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FREQUENTLY ASKED QUESTIONS 

 

How do I hook up this thing? 
 

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See Section 2, beginning on page 3. 

 

Is the FX loop series or parallel?  Active or parallel? 

 

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The FX loop is series, and is currently parallel.  However, we have plans to release an option for a tonally 
transparent solid-state FX loop.  Stay tuned! 

 
When I plug effects into the effects loop, my tone noticeably changes.  Sometimes the effects don’t sound quite right. What’s 
the deal? 
 

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Generally, what you’re hearing is a significant mismatching of impedances, and/or an overloading of the effect 
unit itself. Most rack-mount units have different input impedance than pedals, and thus can 

sometimes 

function fine without a buffer before them. In addition, 

some 

of these rack-mounted effects can pad the 

volume they receive, preventing it from overloading. Pedals do not have proper input impedance or padding 
ability, and therefore do not play nicely.  
 

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For best results, an effects loop interface like the C-lator or Klein-ulator should be used.  These units prevent 
impedance mismatching, as well as provide the ability to pad down the volume sent to the effects units hence 
preventing any overloading. 

 

Can I substitute different tube types for the 12AX7/ECC83s or 6L6GCs? 
 

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Although you can try 12AT7s, 12AU7s, 5751s without any harm, the design is optimized for 12AX7s, and are 
therefore the only recommended tube in the preamp positions.  Usage of other power tubes (ex – 6550s, 

Summary of Contents for JCM 800 2204

Page 1: ...1 JCM 800 2204 50W GUITAR AMPLIFIER User s Manual...

Page 2: ...s based on the British amplifiers built in the late 1970s and 1980s Their iconic sound is signature to countless records ranging from blues to classic rock fusion and heavy metal While their lineage i...

Page 3: ...peaker cabinet using 1 4 speaker cable 4 Set the IMPEDANCE SELECTOR to the match the impedance of your speaker cabinet 5 Set all rotary tone and gain controls on the front panel to 12 00 clock face 6...

Page 4: ...h powers the 2204 on and off With the toggle switch in the DOWN ON position the 2204 is on In the UP position the 2204 is OFF STANDBY applies high voltage to the vacuum tube anodes and screen grids du...

Page 5: ...add sparkle and clarity to your tone BASS adjusts low frequencies MIDRANGE adjusts the mid frequency response TREBLE adjusts the high frequency response MASTER VOLUME sets the overall volume PREAMP G...

Page 6: ...y bypassing the power amplifier Conversely this is usually used as the SEND of the effects loop Plug the input of your effects unit or interface device ex C lator Klein ulator into this jack using ins...

Page 7: ...plifier FULL HALF switches the power output of the power amp For the 100W JCM800 half mode is approximately 50W and for the 50W JCM800 this is approximately 20W HALF mode configures the power tubes to...

Page 8: ...RNAL BIAS JACKS AND ADJUSTMENT From left to right V1 JJ 12AX7 ECC83S input stage 1 and gain stage 2 V2 JJ 12AX7 ECC83S gain stage 3 and tonestack driver V3 JJ 12AX7 ECC83S phase inverter for power amp...

Page 9: ...9 In this diagram we have color coded features for simplicity 1 Blue arrow bias adjustment potentiometer 2 Green arrow bias probe jacks left V4 right V5 3 Red arrow black probe jack ground COM...

Page 10: ...ed probe jack on the right Write down your measurement 6 Adjust bias adjustment blue arrow SLOWLY until your DMM reads approximately 36mV see calculations following page 7 Remeasure V4 bias and adjust...

Page 11: ...your amplifier Extremely high voltages are present and vacuum tubes reach high temperatures during use The risk of electrical shock and or skin burns should ALWAYS be kept in mind Therefore bias at y...

Page 12: ...ce than pedals and thus can sometimes function fine without a buffer before them In addition some of these rack mounted effects can pad the volume they receive preventing it from overloading Pedals do...

Page 13: ...ESR electrolytic capacitors and those used in our British series 1 2W carbon composition resistors 1W carbon film resistors TAD Mustard capacitors high voltage silver mica capacitors Belton tube socke...

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