GamuT GamuT International A/S, Oesterled 28, Bygning A, DK-4300 Holbaek, Denmark Telephone no: int + 45 70 20 22 68 Telefax no: int + 45 59 43 97 26 www.gamutaudio.com Users Guide GamuT D200 MkIII Dual-Mono Power Amplifier GamuT International A/S, Oesterled 28, Bygning A, DK-4300 Holbaek, Denmark Telephone no: int + 45 70 20 22 68 Telefax no: int + 45 59 43 97 26 www.gamutaudio.com Users Guide GamuT D200 MkIII Dual-Mono Power Amplifier SAFETY INSTRUCTIONS: - Never let children (or grownups) push anything into holes or slots in the case - this could result in an electric shock and could cause damage of the set. - Never guess or take chances with electrical equipment of any kind - it is better to be safe than sorry. Warning: To prevent fire or shock hazard do not expose this appliance to rain or moisture Warning: No user serviceable parts inside. Refer servicing to a qualified technician. Never remove covers unless qualified to do so. This unit contains dangerous voltages. DO read the user's guide before you attempt to use this equipment. DO ensure that all electrical connections ( including the mains plug, extension leads and interconnections between pieces of equipment ) are properly set and in accordance with the manufacturer's instructions. Check that the mains fuse rating is set correct for your local mains voltage. DO NOT obstruct the necessary all-around ventilation: Especially DO NOT place the set close to curtains or on soft furnishing such as carpets. Overheating can cause unnecessary damage and shorten the life of the set. 2 Unpacking. Remove the 4 top blue foam corners. Open the inner box, remove the 2 top blue foam parts Lift the amplifier up and place it on its feet. Be careful not to damage the gold plated connectors on the back panel. Keep the box and the blue foam, it is specially made to protect the amplifier well, and you may need it some day, when you move or you want to upgrade the amplifier. Connecting the input cables. The main inputs are the two 3-pin XLR sockets. They are electronically balanced, and they will therefore reduce hum pickup in the input cables. So the best choice of cable is a balanced XLR cable, coming from a balanced output on your preamplifier. In case you have a preamplifier with only RCA outputs, you can use the RCA inputs. Move the switch towards the RCA. Use only one input, RCA or XLR, not both. We recommend purchasing our balanced cable wired with a male XLR in one end, and an RCA plug in the other end. This will give you partly balanced operation in the cable, with an unbalanced source. You release the XLR connector by pressing on the release button next to the XLR socket, and pulling the XLR plug out at the same time. Do not pull on the cable, only on the plug. The XLR connector: always connect Pin 1 (the ground) first and disconnect it last. This way, XLR connectors can be plugged and unplugged while the amplifier is switched on. However, some DC from the preamplifier may still cause loud clicks, so it is recommended to wait 10 seconds and then switch the power amplifier on as the last precaution. If you use a tube preamplifier, please wait several minutes the first time you use it. Also do switch off the power amplifier first, before switching off your preamplifier or any source. DO NOT CONNECT LOUDSPEAKER WIRES OR OTHER HIGH VOLTAGE CABLE TO THE INPUTS. Warming up The GamuT power amplifier will play sound a few seconds after you turn it on. However, please allow minimum 30 minutes before you start serious listening, as the sound quality will slowly improve, because all the parts need to reach their optimum operating temperature. You may also note a slight improvement in the first months of use. This is caused by the capacitors, which do improve with use. A CD player in repeat mode can speed up the process while you are not at home. Do not play too loud. After this break-in period is over, simply switch the GamuT on when you get home, and it will be ready to perform at its best after dinner. Sensitivity (Gain) Inside the cabinet, at the top edge of the circuit boards, is a dual piano switch marked -6 dB and -12 dB. Normally, gain is factory set at -6dB or 29dB total voltage gain. Your dealer can set them for you, so that you get the best match for your preamplifier. To match a passive "preamplifier" like our GamuT control unit, the gain has to be high, so set both switches to "off". Some preamplifiers also need maximum gain, others have a lot of gain in their output section and therefore should be used with the -6 dB or -12 dB switch moved away from "off". If both switches are moved away from "off", then the gain is reduced by 14 dB. We recommend that with 4 Volt sources like our GamuT CD player. Noise levels will be lower. We use switches, because they can be set precisely identical and will preserve the stereo balance. The maximum voltage gain of GamuT D200 MkIII is 35dB, and the GamuT C100, D100, M200 and M250 also have 35 dB maximum gain, so they will all work together in a bi-amped system. 3 Cleaning the cabinet The front panel is made of aluminium. It can be cleaned by using normal mild solvents and clean paper tissue or cloth. Do not use excessive amounts of solvents, and do not let any of the solvent spill into the amplifier. The Brass logopanel is covered with a protective layer. DO NOT USE ANY BRASS POLISH. You will remove the protective layer. The protection circuitry The ideas for the protection circuit come from our professional amplifiers, where it has worked well since 1982. Due to the rugged MOSFET, we can allow high peak currents , and we only need to mute the input signal in case of long-term overload. The protection detects DC errors, high level subsonic signals, long-term ultrasonic signals, high temperature, and to low impedance loads or short circuits. If needed, the protection will simply mute the input signal, and if necessary open the output relay. The relay will normally open only after muting the input signal to avoid relay switching of strong currents that could corrode the relay contacts. So in case of i.e. a short circuit the input is muted for a second. Then a 1 millisecond long pulse is sent out to test again. If the short circuit still is present, it waits a second and tries again, and so on. One second after the user has removed the faulty cable, the system will quickly remove the muting. The protection also detects too low impedance loads, and alerts the user by muting for a second. So the