channel 3 and 4 is normal, due tothe higher gain structures of these channels.

Chapter 5 VH4/VH4S Power amp(s)5.1 Tone and Volume of the Power Amplifier
5.1.1 The Master Volume
controls the final volume of the Power amplifier(s). The layout of the controls is such that fullvolume is achieved at the 1:00 o’clock knob setting. Turning the knob further will overdrive thepower amp(s) to create power amp distortion for those of you that prefer this sort of thing. We
added this feature to round out the distortion sound palette on the extreme end. So you friends ofall things vintage can get colorations and distortion textures that only power amp tubes candeliver. Bring your ear plugs, please.

5.1.2 Parallel Loop Mix
See 3.2.3 for function of the loop. The parallel loop mix control adds effect signal to the original
signal in relation to the control knobs setting. Don't forget: Effects unit 100% wet! Also, this control
allows for a programmable second master volume as described in 3.2.4

5.1.3 PresenceThis knob controls the treble part of the power amps tone spectrum. Its frequency centers at about
4kHz. Treble is produced and dispersed in a very small beam from the speaker, so be sure toposition yourself in the projection area of the speaker when making adjustments.

5.1.4 Deep
The Deep control is an active bass control for the power amp that adds low end punch to thepower amp centered at 80Hz. It does not alter the dynamic behavior of the power amp. Diezel Co.
is not responsible for cabinet handles popping out etc.

5.2 Power Amp Tubes
5.2.1 Function
As the name suggests, the power amp section is the part of the amplifier that produces output
power, measured in watts. Preamp signals are sent to the power amp(s), which amplifies this signal
to a level that is acceptable for loudspeakers.Guitar amplifiers utilize several different type of poweramps which differ in output power and tone. We chose the tube type power amplifier for it’s tried
and true performance and familiar tonal behavior.

5.2.2 Tube Selection
VH4(S) comes factory equipped with KT77 type tubes. The KT77 tube delivers transparent tone withgood warm tendencies and strong low end.

5.2.3 Life Span
Power tubes last 1 to 3 years, depending on care, volume and frequency of use of the amplifier. If
you use your amp only once am month, then the tubes will last longer. Get it? We have heard tubes
that are over 10 years old, but it was not a good thing. Tubes age very slowly, slow enough for theartist to get used to the changing tone. To keep things fresh, we recommend retubing, cleaning andbiasing once a year if the amp is used frequently.

Chapter 6 Red Switches and Switching
6.0 Programming your VH4
It is quite easy to program your Diezel VH4, and easy to explain. Each change in the midi program
must be followed by pushing the “Store” button twice. After the first touch, the selected redfunction switches will blink, then touch again and your program is in memory. Each of the 128
programs (patches, program changes) can be changed as often as is desired.

6.1 Preamp Channel Selection
The 4 channels of the Diezel can be selected manually by activating the red button above eachchannel strip, or can be programmed via the midi control system. If you assign the channel one
switch function to a midi program ( for example “01”), then you can initiate this channel’s switching
via your midi pedal. Push “01” on your midi pedal after programming, and the pedal will send
digital information to the amplifier. The amp will read this information and decide whether or not it
is supposed to respond. When properly programmed, it will then switch on channel one. OK, here itis again: select 01 on your midi pedal. select channel one of the VH4. Now push “Store” twice.
Voila’, it’s a midi program! Now select program change “02” on your pedal, switch the amp tochannel two, hit “Store” twice, and suddenly you have a midi program with 2 program changes.
Continue on until you run out of channels, about 2 more times. All the other function of the amp
can be programmed in the same exact way. Remember: push “Store “ twice to finalize a midi
program procedure. Select the program from the pedal to recall it at the amp.

6.2 Inserts on/off
The “Insert” function always relates to the selected channel. If the “Insert” switch is illuminated,then the corresponding channel insert is activated, and vice versa. You can program thisfunction as well, of course, for all 4 channels.

6.3 Send 2 on/off“Send 2” is programmable as well. When activated, signal will go to the send 2 jack in the rear of
the amp. This is independent of channel selection, but programmable just like the inserts.

6.4 Mute“Mute” mutes the VH4 in it’s entirety. The signal will not go anywhere , not to the inserts, not to themaster sends, not anywhere. That’s why we call it “Mute”. Get it? We thought it would be a very
cool feature for tuning or guitar changes without pops and hums etc, and without changing yourvolume settings every time you have to disconnect your cord. Especially cool when your amp issomewhere on stage where you are not.

6.5 StoreAs discussed earlier, this is the universal programming button. Activating this button twice willverify a intended program procedure. In case you have pushed this button once by accident, or if
you have started to program and don’t want to anymore for whatever reason, then you can push
any other switch ( any switch but the “Store” switch) to cancel the programming procedure. The
previously established program will be preserved .

