i have had this combination in a cupboard for several years whilst i used my leak st20.Now i intend to bring it into service using a variac.Should i connect both the quad11 to the 22,or only connect one at atime.The only load i have at this time is apair of jr 149s.also the kt66s inthe amp are not of the best quality and would like to replace them.the old gec etc valves are far to exspensive and the new ones dont realy get recommended.On some other forums they recomend 6l6gcs,5881.Are these tubes a straight replacement for the kt66.I would welcome any advice you can offer.
best wishes.
best wishes.
No, they're not. They will work, but in the long term may screw up the amp unless you change the internals (the common cathode to ~240R) - in which case it wouldn't be a Quad II. I believe the modern production Quad Classics use Tung-Sol valves.
The caveat to this is that modern KT66s aren't terribly standardised, and a lot of the other components inside may have drifted as well, so the difference might turn out to be negligible all things considered.
The caveat to this is that modern KT66s aren't terribly standardised, and a lot of the other components inside may have drifted as well, so the difference might turn out to be negligible all things considered.
Each one separately and you should monitor the supply voltages so that you know immediately that something has gone wrong. A ballast lamp is not a bad idea in the event that a cap shorts out, the lamp will prevent sufficient current from being drawn to fry the power transformer..
The ballast lamp is just a bulb in series with the load.. Could be 100W or so to start..
The 7581 is a direct replacement for the KT66, unfortunately it is now rare and expensive, the 6L6GC should be fine as well, the 5881 should work but some modern examples are a bit questionable dissipation wise compared to NOS.. There are some reasonably OK KT66 knock offs from New Sensor and China manufacturers as well. Most modern tubes are not that great frankly.. Just get yours tested, burned in and matched..
The ballast lamp is just a bulb in series with the load.. Could be 100W or so to start..
The 7581 is a direct replacement for the KT66, unfortunately it is now rare and expensive, the 6L6GC should be fine as well, the 5881 should work but some modern examples are a bit questionable dissipation wise compared to NOS.. There are some reasonably OK KT66 knock offs from New Sensor and China manufacturers as well. Most modern tubes are not that great frankly.. Just get yours tested, burned in and matched..
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