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Post by purpletele on Jun 8, 2020 18:23:30 GMT -7
That is also my understanding, I believe all 4 tubes need to be there.
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Post by perryr on Jun 9, 2020 22:07:20 GMT -7
I think the DB4 uses a single cathode bias resistor, so a tube mismatch could cause hum. In half power mode i believe all 4 tubes are still idling the same (around 100%), so wear and tear on the set that are idling is likely less, but its probably not like they arent being used. That would be my guess. Maybe occasionally rotate the inside pair to the outside to balance the wear if your mostly using half power.
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Post by DRZ on Jun 13, 2020 0:02:18 GMT -7
Thanks for the thoughts guys! I'll just keep it simple and leave things alone. The amp sounds fantastic! +10000 Z
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hoffy
New Member
Posts: 35
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Post by hoffy on Oct 26, 2021 6:59:46 GMT -7
Hey guys, have you actually found out if the half power mode in DB4 wears all the tubes evenly or is it just a pair of them? Thanks.
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Post by headshrinker (Marc) on Oct 26, 2021 7:54:11 GMT -7
It wears them all evenly.
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hoffy
New Member
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Post by hoffy on Oct 27, 2021 0:03:19 GMT -7
It wears them all evenly. Thanks. So there is no problem using it most of the time in the half power mode? How is the half power achieved in this amp? Will it sound different, inferior to the full power mode (like in pentode-triode switching system)?
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Post by bryan0418 on Nov 1, 2021 20:21:56 GMT -7
It wears them all evenly. Thanks. So there is no problem using it most of the time in the half power mode? How is the half power achieved in this amp? Will it sound different, inferior to the full power mode (like in pentode-triode switching system)? I am not 100% sure but I believe 2 of the tubes are grounded to get the half power feature. I use my DB4 in both full and half power and there is no sound difference. It is not a pentode/triode setup. It is just Dr Z's magic way to cut the power of a non-master volume amp. Any sound difference you may hear is that you aren't moving as much air at 18 watts compared to the 38 ish watts in full power mode. Try it both ways and see what works for you. There is no right or wrong. Either setting is all good.
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Post by Chilly Gibbons (Todd T.) on Nov 2, 2021 3:19:26 GMT -7
This is correct. When Doc uses a pentode/triode switch, he uses it for changing the character of the output section, not as a power reduction tool. As mentioned above, he has his ways of reducing power.
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hoffy
New Member
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Post by hoffy on Nov 4, 2021 9:17:03 GMT -7
Guys, I finally got a reply directly from Z support:
"The 2nd and 4th power tube run idle in half power. 1st and 3rd always get signal. This is counting from the left to right from the back of the amp. If always in ½ power mode, the 2nd and 4th tube would be your fresher set."
It means it is wise to swap the power tubes from time to time to wear them evenly.
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