j'aimerais avoir l'avis de spécialiste sur la méthode proposée par Rivera pour le réglage de Bias sur leurs amplis.
http://www.rivera.com/pdf/Knuc(...)0.pdf
Wave from the output stage on an oscilloscope, with the waveform just bef
ore output stage clip. The Cathodes of the output tubes are all tied together and in parallel. They are connected to the chassis ground through an internal switch on the Speaker Jack #1. When there is no plug
inserted into the speaker Jack #1, the switch is open, and the output tubes do not conduct as the cathodes are lifted from chassis ground. Conversely, when a plug is inserted into speaker Jack #1, the cathodes conduct through this switch to chassis ground, thereby enabling the output stage to operate. This feature allows easy idle current measurement as well as protecting the amp for operating without a speaker load. Use the DC Current measuring capability of a preferably digital multi-meter to observe this current. Observe the location of the Bias adjustment pot on the motherboard. It is located near V5. Observe the two wires connected between the output tube circuit board and the speaker jack board. These wires carry the output tube cathode current. Connect your current meter across the pads of the speaker jack board where these two wires are soldered to. Make sure that nothing is plugged into speaker Jack #1. Place a appropriate load on Speaker Jack #2 if this is possible. If not, you will be ok as there will be no signal present. No signal of any source should be plugged into the front panel input jacks or the rear panel effects loop jacks. Turn the amp on. Make sure that the High/Low Power switch is in the “High” position, and the Standby switch is in the “On” position. After the tubes warm up, observe the idle current. For 55 Versions (2 output tubes), adjust for 80-90 MaDC. For 100 Versions (4 output tubes), adjust for 160-180 MaDC. The actual setting you choose will depend on the particular tubes used and their DC Current gain. For example, a really high
gain EL-34 should be biased colder (40 MaDC per tube) then a low gain tube which may sound best run hotter (45 MaDC per tube).
http://www.rivera.com/pdf/Knuc(...)0.pdf
Citation:
The most accurate way to measure the bias of our amplifiers is by observing the cathode idle current of the output tube, and observe a SineWave from the output stage on an oscilloscope, with the waveform just bef
ore output stage clip. The Cathodes of the output tubes are all tied together and in parallel. They are connected to the chassis ground through an internal switch on the Speaker Jack #1. When there is no plug
inserted into the speaker Jack #1, the switch is open, and the output tubes do not conduct as the cathodes are lifted from chassis ground. Conversely, when a plug is inserted into speaker Jack #1, the cathodes conduct through this switch to chassis ground, thereby enabling the output stage to operate. This feature allows easy idle current measurement as well as protecting the amp for operating without a speaker load. Use the DC Current measuring capability of a preferably digital multi-meter to observe this current. Observe the location of the Bias adjustment pot on the motherboard. It is located near V5. Observe the two wires connected between the output tube circuit board and the speaker jack board. These wires carry the output tube cathode current. Connect your current meter across the pads of the speaker jack board where these two wires are soldered to. Make sure that nothing is plugged into speaker Jack #1. Place a appropriate load on Speaker Jack #2 if this is possible. If not, you will be ok as there will be no signal present. No signal of any source should be plugged into the front panel input jacks or the rear panel effects loop jacks. Turn the amp on. Make sure that the High/Low Power switch is in the “High” position, and the Standby switch is in the “On” position. After the tubes warm up, observe the idle current. For 55 Versions (2 output tubes), adjust for 80-90 MaDC. For 100 Versions (4 output tubes), adjust for 160-180 MaDC. The actual setting you choose will depend on the particular tubes used and their DC Current gain. For example, a really high
gain EL-34 should be biased colder (40 MaDC per tube) then a low gain tube which may sound best run hotter (45 MaDC per tube).
OSEF
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« les gens comme vous » :phrase prononcée par CasseOreille le 11/01/2019, pour désigner ceux qui ne pensent pas comme lui.
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« les gens comme vous » :phrase prononcée par CasseOreille le 11/01/2019, pour désigner ceux qui ne pensent pas comme lui.