Chapter 7 Midi
Midi is short for Musical Instrument Digital Interface, and is an internationally accepted
Communications system between musical instruments of all kinds. We will only need to learn asmall portion of this “language” to use the VH4 and it’s peripheral midi partners. We are going
to learn only about “program change” here.

7.2 Midi In
Midi in is a 5 or 7 pole DIN jack. It must be connected to the midi out jack of your footcontroller (or midi pedal), or the midi out of any effects unit connected to the pedal directly.

7.3 Midi ThroughConnect this port to the midi in of other units to continue the midi chain.

7.4 Midi channels
Midi information can be received on up to 16 midi channels. These channels canbe programmed automatically or manually.

7.4.1 Omni Mode
The Omni mode will allow reading of midi information on all 16 channels. It is an easy way to get into themidi system, but it is not advisable if more midi partners on different channels are in the same system.
Then a certain midi channel should be assigned to the VH4 and it’s program changes should be restricted
to this channel. (see 7.4.2) To put the amp into the Omni mode, hold the “Mute” switch down andactivate the “Channel Insert” switch quickly and then release the mute switch. The Insert, Send 2, andMute switches will be now on to verify that the Omni mode is being accepted.

7.4.2 Single Channel Mode - Automatic Channel Recognition
Your VH4 can automatically recognize the pedal’s send/receive channel. To get your amp into themood ( or mode) for this, push and hold “Mute” and then activate any program change button on
your midi pedal. The amp will look for a program change and recognize the channel it is being
sent on. Then it will switch to this channel and stay there as soon as you let go of “Mute”.

7.4.3 Single Channel Mode - Manual Midi Channel Selection
If you would like to have your VH4 on a certain midi channel, then we can accommodate you here
as well. Here is how this works: Push and hold “Mute” and then turn on the preamp channels in theorder that corresponds to your midi channel preference. For example: if you want to have your VH4
to respond only to midi information that is being sent on channel 12, then you must hold the “Mute”
button down and turn the Preamp channel one selector on, channel two selector on, channel 3
selector off, and channel 4 selector on. If you let go of “Mute” now, then your VH4 is set to respondto Midi channel 12 only. Get it? The table below gives you the sequence for all 16 Midi channels.

Midi Channel
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16

Ch1 CH2 CH3 CH4
off off off off
on off off off
off on off off
on on off off
off off on off
on off on off
off on on off
on on on off
off off off on
on off off on
off on off on
on on off on
off off on on
on off on on
off on on on
on on on on

7.5 Program Change Capability
The VH4(S) can accept up to 128 program changes.

7.6 Phantom PowerThe two outer pins of the Midi port can supply power to the midi controller pedal.

Chapter 8 Cleaning and Servicing the
VH4/VH4S 8.1 Cleaning
Never use a wet method of cleaning the amplifier. Any amplifier. Usually it is sufficient to wipe
down the outside of the amp with a slightly moist cleaning rag. Do not use abrasive cleaningchemicals. Sometimes a vacuum cleaner can be used to remove dust and dirt from nooks andcrevices. Do not remove the chassis from the housing to clean the amp. The inside of your amp
carries dangerous Voltages.

8.2 Care and Feeding
Be gentle with this Amplifier. Any mechanical shocks and wide temperature changes, moisture richenvironments and extreme conditions ( dust, wind, heat, cold, moisture) can substantially shorten
tube life, in some cases even amplifier life. Do not block the air circulation grilles in the front and in
the back of the amp. Do not push the amp right up against objects that would interfere with it’s
normal airflow. The top of the amplifier might get warm after prolonged use, this is normal, but will
melt your ice cream and definitely ruin your beer. Never put beverages on top of the amp where
they could spill and flow inside the amplifier. This would be very bad overall. Get it?

8.3 Tube Change
Tube changes are only to be undertaken by authorized service personnel. If Power tubes withdifferent values then the original ones are to be installed, then the amplifier must be re-biased
before operation can be resumed. The amplifier uses a hard wire bias system. It is quick and easy toaccomplish biasing, but involves removing the chassis and soldering/measuring currents inside theamplifier. Only trained professionals should attempt this procedure.

The Diezel Company wishes to express their gratitude and congratulate youon your decision to purchase the Diezel VH4/VH4S Amplifier.

Diezel GmbH
Donaustrasse 589407 Dillingen
Germany
Email: service (at) diezelamplification.com
Homepage: www.diezelamplification.com
Steuernummer: 1115212440172570441
USt.ID: DE153734466
Geschäftsführer Peter Diezel und Peter Stapfer
Handelsregister Augsburg / HRB 13015