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How am I supposed to monitor changes in tone after adjusting internal trimmers while the amplifier is off? 
 

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Yes, this does pose someone of a problem.  While it is not recommended and highly dangerous, most 

individuals adjust these trimmers while the amplifier is on so they can more easily monitor changes and find 

their preferred endpoint.   

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If you find yourself in this position and unwilling to follow recommended safety guidelines, please follow these 

warnings and recommendations: 

o

 

Use only non-conductive screwdrivers 

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Do not adjust trimmers with your guitar strapped on 

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Do not wear loose clothing or jewelry 

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Adjust only in proper lighting 

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Have a clear idea what trimmer you are going to adjust, and how you are going to adjust it 

o

 

Take your time 

o

 

If you need to measure values with your DMM,  

 

keep the black probe plugged into the black bias probe 

 

when measuring with the red probe, keep your opposite arm bent behind your back 

 

measure from above, holding the probe at an angle can cause arcing and shorts 

 

KEEP PROBE CLEAR OF ALL POINTS YOU DO NOT WANT TO MEASURE 

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Again, Ceriatone is not responsible for any damages or injuries resulting from user adjustments! 

 

Do I need to use matched power tubes? 

 

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Although not necessary, matched power tube sets are recommended for best results. 

 

Do I need to use a matched and balanced phase inverter? 

 

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It is not necessary.  Feel free to experiment with different tubes (of the same type) in your OTS, though! 

 

 

Summary of Contents for 100W Overtone Special

Page 1: ...1 Ceriatone Overtone Special S M Edition 50W and 100W amplifiers...

Page 2: ...of currently 8 different versions within the series In addition we have released the Klein ulator and C lator effects loop interfaces specifically for use with our Overtone amplifiers We have been pl...

Page 3: ...g a 1 4 instrument cable into the NOR input on the lower left of the front panel 2 Plug a suitable power cable from the OTS s rear panel MAINS cable inlet to your wall power receptacle 3 Plug the OTS...

Page 4: ...BY for 30 seconds to allow tube filaments to warm up 12 Set rear panel OPERATE STANDBY switch to OPERATE 13 ROCK 3 FRONT PANEL CONTROLS On the front panel of the S M Overtone Special you can see thirt...

Page 5: ...d tube stage Think of this as a gain control primarily for your clean channel but note it will impact the overdrive mode as well BRIGHT is a high frequency boost that can be used to add sparkle to you...

Page 6: ...mode RATIO OVERDRIVE serves a sort of volume control for the overdrive channel However just like this version of the original amplifier there are not individual master volume controls for the clean a...

Page 7: ...P slow blow fuse 3 MAINS power two way toggle switch 4 OPERATE STANDBY two way toggle switch 5 SPEAKER OUTPUT speaker jacks 6 IMPEDANCE three way rotary selector 7 EFFECTS LOOP RETURN instrument jack...

Page 8: ...our speaker cabinet to the amplifier using these jacks If you use one speaker cabinet use the jack labeled MAIN If you want to run two cabinets in parallel connect the second cabinet to the amplifier...

Page 9: ...ches between boosted and normal configurations In this series of OTS amplifiers the PAB accentuates midrange frequencies and attenuates low frequencies making it great for cutting through during a sol...

Page 10: ...X7 ECC83 clean and overdrive stages 1 and 2 V2 12AX7 ECC83 overdrive stages 3 and 4 V3 12AX7 ECC83 phase inverter for power amplifier V4 6L6GC V5 6L6GC V6 6L6GC 100W version only V7 6L6GC 100W version...

Page 11: ...ry from DMM to DMM 2 Plug a black probe into the color coded jack on your DMM and do the same for a red probe 3 Insert the black probe tip into the black probe jack blue arrow This is GROUND in the OT...

Page 12: ...ation for 6L6GCs 30W and now some math The formula for calculating bias is as follows In most cases amplifiers are biased between 50 and 75 dissipation We bias the OTS to approximately 35mV 40mV readi...

Page 13: ...ecessary A FEW COMMENTS ON BIASING Due to the nature of vacuum tube amplification there are inherent risks when biasing your amplifier Extremely high voltages are present and vacuum tubes reach high t...

Page 14: ...padding ability and therefore do not play nicely For best results an effects loop interface like the C lator or Klein ulator should be used with the OTS amplifiers These units prevent impedance misma...

Page 15: ...hly recommend the use of a non conductive rubber screwdriver and only adjust the trimpot when the amplifier is not powered and disconnected from the wall outlet DO NOT ADJUST THE OD TRIMMER WHILE THE...

Page 16: ...the OTS have it and what does it do Yes the OTS amplifier has a PI short for phase inverter trimmer This is part of the original design that controls the balance of plate voltage between the two triod...

Page 17: ...risk On the next page there are three arrows The ORANGE arrow is the PI trimmer The GREEN arrow is the test point for measuring the plate voltage at V3A The BLUE arrow is the test point for measuring...

Page 18: ...ue arrow indicates V3B test point Green arrow indicates V3A test point Adjusting those trimmers sounds intimidating Am I missing anything if I don t experiment with them Absolutely not We adjust each...

Page 19: ...t only in proper lighting o Have a clear idea what trimmer you are going to adjust and how you are going to adjust it o Take your time o If you need to measure values with your DMM keep the black prob...

Page 20: ...lones Finally we occasionally use NOS components from our vast surplus parts collection in locations they work well and complement the voicing or enhance the performance of the amplifier I like to use...

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