Here's a link to Triode Electronics; this discusses converting a Quicksilver amp using 8417's:
http://www.triodeel.com/8417.htm
Maybe some of this is relevant.
http://www.triodeel.com/8417.htm
Maybe some of this is relevant.
From beyond the grave...
One big problem is going to be biasing- the supply as shown will not control 6550s. There's going to be some cut'n'try for R47 to get the bias voltage up to the -60 or 70 volts you'll need. I'd start with 8-10k. But the real solution is to build a new bias supply with adjustments. That's some design work, not to mention figuring out where to squeeze it in.
Second big problem is drive. V3a is going to have to swing more than double what it would have for the 8417. That's going to be a distortion problem.
This really is a strip and rebuild candidate.
One big problem is going to be biasing- the supply as shown will not control 6550s. There's going to be some cut'n'try for R47 to get the bias voltage up to the -60 or 70 volts you'll need. I'd start with 8-10k. But the real solution is to build a new bias supply with adjustments. That's some design work, not to mention figuring out where to squeeze it in.
Second big problem is drive. V3a is going to have to swing more than double what it would have for the 8417. That's going to be a distortion problem.
This really is a strip and rebuild candidate.
Ok, lets strip the sucker. Lets dump the 6Eu7's for the mic circuits right off the batt. Would I be correct in assuming the 6EU7 could stay for the input tube? Would it be better to replace it with a more common and easy to find 12AX7? Since the 7247 won't cut it
what would you suggest?
How much grunt do we need to drive (4) 6550's or (4) KT88's?
Quote: What tubes will drop into the 8417 sockets?
I would guess that 6550's, KT88's, KT90's for a starter.
OK,
Straighten me out on something... push-pull... if the plates are idling at 600 Volts, and then one plate goes to 500 Volts, then does not the other plate go to 700 Volts?
When you see plate voltage rating on tubes... are those absolute maximums? Or, are they maximums for a given topology?
Straighten me out on something... push-pull... if the plates are idling at 600 Volts, and then one plate goes to 500 Volts, then does not the other plate go to 700 Volts?
When you see plate voltage rating on tubes... are those absolute maximums? Or, are they maximums for a given topology?
So... preach in the warmth of my ignoramity.
A tube with a max plate voltage of say 600 volts, in a PP config, with a 600 B+, could actually go to 900 Volts... assuming the other tube is going to 300 volts?
Are these voltage swings realistic?
Very different from semi ratings where max is MAX.
A tube with a max plate voltage of say 600 volts, in a PP config, with a 600 B+, could actually go to 900 Volts... assuming the other tube is going to 300 volts?
Are these voltage swings realistic?
Very different from semi ratings where max is MAX.
thanks!
The super 6BG6s would work, but are closer to 6L6 in biasing and optimal plate load. I'd use a 6550A or something like that.
Since the amp is running in pentode mode, the driver doesn't have to swing much current (low input capacitance), so the paralleled 12BH7 is probably gross overkill. I'd look first at using a more linear tube and/or topology as the driver/phase-splitter.
Since the amp is running in pentode mode, the driver doesn't have to swing much current (low input capacitance), so the paralleled 12BH7 is probably gross overkill. I'd look first at using a more linear tube and/or topology as the driver/phase-splitter.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.