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Summary of Contents for Ceriatone Overtone Special
- Page 1 Ceriatone Overtone Special S&M Edition 50W and 100W amplifiers...
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Page 2: Table Of Contents
User’s Manual Thank you for the purchase of your Ceriatone Overtone Special guitar amplifier! Here, we hope to explain how best to use your new amp. Table of Contents 1) About the S&M Overtone Special………………………………………..…………………………………………page 2 2) Quick setup……………………………………………………………………………………………………………page 3 3) Front Panel controls………………………………………………………………………………………………….page 4... -
Page 3: Quick Setup
While our work could not have been possible without the gracious information shared over the last decade in the public domain, we hope you appreciate our modifications, component selection, and construction techniques. Most of all, we hope the OTS becomes an integral part of your tone equation to exhilarate your playing and music. Rock on! - Nik Azam 2) QUICK SETUP (for instant gratification) -
Page 4: Front Panel Controls
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 thirteen items of interest. From left to right: 1) INPUT ¼” instrument jacks (FET and NOR) - Page 5 7) MIDDLE control 8) BASS control 9) LEVEL (OVERDRIVE) control 10) RATIO (OVERDRIVE) control 11) MASTER (POWER AMP) control 12) PRESENCE (POWER AMP) control 13) INDICATOR LED INPUT jacks provide two tonal options. First, FET routes your signal through a high-input impedance, low-output impedance JFET gain stage before hitting the first triode tube stage.
- Page 6 the midrange, giving the amplifier more of a hi-fi response. Experiment with both, as great sounds rest in each. With the toggle switch in the UP position, ROCK is on. In the DOWN position, JAZZ is on. TREBLE adjusts the high frequency response for both clean and overdrive modes. At near-maximum settings, you may also notice an increase in gain.
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Page 7: Rear Panel Controls
4) REAR PANEL CONTROLS On the rear panel of the S&M Overtone Special, you can see eleven items of interest. 1) MAINS IEC cable inlet 2) 3 AMP / 2 AMP slow-blow fuse 3) MAINS power two-way toggle switch 4) OPERATE / STANDBY two-way toggle switch 5) SPEAKER OUTPUT ¼”... - Page 8 MAINS IEC cable inlet – plug a suitable IEC power cable into this inlet to power your amplifier 3 AMP / 2 AMP slow-blow fuse – used to protect your amplifier from voltage spikes or excessive current draw. Replace only when necessary.
- Page 9 EFFECTS LOOP SEND ¼” instrument jack can be used to directly interface the preamp of the OTS, thereby bypassing the power amplifier and using the OTS as a preamp. Conversely, this is usually used as the SEND of the effects loop. Plug the input of your effects unit, or interface device (ex –...
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Page 10: Tube Compliment And External Bias Jacks And Adjustment
5) TUBE COMPLIMENT AND EXTERNAL BIAS JACKS AND ADJUSTMENT 50W Overtone Special 100W Overtone Special From left to right: V1 – 12AX7/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 –... - Page 11 In this diagram, we have color coded three features for simplicity 1) Green arrows = red probe jacks 2) Yellow arrow = black probe jack 3) Blue arrow = bias adjustment potentiometer shaft To measure your power tube bias, carefully follow these steps with the amplifier in OPERATE and connected to a speaker load (not doing so may damage your amplifier!): 1) Turn on a digital multimeter (DMM), and set it to read millivolts (mV) in the 100mV range (this will vary from DMM to DMM)
- Page 12 Okay, now I’ve measured my bias. Now what? To calculate bias, there are two pieces of information you need to know: your amplifier’s power tube plate voltage, and the published value for maximum plate dissipation for the power tubes used in your amplifier. To save you some time and energy, here are those two values: - Approximate plate voltage for OTS series amplifiers = 440-450VDC...
- Page 13 Even though the bias test points and adjustment is external to reduce risk of electrical shock, all precautions must be taken while biasing. Again, bias at your own risk. Ceriatone Amplification is not responsible for any damages or injuries resulting from user biasing.
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Page 14: Frequently Asked Questions
- 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 – modern 6V6s like Electro-Harmonix, JJ) may be possible, but please first consult Ceriatone Amplification or your local competent amplifier technician. - Page 15 I have the foot pedal plugged in, but it’s not switching functions? The LEDs on the foot pedal still light up though…. - Make certain the rear toggles for OVERDRIVE and PREAMP BOOST are in the PEDAL positions I’ve read about something called an OD trimmer inside of the amp. Does the OTS have it, and what does it do? - Yes, the OTS amplifier has an OD (short for overdrive) trimmer.
- Page 16 Inside chassis view of OTS 100W. Green arrow indicates OD trimmer. I’ve read about something called a PI trimmer inside of the amp. Does 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 triodes of the phase inverter.
- Page 17 Hmm, the PI trimmer doesn’t sound as fun. Oh well, I still want to play with it! Is that okay? - Again, before we continue, realize that you are adjusting PLATE VOLTAGE. In this case, your screwdriver is about a millimeter away from about 300VDC. DO NOT adjust this trimmer with the amplifier on!!!! Furthermore, measurement of the progress of the adjustment is tricky, because you are measuring near 300VDC! - We highly recommend the use of a non-conductive rubber screwdriver, and only adjust the trimpot when the...
- Page 18 Inside chassis view of OTS 100W. Orange arrow indicates PI trimmer. Blue 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 trimmer to ensure the best results for each amplifier leaving our shop.
- Page 19 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 - Again, Ceriatone is not responsible for any damages or injuries resulting from user adjustments! Do I need to use matched power tubes? - Although not necessary, matched power tube sets are recommended for best results.
- Page 20 I’ve read that the components used in this type of amplifier are really important. What is inside my OTS? - We use a combination of parts custom-made for us to our specifications (power transformer, output transformer, choke, high-temperature / low-ESR electrolytic capacitors) and those used in the original amplifiers (Vishay/Dale RN65 precision metal film resistors, 1W carbon film resistors, SBE 6PS polyester film capacitors, high-quality ceramic disc capacitors, Belton tube sockets, and Alpha potentiometers).
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