user can be sure to hear only clean non-distorted audio. The normal current limiting and momentary distortions of the music are avoided in the GamuT D200 power amplifier. A second of silence You may experience a second of silence while the music is playing loudly. This is the protection acting to protect your tweeters. Any amplifier will start to clip the top of the music if you exceed the maximum power level. Technically, clipping generates a lot of high frequency energy, which can burn out the tweeters in your loudspeakers. The protection constantly checks the energy above 20 kHz, which humans do not hear. The distortion is momentarily very high anyway, because you have exceeded the maximum power, so just reduce the level a bit. You can also provoke the subsonic protection by playing warped records without using a subsonic filter. Please check your tonearm/cartridge resonance frequency, which should be about 8-12 Hz to reduce the effect of warped records. Connecting your loudspeakers to the output terminals Normal power amplifiers have a coil in parallel with a resistor between the amplifier and the output connector. Its purpose is to protect the amplifier against capacitive speaker and cable loads. However, this will slightly reduce the fidelity of the sound in the treble range, when the amplifier is used with normal loudspeakers. So we have added a direct output in addition to the normal filter protected output. The red terminal closest to the heat sinks is the direct output. The other red terminal is the filter output. The white terminals are ground This also gives you the ability to connect biwiring nicely, using the filter output for the bass. and the direct output for the treble In case of biwiring an electrostatic loudspeaker, the reverse should be done. Inside the cabinet the ground terminals are kept biwired until they meet at the main star ground point. So please do not connect them together. 4 The red terminals go positive when there is a positive signal on the Pin 2 on the input XLR. In other words, GamuT amplifiers are non-inverting. Some other brands of amplifiers do not follow this standard. Take care if you want to bi-amp. Do also note that JBL speaker units are wired inverted. WARNING! Do not use this direct output for tests with square waves or sine waves and a capacitor across the output terminals, as you may damage the amplifier. Do not connect output ground to input ground. Do not connect any output grounds together. Do not connect headphones to this amplifier without using protecting resistors. Make sure, that you do not let any tiny part of the speaker cable going to a terminal touch the other terminals. Only connect this amplifier to loudspeakers, and only one loudspeaker on each channel. Do not connect the output of this amplifier to another amplifiers outputs or inputs. DO NOT CONNECT A RED TERMINAL TO ANOTHER RED TERMINAL! DO NOT BRIDGE THE AMPLIFIER! DO NOT USE BOTH CHANNELS TO DRIVE ONE LOUDSPEAKER! Loudspeaker impedance Most loudspeaker are 8 or 4 Ohm, and they are specified so by the manufacturer. Unfortunately, some loudspeakers have an impedance, which is much lower than specified. They will not damage the GamuT power amplifier, because it will simply mute. In the GamuT D200 MkIII, we use a gem of a MOSFET transistor. It handles 500 Watts, and a peak current of 300 Ampere and 100 Ampere long-term. Such high currents will destroy any HiFi loudspeaker we know of. The lower the impedance, the higher the current will be. Somewhere, we have to draw a line between what is a loudspeaker load, and what is a short circuit. We have set this line at 1.5 Ohm, which will draw about 47 Ampere peak. The impedance of a few electrostatic loudspeakers does go down below 1.5 Ohm at high frequencies. The protection circuit will not allow this long-term on test signals. However, it works well with Quad ELS63 and most Martin Logan electrostatic loudspeakers. Please also note that a Quad ELS-63 electrostatic loudspeaker cannot handle more than 55V peak, and the GamuT can give more than 70V peak. So be careful. A lifetime of enjoyment So far, our oldest amplifiers from 1982 still work in professional recording studios, often doing their job 16 or 24 hours a day. So we expect our GamuT amplifiers to do likewise. A more likely cause for change would be your wish to upgrade in some years time. Here our modular approach serves to keep the upgrade cost low, and you avoid selling with a loss on the second hand market. The cabinet should last a lifetime, and the GamuT Logo is engraved down into the surface; wearing the text out will be quite difficult. Apart from being good economy, this long term approach is also better for the environment. Most parts of the cabinet are made of aluminium, which is easy to recycle. All parts are screwed together to enable easy disassembly. Your grandchildren will be pleased with your choice. 5 Normal use When you switch on, the blue light in the front will light up to confirm you have mains power on. One second later two small clicks can be heard from inside the amplifier, they confirm, that the amplifier has connected the loudspeakers using the output relay. One second later still, there will be two clicks in the loudspeakers. These clicks are your confirmation that the protection system have found everything to be OK. The input signal can now pass through to the loudspeakers. Each channel has its own protection circuit, so the click from one channel may arrive delayed compared to the other channel. DO NOT Do not switch the amplifier on, then off, then on again quickly. The blue light must disappear completely, before you switch on again Only switch on and off using the power switch Unplugging the mains cables, while they carry current will corrode and damage the surface of the metal of the mains plugs and sockets. This can cause reduced sound quality and electrical fires. The mains switches have special metals in the contact points selected for handling high in-rush currents, as well as to break large currents. Plugs and sockets are not made of such metals. What you can check if you do not get sound Is there light on the front panel? If not, have you plugged in the mains cable correctly? Is the fuse broken? Check both in the plug and on the back panel of the amplifier. Do you have mains power on? Check the mains socket by plugging in another working unit. Only change a blown fuse once, and use the spare slow blow fuse located in ...