GuitslingerTim
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A matched pair of Mullards arrived yesterday along with a new pair of SED EL34's, and four new EHX 12AX7's.
The first thing I did was turn the bias pots on my DSL50 to the lowest settings and check the power levels with the new SED's installed. The old set of SED's in the head would go as low 34mV and 39mV for each tube. The new ones went as low as 32mV and 35mV, which is good, I've been shooting for an ideal setting of 35mV per tube but could never quite get there.
In comparing the Mullards to the SED's, the Mullards appeared to have longer pins, which turned out to be correct--it took a little extra push to get them to seat properly in the sockets. The only other notable visual difference is the absence of the pretty blue glow the winged-c's emit.
The real surprise was the readings that registered with the bias pots zeroed: 28mV on the left side, 26mV on the right--that's about 10mV lower than the lowest values for other tubes used in the past. Another oddity compared to other brands is the left tube registers higher than the right, just the opposite of other brands. Maybe someone with technical knowledge of power tubes and amps can chime in and explain the practical difference as to why the Mullard reissues act so differently. For instance, are the lower current readings a sign of better or lesser quality?
After installing the Mullards I also changed out all four preamp tubes so as to eliminate any factors that might detract from the tone of the power tubes. The downside in doing that is that making a fair comparison between the Mullards and the SED's requires installing the new SED's and testing them in the same environment, which will include lowering the bias settings to 35mV.
Set at 35mV per tube the Mullards sound very nice. They seem to be much darker than the old SED's, but again, that might be one of several qualities attributable in part to the lower bias settings, or the new preamp tubes. Two qualities that stand out is substantially increased detail/definition, and a pronounced sweetness that might surprise a lot of people coming from a DSL50.
Tomorrow I'll stick the new winged-c's in and make a close comparison to the Mullard reissues and try to narrow down any tonal differences. My initial impression of the Mullards is entirely positive, and worth the extra $7 paid for a matched set
The first thing I did was turn the bias pots on my DSL50 to the lowest settings and check the power levels with the new SED's installed. The old set of SED's in the head would go as low 34mV and 39mV for each tube. The new ones went as low as 32mV and 35mV, which is good, I've been shooting for an ideal setting of 35mV per tube but could never quite get there.
In comparing the Mullards to the SED's, the Mullards appeared to have longer pins, which turned out to be correct--it took a little extra push to get them to seat properly in the sockets. The only other notable visual difference is the absence of the pretty blue glow the winged-c's emit.
The real surprise was the readings that registered with the bias pots zeroed: 28mV on the left side, 26mV on the right--that's about 10mV lower than the lowest values for other tubes used in the past. Another oddity compared to other brands is the left tube registers higher than the right, just the opposite of other brands. Maybe someone with technical knowledge of power tubes and amps can chime in and explain the practical difference as to why the Mullard reissues act so differently. For instance, are the lower current readings a sign of better or lesser quality?
After installing the Mullards I also changed out all four preamp tubes so as to eliminate any factors that might detract from the tone of the power tubes. The downside in doing that is that making a fair comparison between the Mullards and the SED's requires installing the new SED's and testing them in the same environment, which will include lowering the bias settings to 35mV.
Set at 35mV per tube the Mullards sound very nice. They seem to be much darker than the old SED's, but again, that might be one of several qualities attributable in part to the lower bias settings, or the new preamp tubes. Two qualities that stand out is substantially increased detail/definition, and a pronounced sweetness that might surprise a lot of people coming from a DSL50.
Tomorrow I'll stick the new winged-c's in and make a close comparison to the Mullard reissues and try to narrow down any tonal differences. My initial impression of the Mullards is entirely positive, and worth the extra $7 paid for a matched set