MERKUR, 300B-XLS Single Ended Triode Amplifier, with 14 Watt per channel
MERKUR is a Stereo Amplifier, with 2x14 Watt 300B-XLS Single-Ended Amplifier, by Dipl. Ing. J. Leven from Germany. This design is made around the Emission Labs 300B-XLS tube. As driver stage, the powerful tube is used in DC coupled configuration.
This is a circuit diagram of an SE amplifier, designed for an EML 300B XLS tube. The driver stage consists of a DC coupled 6H30 tube, the output tube is the 300BXLS, that is a larger, stronger version of the 300B triode. The larger design is compared with a 300B, allows continuous operation with a higher Anode Dissipation (AVL). In the MERKUR-V1 circuit, this tube is operated with appr. 47 watts AVL. The use of a normal 300B is not possible in this circuit. The operating point of the 300B-XLS is to provide a simple, auto bias and negative bias allows a precise and permanent working point.
This nice design is made by Dipl. Ing. J. Leven from Germany. The 300B-XLS amplifier was tested with various loudspeakers, and supplies enough power for a loudspeaker of 86dB or more. There is only one capacitor in the signal path and together with the Amorphous Core 300B-XLS Transformer by Lundahl, it can be said that all components match together excellent, and a detailed and well balanced sound picture occurs. The bias current of the 300B-XLS tubes can be adjusted easily and precise, because the bias scheme is a mix of Auto Bias and Adjustable Bias. This allows a stabile Bias from the beginning, which will remain stabile for a long time, before it needs re-adjustment.
In the Circuit diagram, the connection schemes of the 300B-XLS Output transformer are given both for 4 Ohms and 8 Ohms.
Note about the mains fuse: You need a 4A fuse if you wire the LL1650 for 115V.
Der Merkur ist ein Stereo Verstaerker mit 2 x 14 Watt im Single Ended Design,
entwickelt von Dipl. Ing. J. Leven aus Deutschland. Die Endroehre, eine 300B-XLS wird ueber eine Gleichstrom – gekoppelte 6H30 Treiberstufe
angesteuert.
Die EML 300B-XLS ist eine groeßere und staerkere Version der 300B und erlaubt den dauerhaften Betrieb mit einer hoeheren Anoden Verlustleistung. Der Einsatz einer normalen 300B ist in dieser Schaltung nicht moeglich .Auto Bias und negative Gittervorspannung erlauben eine praezise und dauerhafte Einstellung des Arbeitspunktes der Roehre. MERKUR V1 liefert genug Leistung um Boxen ab ca. 86 dB zu betreiben, es liegt nur ein Kondensator im Signalweg, in Verbindung mit dem Lundahl Übertrager und passender Abstimmung aller Komponenten ergibt sich ein sehr detailliertes und ausgeglichenes Klangbild. Im Schaltplan sind die Anschlussbelegungen des Lundahl LL1623 Ausgangstransformators eingezeichnet, es koennen 4 oder 8 Ohm Lautsprecher betrieben werden.
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LEVEN MERKUR. 300B-XLS Stereo Amplifier
300B-XLS Schaltbilder mit freundlicher Genehmigung von Dipl. Ing. J. Leven.
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We recommend to use the transformer PCBs.
These do the same as normal wiring by hand will do, but there can be no wiring mistakes, and no wire mess.
In addition, the output impedance can be made switchable between two impedances, or can be made fixed.
Information about the Output Transformers is here
www.4tubes.com
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